ACS Publications. Most Trusted. Most Cited. Most Read
Quick View

OR SEARCH CITATIONS

My Activity
Recently Viewed
You have not visited any articles yet, Please visit some articles to see contents here.
Publications
CONTENT TYPES

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Cent. Sci. 2019, 5, 1, 85-96
RETURN TO ISSUEPREVResearch ArticleNEXT

A Telescoping View of Solute Architectures in a Complex Fluid System

  • Ryuhei Motokawa*
    Ryuhei Motokawa
    Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
    *E-mail: [email protected]
    More by Ryuhei Motokawa
    Orcidhttp://orcid.org/0000-0001-5010-0112
    • , 
  • Tohru Kobayashi
    Tohru Kobayashi
    Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
    More by Tohru Kobayashi
    • , 
  • Hitoshi Endo
    Hitoshi Endo
    Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
    Neutron Science Division, Institute of Materials Structure Science, and Materials and Life Science Division, J-PARC Center, High Energy Accelerator Research Organization, 203-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
    Department of Materials Structure Science, The Graduate University for Advanced Studies (SOKENDAI), 203-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
    More by Hitoshi Endo
    • , 
  • Junju Mu
    Junju Mu
    School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
    More by Junju Mu
    Orcidhttp://orcid.org/0000-0002-7382-2182
    • , 
  • Christopher D. Williams
    Christopher D. Williams
    School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
    More by Christopher D. Williams
    Orcidhttp://orcid.org/0000-0002-5073-5924
    • , 
  • Andrew J. Masters*
    Andrew J. Masters
    School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
    *E-mail: [email protected]
    More by Andrew J. Masters
    Orcidhttp://orcid.org/0000-0003-3998-1769
    • , 
  • Mark R. Antonio
    Mark R. Antonio
    Chemical Sciences & Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
    More by Mark R. Antonio
    Orcidhttp://orcid.org/0000-0002-1208-4534
    • , 
  • William T. Heller
    William T. Heller
    Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
    More by William T. Heller
    Orcidhttp://orcid.org/0000-0001-6456-2975
    • , and 
  • Michihiro Nagao
    Michihiro Nagao
    NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States
    Center for Exploration of Energy and Matter, Department of Physics, Indiana University, Bloomington, Indiana 47408, United States
    More by Michihiro Nagao
    Orcidhttp://orcid.org/0000-0003-3617-251X
Cite this: ACS Cent. Sci. 2019, 5, 1, 85–96
Publication Date (Web):December 31, 2018
https://doi.org/10.1021/acscentsci.8b00669
Copyright © 2018 American Chemical Society
RIGHTS & PERMISSIONS
ACS AuthorChoiceACS AuthorChoicewith CC-BYlicense
Article Views
3028
Altmetric
-
Citations
43
LEARN ABOUT THESE METRICS
PDF (3 MB)
Get e-Alerts
Supporting Info (1)»
SUBJECTS:

Abstract

High Resolution Image
Download MS PowerPoint Slide

Short- and long-range correlations between solutes in solvents can influence the macroscopic chemistry and physical properties of solutions in ways that are not fully understood. The class of liquids known as complex (structured) fluids—containing multiscale aggregates resulting from weak self-assembly—are especially important in energy-relevant systems employed for a variety of chemical- and biological-based purification, separation, and catalytic processes. In these, solute (mass) transfer across liquid–liquid (water, oil) phase boundaries is the core function. Oftentimes the operational success of phase transfer chemistry is dependent upon the bulk fluid structures for which a common functional motif and an archetype aggregate is the micelle. In particular, there is an emerging consensus that mass transfer and bulk organic phase behaviors—notably the critical phenomenon of phase splitting—are impacted by the effects of micellar-like aggregates in water-in-oil microemulsions. In this study, we elucidate the microscopic structures and mesoscopic architectures of metal-, water-, and acid-loaded organic phases using a combination of X-ray and neutron experimentation as well as density functional theory and molecular dynamics simulations. The key conclusion is that the transfer of metal ions between an aqueous phase and an organic one involves the formation of small mononuclear clusters typical of metal–ligand coordination chemistry, at one extreme, in the organic phase, and their aggregation to multinuclear primary clusters that self-assemble to form even larger superclusters typical of supramolecular chemistry, at the other. Our metrical results add an orthogonal perspective to the energetics-based view of phase splitting in chemical separations known as the micellar model—founded upon the interpretation of small-angle neutron scattering data—with respect to a more general phase-space (gas–liquid) model of soft matter self-assembly and particle growth. The structure hierarchy observed in the aggregation of our quinary (zirconium nitrate–nitric acid–water–tri-n-butyl phosphate–n-octane) system is relevant to understanding solution phase transitions, in general, and the function of engineered fluids with metalloamphiphiles, in particular, for mass transfer applications, such as demixing in separation and synthesis in catalysis science.

Synopsis

Multiscale structure perspectives for zirconium-loaded organic phases show hierarchical aggregation built upon coordination complexes that self-assemble into primary clusters that form superclusters.

Introduction

ARTICLE SECTIONS
Jump To
The literature of science and engineering of colloids is filled with ternary phase diagrams comprising two immiscible liquids (e.g., water and oil) and a soluble amphiphilic surfactant. (1,2) Upon mixing, the initially biphasic system can equilibrate as one of four main types of microemulsions described by Winsor. (3) In each of these oil-in-water and water-in-oil phase combinations, the micelle (4) and the reverse micelle, (5) respectively, are the fundamental building blocks in the formation of supramolecular solution structures, including cylindrical, close-packed, and lamellar mesophases. (6,7) In the vernacular of soft matter sciences, such complex (structured) fluids are built upon multiscale correlations resulting from physicochemically soft and weak interactions. The organization of solutes (i.e., neutrals, cations, and anions) into aggregated structures through weak interactions, with energies of 1 kBT and less, (8,9) drives the assembly of aggregate architectures in which a delicate balance between short-range attractive, long-range repulsive (SALR) interactions regulates pattern formation (10) and phase behaviors. Whereas the weak long-range forces are small compared the strong short-range forces in metalloamphiphile chemical bonding (approximately 300 kBT), they influence complex physical responses, often resulting in complicated fluid behaviors, including the critical phenomenon of phase splitting.
In the limit of a vanishing critical temperature and weak attraction, the splitting of SALR fluids into colloid-poor (gas) and colloid-rich (liquid) phases—known as the gas–liquid phase separation model (11,12)—is suppressed (10) in favor of percolation. (13,14) In contrast, strong attraction energy landscapes between nanoscale solute architectures leading to gelation in colloidal SALR systems are a direct consequence of equilibrium gas–liquid phase separation, not percolation. (15) Recently, self-assembly phenomena in SALR colloids at macroscopic length scales were attributed to a previously unrecognized mechanism, dubbed ionic sphericity. (16) In previous research on complex fluids that function in ternary (water–oil–surfactant) systems for chemical separations by liquid–liquid (biphasic) extraction, the splitting of the oil phase—into two oil phases—has been attributed to the gas–liquid model of phase transition. (17) This interpretation, originally proposed in 1998 by Erlinger et al. (18) on the basis of small-angle X-ray scattering (SAXS), is the genesis of the micellar model of phase splitting. (19) In this, a complex fluid of sticky spheres (e.g., reverse micelles with surface adhesion) with a short-range interaction potential that is approximated by a hard repulsive core and a rectangular attractive well (as defined by Baxter) (20) was shown to be consistent with the experimental SAXS data. Despite the system approximations and simplifications required to make the data analyses tractable, the insights obtained from the use of this model with regard to the energetics of the phase transition provide a zeroth-order benchmark for all subsequent phenomenological comparisons, including those reported here.
To address aspects of the complexities with regard to organic phase architectures, in general, and the origins of phase splitting, in particular, we provide new insights into the soft matter chemistry and physics of separation science. In particular, lacking in our understanding of these systems is a robust description of the weak interactions involved in aggregation and how they scale up (and down) as manifest in the type of solution structures that are formed, and how, in combination, they influence technically relevant material behaviors. For example, self-organized, complex fluid systems are exemplified by a wide variety of familiar substances, including polymers, gels, soaps, and inks. Recent advances with X-ray and neutron scattering probes focused on fluid systems have significantly expanded the list of liquids exhibiting aggregation behaviors in a diverse range of applications. Some of these include commercial-scale processes for enhanced oil and gas recovery; production of pharmaceuticals and commodity chemicals; transportation and sequestration of natural gas and CO2; phase transfer and micellar catalysis; and even nuclear fuel reprocessing operations like PUREX (plutonium uranium reduction extraction). (21)
In this latter system and many others like it, there is an emerging consensus that solute aggregation can have a profound impact on the chemical behavior of the organic solution, notably on both the efficiency and selectivity of the process. (22−33) In fact, reverse micellar solvents with the macroscopic appearance of a homogeneous solution are routinely employed in organic- and biological-based separation, purification, and conversion processes with little understanding of the morphology and arrangement of the micelle domains. (34,35) These contemporary applications are revolutionizing fundamental separations concepts by shifting the focus away from the classical enthalpic drivers associated with local, molecular-scale interactions into multiscale-ordering, which is hypothesized to include large entropic contributions that may dominate the energy landscape of bulk behaviors (36) that are hallmarks of coacervation (35) and microemulsions. (37) However, the relationships between the microscopic solute structures and phase behaviors remains largely unresolved. The present study investigates the macroscopic splitting of the organic phase during liquid–liquid (water–oil) extraction by examining the microscopic structures of metal coordination chemistry and the mesoscopic architectures of supramolecular chemistry. Our findings provide a fundamental, telescoping structure perspective into processes that are pivotal to the international energy economies vis-à-vis the refining and purification of platinum group and base metals as well as rare earth and actinide elements.
In these biphasic hydrometallurgical operations, a high metal loading of the organic phase is advantageous to obtain cost-effective separations. However, in practice, it is not possible to achieve this because when the concentration of the extracted metal ion exceeds the critical concentration, a ruinous phase transition occurs. In this, the organic phase splits into a light phase and a heavy one; the heavy organic phase is called the third phase. (21,38) In line with recent research on the subject, (39) we choose to cast organic phase splitting in liquid–liquid extraction as a critical phenomenon. Understanding the mechanism of third-phase formation offers the prospects for the development of advanced, high-performance separation science and technology. With specific regard to the PUREX process—on a molecular scale—it is generally known that the amphiphile tri-n-butyl phosphate (TBP; see the Supporting Information showing the chemical structure) coordinates with tetravalent plutonium as the nitrate complex to form the charge-neutral tetranitrato-disolvate, Pu(NO3)4(TBP)2, (38) in the organic phase. On a supramolecular scale, small-angle neutron scattering (SANS) has been modeled in the Baxter sticky-sphere framework to reveal interactions between small spherical reverse micelles containing three to five TBP molecules in n-dodecane. (40) The critical phenomenon of phase splitting was attributed to the strength of the attractive forces (with a potential energy of up to −2.6 kBT) between the polar cores of the reverse micelles. This is dubbed the micellar interaction model. (41) More recent reports involving computational studies have called into question the validity of the model for both metal-free (42−44) and metal-ion-loaded (45) systems.
As with any model, new experimental and computational data obtained with contemporary methodology oftentimes reveal nuances and subtleties that are not resolved in the original efforts. (41) For example, Baldwin et al. (45) reported that the Baxter model for interpreting SANS profiles in the PUREX system can be misleading about the strength of the interaction energies between reverse micelles. That is, under selected conditions, the model tends to predict nonattractive interactions contrary to direct observations of phase splitting due to strong attractive associations. There are at least two possible reasons for these contradictions. First, to simplify analysis with the Baxter model, the extracted solutes were assumed to occupy the cores of spherical or ellipsoidal micelles without knowledge of the true coordination chemistry and particle morphologies. Second, the incoherent scattering intensity from hydrogen atoms contained in the samples was overly simplified as a fitting parameter in SANS data analyses. (41,45−47) Since the requisite coherent scattering intensity reflecting the structural information on the solutes is typically buried under the level of incoherent scattering intensity, it is crucial to evaluate the incoherent scattering intensity in a rigorous manner. Accordingly, in this study we used neutron polarization analysis, which is the best experimental method for evaluating the incoherent scattering intensity to avoid misinterpretation of the SANS data. (48) This development of an improved method to model long-range aggregate structures beyond coordination chemistry augments our understanding of the solution state of the organic phase following extraction.
In this work, extended X-ray adsorption fine structure (EXAFS) experiments with density functional theory (DFT) calculations, molecular dynamics (MD) simulations, and SANS were carried out in a complementary style to explore the micro- and mesoscopic architectures of the solvate cluster formed by Zr(NO3)4 and TBP, Zr(NO3)4(TBP)2, as a nonradioactive chemical surrogate of Pu(NO3)4(TBP)2 in PUREX. The combination of experimentation and simulation is of great advantage to avoid the above-mentioned uncertainties by accessing a broad spectrum of length scales from 0.1 to 100 nm in a telescoping, hierarchical model (49) that includes the extracted coordination complexes (obtained from EXAFS) and also the morphology of aggregates (by SANS). This multimodal method allows unique data treatment, enabling us to combine EXAFS and SANS with theory, (50,51) to elucidate the molecular nature of the zirconium complexes and their subsequent self-assembly into supramolecular aggregates. The results advance our knowledge about the structures and energetics responsible for the phenomena of phase transitions in SALR fluids as they approach critical point concentrations.

Results and Discussion

ARTICLE SECTIONS
Jump To

Experimental Samples

All samples used for EXAFS and SANS measurements were prepared by biphasic solvent extraction of the Zr(NO3)4–HNO3/TBP–n-octane-d18 system. Equal volumes (3.0 mL) of an aqueous, initial phase of 10.5 M (mol/L) nitric acid solution containing [Zr(NO3)4]aq,in = 0 mM and the organic, initial phase of 0.50 M TBP were shaken for 1 h at room temperature in a glass tube, where [Zr(NO3)4]aq,in is the aqueous, initial concentration of Zr(NO3)4 (prior to the extraction). After centrifugation and separation of the two distinct phases, the organic phase was collected; this is designated as sample no. 1. Next, 3.0 mL of sample no. 1 and 3.0 mL of aqueous, initial phases containing [Zr(NO3)4]aq,in ranging from 0.010 to 0.049 M in 10.5 M nitric acid solution were shaken for 1 h at room temperature. The mixtures were centrifuged to separate the aqueous and organic phases. Aliquots of the organic phases are designated as sample nos. 2–5 (Table 1). Sample nos. 1–5 were examined by both EXAFS and SANS. Note that the phase separation and third-phase formation occur only in cases where [Zr(NO3)4]aq,in > 0.049 M. Therefore, the complex concentration in sample no. 5 is very close to the critical concentration, i.e., the highest Zr concentration in the organic phase achievable without phase separation. In this extraction, Zr(NO3)4(TBP)2 is the predominant extracted coordination species in the organic phase, as will be explained in conjunction with analysis of the EXAFS data. The concentrations of Zr(NO3)4(TBP)2, HNO3, and H2O extracted into the organic, equilibrium phases of all samples are denoted by [Zr(NO3)4(TBP)2]org,eq, [HNO3]org,eq, and [H2O]org,eq, respectively. The concentration of free TBP (uncoordinated with Zr(NO3)4) in the organic phases is denoted by [TBP]org,eq. Additionally, the aqueous, equilibrium concentrations of Zr(NO3)4, [Zr(NO3)4]aq,eq, are shown in Table 1. The values of [Zr(NO3)4]aq,in, [Zr(NO3)4(TBP)2]org,eq, [HNO3]org,eq, [H2O]org,eq, and [TBP]org,eq of the five samples are summarized in Table 1, together with the volume fractions of extracted Zr(NO3)4(TBP)2, HNO3, H2O, uncoordinated TBP, and n-octane-d18, which are defined as ϕZr(NO3)4(TBP)2, ϕHNO3, ϕH2O, ϕTBP, and ϕoctane-d18, respectively. Note that ϕZr(NO3)4(TBP)2 + ϕHNO3 + ϕH2O + ϕTBP + ϕoctane-d18 = 1. The distribution ratios of zirconium, DZr, are shown in Table 1. The values (1.9–2.4) are independent of [Zr(NO3)4]aq,eq, indicating that zirconium is extracted into the organic phases as a mononuclear entity. This represents a stark contrast with the distribution ratios of tetravalent cerium, DCe, reported elsewhere, in which cerium reports to the organic phase as a multinuclear complex. (52) The concentration ratios of [HNO3]org,eq/[Zr(NO3)4(TBP)2]org,eq, [H2O]org,eq/[Zr(NO3)4(TBP)2]org,eq, and [HNO3]org,eq/[H2O]org,eq for sample nos. 1–5 are also shown in the Supporting Information.
Table 1. Composition of the Aqueous (aq) and Organic (org) Phases before (in) and after (eq) the Extraction Process and Distribution Ratio of Zirconium Ions, DZr
     [Zr(NO3)4(TBP)2]org,eq (M)[HNO3]org,eq (M)[H2O]org,eq (M)[TBP]org,eq (M) 
sample no.[Zr(NO3)4]aq,in (M)[HNO3]aq,in (M)[Zr(NO3)4]aq,eq (M)DZrϕZr(NO3)4(TBP)2ϕHNO3ϕH2OϕTBPϕoctane-d18
1010.5  00.280.0450.500 
  00.0110.0010.1170.871
20.01010.50.0032.30.0070.280.0510.486 
0.0050.0070.0010.1320.855
30.02510.50.0082.10.0170.340.0640.466 
0.0130.0140.0010.1270.845
40.03410.50.0102.40.0240.270.0760.452 
0.0190.0110.0010.1040.865
50.04910.50.0171.90.0320.300.0740.436 
0.0250.0130.0010.1190.842

Local Coordination Structure in the Organic Phase

Figure 1a,b show the k3-weighted Zr K-edge EXAFS oscillation, k3χ(k), as a function of the photoelectron wavenumber, k (Å–1), and the corresponding radial structural function, |FT[k3χ(k)]|, with the imaginary part of FT[k3χ(k)], Im{FT[k3χ(k)]} obtained for the organic phases (sample nos. 2–5) as a function of the radial distance from the Zr atom, r + Δr. Here, Δr is the magnitude of the phase shift resulting from a change in the photoelectron wave while traversing the potentials of the absorbing and scattering atoms. The k3χ(k) in Figure 1a and |FT[k3χ(k)]| in Figure 1b do not depend on the increase in [Zr(NO3)4(TBP)2]org,eq in the organic phase. Importantly, this indicates that the local coordination structure of the extracted zirconium complex barely changes at [Zr(NO3)4(TBP)2]org,eq ≤ 32 mM, which is close to the highest complex concentration attainable in the organic phase without third-phase formation. Even in the case of the third phase, the EXAFS data were similar to those of the organic phases, as shown in Figure S6. This mirrors the response observed in the corresponding Ce EXAFS data obtained under comparable conditions. (53)

Figure 1

Figure 1. EXAFS spectra for the extracted Zr coordination complexes, (a) k3-weighted Zr K-edge EXAFS, k3χ(k) (open black circles), and (b) corresponding Fourier transform, |FT[k3χ(k)]| (open black circles), and the imaginary part of FT[k3χ(k)], Im{FT[k3χ(k)]} (filled blue circles), obtained for the organic phases of sample nos. 2–5. The solid black curves in part a, the red curves in part b, and the green curves in part b are the simulated k3χ(k), |FT[k3χ(k)]|, and Im{FT[k3χ(k)]} responses, respectively. The thick arrows highlight the P1, P2, P3, and P4 peaks, which originate from the scattering paths of Zr–OTBP and Zr–ONO3, Zr–NNO3, Zr–PTBP, and Zr–N–Omultiple, respectively (Table 2).

High Resolution Image
Download MS PowerPoint Slide
In Figure 1b, the |FT[k3χ(k)]| shows one significant peak with a shoulder on the longer r + Δr side. The peak, at approximately r + Δr ≈ 0.15 nm and designated as P1, is indicated with a thick arrow. Three further peaks are designated as P2, P3, and P4 at 0.2 nm < r + Δr < 0.4 nm. Peak P1 is attributed to two kinds of Zr–O bonds, namely, directly coordinating oxygen atoms of TBPs and nitrate ions. The peaks P2, P3, and P4 are attributed to the correlations between Zr–P with TBPs, Zr–N with nitrate ions, and/or multiple scattering of Zr–N–O with nitrate ions, respectively.
Curve fitting for quantitative analysis of the EXAFS data was conducted to obtain the structural parameters of the extracted coordination species in the organic phases. In this analysis, the atomic positions from an optimized coordination structure of Zr(NO3)4(TBP)2 obtained by DFT calculation were used as a structural model for initial input in simulation code FEFF version 8.4. (54) The optimized coordination structure is shown in Figure 2a. All significant scattering paths between Zr and its interrelated atoms giving rise to the distinct peaks in |FT[k3χ(k)]| were taken into account in the curve-fitting analysis. The amplitude reduction factor, S02, was fixed as 0.9 in the fitting procedure. All EXAFS data were well reproduced by the best-fitted simulated curves of k3χ(k) (black solid lines), |FT[k3χ(k)]| (red solid lines), and Im{FT[k3χ(k)]} (green solid lines) with the refined structural parameters, as shown in Figure 1.

Figure 2

Figure 2. Schematic diagrams of hierarchical aggregate model of zirconium superclusters. (a) Geometry of the optimized coordination structure of extracted Zr(NO3)4(TBP)2 in the organic phase, determined by DFT calculation. Green, Zr; yellow, P; red, O; blue, N; black, C; and light pink, H. (b) Primary cluster in which the Zr(NO3)4(TBP)2 complexes (red spheres) distribute with radius RS around the central complex, (c) primary clusters assemble into a large aggregate (supercluster), where the primary clusters with radius RS surround the central cluster (light blue sphere) with radius RL. A set of the number of the primary clusters, M = 25, and the number of the complexes, N = 7, corresponds to the characteristic parameters of sample no. 5 from SANS data analysis.

High Resolution Image
Download MS PowerPoint Slide
Representative structural parameters, refined in the fitting analysis of sample no. 4 ([Zr(NO3)4(TBP)2]org,eq = 24 mM), are summarized in Table 2, where CN, rEXAFS, σDB2, and ΔE0 correspond to the coordination number, bond distance, squared Debye–Waller factor, and energy shift parameter, respectively. The oxygen CN due to TBP molecules (Zr–OTBP path) and nitrate ions (Zr–ONO3 path), resulting in P1, are approximately 2 and 8, respectively. The nitrogen CN due to nitrate ions (Zr–NNO3 path), phosphorus due to TBPs (Zr–PTBP path), and multiple scattering due to nitrate ions (Zr–N–Omultiple path), resulting in P2, P3, and P4, are approximately 4, 2, and 4, respectively. Accordingly, the CNs of the Zr–OTBP and Zr–PTBP paths indicate the coordination of two TBP molecules with the inner sphere of zirconium. The O and N CNs of Zr–ONO3, Zr–NNO3, and the Zr–N–Omultiple paths indicate the bidentate coordination of four nitrate ions with the inner sphere of zirconium. As a result, we found that the coordination species in the organic phase is always Zr(NO3)4(TBP)2. This species is therefore expected to be a fundamental building unit of a higher-order, long-range structure formed in the organic phases.
Table 2. Structural Parameters Evaluated by Fitting Analysis of Sample No. 4 Using an Optimized Coordination Structure of Zr(NO3)4(TBP)2 as the Initial Input Model for DFT Calculation
pathaCNrEXAFS (nm)σDW2b (nm2)ΔE0b (eV)S02rDFT (nm)
Zr–OTBP1.9 ± 0.21c0.215 ± 0.0020.000 023.630.90.2205
Zr–ONO37.8 ± 0.370.228 ± 0.0030.000 073.630.90.2349
Zr–NNO33.9 ± 0.330.276 ± 0.0040.000 033.630.90.2795
Zr–PTBP2.1 ± 0.200.361 ± 0.0030.000 043.630.90.3655
Zr–N–Omultiple4.1 ± 0.320.398 ± 0.0030.000 033.630.90.4003
a

Scattering paths calculated by use of program code FEFF version 8.4. (54)

b

Errors in σDW2 and ΔE0 in this study are within ±3.0% accuracy.

c

Error represents ±1 standard deviation throughout the paper.

The result of the DFT calculation shows that directly coordinated oxygen atom of only one nitrate ion is slightly more distant than those of the other three nitrate ions coordinated to Zr, thereby giving rise to the shoulder on peak P1 and to the increase of σDW2 of Zr–ONO3. The average bond distances evaluated by DFT calculation, rDFT, are shown in Table 2 and are in good agreement with rEXAFS. Therefore, the optimized coordination structure of Zr(NO3)4(TBP)2 shown in Figure 2a can be taken as the actual state in the organic phase.

Overall SANS Features

Figure 3a shows the observed SANS intensity distribution as a function of q, Iobs(q), obtained for sample nos. 1–5, which had different concentrations of Zr(NO3)4(TBP)2 in their organic phases, as shown in Table 1. Here, q (=[4π/λ]sinθ) is the magnitude of the scattering vector, and λ and 2θ are the wavelength of the incident neutrons and the scattering angle, respectively. The scattering intensity in the low-q region (q < 1.0 nm–1) gradually increases with increasing [Zr(NO3)4(TBP)2]org,eq, whereas that in the high-q region (q > 1.0 nm–1) barely changes as a function of [Zr(NO3)4(TBP)2]org,eq. Even in the absence of extracted Zr(NO3)4(TBP)2 complex in the organic phase (sample no. 1), scattering intensity is observed in the SANS profile, particularly in the low-q region. This is attributed to aggregates formed by extracted HNO3 and TBP, which have been reported by SANS (41) and computational studies. (43−45) Our preceding research concluded that the TBP aggregates arise from the formation of hydrogen-bonding networks consisting of HNO3, H2O, and the P═O group of TBP, leading to an isotropic microemulsion in the organic phase. (44) Because the scattering from the HNO3–H2O–TBP aggregates for sample nos. 2–5 can vitiate the quantitative structural analyses of the extracted Zr(NO3)4(TBP)2 in the organic phase, the undesirable scattering contributions were subtracted deliberately as described in the Methods section (see the Supporting Information).

Figure 3

Figure 3. Double-logarithmic plots of the SANS profiles, (a) Iobs(q) and (b) Isub(q), with error bars, as a function of [Zr(NO3)4(TBP)2]org,eq. [Zr(NO3)4(TBP)2]org,eq gradually increases with sample no. from 1 to 5. Dashed lines in part b are the form factors of Zr(NO3)4(TBP)2 in the organic phase, determined on the basis of the Debye scattering formula for randomly orientated Zr(NO3)4(TBP)2 using eqs S3, S6, and S7. Solid lines in part b are the best-fit theoretical SANS profiles obtained by using eqs S10–S13 together with the characteristic parameters listed in Table 3.

High Resolution Image
Download MS PowerPoint Slide
Figure 3b shows Isub(q) plots, which are the SANS profiles of sample nos. 2–5 from which the components of the HNO3–H2O–TBP aggregates were subtracted from Iobs(q). The scattering intensity in the high-q region (q ≥ 3.0 nm–1) increases in proportion to the increase in [Zr(NO3)4(TBP)2]org,eq, indicating that the coordination structure of the extracted metal ion species does not depend on the concentration and maintains a specific structure, which is consistent with the EXAFS results discussed above. In addition, the scattering intensity in the low-q region (q < 1.0 nm–1) increases out of proportion to [Zr(NO3)4(TBP)2]org,eq suggesting that Zr(NO3)4(TBP)2 does not disperse homogeneously and, rather, forms supramolecular structures.

Quantitative Analyses of SANS Intensity Distributions

We first numerically analyzed the form factor of a single Zr(NO3)4(TBP)2 complex in sample nos. 2–5 using the optimized coordination of each atom with the DFT calculation by means of the Debye scattering formula for randomly orientated objects; (50,51) the scattering function is described in detail in the Supporting Information (see eqs S3−S9). The four dashed lines in Figure 3b indicate the same q dependence and show the contribution of the form factors of Zr(NO3)4(TBP)2 for sample nos. 2–5. The small-angle scattering intensities are proportional to the number density of the extracted Zr(NO3)4(TBP)2 complex, ncomplex, and agree well with Isub(q) for q ≥ 3.0 nm–1, whereas those for q < 3.0 nm–1 deviate from each form factor. This deviation is attributed to an ordered (aggregate) structure well beyond the inner-sphere coordination about Zr, and thus analyzing the excess scattering components for q < 3.0 nm–1 over the form factor of the coordination species will allow elucidation of the aggregate architecture. Analyses of Isub(q) with Guinier’s law (55) as shown in Figure S7 provide an initial evaluation of the size of the high-order structures formed by Zr(NO3)4(TBP)2 in the organic phase in terms of the radius of gyration, Rg. These were determined to be 3.2, 3.3, 4.5, and 5.0 nm for sample nos. 2–5, respectively. The observed power law scattering, Isub(q) ∼ q–D for 1/Rg < q (nm–1) < 3, shows D ≈ 3 for sample nos. 3–5, which is solid evidence of the existence of an inhomogeneous spatial distribution of Zr(NO3)4(TBP)2 complexes inside the high-order structures.
Given the above findings, we assumed that the hierarchical structure, which comprises primary clusters consisting of extracted Zr(NO3)4(TBP)2 and its aggregates, is formed in the organic phases as shown in Figure 2. A small cluster of Zr(NO3)4(TBP)2 complexes is considered; that is, the N complexes distribute spherically and randomly around the center complex at a distance R (see Figure 2a,b). Then, the small primary clusters consisting of N complexes with radius RS form a large aggregate (supercluster) of M primary clusters with radius RL (see Figure 2c). A similar structure hierarchy was proposed to explain the pseudoliquid phase behaviors of hetero-polyanion cluster compounds. (56) Based on this hierarchical aggregate model, (49) the small-angle scattering intensity can be exactly calculated as described in the Supporting Information, and the SANS data were compared with the model.
Sample no. 2 has the lowest concentration of extracted Zr(NO3)4(TBP)2 in the organic phase; consequently, Isub(q) can be reproduced by the contribution of the primary cluster without considering the supercluster, and thus M was fixed as 1 (the model shown in Figure 2b). By comparison, a clustering of the primary clusters is crucial to reproducing Isub(q) when [Zr(NO3)4(TBP)2]org ≥ 17 mM (sample nos. 3–5), otherwise the theoretical values based on the model in Figure 2b do not agree with the experimental data as shown in Figures S9 and S10.
The solid lines in Figure 3b show the best-fit theoretical scattering curves for the hierarchical aggregates, which exhibit good agreement between the model and the experiments. The refined characteristic parameters are summarized in Table 3. Note that the number density of the superclusters, nsuper, satisfies the relation ncomplex = nsuperMN, and the distributions of RS and RL were necessary to reproduce the scattering intensity distribution precisely; thus the Schultz distribution with the corresponding standard deviations, σL and σS, respectively, was used. (57) Remarkably, the parameters N and RS relating to the primary cluster barely change in sample nos. 3–5, even with increasing M and RL, which relate to the superclusters. This result suggests that the size and aggregation number of the primary cluster are insensitive to [Zr(NO3)4(TBP)2]org,eq for it to be stable in the organic phase when the fundamental building unit is Zr(NO3)4(TBP)2. We believe that aggregation of the hydrophilic parts of Zr(NO3)4(TBP)2 provides the driving force to form the primary cluster, and that this is driven by coordinated nitrate ions, which form a hydrogen-bonding network involving extracted HNO3 and H2O. (43,44,58) Consequently, the surface of the primary cluster should be stably covered with the hydrophobic butyl groups of TBP in the organic phase as will be explained by the MD simulations described below. Subsequently, we speculate that the process of primary cluster aggregation is similar to the formation of concentrated reverse micelle systems, as supported by previous studies. (41,59,60)
Table 3. Summary of the Characteristic Parameters of Hierarchical Aggregates Determined by Model Analysis of Isub(q)
sample no.NRS (nm)σS (nm)MRL (nm)σL (nm)
29.8 ± 2.41.3 ± 0.140.70 ± 0.151  
37.0 ± 1.30.93 ± 0.020.10 ± 0.059.7 ± 1.62.7 ± 0.012.2 ± 0.04
46.9 ± 1.20.95 ± 0.020.11 ± 0.0519 ± 3.33.2 ± 0.022.3 ± 0.05
57.0 ± 1.00.92 ± 0.030.10 ± 0.0625 ± 3.43.7 ± 0.022.5 ± 0.04

MD Simulations and the Structure of the Primary Clusters

MD simulations were carried out for each of the systems given in Table 1. Trajectories from the simulations indicated that the Zr complexes tended to aggregate to form clusters, namely, the primary clusters described above. To analyze this clustering quantitatively, we calculated the Zr–Zr radial distribution function, g(rZr–Zr), and the corresponding coordination number of Zr with the other Zr, CN(rZr–Zr), shown for system no. 5 in Figure 4a. The g(rZr–Zr) function consists of a large peak followed by an extended tail. This large peak, which corresponds to the closest Zr–Zr distance on average, reaches its maximum at approximately 0.88 nm. This value is close to the RS value of 0.92 ± 0.03 nm in the characteristic parameters of the hierarchical aggregates model. To define a cluster, we used the algorithm of Sevick, (61) with the criterion that two Zr complexes are connected if the Zr–Zr distance is less than 1.2 nm. This distance is approximately where the first peak of the radial distribution function ends. This choice is somewhat arbitrary, but the resulting analysis is in reasonable agreement with the conclusions drawn from observing many snapshots. The distribution of the primary cluster aggregation numbers is shown in Figure 4b for system no. 5. It is clear that primary clusters form, several with aggregation numbers of 5–7, in agreement with the SANS analysis. The shapes of the primary clusters, according to our simulations, are not uniform, as they vary from spherical to elongated aggregations. This observation is supported by the coordination number analysis, CN(rZr–Zr), given in Figure 4a, where CN(rZr–Zr) gives the number of Zr atoms within a distance rZr–Zr of a central Zr atom. The value of CN(rZr–Zr) at rZr–Zr = 1.2 nm, the position of the first minimum of the radial distribution function, is 2.72, indicating that there are, on average, about 2.72 other Zr ions surrounding one Zr ion within a 1.2 nm cutoff range. Smaller clusters are also seen, but it is noteworthy that clusters of three or four Zr atoms are relatively uncommon. To check that this was not an equilibration issue, we ran 10 independent MD simulations, starting from random initial configurations. All the simulations used the same simulation protocols as described in the Supporting Information (Computational Methods). The results, which are shown in Figure S2 in the Supporting Information, indicate that the cluster size distribution is identical, to within statistical uncertainty, for all 10 systems.

Figure 4

Figure 4. (a) Zr–Zr radial distribution function, g(rZr–Zr) (solid line), and corresponding coordination number of Zr with the other Zr, CN(rZr–Zr) (dashed line). (b) The primary cluster probability distribution for system no. 5 as determined by the MD. The ordinate gives the probability of finding a primary cluster with a given number of Zr atoms. This probability is the number of primary clusters of a given aggregation number divided by the total number of the primary cluster.

High Resolution Image
Download MS PowerPoint Slide
The system sizes are too small to observe and analyze hierarchical clustering of these primary clusters, but the long broad tail in the radial distribution function in Figure 4a indicates that the primary clusters in the simulated systems are not homogeneously distributed. An examination of simulation snapshots shows the loose aggregation of a small number of primary clusters. An example is given in Figure 5a, where two primary clusters are seen in close proximity, providing an indication of incipient hierarchical structuring.

Figure 5

Figure 5. (a) Snapshot of two, neighboring primary clusters from our MD simulations and (b) magnified snapshot showing the hydrogen-bonding network within the primary clusters. Green, Zr; yellow, P; red, O; blue, N; black, C; light pink, H; and light blue dashed line, hydrogen bond.

High Resolution Image
Download MS PowerPoint Slide
We now consider the structure of the primary clusters. Examples are shown in Figure 5b. Within a primary cluster there are hydrogen bonds, involving uncoordinated TBP, HNO3, and H2O. These play a role in binding the Zr complexes together. There are, in addition, nonspecific polar interactions, for example, involving the charged species within the Zr complexes. Hydrophobic interactions between the nonpolar groups are also in evidence. Turning now to the interactions between primary clusters, any inferences based on simulation results must be extremely tentative, due to the system size issues noted previously. That said, the indications are that there is no direct hydrogen bonding between primary clusters and no specific bridging molecules. This is exemplified by Figure 5a. The available simulation data suggest, instead, that primary clusters interact via a combination of nonspecific electrostatic interactions between the charged groups and hydrophobic interactions between the aliphatic groups. It is noteworthy that recent research by Servis et al., (62) on the structure of the aggregates formed by uranyl nitrate and TBP, also indicated that such electrostatic interactions play a key role in stabilizing the clusters.
Finally, we return to the jagged nature of the cluster distribution (Figure 4b). Our analysis shows that this is not related to the choice of the distance criterion for defining a cluster. The results are insensitive to this. As discussed previously, the fact that 10 independent runs give the same distribution leads us to believe this is an equilibrium distribution. To gain insight into what factors might lead to this distribution, we carried out a hydrogen-bonding analysis, counting the number of hydrogen bonds between NO3–, HNO3, and H2O. The criterion for determining the presence of a hydrogen bond is that the donor–acceptor distance should be no more than 0.35 nm, and the acceptor–donor–hydrogen angle should be no more than 30°. The oxygen atoms that have covalent bonds with the hydrogen atoms in the H2O and HNO3 molecules were regarded as potential donors, and the electronegative atoms that possess a lone electron pair were regarded as potential acceptors. Stable primary clusters, defined for these purposes as clusters with a lifetime greater than 1 ns, were identified and indexed for hydrogen bonding. These primary clusters contained 1, 2, 3, 5, and 6 Zr complexes. Tetramers are apparently too unstable to survive for this length of time. The average number of hydrogen bonds per Zr atom is plotted against cluster size in Figure 6a.

Figure 6

Figure 6. (a) Number of hydrogen bonds per Zr complex as a function of aggregation number. (b) Radial distribution function for octane carbon atoms around a central Zr atom as a function of cluster aggregation number of Zr complexes per primary cluster. (c) Radial distribution function for octane carbon atoms around a central N atom in a nitrate ligand, shown as a function of cluster aggregation number. All results in parts a–c are obtained for system no. 5.

High Resolution Image
Download MS PowerPoint Slide
While the number of hydrogen bonds increases when two monomers form a dimer, there is no increase in the number of hydrogen bonds on forming higher-order clusters. It would thus appear that hydrogen bonding is probably not a governing factor in determining the number of Zr complexes in a primary cluster.
Another factor that might influence the aggregation number is the degree to which the octane solvent is shielded from polar groups in the clusters. Such interactions would be hydrophobically unfavorable. We therefore calculated the radial distribution functions for octane carbon atoms surrounding a central Zr atom and for octane carbon atoms surrounding the N atom of a nitrate ligand. The plots are shown in Figure 6b,c. These two plots show that there is considerably more unfavorable polar–nonpolar contact for the trimer, as compared to either the dimer or the hexamer. Thus, it would appear that the polar groups in the trimer are less well shielded from the diluent than is the case for either the dimer or the hexamer, and this may partly explain the relative stabilities of these clusters.

Thermodynamic Considerations

We relate the extracted parameters from the model fittings of Isub(q) in SANS to the thermodynamic properties of the system. We start with the van’t Hoff equation given by (63)
(1)
where Π is osmotic pressure, v is the occupied volume of the solute per molecule, kB is the Boltzmann constant, and T is the thermodynamic temperature. The osmotic pressure can be related to the forward scattering intensity, Isub(q = 0), by (64)
(2)
with the difference between the scattering length densities of the Zr(NO3)4(TBP)2 complex and the matrix, Δρ, and ϕZr(NO3)4(TBP)2. In the studied system, the volume v in eq 1 can be assumed to be the occupied volume per supercluster, and hence, v ≈ 1/nsuper. The calculated v and the osmotic pressure obtained by eq 1, Πvan’t-Hoff, are listed in Table 4. Because the vapor pressure of octane at 20 °C is 1.33 kPa, and the matrix consists of a mixture of extracted HNO3, extracted H2O, uncoordinated TBP, and n-octane-d18 (Table 1), the calculated Πvan’t-Hoff is a good estimation. The osmotic pressures can also be calculated with eq 2 by using Isub(q = 0) from the experimental data, which were estimated by Guinier plots (Table 4). The osmotic pressures from Isub(q = 0), ΠI(0), and Πvan’t-Hoff agree within 10%, which indicates that our structural model is correct.
Table 4. Thermodynamic Parameter Values
sample no.v (nm3)Isub(q = 0) (cm–1)Πvan’t-Hoff (Pa)ΠI(0) (Pa)RHS (nm)
22.5 × 1030.1221.6 × 1031.8 × 1031.3
36.8 × 1032.436.1 × 1026.0 × 1022.7
48.9 × 1036.724.6 × 1024.9 × 1023.2
59.1 × 10312.44.5 × 1024.4 × 1023.7
The van der Waals equation of state with hard spheres with radius RHS modifies eq 1 to give (63)
(3)
where β = 4ω with ω = 4πRHS3/3 and α = 27kBTcβ/8 with the critical temperature, Tc, for phase separation. By assuming Tc/T = 1, RHS for each sample can be calculated with assigning ΠI(0) and v, which are shown in Table 4. The RHS values agree well with the RL values. The parameter RHS is slightly affected by Tc/T around Tc/T = 1, although the variation of RHS with a ±10% variation of Tc/T = 1 is less than 5%. This result suggests that RL obtained by the model is reasonable.
It is worth noting, at this point, some curious features of this aggregation process. First, as shown in Table 1, the molar concentrations of zirconium in the organic phase are relatively small. The highest concentration studied was sample no. 5, where [Zr(NO3)4(TBP)2]org,eq = 0.032 M, and as noted previously, third-phase formation sets in at concentrations just a little greater than this. A normal solution at such low concentrations might be expected to be approximately ideal-dilute, with Henry’s law applying, but this is clearly far from the case here. To account for the clustering and for the phase transition, it must be the case that the mixture is very far from ideal, implying remarkably strong interactions between the zirconium complexes and, indeed, between the primary clusters. As shown in Table 3, the aggregation number of the primary clusters is approximately 7 and does not change with increasing [Zr(NO3)4(TBP)2]org,eq. This is reminiscent of spherical micelles formed in lyotropic systems, where again there is a favored aggregation number, but it is not clear why this should apply here, where simulation suggests the primary clusters to be far from nicely organized spheres. This is certainly worthy of future study.
Even though the concentrations of primary clusters are small, the results of Table 3 show that they aggregate, indicating strong interactions between them. One may note that the primary clusters, with solvating water, nitric acid, and uncoordinated TBP molecules, are polar entities immersed in a nonpolar, low dielectric medium. This may mean that Coulomb interactions between primary clusters are strong, contributing considerably to the attractive forces between them. Once these superclusters have formed, their concentration is very small, and as shown above, the osmotic pressure may be well estimated by assuming one has an ideal suspension of superclusters.
For values of [Zr(NO3)4(TBP)2]org,eq a little greater than that of sample no. 5, the system separates into two phases. One phase is diluent-rich with little Zr, while the coexisting phase, the third phase, is rich in Zr and has a reduced concentration of diluent. Our data indicate that the aggregation number, M, of the superclusters rises rapidly with [Zr(NO3)4(TBP)2]org,eq, presaging an oncoming phase instability as more and more primary clusters condense. Unfortunately, these data alone are insufficient to cast light on the nature of this phase transition, for this would require information about the structure of the third phase. In the literature, this third phase transition has been treated both as a gas–liquid transition and as a reverse micelle to microemulsion or gel transition. Taken literally, (65,66) the gas–liquid transition model would correspond to a gas of primary clusters (or reverse micelles) condensing to a liquid of primary clusters, but with the primary clusters retaining their integrities. In the second scenario, the primary clusters/reverse micelles would lose their individual identities and merge to form a connected, bicontinuous structure. Of course, another possibility is that the third phase is a bicontinuous emulsion of polar and nonpolar regions, such as appears to be the case in metal-free systems, (44) with distinct Zr clusters embedded in the polar regions of this emulsion. Further study is needed to clarify this situation, but what we have shown is that the strong attractions between primary Zr clusters are the driving force that makes the “gas” phase unstable.

Conclusion

ARTICLE SECTIONS
Jump To
We have clarified the microscopic structure of the organic phases containing extracted Zr(NO3)4(TBP)2 using a method combining EXAFS with DFT calculations, MD simulations, and SANS observations. The coordination structure of the extracted Zr(NO3)4(TBP)2 in the organic phase does not depend on the concentration of Zr(NO3)4(TBP)2 and maintains a specific structure as a fundamental building unit to form high-order (aggregate) architectures. Moreover, quantitative analyses of SANS data using an accurate evaluation of the incoherent scattering intensity and a form factor of randomly oriented Zr(NO3)4(TBP)2 provide a clearer picture of the high-order structures on the basis of scattering theory. Zr(NO3)4(TBP)2 was found to form a hierarchical aggregate composed of small primary clusters comprising a supercluster (Figures 2 and 5). A hybrid interaction consisting of a hydrogen-bonding network for the primary clusters and an attractive interaction for the superclusters induces the formation of the hierarchical aggregate. An increase in [Zr(NO3)4(TBP)2]org,eq has little effect on the size of the primary cluster but increases the size of the superclusters. Furthermore, MD simulations provided direct evidence about the formation of primary clusters, which are assembled by the hydrogen-bonding network involving uncoordinated TBP, HNO3, and H2O. In the clustering analyses of the MD snapshots, the distribution of the primary cluster aggregation numbers of 5–7 agreed well with the SANS data analysis. Accordingly, we conclude that growth of the superclusters is due to an increase in the number of small primary clusters, causing third-phase formation. In this paper, we quantitatively applied the simple aggregation model to analyze SANS profiles. The number of the clusters and their sizes, obtained by SANS data analysis, are fully compliant with van der Waals equations of state. These findings suggest that such behaviors are general ones, extending beyond zirconium in the PUREX process to a wide variety of extraction systems (e.g., DIAMEX, TRUEX, ALSEP) (38) that show multiscale ordering. There is then the intriguing possibility that, by tailoring the interactions between these superclusters, we may afford a new entry into the design of next-generation ionic separation techniques with complex fluids typical of soft matter chemistry.
It is known that the addition of phase modifiers, such as aliphatic alcohols, into organic phases during liquid–liquid extraction allows a higher loading of metal ions (without third-phase formation) than in unmodified systems. (67,68) The fact that the separation selectivity and efficiency are also impacted leads us to speculate that modifiers contribute to the formation of hydrogen-bonding networks inside the primary clusters, and these networks vary in accordance with the intra- and intercluster interactions. In view of the largely empirical use of modifiers in practical chemical separations, the combination of SANS, EXAFS, and computational methods used here can help to elucidate the role of the modifiers in other solvent extraction systems, contributing to the development of high-performance processes in chemical separation science.

Supporting Information

ARTICLE SECTIONS
Jump To

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscentsci.8b00669.

  • Method section and additional data and figures including cluster probabilities, configurations, radial distribution function, chemical structure, EXAFS data, Guinier plots, theoretical modeling of the hierarchical aggregates for SANS data analysis, simulated SANS profiles, and coordination structure of zirconium nitrate complex in initial aqueous phase (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

ARTICLE SECTIONS
Jump To
  • Corresponding Authors
  • Authors
    • Tohru Kobayashi - Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
    • Hitoshi Endo - Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan;  Neutron Science Division, Institute of Materials Structure Science, and Materials and Life Science Division, J-PARC Center, High Energy Accelerator Research Organization, 203-1 Shirakata, Tokai, Ibaraki 319-1106, Japan;  Department of Materials Structure Science, The Graduate University for Advanced Studies (SOKENDAI), 203-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
    • Junju Mu - School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom;  Orcidhttp://orcid.org/0000-0002-7382-2182
    • Christopher D. Williams - School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom;  Orcidhttp://orcid.org/0000-0002-5073-5924
    • Mark R. Antonio - Chemical Sciences & Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States;  Orcidhttp://orcid.org/0000-0002-1208-4534
    • William T. Heller - Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States;  Orcidhttp://orcid.org/0000-0001-6456-2975
    • Michihiro Nagao - NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, United States;  Center for Exploration of Energy and Matter, Department of Physics, Indiana University, Bloomington, Indiana 47408, United States;  Orcidhttp://orcid.org/0000-0003-3617-251X
  • Notes
    The authors declare no competing financial interest.

    Safety statement: no unexpected or unusually high safety hazards were encountered during the course of the experiments.

Acknowledgments

ARTICLE SECTIONS
Jump To

This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology, Japan (Grant-in-Aid for Scientific Research B, 2014–2018, 26289368, and 2018–2022, 18H01921). H.E. and R.M. thank Prof. Tsuyoshi Koga of Kyoto University for helpful discussions about scattering theory. Part of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory. The synchrotron radiation experiment at the BL11XU beamline of SPring-8 was performed with the approval of the Japan Atomic Energy Agency (JAEA; Proposal 2013A3504). We thank Dr. Shinichi Suzuki and Dr. Tsuyoshi Yaita for discussions and Dr. Hideaki Shiwaku for generous technical support with the EXAFS experiments at SPring-8. Access to the NG5-NSE was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology (NIST) and the National Science Foundation under agreement DMR-1508249. M.N. acknowledges funding support of cooperative agreement 70NANB15H259 from NIST, U.S. Department of Commerce. The identification of any commercial product or trade name does not imply endorsement or recommendation by the NIST. M.A. acknowledges the support of the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, under contract DE-AC02-06CH11357.

References

ARTICLE SECTIONS
Jump To

This article references 68 other publications.

  1. 1
    Gompper, G.; Schick, M. In Phase Transitions and Critical Phenomena; Domb, C., Lebowitz, J., Eds.; Academic Press: London, 1994; Vol. 16, pp 1– 176.
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Schwuger, M. J.; Stickdorn, K.; Schomacker, R. Microemulsions in technical processes. Chem. Rev. 1995, 95, 849– 864,  DOI: 10.1021/cr00036a003
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    2
    Microemulsions in Technical Processes
    Schwuger, Milan-Johann; Stickdorn, Katrin; Schomaecker, Reinhard
    Chemical Reviews (Washington, D. C.) (1995), 95 (4), 849-64CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review with 143 refs. of basic properties of microemulsions and their relation to some already established applications includes phase behavior of microemulsions and interfacial tension between water and oil phases and applications such as enhanced oil recovery, liq.-liq. extn., extn. from chem. contaminated soils, lubricants and cutting oils, pharmaceuticals and cosmetics, washing, and impregnation and textile finishing. Chem. reactions in microemulsions discussed include nanoparticle prepn., biochem. reactions, electrochem. and catalytic reactions, polymns., org. reactions, example of reaction process in a microemulsion, and comparison with phase transfer catalysis.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXlvFWlurY%253D&md5=70c53ddd08fd954d5c04524cc0504e71
  3. 3
    Winsor, P. A. Solvent Properties of Amphiphilic Compounds; Butterworths: London, 1954.
    Google Scholar
    There is no corresponding record for this reference.
  4. 4
    Lindman, B.; Wennerström, H. Miceles. Amphiphile aggregation in aqueous solution. Top. Curr. Chem. 1980, 87, 1– 83,  DOI: 10.1007/BFb0048488
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  5. 5
    Eicke, H.-F. Surfactants in nonpolar solvents. Aggregation and micellization. Top. Curr. Chem. 1980, 87, 85– 145,  DOI: 10.1007/BFb0048489
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  6. 6
    Fischer, S.; Exner, A.; Zielske, K.; Perlich, J.; Deloudi, S.; Steurer, W.; Lindner, P.; Forster, S. Colloidal quasicrystals with 12-fold and 18-fold diffraction symmetry. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 1810– 1814,  DOI: 10.1073/pnas.1008695108
    [Crossref], [PubMed], [CAS], Google Scholar
    6
    Colloidal quasicrystals with 12-fold and 18-fold diffraction symmetry
    Fischer, Steffen; Exner, Alexander; Zielske, Kathrin; Perlich, Jan; Deloudi, Sofia; Steurer, Walter; Lindner, Peter; Forster, Stephan
    Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (5), 1810-1814, S1810/1-S1810/2CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Micelles are the simplest example of self-assembly found in nature. As many other colloids, they can self-assemble in aq. soln. to form ordered periodic structures. These structures so far all exhibited classical crystallog. symmetries. Here it is reported that micelles in soln. can self-assemble into quasicryst. phases. Phases with 12-fold and 18-fold diffraction symmetry were obsd. Colloidal water-based quasicrystals are phys. and chem. very simple systems. Macroscopic monodomain samples of centimeter dimension can be easily prepd. Phase transitions between the fcc phase and the two quasicryst. phases can be easily followed in situ by time-resolved diffraction expts. The discovery of quasicryst. colloidal solns. advances the theor. understanding of quasicrystals considerably, as for these systems the stability of quasicryst. states was theor. predicted for the concn. and temp. range, where they are exptl. obsd. Also for the use of quasicrystals in advanced materials this discovery is of particular importance, as it opens the route to quasicryst. photonic band gap materials via established water-based colloidal self-assembly techniques.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhslyjs7o%253D&md5=0e1e0861c86b9cd8dda03e9c7b01281e
  7. 7
    Zemb, T. Flexibility, persistence length and bicontinuous microstructures in microemulsions. C. R. Chim. 2009, 12, 218– 224,  DOI: 10.1016/j.crci.2008.10.008
    [Crossref], [CAS], Google Scholar
    7
    Flexibility, persistence length and bicontinuous microstructures in microemulsions
    Zemb, Thomas
    Comptes Rendus Chimie (2009), 12 (1-2), 218-224CODEN: CRCOCR; ISSN:1631-0748. (Elsevier Masson SAS)
    Three length scales have to be considered to describe microemulsions: persistence length, spontaneous radius of curvature of the surfactant film as intensive variables and finally the characteristic size imposed by the ratio of vol. fraction to available specific area surface. The specific area per unit vol. is an intensive variable linked to sizes and topologies that can be built without tearing the surfactant film. We show here that at least four types of bicontinuous microstructures have been detected so far, and that they can be distinguished by a simple exptl. detn. of the evolution of scattering peak position vs. diln. Besides the classical microstructures dominated by entropy or a priori considered as droplets, the other microstructures identified so far can be approximated as connected cylinders or randomly connected swollen bilayers. All these microstructures can be considered as "molten" precursors of the lyotropic liq. cryst. phases that are adjacent to microemulsions in phase diagrams.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhs1Ontbc%253D&md5=701c55b975b731ec51d945a1ebd0a747
  8. 8
    Zemb, T.; Holmberg, K.; Kunz, W. Special topic: Weak self assembly. Curr. Opin. Colloid Interface Sci. 2016, 22, A1– A3,  DOI: 10.1016/j.cocis.2016.04.001
    [Crossref], [CAS], Google Scholar
    8
    Editorial overview
    Zemb, Thomas; Holmberg, Krister; Kunz, Werner
    Current Opinion in Colloid & Interface Science (2016), 22 (), A1-A3CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
    There is no expanded citation for this reference.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XntlKhsr8%253D&md5=81a38bcaaabcc6bc427c1076bbd97cbe
  9. 9
    Zemb, T.; Kunz, W. Weak aggregation: State of the art, expectations and open questions. Curr. Opin. Colloid Interface Sci. 2016, 22, 113– 119,  DOI: 10.1016/j.cocis.2016.04.002
    [Crossref], [CAS], Google Scholar
    9
    Weak aggregation: State of the art, expectations and open questions
    Zemb, Thomas; Kunz, Werner
    Current Opinion in Colloid & Interface Science (2016), 22 (), 113-119CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
    A review. This paper gives an overview of weak aggregation due to long-range mol. forces beyond the first neighbor. Such subtle self-assemblies are an important part of modern colloidal chem. and concern org. mols. as well as inorg. electrolytes and hybrid aggregates. Diverse aspects of such colloidal aggregations, as described in this special issue, can be characterized by the effective free energy per mol. involved. We discuss here expectations about emerging knowledge in this field and predictive modeling of inorg. as well as org. colloids and hybrid aggregates. Some still open questions are also given.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XotFagt7g%253D&md5=b91ff5702ebd7728e2d629c2cc821ce3
  10. 10
    Pini, D.; Parola, A. Pattern formation and self-assembly driven by competing interactions. Soft Matter 2017, 13, 9259– 9272,  DOI: 10.1039/C7SM02125A
    [Crossref], [PubMed], [CAS], Google Scholar
    10
    Pattern formation and self-assembly driven by competing interactions
    Pini, Davide; Parola, Alberto
    Soft Matter (2017), 13 (48), 9259-9272CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)
    Colloidal fluids interacting via effective potentials which are attractive at the short range and repulsive at the long range have long been raising considerable attention because such an instance provides a simple mechanism leading to pattern formation even for isotropic interactions. If the competition between attraction and repulsion is strong enough, the gas-liq. phase transition is suppressed, and replaced by the formation of mesophases, i.e., inhomogeneous phases displaying periodic d. modulations whose length, although being larger than the particle size, cannot nevertheless be considered macroscopic. We describe a fully numerical implementation of d.-functional theory in three dimensions, tailored to periodic phases. The results for the equil. phase diagram of the model are compared with those already obtained in previous investigations for the present system as well as for other systems which form mesophases. The phase diagram which we find shows a strong similarity with that of block copolymer melts, in which self-assembly also results from frustration of a macroscopic phase sepn. As the inhomogeneous region is swept by increasing the d. from the low-d. side, one encounters clusters, bars, lamellae, inverted bars, and inverted clusters. Moreover, a bicontinuous gyroid phase consisting of two intertwined percolating networks is predicted in a narrow domain between the bar and lamellar phases.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVGnsbbK&md5=9535383902591070ea5d6a4ddb579e2a
  11. 11
    Foffi, G.; De Michele, C.; Sciortino, F.; Tartaglia, P. Scaling of dynamics with the range of interaction in short-range attractive colloids. Phys. Rev. Lett. 2005, 94, 078301,  DOI: 10.1103/PhysRevLett.94.078301
    [Crossref], [PubMed], [CAS], Google Scholar
    11
    Scaling of Dynamics with the Range of Interaction in Short-Range Attractive Colloids
    Foffi, G.; De Michele, C.; Sciortino, F.; Tartaglia, P.
    Physical Review Letters (2005), 94 (7), 078301/1-078301/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    We numerically study the dependence of the dynamics on the range of interaction Δ for the short-range square well potential. We find that, for small Δ, dynamics scale exactly in the same way as thermodn., both for Newtonian and Brownian microscopic dynamics. For interaction ranges from a few percent down to the Baxter limit, the relative location of the attractive-glass line and the liq.-gas line does not depend on Δ. This proves that, in this class of potentials, disordered arrested states (gels) can be generated only as a result of a kinetically arrested phase sepn.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhslarsrc%253D&md5=ddae05a959b88257944ecab0188a0630
  12. 12
    Zaccarelli, E. Colloidal gels: equilibrium and non-equilibrium routes. J. Phys.: Condens. Matter 2007, 19, 323101,  DOI: 10.1088/0953-8984/19/32/323101
    [Crossref], [CAS], Google Scholar
    12
    Colloidal gels: equilibrium and non-equilibrium routes
    Zaccarelli, Emanuela
    Journal of Physics: Condensed Matter (2007), 19 (32), 323101/1-323101/50CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
    A review. We attempt a classification of different colloidal gels based on colloid-colloid interactions. We discriminate primarily between non-equil. and equil. routes to gelation, the former case being slaved to thermodn. phase sepn. while the latter is individuated in the framework of competing interactions and of patchy colloids. Emphasis is put on recent numerical simulations of colloidal gelation and their connection to expts. Finally, we underline typical signatures of different gel types, to be looked at, in more detail, in expts.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVehsbzF&md5=83d8accf5c2d21da133781fadacd5d27
  13. 13
    Bera, M. K.; Qiao, B. F.; Seifert, S.; Burton-Pye, B. P.; Olvela de la Cruz, M.; Antonio, M. R. Aggregation of heteropolyanions in aqueous solutions exhibiting short-range attractions and long-range repulsions. J. Phys. Chem. C 2016, 120, 1317– 1327,  DOI: 10.1021/acs.jpcc.5b10609
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    13
    Aggregation of Heteropolyanions in Aqueous Solutions Exhibiting Short-Range Attractions and Long-Range Repulsions
    Bera, Mrinal K.; Qiao, Baofu; Seifert, Soenke; Burton-Pye, Benjamin P.; Olvera de la Cruz, Monica; Antonio, Mark R.
    Journal of Physical Chemistry C (2016), 120 (2), 1317-1327CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Charged colloids and proteins in aq. solns. interact via short-range attractions and long-range repulsions (SALR) and exhibit complex structural phases. These include homogeneously dispersed monomers, percolated monomers, clusters, and percolated clusters. We report the structural architectures of simple charged systems in the form of spherical, Keggin-type heteropolyanions (HPAs) by small-angle X-ray scattering (SAXS) and mol. dynamics (MD) simulations. Structure factors obtained from the SAXS measurements show that the HPAs interact via SALR. Concn. and temp. dependences of the structure factors for HPAs with -3e (e is the charge of an electron) charge are consistent with a mixt. of nonassocd. monomers and assocd. randomly percolated monomers, whereas those for HPAs with -4e and -5e charges exhibit only nonassocd. monomers in aq. solns. Our expts. show that the increase in magnitude of the charge of the HPAs increases their repulsive interactions and inhibits their aggregation in aq. solns. MD simulations were done to reveal the atomistic scale origins of SALR between HPAs. The short-range attractions result from water or proton-mediated hydrogen bonds between neighboring HPAs, whereas the long-range repulsions are due to the distributions of ions surrounding the HPAs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVejtL%252FK&md5=64525b4529c3ca671d46a270174efdb3
  14. 14
    Poon, W. C. K.; Haw, M. D. Mesoscopic structure formation in colloidal aggregation and gelation. Adv. Colloid Interface Sci. 1997, 73, 71– 126,  DOI: 10.1016/S0001-8686(97)90003-8
    [Crossref], [CAS], Google Scholar
    14
    Mesoscopic structure formation in colloidal aggregation and gelation
    Poon, W. C. K.; Haw, M. D.
    Advances in Colloid and Interface Science (1997), 73 (), 71-126CODEN: ACISB9; ISSN:0001-8686. (Elsevier Science B.V.)
    A review with 117 refs. on recent small-angle light scattering expts. that have revealed diffusively aggregating spherical particles develop structure on a mesoscopic length scale (∼ tens of particles). The mesoscopic structural length scale persists even when the aggregation proceeds to the formation of a space-spanning network (a gel). The authors review the techniques of small-angle light scattering, survey the exptl. evidence for mesoscopic structure formation, discuss attempts at understanding these exptl. observations by computer simulation of irreversible and reversible diffusion-limited cluster aggregation (DLCA), and propose a coherent picture for the understanding of non-equil. aggregation in the context of phase transitions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXotVChtLs%253D&md5=1460e50c5c4841470cc65bf6a49d2532
  15. 15
    Lu, P. J.; Zaccarelli, E.; Ciulla, F.; Schofield, A. B.; Sciortino, F.; Weitz, D. A. Gelation of particles with short-range attraction. Nature 2008, 453, 499– 505,  DOI: 10.1038/nature06931
    [Crossref], [PubMed], [CAS], Google Scholar
    15
    Gelation of particles with short-range attraction
    Lu, Peter J.; Zaccarelli, Emanuela; Ciulla, Fabio; Schofield, Andrew B.; Sciortino, Francesco; Weitz, David A.
    Nature (London, United Kingdom) (2008), 453 (7194), 499-503CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    Nanoscale or colloidal particles are important in many realms of science and technol. They can dramatically change the properties of materials, imparting solid-like behavior to a wide variety of complex fluids. This behavior arises when particles aggregate to form mesoscopic clusters and networks. The essential component leading to aggregation is an interparticle attraction, which can be generated by many phys. and chem. mechanisms. In the limit of irreversible aggregation, infinitely strong interparticle bonds lead to diffusion-limited cluster aggregation (DLCA). This is understood as a purely kinetic phenomenon that can form solid-like gels at arbitrarily low particle vol. fraction. Far more important technol. are systems with weaker attractions, where gel formation requires higher vol. fractions. Numerous scenarios for gelation have been proposed, including DLCA, kinetic or dynamic arrest, phase sepn., percolation and jamming. No consensus has emerged and, despite its ubiquity and significance, gelation is far from understood-even the location of the gelation phase boundary is not agreed on. Here we report expts. showing that gelation of spherical particles with isotropic, short-range attractions is initiated by spinodal decompn.; this thermodn. instability triggers the formation of d. fluctuations, leading to spanning clusters that dynamically arrest to create a gel. This simple picture of gelation does not depend on microscopic system-specific details, and should thus apply broadly to any particle system with short-range attractions. Our results suggest that gelation-often considered a purely kinetic phenomenon-is in fact a direct consequence of equil. liq.-gas phase sepn. Without exception, we observe gelation in all of our samples predicted by theory and simulation to phase-sep.; this suggests that it is phase sepn., not percolation, that corresponds to gelation in models for attractive spheres.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmt1Ortb4%253D&md5=245f6c35480169f4ea03cb2ff3ae6f92
  16. 16
    Kim, S. A.; Jeong, K. J.; Yethiraj, A.; Mahanthappa, M. K. Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity. Proc. Natl. Acad. Sci. U. S. A. 2017, 114, 4072– 4077,  DOI: 10.1073/pnas.1701608114
    [Crossref], [PubMed], [CAS], Google Scholar
    16
    Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity
    Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun; Mahanthappa, Mahesh K.
    Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (16), 4072-4077CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Supramol. self-assembly enables access to designer soft materials that typically exhibit high-symmetry packing arrangements, which optimize the interactions between their mesoscopic constituents over multiple length scales. The authors report the discovery of an ionic small mol. surfactant that undergoes H2O-induced self-assembly into spherical micelles, which pack into a previously unknown, low-symmetry lyotropic liq. cryst. Frank-Kasper σ phase. Small-angle x-ray scattering studies reveal that this complex phase is characterized by a gigantic tetragonal unit cell, in which 30 sub-2-nm quasispherical micelles of 5 discrete sizes are arranged into a tetrahedral close packing, with exceptional translational order over length scales exceeding 100 nm. Varying the relative concns. of H2O and surfactant in these lyotropic phases also triggers formation of the related Frank-Kasper A15 sphere packing as well as a common bcc. structure. Mol. dynamics simulations reveal that the symmetry breaking that drives the formation of the σ and A15 phases arises from minimization of local deviations in surfactant headgroup and counterion solvation to maintain a nearly spherical counterion atm. around each micelle, while maximizing counterion-mediated electrostatic cohesion among the ensemble of charged particles.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlsV2ntr8%253D&md5=793e22c1a4dcd276a815bb1ab3e4f973
  17. 17
    Bauer, C.; Bauduin, P.; Dufreche, J. F.; Zemb, T.; Diat, O. Liquid/liquid metal extraction: Phase diagram topology resulting from molecular interactions between extractant, ion, oil and water. Eur. Phys. J.: Spec. Top. 2012, 213, 225– 241,  DOI: 10.1140/epjst/e2012-01673-4
    [Crossref], [CAS], Google Scholar
    17
    Liquid/liquid metal extraction: phase diagram topology resulting from molecular interactions between extractant, ion, oil and water
    Bauer, C.; Bauduin, P.; Dufreche, J. F.; Zemb, T.; Diat, O.
    European Physical Journal: Special Topics (2012), 213 (), 225-241CODEN: EPJSAC; ISSN:1951-6401. (EDP Sciences)
    A review. We consider the class of surfactants called "extractants" since they specifically interact with some cations and are used in liq.-liq. sepn. processes. We review here features of water-poor reverse micelles in water/oil/ extractant systems as detd. by combined structural studies including small angle scattering techniques on abs. scale. Origins of instabilities, liq.-liq. sepn. as well as emulsification failure are detected. Phase diagrams contain the same multi-phase domains as classical microemulsions, but special unusual features appear due to the high spontaneous curvature directed towards the polar cores of aggregates as well as rigidity of the film made by extg. mols.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmtFajsbo%253D&md5=ccc33a717df264901b7e106e0c3b8a86
  18. 18
    Erlinger, C.; Gazeau, D.; Zemb, T.; Madic, C.; Lefrancois, L.; Hebrant, M.; Tondre, C. Effect of nitric acid extraction on phase behavior, microstructure and interactions between primary aggregates in the system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/water: A phase analysis and small angle X-ray scattering (SAXS) characterisation study. Solvent Extr. Ion Exch. 1998, 16, 707– 738,  DOI: 10.1080/07366299808934549
    [Crossref], [CAS], Google Scholar
    18
    Effect of nitric acid extraction on phase behavior, microstructure and interactions between primary aggregates in the system dimethyldibutyltetradecylmalonamide (DMDBTDMA) / n-DODECANE / water: a phase analysis and small angle x-ray scattering (SAXS) characterization study
    Erlinger, C.; Gazeau, D.; Zemb, T.; Madic, C.; Lefrancois, L.; Hebrant, M.; Tondre, C.
    Solvent Extraction and Ion Exchange (1998), 16 (3), 707-738CODEN: SEIEDB; ISSN:0736-6299. (Marcel Dekker, Inc.)
    In some conditions the formation of a 3rd phase is obsd. with dimethyldibutyltetradecylmalonamide (DMDBTDMA), a potential extractant used in the DIAMEX process. The authors have studied the phase behavior of the system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/H2O/HNO3, in the acceptable concn. limits for the DIAMEX process. The compn. of the different phases and the surface properties of the 2-phase system were measured. The max. incorporation of H2O in the 2-phase system corresponds to ∼0.75 H2O mol. per DMDBTDMA mol., whereas at satn. in the 3-phase system it is ∼1.25 H2O mols. per extractant mol. At 0.22M and 0.46M DMDBTDMA concns., the transitions from the 2-phase to the 3-phase domain takes place in a region where the [HNO3]extr./ [DMDBTDMA]init ratio is ∼0.8. The 2-phase to 3-phase transition occurs when the H2O/acid ratio in the org. phase approaches 1. A sharp change of slope of the interfacial tension vs. extractant concn. is attributed to aggregate formation in the org. phase. Assuming a neutral form of the mol. in the absence of HNO3, the interfacial area is in this case 112 Å2. The microstructure of mixts. DMDBTDMA, H2O and HNO3 in n-dodecane also was studied using small angle x-ray scattering (SAXS) to det. the size and shape of the primary aggregates of DMDBTDMA as well as the interactions between them in the midst of the org. phase. The complexation of HNO3 at const. diamide concn., strongly favors attractive interactions between the aggregates. On the contrary, the increase of the aggregates vol. fraction, at a const. ratio of HNO3 and diamide concns. to control the attractions, force the aggregates to repel each other, and repulsive hard sphere interactions are pointed out. The information obtained in the present work from the SAXS study, and from the interfacial tension measurements, appear to be consistent since they both evidence the onset of an aggregation process at the approach of the org. phase splitting. The simple short range attractive potential defined by Baxter, describing a complex fluid of sticky spheres, is self-consistent to model the exptl. data. In the org. phase, the extractant mols. of DMDBTDMA self-assemble into small reversed micelles with a polar core of ∼6-7 Å radius when the org. phase is contacted with an aq. phase (acidic or not). Within the org. phase, the aggregates are submitted to 3 major interactions: (i) the destabilizing Van der Waals interaction and (ii) the stabilizing hard sphere repulsion and (iii) a repulsive steric contribution from the remaining aliph. chains of the extractant mols. The observable macroscopic effect which is the phase split of the org. phase with 3rd phase formation is the macroscopic translation of the effect of these 3 interactions acting at the microscopic level.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXjtlSgsrw%253D&md5=bd4424e00f0a26317d0f6047c06b0751
  19. 19
    Testard, F.; Zemb, T.; Bauduin, P.; Berthon, L. In Ion Exchange and Solvent Extraction: A Series of Advances; Moyer, B. A., Ed.; CRC Press: Boca Raton, FL, 2010; Vol. 19, pp 381– 428.
    Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Baxter, R. J. Percus-Yevick equation for hard spheres with surface adhesion. J. Chem. Phys. 1968, 49, 2770– 2774,  DOI: 10.1063/1.1670482
    [Crossref], [CAS], Google Scholar
    20
    Percus-Yevick equation of hard spheres with surface adhesion
    Baxter, R. J.
    Journal of Chemical Physics (1968), 49 (6), 2770-4CODEN: JCPSA6; ISSN:0021-9606.
    It is shown that the Percus-Yevick approxn. can be solved anal. for a potential consisting of a hard core together with a rectangular attractive well, provided that a certain limit is taken in which the range of the well becomes zero and its depth infinite. The results show a first-order phase transition which appears to be of the type observed numerically for the Lennard-Jones 12-6 potential.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXkvF2lsbs%253D&md5=bd0c0daccd5e0b3eef20b91c626e1c4e
  21. 21
    Schulz, W. W.; Navratil, J. D. Science and Technology of Tributyl Phosphate; CRC Press: Boca Raton, FL, 1984.
    Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Osseo-Asare, K. Aggregation, reversed micelles, and microemulsions in liquid-liquid extraction: the tri-n-butyl phosphate-diluent-water-electrolyte system. Adv. Colloid Interface Sci. 1991, 37, 123– 173,  DOI: 10.1016/0001-8686(91)80041-H
    [Crossref], [CAS], Google Scholar
    22
    Aggregation, reversed micelles, and microemulsions in liquid-liquid extraction: the tri-n-butyl phosphate-diluent-water-electrolyte system
    Osseo-Asare, K.
    Advances in Colloid and Interface Science (1991), 37 (1-2), 123-73CODEN: ACISB9; ISSN:0001-8686.
    The exptl. evidence (e.g. distribution, viscosity, cond., and mol. wt. measurements) suggesting the presence of aggregates in TBP exts. is reviewed. 244 Refs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XivVGrsw%253D%253D&md5=f7d934dae4171cd1fcb8ab302d8e8f63
  23. 23
    Diss, R.; Wipff, G. Lanthanide cation extraction by malonamide ligands: from liquid-liquid interfaces to microemulsions. A molecular dynamics study. Phys. Chem. Chem. Phys. 2005, 7, 264– 272,  DOI: 10.1039/B410137E
    [Crossref], [PubMed], [CAS], Google Scholar
    23
    Lanthanide cation extraction by malonamide ligands: from liquid-liquid interfaces to microemulsions. A molecular dynamics study
    Diss, Romain; Wipff, Georges
    Physical Chemistry Chemical Physics (2005), 7 (2), 264-272CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    According to mol. dynamics simulations, uncomplexed malonamide ligands L and their neutral Eu(NO3)3L2 or charged EuL43+ complexes are surface active and adsorb at a water-"oil" interface, where "oil" is modeled by chloroform. Aq. solvation at the interface is found to induce a trans to gauche rearrangement of the carbonyl groups, i.e. to preorganize the chelating L ligands for complexation. The interface also induces a larger proportion of extended amphiphilic forms, of EE-gauche type. The effect of increased oil/water ratio is also investigated. It shown that the system evolves from a well-defined interface between immiscible phases to water-in-oil cylindrical micelles and micro-droplets, onto which L ligands and the lanthanide complexes adsorb, while other ligands are extd. in org. phase. Two electrostatic models of the complexes are compared and, in no case is the neutral or charged complex fully extd. to the org. phase. These features allow us to better understand synergistic and solvation effects in the assisted liq.-liq. extn. of lanthanide or actinide cations.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFeisLbI&md5=4c0e22d7cf26d97c2db9dabba6b8e695
  24. 24
    Jensen, M. P.; Yaita, T.; Chiarizia, R. Reverse-micelle formation in the partitioning of trivalent f-element cations by biphasic systems containing a tetraalkyldiglycolamide. Langmuir 2007, 23, 4765– 4774,  DOI: 10.1021/la0631926
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    24
    Reverse-Micelle Formation in the Partitioning of Trivalent f-Element Cations by Biphasic Systems Containing a Tetraalkyldiglycolamide
    Jensen, Mark P.; Yaita, Tsuyoshi; Chiarizia, Renato
    Langmuir (2007), 23 (9), 4765-4774CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
    The conditions for reverse-micelle formation were studied for solns. of tetra-n-octyldiglycolamide (TODGA) in alkane diluents equilibrated with aq. solns. of nitric or hydrochloric acids in the presence and absence of Nd3+. Small-angle neutron scattering, vapor-pressure osmometry, and tensiometry are all consistent with the partial formation of TODGA dimers at the lowest acidities, transitioning to a polydisperse mixt. contg. TODGA monomers, dimers, and small reverse-micelles of TODGA tetramers at aq. nitric acid acidities of 0.7 M or higher in the absence of Nd. Application of the Baxter model to the samples contg. 0.005-0.015 M Nd reveals the persistence of tetrameric TODGA reverse-micelles with significant interparticle attraction between the polar cores of the micelles that increases with increasing org. phase concns. of acid or Nd. The exptl. findings suggest that the peculiar behavior of TODGA with respect to the extn. of trivalent lanthanide and actinide cations arises from the affinity of these metal cations for the preformed TODGA reverse-micelle tetramers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjsV2lsLY%253D&md5=6066bdbe17cf24a3d09fd7af50285952
  25. 25
    Guo, F. Q.; Li, H. F.; Zhang, Z. F.; Meng, S. L.; Li, D. Q. Reversed micelle formation in a model liquid-liquid extraction system. J. Colloid Interface Sci. 2008, 322, 605– 610,  DOI: 10.1016/j.jcis.2008.03.011
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Chiarizia, R.; Briand, A.; Jensen, M. P.; Thiyagarajan, P. SANS study of reverse micelles formed upon the extraction of inorganic acids by TBP in n-octane. Solvent Extr. Ion Exch. 2008, 26, 333– 359,  DOI: 10.1080/07366290802182394
    [Crossref], [CAS], Google Scholar
    26
    Sans Study of Reverse Micelles Formed upon the Extraction of Inorganic Acids by TBP in n-Octane
    Chiarizia, R.; Briand, A.; Jensen, M. P.; Thiyagarajan, P.
    Solvent Extraction and Ion Exchange (2008), 26 (4), 333-359CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
    Small-angle neutron scattering (SANS) data for n-octane solns. of TBP loaded with progressively larger amts. of HNO3, HClO4, H2SO4, and H3PO4 up to and beyond the LOC (limiting org. concn. of acid) condition, were interpreted using the Baxter model for hard spheres with surface adhesion. The coherent picture of the behavior of the TBP solns. derived from the SANS investigation discussed in this paper confirmed our recently developed model for third phase formation. This model analyses the features of the scattering data in the low Q region as arising from van der Waals interactions between the polar cores of reverse micelles. Our SANS data indicated that the TBP micelles swell when acid and water are extd. into their polar core. The swollen micelles have crit. diams. ranging from 15 to 22 Å, and polar core diams. between 10 and 15 Å, depending on the specific system. At the resp. LOC conditions, the TBP wt.-av. aggregation nos. are ∼4 for HClO4, ∼6 for H2SO4, ∼7 for HCl, and ∼10 for H3PO4. The comparison between the behavior of HNO3, a non-third phase forming acid, and the other acids provided an explanation of the effect of the water mols. present in the polar core of the micelles on third phase formation. The thickness of the lipophilic shell of the micelles indicated that the Bu groups of TBP lie at an angle of ∼25 degrees relative to a plane tangent to the micellar core. The crit. energy of intermicellar attraction, U(r), was about -2 kBT for all the acids investigated. This value is the same as that reported in our previous publications on the extn. of metal nitrates by TBP, confirming that the same mechanism and energetics are operative in the formation of a third phase, independent of whether the chem. species extd. are metal nitrate salts or inorg. acids.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosFCqsrs%253D&md5=05b635c868df9fa0745bf40165657a3b
  27. 27
    Ganguly, R.; Sharma, J. N.; Choudhury, N. TODGA based w/o microemulsion in dodecane: An insight into the micellar aggregation characteristics by dynamic light scattering and viscometry. J. Colloid Interface Sci. 2011, 355, 458– 463,  DOI: 10.1016/j.jcis.2010.12.039
    [Crossref], [PubMed], [CAS], Google Scholar
    27
    TODGA based w/o microemulsion in dodecane: An insight into the micellar aggregation characteristics by dynamic light scattering and viscometry
    Ganguly, Rajib; Sharma, Joti N.; Choudhury, Niharendu
    Journal of Colloid and Interface Science (2011), 355 (2), 458-463CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
    N,N,N',N'-tetraoctyl diglycolamide abbreviated as TODGA, is one of the most promising extractant for actinide partitioning from high level nuclear waste. It forms reverse micelles in non polar solvents on equilibration with aq. HNO3 solns. This reverse micellar system undergoes phase sepn. into dil. and concd. reverse micellar solns. at high aq. acid concn. Small angle neutron scattering (SANS) studies reported in the literature explained this phenomenon based on gas-liq. type phase transition in the framework of Baxter adhesive hard sphere theory in the presence of a strong inter-micellar attractive interaction. The present investigation attempts to throw further light on this system by carrying out systematic dynamic light scattering (DLS) and viscometry studies, and their modeling on the TODGA reverse micellar solns. in the dodecane medium. The variation of the diffusion coeff. with the micellar vol. fraction obsd. from the DLS studies is suggestive of the presence of an attractive interaction between the TODGA reverse micelles, which weakens at the high micellar vol. fraction due to the increased dominance of the excluded vol. effect. It is suggested that this weakened interaction is responsible for the absence of phase sepn. in this system at high TODGA concn. The results thus highlight the importance of the presence of an attractive interaction between the TODGA micelles in detg. the obsd. phase sepn. in the TODGA reverse micellar systems. The modeling of the DLS and viscosity data, however, suggest that the characteristic stickiness parameter of this system could be smaller than the crit. value required for inducing a gas-liq. type phase transition.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFartrw%253D&md5=ae30de7c865e456632311e5dbc425c84
  28. 28
    Ellis, R. J.; Meridiano, Y.; Chiarizia, R.; Berthon, L.; Muller, J.; Couston, L.; Antonio, M. R. Periodic behavior of lanthanide coordination within reverse micelles. Chem. - Eur. J. 2013, 19, 2663– 2675,  DOI: 10.1002/chem.201202880
    [Crossref], [PubMed], [CAS], Google Scholar
    28
    Periodic Behavior of Lanthanide Coordination within Reverse Micelles
    Ellis, Ross J.; Meridiano, Yannick; Chiarizia, Renato; Berthon, Laurence; Muller, Julie; Couston, Laurent; Antonio, Mark R.
    Chemistry - A European Journal (2013), 19 (8), 2663-2675CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Trends in lanthanide(III) (LnIII) coordination were studied within nanoconfined solvation environments. LnIII ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aq. phases contg. nitrate and LnIII; both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the org. phase is acidic or neutral, resp. Structural aspects of the LnIII complex formation and the RM morphol. were obtained using XAS (x-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The LnIII coordination environments were detd. through use of L3-edge XANES (x-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chem. across the period. Hydration nos. for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the Ln-O interat. distances and no. of coordinating O atoms for the extd. complexes of LnIII in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the no. of coordinating O atoms decrease from 9 O for early lanthanides to 8 O for the late ones-a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to LnIII. The coordination chem. of lanthanides within nanoconfined environments is neither equiv. to the solid nor bulk soln. behaviors. Herein the authors address at.- and mesoscale phenomena in the under-explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chem. of growing importance in technologies as diverse as nanosynthesis and sepns. science.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkvFGmtw%253D%253D&md5=e7db983a97b06d96816b8a2f37a10cb7
  29. 29
    Guilbaud, P.; Zemb, T. Depletion of water-in-oil aggregates from poor solvents: Transition from weak aggregates towards reverse micelles. Curr. Opin. Colloid Interface Sci. 2015, 20, 71– 77,  DOI: 10.1016/j.cocis.2014.11.011
    [Crossref], [CAS], Google Scholar
    29
    Depletion of water-in-oil aggregates from poor solvents: Transition from weak aggregates towards reverse micelles
    Guilbaud, Philippe; Zemb, Thomas
    Current Opinion in Colloid & Interface Science (2015), 20 (1), 71-77CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
    We assemble here all available descriptions of oil-sol. surfactant aggregates with or without solutes, assumed to be located in the polar cores of reverse micelles. The presence of solutes is crucial for the formation of a well-defined interface, thus inducing a transition from a loose reverse aggregate into a more structured micelle. This transition can be followed by the concomitant decrease of the "crit. aggregation concn." (c.a.c.). The less organized state as reverse aggregates is predominant when no "nucleating" species such as water, salts, or acids are present. One way to understand this weak aggregation is a depletion driving to aggregates as pseudo-phases introduced by Tanford. Analogs coexisting pseudo-phases seem to exist: weak oil-in-water (o/w) aggregation with the so-called surfactant-free microemulsions, contg. loose aggregates, and re-entrant phase diagrams presenting a lowest aggregation concn. (l.a.c.), as described in the seventies.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitV2ms7%252FM&md5=5f6b62da69c136bd97b7ea97106414f1
  30. 30
    Bley, M.; Siboulet, B.; Karmakar, A.; Zemb, T.; Dufreche, J. F. A predictive model of reverse micelles solubilizing water for solvent extraction. J. Colloid Interface Sci. 2016, 479, 106– 114,  DOI: 10.1016/j.jcis.2016.06.044
    [Crossref], [PubMed], [CAS], Google Scholar
    30
    A predictive model of reverse micelles solubilizing water for solvent extraction
    Bley, Michael; Siboulet, Bertrand; Karmakar, Anwesa; Zemb, Thomas; Dufreche, Jean-Francois
    Journal of Colloid and Interface Science (2016), 479 (), 106-114CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
    Herein, a minimal model for the common case of W/O solubilization of badly sol. compds. present in an excess phase by reverse micellar aggregates in chem. equil. with its single compds. is introduced. A simple model of such liq.-liq. extns. is crucial for obtaining predictive parameter for the modeling of nuclear waste management and hydrometallurgic recycling strategies. The std. Gibbs free energy of aggregation and the concn. of the corresponding aggregate is calcd. within a multiple-equil. approach for a set of aggregate compns. of solute and amphiphilic extractant mols. This minimal model provides potential surfaces estg. the stability of different aggregate compns. with 6.2 kJ mol-1 as a generalized bending const. The complete concns. of free and aggregated extractant species as well as the favored aggregation nos., the polydispersity, the activity of the org. solvent, and the crit. concns. are captured by this thermodn. model. An increase of the apparent crit. micelle concn. for an increasing solute content in the aq. phase is detected by this method.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtFWjsbbM&md5=eb3e9956036d14d278d39f2bf58e47b9
  31. 31
    Diamant, H.; Andelman, D. Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics. Curr. Opin. Colloid Interface Sci. 2016, 22, 94– 98,  DOI: 10.1016/j.cocis.2016.03.004
    [Crossref], [CAS], Google Scholar
    31
    Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics
    Diamant, Haim; Andelman, David
    Current Opinion in Colloid & Interface Science (2016), 22 (), 94-98CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
    We review a recently developed micellization theory, which is based on a free-energy approach and offers several advantages over the conventional one, based on mass action and rate equations. As all the results are derived from a single free-energy expression, one can adapt the theory to different scenarios by merely modifying the initial expression. We present results concerning various features of micellization out of equil., such as the existence of metastable aggregates (premicelles), micellar nucleation and growth, transient aggregates, and final relaxation toward equil. Several predictions that await exptl. investigation are discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmvVGjsrw%253D&md5=7abec1b80cd34472c5bf8b40d506f306
  32. 32
    Gao, S.; Sun, T. X.; Chen, Q. D.; Shen, X. H. Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology. Radiochim. Acta 2016, 104, 457– 469,  DOI: 10.1515/ract-2015-2538
    [Crossref], [CAS], Google Scholar
    32
    Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology
    Gao, Song; Sun, Taoxiang; Chen, Qingde; Shen, Xinghai
    Radiochimica Acta (2016), 104 (7), 457-469CODEN: RAACAP; ISSN:0033-8230. (Oldenbourg Wissenschaftsverlag GmbH)
    The reversed micelles formed in solvent extn. of thorium(IV) by bis(2-ethylhexyl) phosphoric acid (HDEHP) in n-heptane were studied. IR spectra, dynamic/static light scattering and zero shear viscosity measurements indicated that thorium complexes formed rodlike reversed micelles, and both the size of aggregates and the viscosity of the org. phase increased with the increasing loadage of thorium(IV). The entanglement of reversed micelles resulted in their transformation to wormlike reversed micelles, inducing the very high viscosity of the org. phase. The structural compn. of thorium complexes was proposed to be Th(DEHP)3(NO3) according to the results of log -log plot and job method anal. Furthermore, mol. modeling was employed to clarify the structures of reversed micelles as well as the state of water inside. It was found that the complexes linked together via hydrogen bonding and van der Waals forces and that the existence of NO3- and H2O improved the stability of reversed micelles.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtF2nsbnF&md5=002c343aaf5ca7bdda84e54f22d2c8b2
  33. 33
    Chen, Y. S.; Duvail, M.; Guilbaud, P.; Dufreche, J. F. Stability of reverse micelles in rare-earth separation: a chemical model based on a molecular approach. Phys. Chem. Chem. Phys. 2017, 19, 7094– 7100,  DOI: 10.1039/C6CP07843E
    [Crossref], [PubMed], [CAS], Google Scholar
    33
    Stability of reverse micelles in rare-earth separation: a chemical model based on a molecular approach
    Chen, Yushu; Duvail, Magali; Guilbaud, Philippe; Dufreche, Jean-Francois
    Physical Chemistry Chemical Physics (2017), 19 (10), 7094-7100CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Mol. complexes formed in the org. phase during solvent extn. may self-assemble as reverse micelles, and therefore induce a supramol. organization of this phase. In most of the cases, water mols. play an essential role in the organization of this non polar medium. The aim of this work is to investigate the speciation of the aggregates formed in the org. phase during solvent extn., and esp. to assess their stability as a function of the no. of water mols. included in their polar core. We have focused on malonamide extractants that have already been investigated exptl. Different stoichiometries of reverse micelles in the org. phase have been studied by means of classical mol. dynamics simulations. Furthermore, umbrella-sampling mol. dynamics simulations have been used to calc. the equil. const. (K°) representing the assocn./dissocn. pathways of water mols. in the aggregates and the corresponding reaction free energies (ΔrG°).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXisVGhsbk%253D&md5=79b866ab984766369b7e9cfd6188db4b
  34. 34
    Tonova, K.; Lazarova, Z. Reversed micelle solvents as tools of enzyme purification and enzyme-catalyzed conversion. Biotechnol. Adv. 2008, 26, 516– 532,  DOI: 10.1016/j.biotechadv.2008.06.002
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Ballesteros-Gomez, A.; Sicilia, M. D.; Rubio, S. Supramolecular solvents in the extraction of organic compounds. A review. Anal. Chim. Acta 2010, 677, 108– 130,  DOI: 10.1016/j.aca.2010.07.027
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Poirot, R.; Le Goff, X.; Diat, O.; Bourgeois, D.; Meyer, D. Metal recognition driven by weak interactions: A case study in solvent extraction. ChemPhysChem 2016, 17, 2112– 2117,  DOI: 10.1002/cphc.201600305
    [Crossref], [PubMed], [CAS], Google Scholar
    36
    Metal Recognition Driven by Weak Interactions: A Case Study in Solvent Extraction
    Poirot, Remi; Le Goff, Xavier; Diat, Olivier; Bourgeois, Damien; Meyer, Daniel
    ChemPhysChem (2016), 17 (14), 2112-2117CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Tuning the affinity of a medium for a given metallic cation with the sole modification of weak interactions is a challenge for mol. recognition. Solvent extn. is a key technique employed in the recovery and purifn. of valuable metals, and it is facing an increased complexity of metal fluxes to deal with. The selectivity of such processes generally relies on the use of specific ligands, designed after their coordination chem. In the present study, we illustrate the possibility to employ the sole control of weak interactions to achieve the selective extn. of PdII over NdIII: the control over selectivity is obtained by tuning the self-assembly of the org. phase. A model is proposed, after detailed exptl. anal. of mol. (XRD, NMR) and supra-mol. (SAXS) features of the org. phases. We thus demonstrate that PdII extn. is driven by metal coordination, whereas NdIII extn. requires aggregation of the extractant in addn. to metal coordination. These results are of general interest for the applications which rely on the stabilization of metals in org. phases.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xos1ansL4%253D&md5=925fefafc8144d8ee4f5fa953a96780a
  37. 37
    Prevost, S.; Gradzielski, M.; Zemb, T. Self-assembly, phase behaviour and structural behaviour as observed by scattering for classical and non-classical microemulsions. Adv. Colloid Interface Sci. 2017, 247, 374– 396,  DOI: 10.1016/j.cis.2017.07.022
    [Crossref], [PubMed], [CAS], Google Scholar
    37
    Self-assembly, phase behaviour and structural behaviour as observed by scattering for classical and non-classical microemulsions
    Prevost, Sylvain; Gradzielski, Michael; Zemb, Thomas
    Advances in Colloid and Interface Science (2017), 247 (), 374-396CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)
    A review. In this review, we discuss the conditions for forming microemulsions, systems which are thermodynamically stable mixts. of oil and water made stable by the presence of an interfacial film contg. surface active mols. There are several types of microemulsions, depending largely on the stiffness of the amphiphilic monolayer that separates the oily and the aq. micro-domain. We first discuss and compare the phase behavior of these different types, starting from the classical microemulsion made from a flexible surfactant film but then also moving on to less classical situations: this occurs when the interfacial film is stiff or when microemulsions are formed in the absence of a classical surfactant. In the second part, we relate these different microemulsion types to the structural features as can be detd. via different methodologies by small angle scattering (SAS). Using abs. scaling, general theorems as well as fitting under constraints or to pre-supposed shapes in real space or correlation functions in reciprocal space allows to classify all microemulsions into classical flexible, rigid or ultra-flexible microemulsions with either globular, connected cylinder of locally flat interfaces, with the corresponding cond. and phase stability properties.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Ols77I&md5=bf7e5bcfaf544b8dfa2af0030375e23e
  38. 38
    Moyer, B. A., Ed. Ion Exchange and Solvent Extraction: A Series of Advances; CRC Press: Boca Raton, FL, 2010; p 19.
    Google Scholar
    There is no corresponding record for this reference.
  39. 39
    Ellis, R. J. Critical exponents for solvent extraction resolved using SAXS. J. Phys. Chem. B 2014, 118, 315– 322,  DOI: 10.1021/jp408078v
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    39
    Critical Exponents for Solvent Extraction Resolved Using SAXS
    Ellis, Ross J.
    Journal of Physical Chemistry B (2014), 118 (1), 315-322CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
    The solvent extn. of an ionizable solute (H3PO4) from water into a water-in-oil microemulsion, and subsequent org. phase splitting (known as third phase formation), has been recast as a crit. phenomenon by linking system structure to solute concn. via a crit. exponent. The transuranic extn. (TRUEX) system was investigated by extg. increasing concns. of H3PO4 into a microemulsion - consisting of two extractant amphiphiles (CMPO and TBP) and water in n-dodecane - and taking small-angle X-ray scattering (SAXS) measurements from the resulting solns. The H3PO4 concn. at which phase splitting occurred was defined as the crit. concn. (XC), and this was related to the precrit. concns. (X) by the reduced parameter ε = (XC - X)/XC. The scattering intensity at the zero angle I(0), relating to the interaction between reverse micellar aggregates, conformed to the relation I(0) = I0ε-γ, with crit. exponent γ = 2.20. To check γ, SAXS measurements were taken from the org. phase in situ with variable temp. through the point at which third phase formation initiates (the crit. temp.), giving I(0) = I0t-γ, where t = (T - TC)/TC and TC and T are the crit. and precrit. temps., with crit. exponent γ = 2.55. These γ values suggest third phase formation is a universal phenomenon manifest from a crit. double point. Thus, solvent extn. is reduced to its fundamental phys. roots where the system is not defined by detailed anal. of metrical properties but by linking the fundamental order to thermodn. parameters via an exponent, working toward a more predictive understanding of third phase formation.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvFejur3N&md5=b585a55ca00fc242fb70bf8ddb65dac8
  40. 40
    Plaue, J.; Gelis, A.; Czerwinski, K.; Thiyagarajan, P.; Chiarizia, R. Small-angle neutron scattering study of plutonium third phase formation in 30% TBP/HNO3/alkane diluent systems. Solvent Extr. Solvent Extr. Ion Exch. 2006, 24, 283– 298,  DOI: 10.1080/07366290600646970
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Chiarizia, R.; Jensen, M. P.; Rickert, P. G.; Kolarik, Z.; Borkowski, M.; Thiyagarajan, P. Extraction of zirconium nitrate by TBP in n-octane: Influence of cation type on third phase formation according to the ″sticky spheres″ model. Langmuir 2004, 20, 10798– 10808,  DOI: 10.1021/la0488957
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    41
    Extraction of zirconium nitrate by TBP in n-octane: influence of cation type on third phase formation according to the "sticky spheres" model
    Chiarizia, Renato; Jensen, Mark P.; Rickert, Paul G.; Kolarik, Zdenek; Borkowski, Marian; Thiyagarajan, Pappanan
    Langmuir (2004), 20 (25), 10798-10808CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
    Small-angle neutron scattering (SANS) data for the tri-Bu phosphate (TBP)-n-octane, HNO3-Zr(NO3)4 solvent extn. system, obtained under a variety of exptl. conditions, have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in scattering intensity in the low Q range obsd. when increasing amts. of Zr(NO3)4 were extd. into the org. phase was interpreted as arising from interactions between small reverse micelle-like particles contg. two to three TBP mols. Upon extn. of Zr(NO3)4, the particles interact through attractive forces between their polar cores with a potential energy that exceeds 2 kBT. The interparticle attraction, under suitable conditions, leads to third phase formation. A linear relationship exists between the deriv. of the potential energy of attraction with respect to the concn. of nitrate ions in the org. phase and the ionization potential or the hydration enthalpy of the extd. metal cations.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXmvVeju7o%253D&md5=4ca5c19b8f5605770743ea5c344d4a2f
  42. 42
    Ivanov, P.; Mu, J.; Leay, L.; Chang, S. Y.; Sharrad, C. A.; Masters, A. J.; Schroeder, S. L. M. Organic and third phase in HNO3/TBP/n-dodecane system: No reverse micelles. Solvent Extr. Ion Exch. 2017, 35, 251– 265,  DOI: 10.1080/07366299.2017.1336048
    [Crossref], [CAS], Google Scholar
    42
    Organic and Third Phase in HNO3/TBP/n-Dodecane System: No Reverse Micelles
    Ivanov, P.; Mu, J.; Leay, L.; Chang, S.-Y.; Sharrad, C. A.; Masters, A. J.; Schroeder, S. L. M.
    Solvent Extraction and Ion Exchange (2017), 35 (4), 251-265CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
    The compn. and speciation of the org. and third phases in the system HNO3/TBP (tri-Bu phosphate)/n-dodecane have been examd. by a combination of gravimetric, Karl Fischer anal., chem. anal., FTIR, and 31P NMR spectroscopy, with particular emphasis on the transition from the two-phase to the three-phase region. Phase densities indicate that third-phase formation takes place for initial aq. HNO3 concns. above 15 M, while the results from the stoichiometric anal. imply that the org. and third phases are characterized by two distinct species, namely the mono-solvate TBP·HNO3 and the hemi-solvate TBP·2HNO3, resp. Furthermore, the 31P NMR spectra of org. and third phase show no significant chem. differences at the phosphorus centers, suggesting that the second HNO3 mol. in the third phase is bound to HNO3 rather than TBP. The third-phase FTIR spectra reveal stronger vibrational absorption bands at 1028, 1310, 1653, and 3200-3500 cm-1, reflecting higher concns. of H2O, HNO3, and TBP. The mol. dynamics simulation data predict structures in accord with the spectroscopically identified speciation, indicating inequivalent HNO3 mols. in the third phase. The predicted structures of the org. and third phases are more akin to microemulsion networks rather than the distinct, reverse micelles assumed in previous studies. H2O appears to be present as a disordered hydrogen-bonded solvate stabilizing the polar TBP/HNO3 aggregates in the org. matrix, and not as a strongly bound hydrate species in aggregates with defined stoichiometry.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFCltLnK&md5=1b55aa151fba0c853a95d2a42fbebecc
  43. 43
    Servis, M.; Wu, D.; Braley, J. Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate. Phys. Chem. Chem. Phys. 2017, 19, 11326– 11339,  DOI: 10.1039/C7CP01845B
    [Crossref], [PubMed], [CAS], Google Scholar
    43
    Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate
    Servis, Michael J.; Wu, David T.; Braley, Jenifer C.
    Physical Chemistry Chemical Physics (2017), 19 (18), 11326-11339CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Extn. of polar mols. by amphiphilic species results in a complex variety of clusters whose topologies and energetics control phase behavior and efficiency of liq.-liq. sepns. A computational approach including quantum mech. vibrational frequency calcns. and mol. dynamics simulation with intermol. network theory is used to provide a robust assessment of extractant and polar solute assocn. through hydrogen bonding in the tri-Bu phosphate (TBP)/HNO3/H2O/dodecane system for the first time. The distribution of local topologies of the TBP/HNO3/H2O hydrogen bonded clusters is shown to be consistent with an equil. binding model. Mixed TBP/HNO3/H2O clusters are predicted that have not been previously observable in expt. due to limitations in scattering and spectroscopic resoln. Vibrational frequency calcns. are compared with exptl. data to validate the exptl. obsd. TBP-HNO3-HNO3 Chain structure. At high nitric acid and water loading, large hydrogen-bonded clusters of 20 to 80 polar solutes formed. The cluster sizes were found to be exponentially distributed, consistent with a const. av. solute assocn. free energy in that size range. Due to the deficit of hydrogen bond donors in the predominantly TBP/HNO3 org. phase, increased water concns. lower the assocn. free energy and enable growth of larger cluster sizes. For sufficiently high water concns., changes in the cluster size distribution are found to be consistent with the formation of a percolating cluster rather than reverse micelles, as has been commonly assumed for the occurrence of an extractant-rich third phase in metal-free solvent extn. systems. Moreover, the compns. of the large clusters leading to percolation agrees with the 1:3TBP:HNO3 ratio reported in the exptl. literature for TBP/HNO3/H2O third phases. More generally, the network anal. of cluster formation from at. level interactions could allow for control of phase behavior in multi-component solns. of species with a variety of hydrogen bond types.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslCrtL8%253D&md5=6256e89964eff4664907fc5beefc0268
  44. 44
    Mu, J.; Motokawa, R.; Akutsu, K.; Nishitsuji, S.; Masters, A. J. A novel microemulsion phase transition: Toward the elucidation of third-phase formation in spent nuclear fuel reprocessing. J. Phys. Chem. B 2018, 122, 1439– 1452,  DOI: 10.1021/acs.jpcb.7b08515
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    44
    A Novel Microemulsion Phase Transition: Toward the Elucidation of Third-Phase Formation in Spent Nuclear Fuel Reprocessing
    Mu, Junju; Motokawa, Ryuhei; Akutsu, Kazuhiro; Nishitsuji, Shotaro; Masters, Andrew J.
    Journal of Physical Chemistry B (2018), 122 (4), 1439-1452CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
    We present evidence that the transition between org. and third phases, which can be obsd. in the plutonium uranium redn. extn. (PUREX) process at high metal loading, is an unusual transition between two isotropic bicontinuous microemulsion phases. As this system contains so many components, however, we have been seeking first to investigate the properties of a simpler system, namely, the related metal-free, quaternary water/n-dodecane/nitric acid/tributyl phosphate (TBP) system. This quaternary system has been shown to exhibit, under appropriate conditions, three coexisting phases: a light org. phase, an aq. phase, and the so-called third phase. In the current work, we focused on the coexistence of the light org. phase with the third phase. Using Gibbs ensemble Monte Carlo (GEMC) simulations, we found coexistence of a phase rich in nitric acid and dil. in n-dodecane (the third phase) with a phase more dil. in nitric acid but rich in n-dodecane (the light org. phase). The compns. and densities of these two coexisting phases detd. using the simulations were in good agreement with those detd. exptl. Because such systems are generally dense and the mols. involved are not simple, the particle exchange rate in their GEMC simulations can be rather low. To test whether a system having a compn. between those of the obsd. third and org. phases is indeed unstable with respect to phase sepn., we used the Bennett acceptance ratio method to calc. the Gibbs energies of the homogeneous phase and the weighted av. of the two coexisting phases, where the compns. of these phases were taken both from exptl. results and from the results of the GEMC simulations. Both demixed states were detd. to have statistically significant lower Gibbs energies than the uniform, mixed phase, providing confirmation that the GEMC simulations correctly predicted the phase sepn. Snapshots from the simulations and a cluster anal. of the org. and third phases revealed structures akin to bicontinuous microemulsion phases, with the polar species residing within a mesh and with the surface of the mesh formed by amphiphilic TBP mols. The nonpolar n-dodecane mols. were obsd. in these snapshots to be outside this mesh. The only large-scale structural differences obsd. between the two phases were the dimensions of the mesh. Evidence for the correctness of these structures was provided by the results of small-angle X-ray scattering (SAXS) studies, where the profiles obtained for both the org. and third phases agreed well with those calcd. from simulations. Finally, we looked at the microscopic structures of the two phases. In the org. phase, the basic motif was obsd. to be one nitric acid mol. hydrogen-bonded to a TBP mol. In the third phase, the most common structure was that of the hydrogen-bonded TBP-HNO3-HNO3 chain. A cluster anal. provided evidence for TBP forming an extended, connected network in both phases. Studies of the effects of metal ions on these systems will be presented elsewhere.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGjtL7K&md5=d7ddd4cca1561bf5eb06056a3400cb1f
  45. 45
    Baldwin, A. G.; Servis, M. J.; Yang, Y.; Bridges, N. J.; Wu, D. T.; Shafer, J. C. The structure of tributyl phosphate solutions: Nitric acid, uranium(VI), and zirconium(IV). J. Mol. Liq. 2017, 246, 225– 235,  DOI: 10.1016/j.molliq.2017.09.032
    [Crossref], [CAS], Google Scholar
    45
    The structure of tributyl phosphate solutions: Nitric acid, uranium (VI), and zirconium (IV)
    Baldwin, Anna G.; Servis, Michael J.; Yang, Yuan; Bridges, Nicholas J.; Wu, David T.; Shafer, Jenifer C.
    Journal of Molecular Liquids (2017), 246 (), 225-235CODEN: JMLIDT; ISSN:0167-7322. (Elsevier B.V.)
    Diffusion, rheol., and small angle neutron scattering (SANS) data for org. phase 30 vol./vol.% tri-Bu phosphate (TBP) samples contg. varying amts. of water, nitric acid, and uranium or zirconium nitrate were interpreted from a colloidal perspective to give information on the types of structures formed by TBP under different conditions. Taken as a whole, the results of the different analyses were contradictory, suggesting that these samples should be treated as mol. solns. rather than colloids. This conclusion is supported by mol. dynamics (MD) simulations showing the existence of small, mol. aggregates in TBP samples contg. water and nitric acid. Interpretation of TBP and nitric acid diffusion measurements from a mol. perspective suggest that nitric acid and metal species formed are consistent with the stoichiometric solvates that have traditionally been considered to exist in soln.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFGntb3E&md5=7c78e6805279827ebbdb82367a775dd0
  46. 46
    Borkowski, M.; Chiarizia, R.; Jensen, M. P.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C. SANS study of third phase formation in the Th(IV)-HNO3/TBP-n-octane system. Sep. Sci. Technol. 2003, 38, 3333– 3351,  DOI: 10.1081/SS-120022600
    [Crossref], [CAS], Google Scholar
    46
    SANS Study of Third Phase Formation in the Th(IV)-HNO3/TBP-n-Octane System
    Borkowski, M.; Chiarizia, R.; Jensen, M. P.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C.
    Separation Science and Technology (2003), 38 (12 & 13), 3333-3351CODEN: SSTEDS; ISSN:0149-6395. (Marcel Dekker, Inc.)
    Formation of a third org. phase at high metal loading in the extn. of tetravalent actinides by TBP in aliph. diluents has been investigated mostly from the standpoint of the compn. of the org. phase species before and after phase splitting. Very little is known of the structure and morphol. of the org. phase species. In this work, a study of third phase formation upon either dissoln. of Th(NO3)4 in 20 % TBP in n-octane or Th(NO3)4 extn. from 1 M HNO3 by 20% TBP in n-octane is reported. Chem. analyses have shown that, under the conditions of this work, Th(IV) exists in the org. phase mainly as the trisolvate Th(NO3)4·(TBP)3. The third phase species also contains a small amt. of HNO3, presumably hydrogen-bonded to the trisolvate complex. Small-angle neutron scattering measurements on Th(IV) revealed the presence, before phase splitting, of large ellipsoidal aggregates with the parallel and perpendicular axes having lengths up to about 230 and 24 Å, resp. Although the formation of these aggregates is obsd. in all cases, i.e., when only HNO3, only Th(NO3)4, or both HNO3 and Th(NO3)4 are extd. by the TBP soln., the size of the aggregates is largest in the latter case. Formation of these aggregates is probably the main reason for phase splitting.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXltlOntr0%253D&md5=0daf9f2391aa764d7bbab7e72c811051
  47. 47
    Chiarizia, R.; Jensen, M. P.; Borkowski, M.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C. Third phase formation revisited: The U(VI), HNO3-TBP, n-dodecane system. Solvent Extr. Ion Exch. 2003, 21, 1– 27,  DOI: 10.1081/SEI-120017545
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  48. 48
    Motokawa, R.; Endo, H.; Nagao, M.; Heller, W. T. Neutron polarization analysis for biphasic solvent extraction systems. Solvent Extr. Ion Exch. 2016, 34, 399– 406,  DOI: 10.1080/07366299.2016.1201980
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  49. 49
    Koga, T.; Tanaka, F.; Motokawa, R.; Koizumi, S.; Winnik, F. M. Theoretical modeling of associated structures in aqueous solutions of hydrophobically modified telechelic PNIPAM based on a neutron scattering study. Macromolecules 2008, 41, 9413– 9422,  DOI: 10.1021/ma800957z
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    49
    Theoretical Modeling of Associated Structures in Aqueous Solutions of Hydrophobically Modified Telechelic PNIPAM Based on a Neutron Scattering Study
    Koga, Tsuyoshi; Tanaka, Fumihiko; Motokawa, Ryuhei; Koizumi, Satoshi; Winnik, Francoise M.
    Macromolecules (Washington, DC, United States) (2008), 41 (23), 9413-9422CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    On the basis of results from a small-angle neutron scattering (SANS) study of aq. solns. of a telechelic PNIPAM with octadecyl end groups, we developed a theor. model of the self-assembly of this polymer in water as a function of temp. and concn. This model leads us to the following description. In solns. of concn. 10 g L-1 kept between 10 and 20°, telechelic PNIPAMs (Mn=22,200 g mol-1) assoc. in the form of flower micelles, contg. about 12 polymer chains, assembled in a three-layered core-shell morphol. with an inner core consisting of the octadecyl units, a dense inner shell consisting of partly collapsed PNIPAM chains, and an outer shell of swollen hydrated chains. Drastic changes in the scattering profile of the soln. heated above 31° are attributed to the formation of mesoglobules (diam. of ∼40 nm) consisting of about 1000 polymer chains. On further heating, the aggregation no. of the mesoglobules increases. It reaches a value of ∼9000 at 34° and stays const. upon further heating. In solns. of lower concn. (1 g L-1), assocn. of flower micelles and mesoglobules does not occur; however, the structure of individual flower micelles and mesoglobules is not affected by the change in concn. In solns. of 50 g L-1 in which flower micelles are expected to be partially connected by bridge chains, a peak attributed to correlation between flower micelles appears in the scattering profiles recorded at low temp. (10-20°). In spite of the intermicellar bridging connection, the overall temp. dependence of the scattering profile at 50 g L-1 remains similar to that at 10 g L-1. Distinct features of the self-assembled structures formed in aq. telechelic PNIPAM solns. are discussed in terms of the interactions between water and the polymer main chains.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtlemt7%252FM&md5=12c3a7bed1ecd018fb337e4ab78c151b
  50. 50
    Debye, P. Zerstreuung von röntgenstrahlen. Ann. Phys. (Berlin, Ger.) 1915, 351, 809– 823,  DOI: 10.1002/andp.19153510606
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  51. 51
    Svergun, D.; Barberato, C.; Koch, M. H. J. J. CRYSOL– a program to evaluate X-ray solution scattering of biological macromolecules from atomic coordinates. J. Appl. Crystallogr. 1995, 28, 768– 773,  DOI: 10.1107/S0021889895007047
    [Crossref], [CAS], Google Scholar
    51
    CRYSOL - a program to evaluate x-ray solution scattering of biological macromolecules from atomic coordinates
    Svergun, D.; Barberato, C.; Koch, M. H. J.
    Journal of Applied Crystallography (1995), 28 (6), 768-73CODEN: JACGAR; ISSN:0021-8898. (Munksgaard)
    A program for evaluating the soln. scattering from macromols. with known at. structure is presented. The program uses multiple expansion for fast calcn. of the spherically averaged scattering pattern and takes into account the hydration shell. Given the at. coordinates (e.g., from the Brookhaven Protein Data Bank) it can either predict the soln. scattering curve or fit the exptl. scattering curve using only 2 free parameters, the av. displaced solvent vol. per at. group and the contrast of the hydration layer. The program runs on IBM PCs and on the major UNIX platforms.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XksFektg%253D%253D&md5=ebcc992d5c7af97987ea4f5e1b014d02
  52. 52
    Antonio, M. R.; Demars, T. J.; Audras, M.; Ellis, R. J. Third phase inversion, red oil formation, and multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system. Sep. Sci. Technol. 2018, 53, 1834– 1847,  DOI: 10.1080/01496395.2017.1281303
    [Crossref], [CAS], Google Scholar
    52
    Third phase inversion, red oil formation, and multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system
    Antonio, Mark R.; Demars, Thomas J.; Audras, Matthieu; Ellis, Ross J.
    Separation Science and Technology (Philadelphia, PA, United States) (2018), 53 (12), 1834-1847CODEN: SSTEDS; ISSN:0149-6395. (Taylor & Francis, Inc.)
    The extn. of tetravalent cerium, Ce(IV), from aq. nitric acid with tri-Bu phosphate (TBP) in n-dodecane was studied by varying the aq., initial cerium(IV) concn., [Ce4+]aq,init, up to and beyond the point of third phase formation, defined by the crit. aq. concn. (or CAC) and the limiting org. concn. (or LOC). The new chem., elaborated here for the nearly-century-old Ce(IV)-20% TBP system, focuses on the phenomena of third phase inversion and the distribution of four solutes-Ce(IV), HNO3, H2O, and TBP-between the aq. and org. phases, which are of direct relevance to the PUREX process. We demonstrate that multinuclear Ce(IV) entities are present in the org. phases.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjt1agu7c%253D&md5=26976b1ec8534a9885033e0fd5c4ece0
  53. 53
    Antonio, M. R.; Ellis, R. J.; Estes, S. L.; Bera, M. K. Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system. Phys. Chem. Chem. Phys. 2017, 19, 21304– 21316,  DOI: 10.1039/C7CP03350H
    [Crossref], [PubMed], [CAS], Google Scholar
    53
    Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system
    Antonio, Mark R.; Ellis, Ross J.; Estes, Shanna L.; Bera, Mrinal K.
    Physical Chemistry Chemical Physics (2017), 19 (32), 21304-21316CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    X-ray and electrochem. studies of org. phases obtained by the extn. of tetravalent cerium, Ce(IV), from aq. nitric acid (3 M) with tri-Bu phosphate (TBP) in n-dodecane reveal a tetranuclear Ce(IV) structural motif. This finding is consistent with the results of previous liq.-liq. extn. (LLE) studies that implicate the aggregation of (Ce-O-Ce)6+ dimers into multinuclear Ce(IV)·TBP solvates. The org. soln. structures elaborated here for the Ce(IV)-HNO3-20% TBP-n-C12H26 system are correlated with multiscale phenomena-from the at. level of the cerium coordination environment to the supramol. scale of solute aggregates-in the org. phases, which are of relevance to the PUREX (Plutonium Uranium Redn. Extn.) process. The combination of XANES, EXAFS, and SAXS results indicate the presence of tetranuclear cerium(IV)-oxo core structures in each of the org. phases investigated. In addn. to the use of X-ray spectroscopy and scattering for direct metrical details about the org. phase solute speciation, three-phase-electrode differential pulse voltammetry (DPV) of the third phase reveals a wave attributable to Ce(IV) redn. The electrode potential is consistent with values for the redn. of Ce(IV) in (Ce-O-Ce)6+ dimers in aq. electrolytes. The Ce(IV) coordination chem. of the org. solvates is independent of the bulk phenomenon of phase splitting, namely third phase formation. The local, mol. environment of Ce in the org. phase before splitting is identical to those in the two org. phases (the dense third phase and the light phase) after splitting. SAXS data are consistent with the formation of small spherical reverse micelles with core diams. (approx. 6 Å) that can accommodate a tetranuclear Ce(IV) oxo-cluster solvate of TBP. Sticky sphere modeling of the SAXS data for the org. phases with low cerium concns. ( < 0.14 M) is consistent with the presence of randomly- and homogeneously-dispersed micelles in combination with short-range percolated, assocd. micelles. At high cerium concns. (approx. 1.5 M) in the third phase, the SAXS modeling is consistent with correlated, long-range percolated micellar aggregates. The presence of strong inter-micellar interactions (-3 to -5kBT) in all org. phases of the Ce(IV)-HNO3-TBP-n-C12H26 LLE system suggests that the phenomena of phase splitting and third phase inversion are due to liq. pptn. that is dependent solely on the concn. of the tetranuclear Ce solvate.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFamsLfJ&md5=3acbf6dd8741f9e9998e4211abc87a65
  54. 54
    Ankudinov, A. L.; Ravel, B.; Rehr, J. J.; Conradson, S. D. Real-space multiple-scattering calculation and interpretation of X-ray-absorption near-edge structure. Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 58, 7565– 7576,  DOI: 10.1103/PhysRevB.58.7565
    [Crossref], [CAS], Google Scholar
    54
    Real-space multiple-scattering calculation and interpretation of x-ray-absorption near-edge structure
    Ankudinov, A. L.; Ravel, B.; Rehr, J. J.; Conradson, S. D.
    Physical Review B: Condensed Matter and Materials Physics (1998), 58 (12), 7565-7576CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    A self-consistent real-space multiple-scattering (RSMS) approach for calcns. of x-ray-absorption near-edge structure (XANES) is presented and implemented in an ab initio code applicable to arbitrary aperiodic or periodic systems. This approach yields a quant. interpretation of XANES based on simultaneous, SCF calcns. of local electronic structure and x-ray absorption spectra, which include full multiple scattering from atoms within a small cluster and the contributions of high-order MS from scatterers outside that cluster. The code includes a SCF est. of the Fermi energy and an account of orbital occupancy and charge transfer. The authors also present a qual., scattering-theoretic interpretation of XANES. Sample applications are presented for cubic BN, UF6, Pu hydrates, and distorted PbTiO3. Limitations and various extensions are also discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmtVCgu78%253D&md5=b7b8ea5b5d5798475d65c324de1b0849
  55. 55
    Roe, R.-J. Methods of X-ray and Neutron Scattering in Polymer Science, 1st ed.; Oxford University Press: NY, 2000.
    Google Scholar
    There is no corresponding record for this reference.
  56. 56
    Okuhara, T.; Mizuno, N.; Misono, M. In Adv. Catal.; Eley, D. D., Haag, W. O., Gates, B., Eds.; 1996; Vol. 41, pp 113– 252.
    Google Scholar
    There is no corresponding record for this reference.
  57. 57
    Bartlett, P.; Ottewill, R. H. A neutron scattering study of the structure of a bimodal colloidal crystal. J. Chem. Phys. 1992, 96, 3306– 3318,  DOI: 10.1063/1.461926
    [Crossref], [CAS], Google Scholar
    57
    A neutron-scattering study of the structure of a bimodal colloidal crystal
    Bartlett, P.; Ottewill, R. H.
    Journal of Chemical Physics (1992), 96 (4), 3306-18CODEN: JCPSA6; ISSN:0021-9606.
    The authors have studied the freezing of a binary mixt. of colloidal poly(Me methacrylate) spheres of size ratio 0.31 and compn. AB4 (here A refers to the larger spheres). When suspended in a suitable liq. these particles interact via a steeply repulsive (approx. hard sphere) potential. The structure of the colloidal crystals formed in this binary system was established from a combination of small-angle neutron and light scattering measurements. There is an almost complete size sepn. on freezing. The cryst. phase contains almost exclusively large spheres while the smaller spheres are excluded from the crystal into a coexisting binary fluid. This observation is in agreement with recent d. functional calcns. for the freezing of hard sphere mixts.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XhvVaisrc%253D&md5=3b1e72a4b407519300de657c9f5b70e7
  58. 58
    Qiao, B.; Demars, T.; Olvela de la Cruz, M.; Ellis, R. J. How hydrogen bonds affect the growth of reverse micelles around coordinating metal ions. J. Phys. Chem. Lett. 2014, 5, 1440– 1444,  DOI: 10.1021/jz500495p
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    58
    How Hydrogen Bonds Affect the Growth of Reverse Micelles around Coordinating Metal Ions
    Qiao, Baofu; Demars, Thomas; Olvera de la Cruz, Monica; Ellis, Ross J.
    Journal of Physical Chemistry Letters (2014), 5 (8), 1440-1444CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    The role of hydrogen bonds on the hierarchical structure of an aggregating amphiphile-oil soln. contg. a coordinating metal complex has been studied by means of atomistic mol. dynamics simulations and X-ray techniques. Hydrogen bonds not only stabilize the metal complex in the hydrophobic environment by coordinating between the Eu(NO3)3 outer-sphere and aggregating amphiphiles, but also affect the growth of such reverse micellar aggregates. The formation of swollen, elongated reverse micelles elevates the extn. of metal ions with increased H-bonds under acidic condition. These new insights into H-bonds are of broad interest to nanosynthesis and biol. applications, in addn. to metal ion sepns.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXltF2kur0%253D&md5=dbc5a6098b8716bf3fb98b9ea7bc760d
  59. 59
    Ellis, R. J.; Meridiano, Y.; Muller, J.; Berthon, L.; Guilbaud, P.; Zorz, N.; Antonio, M. R.; Demars, T.; Zemb, T. Complexation-induced supramolecular assembly drives metal-ion extraction. Chem. - Eur. J. 2014, 20, 12796– 12807,  DOI: 10.1002/chem.201403859
    [Crossref], [PubMed], [CAS], Google Scholar
    59
    Complexation-Induced Supramolecular Assembly Drives Metal-Ion Extraction
    Ellis, Ross J.; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R.; Demars, Thomas; Zemb, Thomas
    Chemistry - A European Journal (2014), 20 (40), 12796-12807CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Combining expt. with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extd. from water into oil by a lipophilic neutral amphiphile. Mol. dynamics simulations were coupled to exptl. spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the org. phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extn. of the Eu3+-3(NO3-) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear EuIII-contg. aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, contg. high densities of O-donor ligands and anions, provide improved EuIII solvation environments that help drive interfacial transfer, as is reflected by the increasing EuIII partitioning ratios (oil/aq.) despite the org. phase approaching satn. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsVGgur7F&md5=07308486b263267f7a2041db86e0bc11
  60. 60
    Qiao, B. F.; Ferru, G.; Olvela de la Cruz, M.; Ellis, R. J. Molecular origins of mesoscale ordering in a metalloamphiphile phase. ACS Cent. Sci. 2015, 1, 493– 503,  DOI: 10.1021/acscentsci.5b00306
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    60
    Molecular Origins of Mesoscale Ordering in a Metalloamphiphile Phase
    Qiao, Baofu; Ferru, Geoffroy; Olvera de la Cruz, Monica; Ellis, Ross J.
    ACS Central Science (2015), 1 (9), 493-503CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
    A metalloamphiphile-oil soln. that organizes on multiple length scales has been studied using d synchrotron small- and wide-angle X-ray scattering combined with large-scale atomistic mol. dynamics simulations. The mols. assoc. into aggregates, and aggregates flocculate into meso-ordered phases. The dipolar interactions, centered on the amphiphile headgroup, bridge ionic aggregate cores and drive aggregate flocculation. By identifying specific intermol. interactions that drive mesoscale ordering in soln., the authors bridge two different length scales that are classically addressed sep. These results highlight the importance of individual intermol. interactions in driving mesoscale ordering.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVanurfK&md5=50faee10cf0a6440d18903d8543c429b
  61. 61
    Sevick, E.; Monson, P.; Ottino, J. Monte-carlo calculations of cluster statistics in continuum models of composite morphology. J. Chem. Phys. 1988, 88, 1198– 1206,  DOI: 10.1063/1.454720
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  62. 62
    Servis, M.; Wu, D.; Jenifer, S.; Clark, A. Square supramolecular assemblies of uranyl complexes in organic solvents. Chem. Commun. 2018, 54, 10064– 10067,  DOI: 10.1039/C8CC05277H
    [Crossref], [PubMed], [CAS], Google Scholar
    62
    Square supramolecular assemblies of uranyl complexes in organic solvents
    Servis, Michael J.; Wu, David T.; Shafer, Jenifer C.; Clark, Aurora E.
    Chemical Communications (Cambridge, United Kingdom) (2018), 54 (72), 10064-10067CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Uranyl nitrate/extractant complexes form long-range isotropic pairs and short-range ordered dimeric assemblies with a unique square configuration comprised of noncovalent ligand and acid anion mediated interactions, further stabilized by org. phase solvation.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVyns73J&md5=1dc4065e6badb22c4cb792b74bf80cc4
  63. 63
    Hill, T. L. An Introduction to Statistical Thermodynamics; Addison-Wesley: Reading, MA, 1960.
    Google Scholar
    There is no corresponding record for this reference.
  64. 64
    Higgins, J. S.; Benoît, H. C. Polymers and Neutron Scattering; Oxford University Press: Oxford, 1994.
    Google Scholar
    There is no corresponding record for this reference.
  65. 65
    Berthon, L.; Martinet, L.; Testard, F.; Madic, C.; Zemb, T. Solvent penetration and sterical stabilization of reverse aggregates based on the DIAMEX process extracting molecules: Consequences for the third phase formation. Solvent Extr. Ion Exch. 2007, 25, 545– 576,  DOI: 10.1080/07366290701512576
    [Crossref], [CAS], Google Scholar
    65
    Solvent Penetration and Sterical Stabilization of Reverse Aggregates based on the DIAMEX Process Extracting Molecules: Consequences for the Third Phase Formation
    Berthon, L.; Martinet, L.; Testard, F.; Madic, C.; Zemb, Th.
    Solvent Extraction and Ion Exchange (2007), 25 (5), 545-576CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
    Studies on third phase formation during the extn. of nitric acid by malonamide extractants in various diluents are investigated. This "third phase transition" is studied from a fundamental point of view, combining vapor pressure osmometry, phase diagram, and scattering studies. The organization of the org. phases of the "malonamides/alkane/water/nitric acid" systems was studied at three "scales" enumerated below. 1. At a mol. scale by detg. the compns. of the extd. complexes. 2. At a macroscopic scale by detg. the phase transition boundaries quantified by the limiting org. concn. (LOC) of solutes. 3. At a supramol. scale by analyzing the organization of the species in the org. phases (i.e. measuring the crit. micellization concn., the aggregation no., and the interactions between the aggregates). The instability (third phase apparition) has a supramol. origin: It is a "long range" attraction between polar cores of the reverse micelles formed by the extg. agent. Water and nitric acid extn. are decoupled from these interactions. The alkyl chains of the extractant and the diluent play a sym. role in the phys. stability of the org. phase: Decreasing the diluent chain length or increasing the chain length of the complexing agent both promotes phase stability, i.e., they increase the LOC. The authors demonstrate here that this effect is the same as the effect obsd. and known for all other w/o "reverse" micelles: Chains protruding from any aggregate stabilize polar solute in oil and shorts oil penetrate and swells the reverse micelles apolar layer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXptlSrtLY%253D&md5=686cce21070ffa366b5d2bdab276aa57
  66. 66
    Zemb, T.; Bauer, C.; Bauduin, P.; Belloni, L.; Dejugnat, C.; Diat, O.; Dubois, V.; Dufreche, J. F.; Dourdain, S.; Duvail, M.; Larpent, C.; Testard, F.; Pellet-Rostaing, S. Recycling metals by controlled transfer of ionic species between complex fluids: en route to ″ienaics″. Colloid Polym. Sci. 2015, 293, 1– 22,  DOI: 10.1007/s00396-014-3447-x
    [Crossref], [CAS], Google Scholar
    66
    Recycling metals by controlled transfer of ionic species between complex fluids. En route to "ienaics"
    Zemb, Thomas; Bauer, Caroline; Bauduin, Pierre; Belloni, Luc; Dejugnat, Christophe; Diat, Olivier; Dubois, Veronique; Dufreche, Jean-Francois; Dourdain, Sandrine; Duvail, Magali; Larpent, Chantal; Testard, Fabienne; Pellet-Rostaing, Stephane
    Colloid and Polymer Science (2015), 293 (1), 1-22CODEN: CPMSB6; ISSN:0303-402X. (Springer)
    A review. Recycling chem. of metals and oxides relies on 3 steps: dissoln., sepn. and material reformation. We review in this work the colloidal approach of the transfer of ions between 2 complex fluids, i.e. the mechanism at the basis of the liq.-liq. extn. technol. This approach allows for rationalizing in a unified model transformation such as accidently splitting from 2 to 3 phases, or uncontrolled viscosity variations, as linked to the transformation in the phase diagram due to ion transfer. Moreover, differences in free energies assocd. to ion transfer between phases that are the origin of the selectivity need to be considered at the meso-scale beyond parameterization of an arbitrary no. of competing "complexes". Entropy and electrostatics are taken into account in relation to solvent formulation. By analogy with electronics dealing about electrons transported in conductors and semi-conductors, this "ienaic" approach deals with ions transported between nanostructures present in colloidal fluids under the influence of chem. potential gradients between nanostructures coexisting in colloidal fluids. We show in this review how this colloidal approach generalizes the multiple chem. equil. models used in supra-mol. chem. Statistical thermodn. applied to self-assembled fluids requires only a few measurable parameters to predict liq.-liq. extn. isotherms and selectivity in multi-phase chem. systems contg. at least one concd. emulsified water in oil (w/o) or oil in water (o/w) microemulsion.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvFOhtb%252FO&md5=a223fd32d4f7ea6b53e11cf6c3e0f3b2
  67. 67
    Abécassis, B.; Testard, F.; Zemb, T.; Berthon, L.; Madic, C. Effect of n-octanol on the structure at the supramolecular scale of concentrated dimethyldioctylhexylethoxymalonamide extractant solutions. Langmuir 2003, 19, 6638– 6644,  DOI: 10.1021/la034088g
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    67
    Effect of n-Octanol on the Structure at the Supramolecular Scale of Concentrated Dimethyldioctylhexylethoxymalonamide Extractant Solutions
    Abecassis, B.; Testard, F.; Zemb, Th.; Berthon, L.; Madic, C.
    Langmuir (2003), 19 (17), 6638-6644CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
    Using small-angle X-ray scattering (SAXS) and interfacial tension measurements, we show that concd. solns. of dimethyldioctylhexyloxyethylmalonamide dild. in dodecane are organized in reverse aggregates that have many features in common with reverse micelles. The crit. micellar concn. is detd. from interfacial tension measurements using the pendant-drop technique, and the aggregation no. is given by fitting SAXS data on the abs. scale. The effect of the addn. of n-octanol, a modifier widely used in liq./liq. extn., is studied by SAXS. It is shown that, for small amts. of alc., the modifier acts as a cosurfactant; it swells the reverse micelles by adsorbing onto the aggregates and increases the surface per extractant polar head. When n-octanol is added in larger quantities, a new microstructure appears, and the amt. of octanol required for this transition depends on the amt. of diamide in soln. (for example, octanol concn. ≥ 1 M for 0.7 M diamide). Therefore, a hydrogen-bond network is present in soln., and the presence of areas of high electronic d. sepd. by a distance varying from 15 to 20 Å is found to explain the scattering patterns.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvFWlsb8%253D&md5=2c98ea122bcc228051291287efa2a7c7
  68. 68
    Whittaker, D.; Geist, A.; Modolo, G.; Taylor, R.; Sarsfield, M.; Wilden, A. Applications of diglycolamide based solvent extraction processes in spent nuclear fuel reprocessing, Part 1: TODGA. Solvent Extr. Ion Exch. 2018, 36, 223– 256,  DOI: 10.1080/07366299.2018.1464269
    [Crossref], [CAS], Google Scholar
    68
    Applications of Diglycolamide Based Solvent Extraction Processes in Spent Nuclear Fuel Reprocessing, Part 1: TODGA
    Whittaker, Daniel; Geist, Andreas; Modolo, Giuseppe; Taylor, Robin; Sarsfield, Mark; Wilden, Andreas
    Solvent Extraction and Ion Exchange (2018), 36 (3), 223-256CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
    Over the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extn. of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N',N'-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A no. of new actinide sepn. processes have been proposed based on extn. with TODGA. This review covers TODGA-based processes and extn. data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the org. phase speciation are reviewed in this context. Relevant aspects of the extn. chem. of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide sepn. processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chem. occurring in the org. phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGA-based flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVSkur7M&md5=f02d4fa90a5a05427d0503412ed99688

Cited By

This article is cited by 43 publications.

  1. Daniel Massey, Christopher D. Williams, Junju Mu, Andrew J. Masters, Ryuhei Motokawa, Noboru Aoyagi, Yuki Ueda, Mark R. Antonio. Hierarchical Aggregation in a Complex Fluid─The Role of Isomeric Interconversion. The Journal of Physical Chemistry B 2023, 127 (9) , 2052-2065. https://doi.org/10.1021/acs.jpcb.2c07527
  2. Darren M. Driscoll, Hongjun Liu, Benjamin Reinhart, Ilja Popovs, Vera Bocharova, Santa Jansone-Popova, De-en Jiang, Alexander S. Ivanov. Noncoordinating Secondary Sphere Ion Modulates Supramolecular Clustering of Lanthanides. The Journal of Physical Chemistry Letters 2022, 13 (51) , 12076-12081. https://doi.org/10.1021/acs.jpclett.2c03423
  3. Daniel Massey, Andrew Masters, Jonathan Macdonald-Taylor, David Woodhead, Robin Taylor. Molecular Dynamics Study of the Aggregation Behavior of N,N,N′,N′-Tetraoctyl Diglycolamide. The Journal of Physical Chemistry B 2022, 126 (33) , 6290-6300. https://doi.org/10.1021/acs.jpcb.2c02198
  4. Yuki Ueda, Ayano Eguchi, Kohei Tokunaga, Kei Kikuchi, Tsuyoshi Sugita, Hiroyuki Okamura, Hirochika Naganawa. Urea-Introduced Ionic Liquid for the Effective Extraction of Pt(IV) and Pd(II) Ions. Industrial & Engineering Chemistry Research 2022, 61 (19) , 6640-6649. https://doi.org/10.1021/acs.iecr.2c00304
  5. D. Sheyfer, Michael J. Servis, Qingteng Zhang, J. Lal, T. Loeffler, E. M. Dufresne, A. R. Sandy, S. Narayanan, Subramanian K.R.S. Sankaranarayanan, R. Szczygiel, P. Maj, L. Soderholm, Mark R. Antonio, G. B. Stephenson. Advancing Chemical Separations: Unraveling the Structure and Dynamics of Phase Splitting in Liquid–Liquid Extraction. The Journal of Physical Chemistry B 2022, 126 (12) , 2420-2429. https://doi.org/10.1021/acs.jpcb.1c09996
  6. Mario Špadina, Jean-François Dufrêche, Stephane Pellet-Rostaing, Stjepan Marčelja, Thomas Zemb. Molecular Forces in Liquid–Liquid Extraction. Langmuir 2021, 37 (36) , 10637-10656. https://doi.org/10.1021/acs.langmuir.1c00673
  7. Michael J. Servis, Marek Piechowicz, L. Soderholm. Impact of Water Extraction on Malonamide Aggregation: A Molecular Dynamics and Graph Theoretic Approach. The Journal of Physical Chemistry B 2021, 125 (24) , 6629-6638. https://doi.org/10.1021/acs.jpcb.1c02962
  8. Michael J. Servis, G. B. Stephenson. Mesostructuring in Liquid–Liquid Extraction Organic Phases Originating from Critical Points. The Journal of Physical Chemistry Letters 2021, 12 (24) , 5807-5812. https://doi.org/10.1021/acs.jpclett.1c01429
  9. Srikanth Nayak, Raju R. Kumal, Zhu Liu, Baofu Qiao, Aurora E. Clark, Ahmet Uysal. Origins of Clustering of Metalate–Extractant Complexes in Liquid–Liquid Extraction. ACS Applied Materials & Interfaces 2021, 13 (20) , 24194-24206. https://doi.org/10.1021/acsami.0c23158
  10. Michael J. Servis, Aurora E. Clark. Cluster Identification Using Modularity Optimization to Uncover Chemical Heterogeneity in Complex Solutions. The Journal of Physical Chemistry A 2021, 125 (18) , 3986-3993. https://doi.org/10.1021/acs.jpca.0c11320
  11. Michael J. Servis, Marek Piechowicz, Ilya A. Shkrob, L. Soderholm, Aurora E. Clark. Amphiphile Organization in Organic Solutions: An Alternative Explanation for Small-Angle X-ray Scattering Features in Malonamide/Alkane Mixtures. The Journal of Physical Chemistry B 2020, 124 (47) , 10822-10831. https://doi.org/10.1021/acs.jpcb.0c07080
  12. Mario Špadina, Klemen Bohinc, Thomas Zemb, Jean-François Dufrêche. Synergistic Solvent Extraction Is Driven by Entropy. ACS Nano 2019, 13 (12) , 13745-13758. https://doi.org/10.1021/acsnano.9b07605
  13. Hirokazu Narita, Rebecca M. Nicolson, Ryuhei Motokawa, Fumiyuki Ito, Kazuko Morisaku, Midori Goto, Mikiya Tanaka, William T. Heller, Hideaki Shiwaku, Tsuyoshi Yaita, Ross J. Gordon, Jason B. Love, Peter A. Tasker, Emma R. Schofield, Mark R. Antonio, Carole A. Morrison. Proton Chelating Ligands Drive Improved Chemical Separations for Rhodium. Inorganic Chemistry 2019, 58 (13) , 8720-8734. https://doi.org/10.1021/acs.inorgchem.9b01136
  14. Taishi Kobayashi, Shogo Nakajima, Ryuhei Motokawa, Daiju Matsumura, Takumi Saito, Takayuki Sasaki. Structural Approach to Understanding the Solubility of Metal Hydroxides. Langmuir 2019, 35 (24) , 7995-8006. https://doi.org/10.1021/acs.langmuir.9b01132
  15. Aurora E. Clark. Amphiphile-Based Complex Fluids: The Self-Assembly Ensemble as Protagonist. ACS Central Science 2019, 5 (1) , 10-12. https://doi.org/10.1021/acscentsci.8b00927
  16. Allison A. Peroutka, Shane S. Galley, Jenifer C. Shafer. Elucidating the speciation of extracted lanthanides by diglycolamides. Coordination Chemistry Reviews 2023, 482 , 215071. https://doi.org/10.1016/j.ccr.2023.215071
  17. Ueslei G. Favero, Nicolas Schaeffer, Helena Passos, Kaíque A. M. L. Cruz, Duarte Ananias, Sandrine Dourdain, Maria C. Hespanhol. Solvent extraction in non-ideal eutectic solvents – application towards lanthanide separation. Separation and Purification Technology 2023, 337 , 123592. https://doi.org/10.1016/j.seppur.2023.123592
  18. Cyril Micheau, Yuki Ueda, Kazuhiro Akutsu-Suyama, Damien Bourgeois, Ryuhei Motokawa. Deuterated Malonamide Synthesis for Fundamental Research on Solvent Extraction Systems. Solvent Extraction and Ion Exchange 2023, 41 (2) , 221-240. https://doi.org/10.1080/07366299.2023.2166351
  19. Anna P.S. Crema, Nicolas Schaeffer, Henrique Bastos, Liliana P. Silva, Dinis O. Abranches, Helena Passos, Maria C. Hespanhol, João A.P. Coutinho. New family of Type V eutectic solvents based on 1,10-phenanthroline and their application in metal extraction. Hydrometallurgy 2023, 215 , 105971. https://doi.org/10.1016/j.hydromet.2022.105971
  20. Alexander P. Antonov, Sören Schweers, Artem Ryabov, Philipp Maass. Brownian dynamics simulations of hard rods in external fields and with contact interactions. Physical Review E 2022, 106 (5) https://doi.org/10.1103/PhysRevE.106.054606
  21. Subramee Sarkar, A. Suresh, N. Sivaraman, Vinod K Aswal. Studies on the aggregation behavior of mineral acid and Zr(IV) loaded Tris(2-methylbutyl) phosphate and tri- n -alkyl phosphate systems using small angle neutron scattering. Separation Science and Technology 2022, 57 (6) , 968-978. https://doi.org/10.1080/01496395.2021.1954021
  22. Zijun Lu, Sandrine Dourdain, Jean-François Dufrêche, Bruno Demé, Thomas Zemb, Stéphane Pellet-Rostaing. Effect of alkyl chains configurations of tertiary amines on uranium extraction and phase stability – part II: Curvature free energy controlling the ion transfer. Journal of Molecular Liquids 2022, 349 , 118487. https://doi.org/10.1016/j.molliq.2022.118487
  23. Simon Stemplinger, Magali Duvail, Jean-François Dufrêche. Molecular dynamics simulations of Eu(NO3)3 salt with DMDOHEMA in n-alkanes: Unravelling curvature properties in liquid-liquid extraction. Journal of Molecular Liquids 2022, 348 , 118035. https://doi.org/10.1016/j.molliq.2021.118035
  24. M. Špadina, S. Dourdain, J. Rey, K. Bohinc, S. Pellet-Rostaing, Jean-François Dufrêche, T. Zemb. How acidity rules synergism and antagonism in liquid–liquid extraction by lipophilic extractants—Part II: application of the ienaic modelling. Solvent Extraction and Ion Exchange 2022, 40 (1-2) , 106-139. https://doi.org/10.1080/07366299.2021.1899614
  25. Michael J. Servis, Srikanth Nayak, Soenke Seifert. The pervasive impact of critical fluctuations in liquid–liquid extraction organic phases. The Journal of Chemical Physics 2021, 155 (24) , 244506. https://doi.org/10.1063/5.0074995
  26. Norman Kelly, Thomas Doert, Felix Hennersdorf, Karsten Gloe. Synergistic lanthanide extraction triggered by self-assembly of heterodinuclear Zn(II)/Ln(III) Schiff base/carboxylic acid complexes. Solvent Extraction and Ion Exchange 2021, 39 (5-6) , 545-572. https://doi.org/10.1080/07366299.2021.1876383
  27. Yuki Ueda, Shintaro Morisada, Hidetaka Kawakita, Keisuke Ohto. Selective Extraction of Platinum(IV) from the Simulated Secondary Resources Using Simple Secondary Amide and Urea Extractants. Separations 2021, 8 (9) , 139. https://doi.org/10.3390/separations8090139
  28. Nicolas Schaeffer, Silvia J. R. Vargas, Helena Passos, Paula Brandão, Helena I. S. Nogueira, Lenka Svecova, Papaiconomou, João A. P. Coutinho. A HNO 3 ‐Responsive Aqueous Biphasic System for Metal Separation: Application towards Ce IV Recovery. ChemSusChem 2021, 14 (14) , 3018-3026. https://doi.org/10.1002/cssc.202101149
  29. Margarita Kruteva. Dynamics studied by Quasielastic Neutron Scattering (QENS). Adsorption 2021, 27 (5) , 875-889. https://doi.org/10.1007/s10450-020-00295-4
  30. Silvia J. R. Vargas, Germán Pérez-Sánchez, Nicolas Schaeffer, João A. P. Coutinho. Solvent extraction in extended hydrogen bonded fluids – separation of Pt( iv ) from Pd( ii ) using TOPO-based type V DES. Green Chemistry 2021, 23 (12) , 4540-4550. https://doi.org/10.1039/D1GC00829C
  31. Bassam I. El-Eswed, Mahmoud Sunjuk, Raed Ghuneim, Yahya.S. Al-Degs, Maha Al Rimawi, Yanal Albawarshi. Competitive extraction of Li, Na, K, Mg and Ca ions from acidified aqueous solutions into chloroform layer containing diluted alkyl phosphates. Journal of Colloid and Interface Science 2021, 587 , 229-239. https://doi.org/10.1016/j.jcis.2020.12.029
  32. Takuya Okudaira, Yuki Ueda, Kosuke Hiroi, Ryuhei Motokawa, Yasuhiro Inamura, Shin-ichi Takata, Takayuki Oku, Jun-ichi Suzuki, Shingo Takahashi, Hitoshi Endo, Hiroki Iwase. Polarization analysis for small-angle neutron scattering with a 3 He spin filter at a pulsed neutron source. Journal of Applied Crystallography 2021, 54 (2) , 548-556. https://doi.org/10.1107/S1600576721001643
  33. Hirokazu Narita, Ryo Kasuya, Tomoya Suzuki, Ryuhei Motokawa, Mikiya Tanaka. Precious Metal Separations. 2020, 1-28. https://doi.org/10.1002/9781119951438.eibc2756
  34. Srikanth Nayak, Kaitlin Lovering, Ahmet Uysal. Ion-specific clustering of metal–amphiphile complexes in rare earth separations. Nanoscale 2020, 12 (39) , 20202-20210. https://doi.org/10.1039/D0NR04231E
  35. Koichiro Takao, Yasuhisa Ikeda. Coordination Chemistry of Actinide Nitrates with Cyclic Amide Derivatives for the Development of the Nuclear Fuel Materials Selective Precipitation (NUMAP) Reprocessing Method. European Journal of Inorganic Chemistry 2020, 2020 (36) , 3443-3459. https://doi.org/10.1002/ejic.202000504
  36. D. Sheyfer, Qingteng Zhang, J. Lal, T. Loeffler, E. M. Dufresne, A. R. Sandy, S. Narayanan, S. K. R. S. Sankaranarayanan, R. Szczygiel, P. Maj, L. Soderholm, M. R. Antonio, G. B. Stephenson. Nanoscale Critical Phenomena in a Complex Fluid Studied by X-Ray Photon Correlation Spectroscopy. Physical Review Letters 2020, 125 (12) https://doi.org/10.1103/PhysRevLett.125.125504
  37. Yojiro Oba, Ryuhei Motokawa, Masahiro Hino, Nozomu Adachi, Yoshikazu Todaka, Rintaro Inoue, Masaaki Sugiyama. Nanostructural Characterization of Oleyl Acid Phosphate in Poly-α-olefin Using Small-angle X-ray Scattering. Chemistry Letters 2020, 49 (7) , 823-825. https://doi.org/10.1246/cl.200204
  38. Michael J. Servis, Ernesto Martinez-Baez, Aurora E. Clark. Hierarchical phenomena in multicomponent liquids: simulation methods, analysis, chemistry. Physical Chemistry Chemical Physics 2020, 22 (18) , 9850-9874. https://doi.org/10.1039/D0CP00164C
  39. Damien Bourgeois, Asmae El Maangar, Sandrine Dourdain. Importance of weak interactions in the formulation of organic phases for efficient liquid/liquid extraction of metals. Current Opinion in Colloid & Interface Science 2020, 46 , 36-51. https://doi.org/10.1016/j.cocis.2020.03.004
  40. Mario Špadina, Klemen Bohinc. Multiscale modeling of solvent extraction and the choice of reference state: Mesoscopic modeling as a bridge between nanoscale and chemical engineering. Current Opinion in Colloid & Interface Science 2020, 46 , 94-113. https://doi.org/10.1016/j.cocis.2020.03.011
  41. Asmae El Maangar, Johannes Theisen, Christophe Penisson, Thomas Zemb, Jean-Christophe P. Gabriel. A microfluidic study of synergic liquid–liquid extraction of rare earth elements. Physical Chemistry Chemical Physics 2020, 22 (10) , 5449-5462. https://doi.org/10.1039/C9CP06569E
  42. Yuki Ueda, Kei Kikuchi, Tsuyoshi Sugita, Ryuhei Motokawa. Extraction Performance of a Fluorous Phosphate for Zr(IV) from HNO 3 Solution: Comparison with Tri- n -Butyl Phosphate. Solvent Extraction and Ion Exchange 2019, 37 (5) , 347-359. https://doi.org/10.1080/07366299.2019.1638015
  43. J. Durain, D. Bourgeois, M. Bertrand, D. Meyer. Comprehensive Studies on Third Phase Formation: Application to U (VI) /Th (IV) Mixtures Extracted by TBP in N -dodecane. Solvent Extraction and Ion Exchange 2019, 37 (5) , 328-346. https://doi.org/10.1080/07366299.2019.1656853

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. EXAFS spectra for the extracted Zr coordination complexes, (a) k3-weighted Zr K-edge EXAFS, k3χ(k) (open black circles), and (b) corresponding Fourier transform, |FT[k3χ(k)]| (open black circles), and the imaginary part of FT[k3χ(k)], Im{FT[k3χ(k)]} (filled blue circles), obtained for the organic phases of sample nos. 2–5. The solid black curves in part a, the red curves in part b, and the green curves in part b are the simulated k3χ(k), |FT[k3χ(k)]|, and Im{FT[k3χ(k)]} responses, respectively. The thick arrows highlight the P1, P2, P3, and P4 peaks, which originate from the scattering paths of Zr–OTBP and Zr–ONO3, Zr–NNO3, Zr–PTBP, and Zr–N–Omultiple, respectively (Table 2).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. Schematic diagrams of hierarchical aggregate model of zirconium superclusters. (a) Geometry of the optimized coordination structure of extracted Zr(NO3)4(TBP)2 in the organic phase, determined by DFT calculation. Green, Zr; yellow, P; red, O; blue, N; black, C; and light pink, H. (b) Primary cluster in which the Zr(NO3)4(TBP)2 complexes (red spheres) distribute with radius RS around the central complex, (c) primary clusters assemble into a large aggregate (supercluster), where the primary clusters with radius RS surround the central cluster (light blue sphere) with radius RL. A set of the number of the primary clusters, M = 25, and the number of the complexes, N = 7, corresponds to the characteristic parameters of sample no. 5 from SANS data analysis.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. Double-logarithmic plots of the SANS profiles, (a) Iobs(q) and (b) Isub(q), with error bars, as a function of [Zr(NO3)4(TBP)2]org,eq. [Zr(NO3)4(TBP)2]org,eq gradually increases with sample no. from 1 to 5. Dashed lines in part b are the form factors of Zr(NO3)4(TBP)2 in the organic phase, determined on the basis of the Debye scattering formula for randomly orientated Zr(NO3)4(TBP)2 using eqs S3, S6, and S7. Solid lines in part b are the best-fit theoretical SANS profiles obtained by using eqs S10–S13 together with the characteristic parameters listed in Table 3.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. (a) Zr–Zr radial distribution function, g(rZr–Zr) (solid line), and corresponding coordination number of Zr with the other Zr, CN(rZr–Zr) (dashed line). (b) The primary cluster probability distribution for system no. 5 as determined by the MD. The ordinate gives the probability of finding a primary cluster with a given number of Zr atoms. This probability is the number of primary clusters of a given aggregation number divided by the total number of the primary cluster.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. (a) Snapshot of two, neighboring primary clusters from our MD simulations and (b) magnified snapshot showing the hydrogen-bonding network within the primary clusters. Green, Zr; yellow, P; red, O; blue, N; black, C; light pink, H; and light blue dashed line, hydrogen bond.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 6

    Figure 6. (a) Number of hydrogen bonds per Zr complex as a function of aggregation number. (b) Radial distribution function for octane carbon atoms around a central Zr atom as a function of cluster aggregation number of Zr complexes per primary cluster. (c) Radial distribution function for octane carbon atoms around a central N atom in a nitrate ligand, shown as a function of cluster aggregation number. All results in parts a–c are obtained for system no. 5.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    ARTICLE SECTIONS
    Jump To

    This article references 68 other publications.

    1. 1
      Gompper, G.; Schick, M. In Phase Transitions and Critical Phenomena; Domb, C., Lebowitz, J., Eds.; Academic Press: London, 1994; Vol. 16, pp 1– 176.
      Google Scholar
      There is no corresponding record for this reference.
    2. 2
      Schwuger, M. J.; Stickdorn, K.; Schomacker, R. Microemulsions in technical processes. Chem. Rev. 1995, 95, 849– 864,  DOI: 10.1021/cr00036a003
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      2
      Microemulsions in Technical Processes
      Schwuger, Milan-Johann; Stickdorn, Katrin; Schomaecker, Reinhard
      Chemical Reviews (Washington, D. C.) (1995), 95 (4), 849-64CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review with 143 refs. of basic properties of microemulsions and their relation to some already established applications includes phase behavior of microemulsions and interfacial tension between water and oil phases and applications such as enhanced oil recovery, liq.-liq. extn., extn. from chem. contaminated soils, lubricants and cutting oils, pharmaceuticals and cosmetics, washing, and impregnation and textile finishing. Chem. reactions in microemulsions discussed include nanoparticle prepn., biochem. reactions, electrochem. and catalytic reactions, polymns., org. reactions, example of reaction process in a microemulsion, and comparison with phase transfer catalysis.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXlvFWlurY%253D&md5=70c53ddd08fd954d5c04524cc0504e71
    3. 3
      Winsor, P. A. Solvent Properties of Amphiphilic Compounds; Butterworths: London, 1954.
      Google Scholar
      There is no corresponding record for this reference.
    4. 4
      Lindman, B.; Wennerström, H. Miceles. Amphiphile aggregation in aqueous solution. Top. Curr. Chem. 1980, 87, 1– 83,  DOI: 10.1007/BFb0048488
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    5. 5
      Eicke, H.-F. Surfactants in nonpolar solvents. Aggregation and micellization. Top. Curr. Chem. 1980, 87, 85– 145,  DOI: 10.1007/BFb0048489
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    6. 6
      Fischer, S.; Exner, A.; Zielske, K.; Perlich, J.; Deloudi, S.; Steurer, W.; Lindner, P.; Forster, S. Colloidal quasicrystals with 12-fold and 18-fold diffraction symmetry. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 1810– 1814,  DOI: 10.1073/pnas.1008695108
      [Crossref], [PubMed], [CAS], Google Scholar
      6
      Colloidal quasicrystals with 12-fold and 18-fold diffraction symmetry
      Fischer, Steffen; Exner, Alexander; Zielske, Kathrin; Perlich, Jan; Deloudi, Sofia; Steurer, Walter; Lindner, Peter; Forster, Stephan
      Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (5), 1810-1814, S1810/1-S1810/2CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Micelles are the simplest example of self-assembly found in nature. As many other colloids, they can self-assemble in aq. soln. to form ordered periodic structures. These structures so far all exhibited classical crystallog. symmetries. Here it is reported that micelles in soln. can self-assemble into quasicryst. phases. Phases with 12-fold and 18-fold diffraction symmetry were obsd. Colloidal water-based quasicrystals are phys. and chem. very simple systems. Macroscopic monodomain samples of centimeter dimension can be easily prepd. Phase transitions between the fcc phase and the two quasicryst. phases can be easily followed in situ by time-resolved diffraction expts. The discovery of quasicryst. colloidal solns. advances the theor. understanding of quasicrystals considerably, as for these systems the stability of quasicryst. states was theor. predicted for the concn. and temp. range, where they are exptl. obsd. Also for the use of quasicrystals in advanced materials this discovery is of particular importance, as it opens the route to quasicryst. photonic band gap materials via established water-based colloidal self-assembly techniques.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhslyjs7o%253D&md5=0e1e0861c86b9cd8dda03e9c7b01281e
    7. 7
      Zemb, T. Flexibility, persistence length and bicontinuous microstructures in microemulsions. C. R. Chim. 2009, 12, 218– 224,  DOI: 10.1016/j.crci.2008.10.008
      [Crossref], [CAS], Google Scholar
      7
      Flexibility, persistence length and bicontinuous microstructures in microemulsions
      Zemb, Thomas
      Comptes Rendus Chimie (2009), 12 (1-2), 218-224CODEN: CRCOCR; ISSN:1631-0748. (Elsevier Masson SAS)
      Three length scales have to be considered to describe microemulsions: persistence length, spontaneous radius of curvature of the surfactant film as intensive variables and finally the characteristic size imposed by the ratio of vol. fraction to available specific area surface. The specific area per unit vol. is an intensive variable linked to sizes and topologies that can be built without tearing the surfactant film. We show here that at least four types of bicontinuous microstructures have been detected so far, and that they can be distinguished by a simple exptl. detn. of the evolution of scattering peak position vs. diln. Besides the classical microstructures dominated by entropy or a priori considered as droplets, the other microstructures identified so far can be approximated as connected cylinders or randomly connected swollen bilayers. All these microstructures can be considered as "molten" precursors of the lyotropic liq. cryst. phases that are adjacent to microemulsions in phase diagrams.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhs1Ontbc%253D&md5=701c55b975b731ec51d945a1ebd0a747
    8. 8
      Zemb, T.; Holmberg, K.; Kunz, W. Special topic: Weak self assembly. Curr. Opin. Colloid Interface Sci. 2016, 22, A1– A3,  DOI: 10.1016/j.cocis.2016.04.001
      [Crossref], [CAS], Google Scholar
      8
      Editorial overview
      Zemb, Thomas; Holmberg, Krister; Kunz, Werner
      Current Opinion in Colloid & Interface Science (2016), 22 (), A1-A3CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
      There is no expanded citation for this reference.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XntlKhsr8%253D&md5=81a38bcaaabcc6bc427c1076bbd97cbe
    9. 9
      Zemb, T.; Kunz, W. Weak aggregation: State of the art, expectations and open questions. Curr. Opin. Colloid Interface Sci. 2016, 22, 113– 119,  DOI: 10.1016/j.cocis.2016.04.002
      [Crossref], [CAS], Google Scholar
      9
      Weak aggregation: State of the art, expectations and open questions
      Zemb, Thomas; Kunz, Werner
      Current Opinion in Colloid & Interface Science (2016), 22 (), 113-119CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
      A review. This paper gives an overview of weak aggregation due to long-range mol. forces beyond the first neighbor. Such subtle self-assemblies are an important part of modern colloidal chem. and concern org. mols. as well as inorg. electrolytes and hybrid aggregates. Diverse aspects of such colloidal aggregations, as described in this special issue, can be characterized by the effective free energy per mol. involved. We discuss here expectations about emerging knowledge in this field and predictive modeling of inorg. as well as org. colloids and hybrid aggregates. Some still open questions are also given.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XotFagt7g%253D&md5=b91ff5702ebd7728e2d629c2cc821ce3
    10. 10
      Pini, D.; Parola, A. Pattern formation and self-assembly driven by competing interactions. Soft Matter 2017, 13, 9259– 9272,  DOI: 10.1039/C7SM02125A
      [Crossref], [PubMed], [CAS], Google Scholar
      10
      Pattern formation and self-assembly driven by competing interactions
      Pini, Davide; Parola, Alberto
      Soft Matter (2017), 13 (48), 9259-9272CODEN: SMOABF; ISSN:1744-6848. (Royal Society of Chemistry)
      Colloidal fluids interacting via effective potentials which are attractive at the short range and repulsive at the long range have long been raising considerable attention because such an instance provides a simple mechanism leading to pattern formation even for isotropic interactions. If the competition between attraction and repulsion is strong enough, the gas-liq. phase transition is suppressed, and replaced by the formation of mesophases, i.e., inhomogeneous phases displaying periodic d. modulations whose length, although being larger than the particle size, cannot nevertheless be considered macroscopic. We describe a fully numerical implementation of d.-functional theory in three dimensions, tailored to periodic phases. The results for the equil. phase diagram of the model are compared with those already obtained in previous investigations for the present system as well as for other systems which form mesophases. The phase diagram which we find shows a strong similarity with that of block copolymer melts, in which self-assembly also results from frustration of a macroscopic phase sepn. As the inhomogeneous region is swept by increasing the d. from the low-d. side, one encounters clusters, bars, lamellae, inverted bars, and inverted clusters. Moreover, a bicontinuous gyroid phase consisting of two intertwined percolating networks is predicted in a narrow domain between the bar and lamellar phases.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVGnsbbK&md5=9535383902591070ea5d6a4ddb579e2a
    11. 11
      Foffi, G.; De Michele, C.; Sciortino, F.; Tartaglia, P. Scaling of dynamics with the range of interaction in short-range attractive colloids. Phys. Rev. Lett. 2005, 94, 078301,  DOI: 10.1103/PhysRevLett.94.078301
      [Crossref], [PubMed], [CAS], Google Scholar
      11
      Scaling of Dynamics with the Range of Interaction in Short-Range Attractive Colloids
      Foffi, G.; De Michele, C.; Sciortino, F.; Tartaglia, P.
      Physical Review Letters (2005), 94 (7), 078301/1-078301/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      We numerically study the dependence of the dynamics on the range of interaction Δ for the short-range square well potential. We find that, for small Δ, dynamics scale exactly in the same way as thermodn., both for Newtonian and Brownian microscopic dynamics. For interaction ranges from a few percent down to the Baxter limit, the relative location of the attractive-glass line and the liq.-gas line does not depend on Δ. This proves that, in this class of potentials, disordered arrested states (gels) can be generated only as a result of a kinetically arrested phase sepn.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhslarsrc%253D&md5=ddae05a959b88257944ecab0188a0630
    12. 12
      Zaccarelli, E. Colloidal gels: equilibrium and non-equilibrium routes. J. Phys.: Condens. Matter 2007, 19, 323101,  DOI: 10.1088/0953-8984/19/32/323101
      [Crossref], [CAS], Google Scholar
      12
      Colloidal gels: equilibrium and non-equilibrium routes
      Zaccarelli, Emanuela
      Journal of Physics: Condensed Matter (2007), 19 (32), 323101/1-323101/50CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)
      A review. We attempt a classification of different colloidal gels based on colloid-colloid interactions. We discriminate primarily between non-equil. and equil. routes to gelation, the former case being slaved to thermodn. phase sepn. while the latter is individuated in the framework of competing interactions and of patchy colloids. Emphasis is put on recent numerical simulations of colloidal gelation and their connection to expts. Finally, we underline typical signatures of different gel types, to be looked at, in more detail, in expts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVehsbzF&md5=83d8accf5c2d21da133781fadacd5d27
    13. 13
      Bera, M. K.; Qiao, B. F.; Seifert, S.; Burton-Pye, B. P.; Olvela de la Cruz, M.; Antonio, M. R. Aggregation of heteropolyanions in aqueous solutions exhibiting short-range attractions and long-range repulsions. J. Phys. Chem. C 2016, 120, 1317– 1327,  DOI: 10.1021/acs.jpcc.5b10609
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      13
      Aggregation of Heteropolyanions in Aqueous Solutions Exhibiting Short-Range Attractions and Long-Range Repulsions
      Bera, Mrinal K.; Qiao, Baofu; Seifert, Soenke; Burton-Pye, Benjamin P.; Olvera de la Cruz, Monica; Antonio, Mark R.
      Journal of Physical Chemistry C (2016), 120 (2), 1317-1327CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Charged colloids and proteins in aq. solns. interact via short-range attractions and long-range repulsions (SALR) and exhibit complex structural phases. These include homogeneously dispersed monomers, percolated monomers, clusters, and percolated clusters. We report the structural architectures of simple charged systems in the form of spherical, Keggin-type heteropolyanions (HPAs) by small-angle X-ray scattering (SAXS) and mol. dynamics (MD) simulations. Structure factors obtained from the SAXS measurements show that the HPAs interact via SALR. Concn. and temp. dependences of the structure factors for HPAs with -3e (e is the charge of an electron) charge are consistent with a mixt. of nonassocd. monomers and assocd. randomly percolated monomers, whereas those for HPAs with -4e and -5e charges exhibit only nonassocd. monomers in aq. solns. Our expts. show that the increase in magnitude of the charge of the HPAs increases their repulsive interactions and inhibits their aggregation in aq. solns. MD simulations were done to reveal the atomistic scale origins of SALR between HPAs. The short-range attractions result from water or proton-mediated hydrogen bonds between neighboring HPAs, whereas the long-range repulsions are due to the distributions of ions surrounding the HPAs.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVejtL%252FK&md5=64525b4529c3ca671d46a270174efdb3
    14. 14
      Poon, W. C. K.; Haw, M. D. Mesoscopic structure formation in colloidal aggregation and gelation. Adv. Colloid Interface Sci. 1997, 73, 71– 126,  DOI: 10.1016/S0001-8686(97)90003-8
      [Crossref], [CAS], Google Scholar
      14
      Mesoscopic structure formation in colloidal aggregation and gelation
      Poon, W. C. K.; Haw, M. D.
      Advances in Colloid and Interface Science (1997), 73 (), 71-126CODEN: ACISB9; ISSN:0001-8686. (Elsevier Science B.V.)
      A review with 117 refs. on recent small-angle light scattering expts. that have revealed diffusively aggregating spherical particles develop structure on a mesoscopic length scale (∼ tens of particles). The mesoscopic structural length scale persists even when the aggregation proceeds to the formation of a space-spanning network (a gel). The authors review the techniques of small-angle light scattering, survey the exptl. evidence for mesoscopic structure formation, discuss attempts at understanding these exptl. observations by computer simulation of irreversible and reversible diffusion-limited cluster aggregation (DLCA), and propose a coherent picture for the understanding of non-equil. aggregation in the context of phase transitions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXotVChtLs%253D&md5=1460e50c5c4841470cc65bf6a49d2532
    15. 15
      Lu, P. J.; Zaccarelli, E.; Ciulla, F.; Schofield, A. B.; Sciortino, F.; Weitz, D. A. Gelation of particles with short-range attraction. Nature 2008, 453, 499– 505,  DOI: 10.1038/nature06931
      [Crossref], [PubMed], [CAS], Google Scholar
      15
      Gelation of particles with short-range attraction
      Lu, Peter J.; Zaccarelli, Emanuela; Ciulla, Fabio; Schofield, Andrew B.; Sciortino, Francesco; Weitz, David A.
      Nature (London, United Kingdom) (2008), 453 (7194), 499-503CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      Nanoscale or colloidal particles are important in many realms of science and technol. They can dramatically change the properties of materials, imparting solid-like behavior to a wide variety of complex fluids. This behavior arises when particles aggregate to form mesoscopic clusters and networks. The essential component leading to aggregation is an interparticle attraction, which can be generated by many phys. and chem. mechanisms. In the limit of irreversible aggregation, infinitely strong interparticle bonds lead to diffusion-limited cluster aggregation (DLCA). This is understood as a purely kinetic phenomenon that can form solid-like gels at arbitrarily low particle vol. fraction. Far more important technol. are systems with weaker attractions, where gel formation requires higher vol. fractions. Numerous scenarios for gelation have been proposed, including DLCA, kinetic or dynamic arrest, phase sepn., percolation and jamming. No consensus has emerged and, despite its ubiquity and significance, gelation is far from understood-even the location of the gelation phase boundary is not agreed on. Here we report expts. showing that gelation of spherical particles with isotropic, short-range attractions is initiated by spinodal decompn.; this thermodn. instability triggers the formation of d. fluctuations, leading to spanning clusters that dynamically arrest to create a gel. This simple picture of gelation does not depend on microscopic system-specific details, and should thus apply broadly to any particle system with short-range attractions. Our results suggest that gelation-often considered a purely kinetic phenomenon-is in fact a direct consequence of equil. liq.-gas phase sepn. Without exception, we observe gelation in all of our samples predicted by theory and simulation to phase-sep.; this suggests that it is phase sepn., not percolation, that corresponds to gelation in models for attractive spheres.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmt1Ortb4%253D&md5=245f6c35480169f4ea03cb2ff3ae6f92
    16. 16
      Kim, S. A.; Jeong, K. J.; Yethiraj, A.; Mahanthappa, M. K. Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity. Proc. Natl. Acad. Sci. U. S. A. 2017, 114, 4072– 4077,  DOI: 10.1073/pnas.1701608114
      [Crossref], [PubMed], [CAS], Google Scholar
      16
      Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity
      Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun; Mahanthappa, Mahesh K.
      Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (16), 4072-4077CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Supramol. self-assembly enables access to designer soft materials that typically exhibit high-symmetry packing arrangements, which optimize the interactions between their mesoscopic constituents over multiple length scales. The authors report the discovery of an ionic small mol. surfactant that undergoes H2O-induced self-assembly into spherical micelles, which pack into a previously unknown, low-symmetry lyotropic liq. cryst. Frank-Kasper σ phase. Small-angle x-ray scattering studies reveal that this complex phase is characterized by a gigantic tetragonal unit cell, in which 30 sub-2-nm quasispherical micelles of 5 discrete sizes are arranged into a tetrahedral close packing, with exceptional translational order over length scales exceeding 100 nm. Varying the relative concns. of H2O and surfactant in these lyotropic phases also triggers formation of the related Frank-Kasper A15 sphere packing as well as a common bcc. structure. Mol. dynamics simulations reveal that the symmetry breaking that drives the formation of the σ and A15 phases arises from minimization of local deviations in surfactant headgroup and counterion solvation to maintain a nearly spherical counterion atm. around each micelle, while maximizing counterion-mediated electrostatic cohesion among the ensemble of charged particles.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlsV2ntr8%253D&md5=793e22c1a4dcd276a815bb1ab3e4f973
    17. 17
      Bauer, C.; Bauduin, P.; Dufreche, J. F.; Zemb, T.; Diat, O. Liquid/liquid metal extraction: Phase diagram topology resulting from molecular interactions between extractant, ion, oil and water. Eur. Phys. J.: Spec. Top. 2012, 213, 225– 241,  DOI: 10.1140/epjst/e2012-01673-4
      [Crossref], [CAS], Google Scholar
      17
      Liquid/liquid metal extraction: phase diagram topology resulting from molecular interactions between extractant, ion, oil and water
      Bauer, C.; Bauduin, P.; Dufreche, J. F.; Zemb, T.; Diat, O.
      European Physical Journal: Special Topics (2012), 213 (), 225-241CODEN: EPJSAC; ISSN:1951-6401. (EDP Sciences)
      A review. We consider the class of surfactants called "extractants" since they specifically interact with some cations and are used in liq.-liq. sepn. processes. We review here features of water-poor reverse micelles in water/oil/ extractant systems as detd. by combined structural studies including small angle scattering techniques on abs. scale. Origins of instabilities, liq.-liq. sepn. as well as emulsification failure are detected. Phase diagrams contain the same multi-phase domains as classical microemulsions, but special unusual features appear due to the high spontaneous curvature directed towards the polar cores of aggregates as well as rigidity of the film made by extg. mols.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmtFajsbo%253D&md5=ccc33a717df264901b7e106e0c3b8a86
    18. 18
      Erlinger, C.; Gazeau, D.; Zemb, T.; Madic, C.; Lefrancois, L.; Hebrant, M.; Tondre, C. Effect of nitric acid extraction on phase behavior, microstructure and interactions between primary aggregates in the system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/water: A phase analysis and small angle X-ray scattering (SAXS) characterisation study. Solvent Extr. Ion Exch. 1998, 16, 707– 738,  DOI: 10.1080/07366299808934549
      [Crossref], [CAS], Google Scholar
      18
      Effect of nitric acid extraction on phase behavior, microstructure and interactions between primary aggregates in the system dimethyldibutyltetradecylmalonamide (DMDBTDMA) / n-DODECANE / water: a phase analysis and small angle x-ray scattering (SAXS) characterization study
      Erlinger, C.; Gazeau, D.; Zemb, T.; Madic, C.; Lefrancois, L.; Hebrant, M.; Tondre, C.
      Solvent Extraction and Ion Exchange (1998), 16 (3), 707-738CODEN: SEIEDB; ISSN:0736-6299. (Marcel Dekker, Inc.)
      In some conditions the formation of a 3rd phase is obsd. with dimethyldibutyltetradecylmalonamide (DMDBTDMA), a potential extractant used in the DIAMEX process. The authors have studied the phase behavior of the system dimethyldibutyltetradecylmalonamide (DMDBTDMA)/n-dodecane/H2O/HNO3, in the acceptable concn. limits for the DIAMEX process. The compn. of the different phases and the surface properties of the 2-phase system were measured. The max. incorporation of H2O in the 2-phase system corresponds to ∼0.75 H2O mol. per DMDBTDMA mol., whereas at satn. in the 3-phase system it is ∼1.25 H2O mols. per extractant mol. At 0.22M and 0.46M DMDBTDMA concns., the transitions from the 2-phase to the 3-phase domain takes place in a region where the [HNO3]extr./ [DMDBTDMA]init ratio is ∼0.8. The 2-phase to 3-phase transition occurs when the H2O/acid ratio in the org. phase approaches 1. A sharp change of slope of the interfacial tension vs. extractant concn. is attributed to aggregate formation in the org. phase. Assuming a neutral form of the mol. in the absence of HNO3, the interfacial area is in this case 112 Å2. The microstructure of mixts. DMDBTDMA, H2O and HNO3 in n-dodecane also was studied using small angle x-ray scattering (SAXS) to det. the size and shape of the primary aggregates of DMDBTDMA as well as the interactions between them in the midst of the org. phase. The complexation of HNO3 at const. diamide concn., strongly favors attractive interactions between the aggregates. On the contrary, the increase of the aggregates vol. fraction, at a const. ratio of HNO3 and diamide concns. to control the attractions, force the aggregates to repel each other, and repulsive hard sphere interactions are pointed out. The information obtained in the present work from the SAXS study, and from the interfacial tension measurements, appear to be consistent since they both evidence the onset of an aggregation process at the approach of the org. phase splitting. The simple short range attractive potential defined by Baxter, describing a complex fluid of sticky spheres, is self-consistent to model the exptl. data. In the org. phase, the extractant mols. of DMDBTDMA self-assemble into small reversed micelles with a polar core of ∼6-7 Å radius when the org. phase is contacted with an aq. phase (acidic or not). Within the org. phase, the aggregates are submitted to 3 major interactions: (i) the destabilizing Van der Waals interaction and (ii) the stabilizing hard sphere repulsion and (iii) a repulsive steric contribution from the remaining aliph. chains of the extractant mols. The observable macroscopic effect which is the phase split of the org. phase with 3rd phase formation is the macroscopic translation of the effect of these 3 interactions acting at the microscopic level.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXjtlSgsrw%253D&md5=bd4424e00f0a26317d0f6047c06b0751
    19. 19
      Testard, F.; Zemb, T.; Bauduin, P.; Berthon, L. In Ion Exchange and Solvent Extraction: A Series of Advances; Moyer, B. A., Ed.; CRC Press: Boca Raton, FL, 2010; Vol. 19, pp 381– 428.
      Google Scholar
      There is no corresponding record for this reference.
    20. 20
      Baxter, R. J. Percus-Yevick equation for hard spheres with surface adhesion. J. Chem. Phys. 1968, 49, 2770– 2774,  DOI: 10.1063/1.1670482
      [Crossref], [CAS], Google Scholar
      20
      Percus-Yevick equation of hard spheres with surface adhesion
      Baxter, R. J.
      Journal of Chemical Physics (1968), 49 (6), 2770-4CODEN: JCPSA6; ISSN:0021-9606.
      It is shown that the Percus-Yevick approxn. can be solved anal. for a potential consisting of a hard core together with a rectangular attractive well, provided that a certain limit is taken in which the range of the well becomes zero and its depth infinite. The results show a first-order phase transition which appears to be of the type observed numerically for the Lennard-Jones 12-6 potential.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1cXkvF2lsbs%253D&md5=bd0c0daccd5e0b3eef20b91c626e1c4e
    21. 21
      Schulz, W. W.; Navratil, J. D. Science and Technology of Tributyl Phosphate; CRC Press: Boca Raton, FL, 1984.
      Google Scholar
      There is no corresponding record for this reference.
    22. 22
      Osseo-Asare, K. Aggregation, reversed micelles, and microemulsions in liquid-liquid extraction: the tri-n-butyl phosphate-diluent-water-electrolyte system. Adv. Colloid Interface Sci. 1991, 37, 123– 173,  DOI: 10.1016/0001-8686(91)80041-H
      [Crossref], [CAS], Google Scholar
      22
      Aggregation, reversed micelles, and microemulsions in liquid-liquid extraction: the tri-n-butyl phosphate-diluent-water-electrolyte system
      Osseo-Asare, K.
      Advances in Colloid and Interface Science (1991), 37 (1-2), 123-73CODEN: ACISB9; ISSN:0001-8686.
      The exptl. evidence (e.g. distribution, viscosity, cond., and mol. wt. measurements) suggesting the presence of aggregates in TBP exts. is reviewed. 244 Refs.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XivVGrsw%253D%253D&md5=f7d934dae4171cd1fcb8ab302d8e8f63
    23. 23
      Diss, R.; Wipff, G. Lanthanide cation extraction by malonamide ligands: from liquid-liquid interfaces to microemulsions. A molecular dynamics study. Phys. Chem. Chem. Phys. 2005, 7, 264– 272,  DOI: 10.1039/B410137E
      [Crossref], [PubMed], [CAS], Google Scholar
      23
      Lanthanide cation extraction by malonamide ligands: from liquid-liquid interfaces to microemulsions. A molecular dynamics study
      Diss, Romain; Wipff, Georges
      Physical Chemistry Chemical Physics (2005), 7 (2), 264-272CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      According to mol. dynamics simulations, uncomplexed malonamide ligands L and their neutral Eu(NO3)3L2 or charged EuL43+ complexes are surface active and adsorb at a water-"oil" interface, where "oil" is modeled by chloroform. Aq. solvation at the interface is found to induce a trans to gauche rearrangement of the carbonyl groups, i.e. to preorganize the chelating L ligands for complexation. The interface also induces a larger proportion of extended amphiphilic forms, of EE-gauche type. The effect of increased oil/water ratio is also investigated. It shown that the system evolves from a well-defined interface between immiscible phases to water-in-oil cylindrical micelles and micro-droplets, onto which L ligands and the lanthanide complexes adsorb, while other ligands are extd. in org. phase. Two electrostatic models of the complexes are compared and, in no case is the neutral or charged complex fully extd. to the org. phase. These features allow us to better understand synergistic and solvation effects in the assisted liq.-liq. extn. of lanthanide or actinide cations.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFeisLbI&md5=4c0e22d7cf26d97c2db9dabba6b8e695
    24. 24
      Jensen, M. P.; Yaita, T.; Chiarizia, R. Reverse-micelle formation in the partitioning of trivalent f-element cations by biphasic systems containing a tetraalkyldiglycolamide. Langmuir 2007, 23, 4765– 4774,  DOI: 10.1021/la0631926
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      24
      Reverse-Micelle Formation in the Partitioning of Trivalent f-Element Cations by Biphasic Systems Containing a Tetraalkyldiglycolamide
      Jensen, Mark P.; Yaita, Tsuyoshi; Chiarizia, Renato
      Langmuir (2007), 23 (9), 4765-4774CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      The conditions for reverse-micelle formation were studied for solns. of tetra-n-octyldiglycolamide (TODGA) in alkane diluents equilibrated with aq. solns. of nitric or hydrochloric acids in the presence and absence of Nd3+. Small-angle neutron scattering, vapor-pressure osmometry, and tensiometry are all consistent with the partial formation of TODGA dimers at the lowest acidities, transitioning to a polydisperse mixt. contg. TODGA monomers, dimers, and small reverse-micelles of TODGA tetramers at aq. nitric acid acidities of 0.7 M or higher in the absence of Nd. Application of the Baxter model to the samples contg. 0.005-0.015 M Nd reveals the persistence of tetrameric TODGA reverse-micelles with significant interparticle attraction between the polar cores of the micelles that increases with increasing org. phase concns. of acid or Nd. The exptl. findings suggest that the peculiar behavior of TODGA with respect to the extn. of trivalent lanthanide and actinide cations arises from the affinity of these metal cations for the preformed TODGA reverse-micelle tetramers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjsV2lsLY%253D&md5=6066bdbe17cf24a3d09fd7af50285952
    25. 25
      Guo, F. Q.; Li, H. F.; Zhang, Z. F.; Meng, S. L.; Li, D. Q. Reversed micelle formation in a model liquid-liquid extraction system. J. Colloid Interface Sci. 2008, 322, 605– 610,  DOI: 10.1016/j.jcis.2008.03.011
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    26. 26
      Chiarizia, R.; Briand, A.; Jensen, M. P.; Thiyagarajan, P. SANS study of reverse micelles formed upon the extraction of inorganic acids by TBP in n-octane. Solvent Extr. Ion Exch. 2008, 26, 333– 359,  DOI: 10.1080/07366290802182394
      [Crossref], [CAS], Google Scholar
      26
      Sans Study of Reverse Micelles Formed upon the Extraction of Inorganic Acids by TBP in n-Octane
      Chiarizia, R.; Briand, A.; Jensen, M. P.; Thiyagarajan, P.
      Solvent Extraction and Ion Exchange (2008), 26 (4), 333-359CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
      Small-angle neutron scattering (SANS) data for n-octane solns. of TBP loaded with progressively larger amts. of HNO3, HClO4, H2SO4, and H3PO4 up to and beyond the LOC (limiting org. concn. of acid) condition, were interpreted using the Baxter model for hard spheres with surface adhesion. The coherent picture of the behavior of the TBP solns. derived from the SANS investigation discussed in this paper confirmed our recently developed model for third phase formation. This model analyses the features of the scattering data in the low Q region as arising from van der Waals interactions between the polar cores of reverse micelles. Our SANS data indicated that the TBP micelles swell when acid and water are extd. into their polar core. The swollen micelles have crit. diams. ranging from 15 to 22 Å, and polar core diams. between 10 and 15 Å, depending on the specific system. At the resp. LOC conditions, the TBP wt.-av. aggregation nos. are ∼4 for HClO4, ∼6 for H2SO4, ∼7 for HCl, and ∼10 for H3PO4. The comparison between the behavior of HNO3, a non-third phase forming acid, and the other acids provided an explanation of the effect of the water mols. present in the polar core of the micelles on third phase formation. The thickness of the lipophilic shell of the micelles indicated that the Bu groups of TBP lie at an angle of ∼25 degrees relative to a plane tangent to the micellar core. The crit. energy of intermicellar attraction, U(r), was about -2 kBT for all the acids investigated. This value is the same as that reported in our previous publications on the extn. of metal nitrates by TBP, confirming that the same mechanism and energetics are operative in the formation of a third phase, independent of whether the chem. species extd. are metal nitrate salts or inorg. acids.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosFCqsrs%253D&md5=05b635c868df9fa0745bf40165657a3b
    27. 27
      Ganguly, R.; Sharma, J. N.; Choudhury, N. TODGA based w/o microemulsion in dodecane: An insight into the micellar aggregation characteristics by dynamic light scattering and viscometry. J. Colloid Interface Sci. 2011, 355, 458– 463,  DOI: 10.1016/j.jcis.2010.12.039
      [Crossref], [PubMed], [CAS], Google Scholar
      27
      TODGA based w/o microemulsion in dodecane: An insight into the micellar aggregation characteristics by dynamic light scattering and viscometry
      Ganguly, Rajib; Sharma, Joti N.; Choudhury, Niharendu
      Journal of Colloid and Interface Science (2011), 355 (2), 458-463CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
      N,N,N',N'-tetraoctyl diglycolamide abbreviated as TODGA, is one of the most promising extractant for actinide partitioning from high level nuclear waste. It forms reverse micelles in non polar solvents on equilibration with aq. HNO3 solns. This reverse micellar system undergoes phase sepn. into dil. and concd. reverse micellar solns. at high aq. acid concn. Small angle neutron scattering (SANS) studies reported in the literature explained this phenomenon based on gas-liq. type phase transition in the framework of Baxter adhesive hard sphere theory in the presence of a strong inter-micellar attractive interaction. The present investigation attempts to throw further light on this system by carrying out systematic dynamic light scattering (DLS) and viscometry studies, and their modeling on the TODGA reverse micellar solns. in the dodecane medium. The variation of the diffusion coeff. with the micellar vol. fraction obsd. from the DLS studies is suggestive of the presence of an attractive interaction between the TODGA reverse micelles, which weakens at the high micellar vol. fraction due to the increased dominance of the excluded vol. effect. It is suggested that this weakened interaction is responsible for the absence of phase sepn. in this system at high TODGA concn. The results thus highlight the importance of the presence of an attractive interaction between the TODGA micelles in detg. the obsd. phase sepn. in the TODGA reverse micellar systems. The modeling of the DLS and viscosity data, however, suggest that the characteristic stickiness parameter of this system could be smaller than the crit. value required for inducing a gas-liq. type phase transition.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFartrw%253D&md5=ae30de7c865e456632311e5dbc425c84
    28. 28
      Ellis, R. J.; Meridiano, Y.; Chiarizia, R.; Berthon, L.; Muller, J.; Couston, L.; Antonio, M. R. Periodic behavior of lanthanide coordination within reverse micelles. Chem. - Eur. J. 2013, 19, 2663– 2675,  DOI: 10.1002/chem.201202880
      [Crossref], [PubMed], [CAS], Google Scholar
      28
      Periodic Behavior of Lanthanide Coordination within Reverse Micelles
      Ellis, Ross J.; Meridiano, Yannick; Chiarizia, Renato; Berthon, Laurence; Muller, Julie; Couston, Laurent; Antonio, Mark R.
      Chemistry - A European Journal (2013), 19 (8), 2663-2675CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Trends in lanthanide(III) (LnIII) coordination were studied within nanoconfined solvation environments. LnIII ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aq. phases contg. nitrate and LnIII; both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the org. phase is acidic or neutral, resp. Structural aspects of the LnIII complex formation and the RM morphol. were obtained using XAS (x-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The LnIII coordination environments were detd. through use of L3-edge XANES (x-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chem. across the period. Hydration nos. for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the Ln-O interat. distances and no. of coordinating O atoms for the extd. complexes of LnIII in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the no. of coordinating O atoms decrease from 9 O for early lanthanides to 8 O for the late ones-a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to LnIII. The coordination chem. of lanthanides within nanoconfined environments is neither equiv. to the solid nor bulk soln. behaviors. Herein the authors address at.- and mesoscale phenomena in the under-explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chem. of growing importance in technologies as diverse as nanosynthesis and sepns. science.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkvFGmtw%253D%253D&md5=e7db983a97b06d96816b8a2f37a10cb7
    29. 29
      Guilbaud, P.; Zemb, T. Depletion of water-in-oil aggregates from poor solvents: Transition from weak aggregates towards reverse micelles. Curr. Opin. Colloid Interface Sci. 2015, 20, 71– 77,  DOI: 10.1016/j.cocis.2014.11.011
      [Crossref], [CAS], Google Scholar
      29
      Depletion of water-in-oil aggregates from poor solvents: Transition from weak aggregates towards reverse micelles
      Guilbaud, Philippe; Zemb, Thomas
      Current Opinion in Colloid & Interface Science (2015), 20 (1), 71-77CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
      We assemble here all available descriptions of oil-sol. surfactant aggregates with or without solutes, assumed to be located in the polar cores of reverse micelles. The presence of solutes is crucial for the formation of a well-defined interface, thus inducing a transition from a loose reverse aggregate into a more structured micelle. This transition can be followed by the concomitant decrease of the "crit. aggregation concn." (c.a.c.). The less organized state as reverse aggregates is predominant when no "nucleating" species such as water, salts, or acids are present. One way to understand this weak aggregation is a depletion driving to aggregates as pseudo-phases introduced by Tanford. Analogs coexisting pseudo-phases seem to exist: weak oil-in-water (o/w) aggregation with the so-called surfactant-free microemulsions, contg. loose aggregates, and re-entrant phase diagrams presenting a lowest aggregation concn. (l.a.c.), as described in the seventies.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitV2ms7%252FM&md5=5f6b62da69c136bd97b7ea97106414f1
    30. 30
      Bley, M.; Siboulet, B.; Karmakar, A.; Zemb, T.; Dufreche, J. F. A predictive model of reverse micelles solubilizing water for solvent extraction. J. Colloid Interface Sci. 2016, 479, 106– 114,  DOI: 10.1016/j.jcis.2016.06.044
      [Crossref], [PubMed], [CAS], Google Scholar
      30
      A predictive model of reverse micelles solubilizing water for solvent extraction
      Bley, Michael; Siboulet, Bertrand; Karmakar, Anwesa; Zemb, Thomas; Dufreche, Jean-Francois
      Journal of Colloid and Interface Science (2016), 479 (), 106-114CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
      Herein, a minimal model for the common case of W/O solubilization of badly sol. compds. present in an excess phase by reverse micellar aggregates in chem. equil. with its single compds. is introduced. A simple model of such liq.-liq. extns. is crucial for obtaining predictive parameter for the modeling of nuclear waste management and hydrometallurgic recycling strategies. The std. Gibbs free energy of aggregation and the concn. of the corresponding aggregate is calcd. within a multiple-equil. approach for a set of aggregate compns. of solute and amphiphilic extractant mols. This minimal model provides potential surfaces estg. the stability of different aggregate compns. with 6.2 kJ mol-1 as a generalized bending const. The complete concns. of free and aggregated extractant species as well as the favored aggregation nos., the polydispersity, the activity of the org. solvent, and the crit. concns. are captured by this thermodn. model. An increase of the apparent crit. micelle concn. for an increasing solute content in the aq. phase is detected by this method.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtFWjsbbM&md5=eb3e9956036d14d278d39f2bf58e47b9
    31. 31
      Diamant, H.; Andelman, D. Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics. Curr. Opin. Colloid Interface Sci. 2016, 22, 94– 98,  DOI: 10.1016/j.cocis.2016.03.004
      [Crossref], [CAS], Google Scholar
      31
      Free energy approach to micellization and aggregation: Equilibrium, metastability, and kinetics
      Diamant, Haim; Andelman, David
      Current Opinion in Colloid & Interface Science (2016), 22 (), 94-98CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
      We review a recently developed micellization theory, which is based on a free-energy approach and offers several advantages over the conventional one, based on mass action and rate equations. As all the results are derived from a single free-energy expression, one can adapt the theory to different scenarios by merely modifying the initial expression. We present results concerning various features of micellization out of equil., such as the existence of metastable aggregates (premicelles), micellar nucleation and growth, transient aggregates, and final relaxation toward equil. Several predictions that await exptl. investigation are discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmvVGjsrw%253D&md5=7abec1b80cd34472c5bf8b40d506f306
    32. 32
      Gao, S.; Sun, T. X.; Chen, Q. D.; Shen, X. H. Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology. Radiochim. Acta 2016, 104, 457– 469,  DOI: 10.1515/ract-2015-2538
      [Crossref], [CAS], Google Scholar
      32
      Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology
      Gao, Song; Sun, Taoxiang; Chen, Qingde; Shen, Xinghai
      Radiochimica Acta (2016), 104 (7), 457-469CODEN: RAACAP; ISSN:0033-8230. (Oldenbourg Wissenschaftsverlag GmbH)
      The reversed micelles formed in solvent extn. of thorium(IV) by bis(2-ethylhexyl) phosphoric acid (HDEHP) in n-heptane were studied. IR spectra, dynamic/static light scattering and zero shear viscosity measurements indicated that thorium complexes formed rodlike reversed micelles, and both the size of aggregates and the viscosity of the org. phase increased with the increasing loadage of thorium(IV). The entanglement of reversed micelles resulted in their transformation to wormlike reversed micelles, inducing the very high viscosity of the org. phase. The structural compn. of thorium complexes was proposed to be Th(DEHP)3(NO3) according to the results of log -log plot and job method anal. Furthermore, mol. modeling was employed to clarify the structures of reversed micelles as well as the state of water inside. It was found that the complexes linked together via hydrogen bonding and van der Waals forces and that the existence of NO3- and H2O improved the stability of reversed micelles.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtF2nsbnF&md5=002c343aaf5ca7bdda84e54f22d2c8b2
    33. 33
      Chen, Y. S.; Duvail, M.; Guilbaud, P.; Dufreche, J. F. Stability of reverse micelles in rare-earth separation: a chemical model based on a molecular approach. Phys. Chem. Chem. Phys. 2017, 19, 7094– 7100,  DOI: 10.1039/C6CP07843E
      [Crossref], [PubMed], [CAS], Google Scholar
      33
      Stability of reverse micelles in rare-earth separation: a chemical model based on a molecular approach
      Chen, Yushu; Duvail, Magali; Guilbaud, Philippe; Dufreche, Jean-Francois
      Physical Chemistry Chemical Physics (2017), 19 (10), 7094-7100CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Mol. complexes formed in the org. phase during solvent extn. may self-assemble as reverse micelles, and therefore induce a supramol. organization of this phase. In most of the cases, water mols. play an essential role in the organization of this non polar medium. The aim of this work is to investigate the speciation of the aggregates formed in the org. phase during solvent extn., and esp. to assess their stability as a function of the no. of water mols. included in their polar core. We have focused on malonamide extractants that have already been investigated exptl. Different stoichiometries of reverse micelles in the org. phase have been studied by means of classical mol. dynamics simulations. Furthermore, umbrella-sampling mol. dynamics simulations have been used to calc. the equil. const. (K°) representing the assocn./dissocn. pathways of water mols. in the aggregates and the corresponding reaction free energies (ΔrG°).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXisVGhsbk%253D&md5=79b866ab984766369b7e9cfd6188db4b
    34. 34
      Tonova, K.; Lazarova, Z. Reversed micelle solvents as tools of enzyme purification and enzyme-catalyzed conversion. Biotechnol. Adv. 2008, 26, 516– 532,  DOI: 10.1016/j.biotechadv.2008.06.002
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    35. 35
      Ballesteros-Gomez, A.; Sicilia, M. D.; Rubio, S. Supramolecular solvents in the extraction of organic compounds. A review. Anal. Chim. Acta 2010, 677, 108– 130,  DOI: 10.1016/j.aca.2010.07.027
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    36. 36
      Poirot, R.; Le Goff, X.; Diat, O.; Bourgeois, D.; Meyer, D. Metal recognition driven by weak interactions: A case study in solvent extraction. ChemPhysChem 2016, 17, 2112– 2117,  DOI: 10.1002/cphc.201600305
      [Crossref], [PubMed], [CAS], Google Scholar
      36
      Metal Recognition Driven by Weak Interactions: A Case Study in Solvent Extraction
      Poirot, Remi; Le Goff, Xavier; Diat, Olivier; Bourgeois, Damien; Meyer, Daniel
      ChemPhysChem (2016), 17 (14), 2112-2117CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Tuning the affinity of a medium for a given metallic cation with the sole modification of weak interactions is a challenge for mol. recognition. Solvent extn. is a key technique employed in the recovery and purifn. of valuable metals, and it is facing an increased complexity of metal fluxes to deal with. The selectivity of such processes generally relies on the use of specific ligands, designed after their coordination chem. In the present study, we illustrate the possibility to employ the sole control of weak interactions to achieve the selective extn. of PdII over NdIII: the control over selectivity is obtained by tuning the self-assembly of the org. phase. A model is proposed, after detailed exptl. anal. of mol. (XRD, NMR) and supra-mol. (SAXS) features of the org. phases. We thus demonstrate that PdII extn. is driven by metal coordination, whereas NdIII extn. requires aggregation of the extractant in addn. to metal coordination. These results are of general interest for the applications which rely on the stabilization of metals in org. phases.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xos1ansL4%253D&md5=925fefafc8144d8ee4f5fa953a96780a
    37. 37
      Prevost, S.; Gradzielski, M.; Zemb, T. Self-assembly, phase behaviour and structural behaviour as observed by scattering for classical and non-classical microemulsions. Adv. Colloid Interface Sci. 2017, 247, 374– 396,  DOI: 10.1016/j.cis.2017.07.022
      [Crossref], [PubMed], [CAS], Google Scholar
      37
      Self-assembly, phase behaviour and structural behaviour as observed by scattering for classical and non-classical microemulsions
      Prevost, Sylvain; Gradzielski, Michael; Zemb, Thomas
      Advances in Colloid and Interface Science (2017), 247 (), 374-396CODEN: ACISB9; ISSN:0001-8686. (Elsevier B.V.)
      A review. In this review, we discuss the conditions for forming microemulsions, systems which are thermodynamically stable mixts. of oil and water made stable by the presence of an interfacial film contg. surface active mols. There are several types of microemulsions, depending largely on the stiffness of the amphiphilic monolayer that separates the oily and the aq. micro-domain. We first discuss and compare the phase behavior of these different types, starting from the classical microemulsion made from a flexible surfactant film but then also moving on to less classical situations: this occurs when the interfacial film is stiff or when microemulsions are formed in the absence of a classical surfactant. In the second part, we relate these different microemulsion types to the structural features as can be detd. via different methodologies by small angle scattering (SAS). Using abs. scaling, general theorems as well as fitting under constraints or to pre-supposed shapes in real space or correlation functions in reciprocal space allows to classify all microemulsions into classical flexible, rigid or ultra-flexible microemulsions with either globular, connected cylinder of locally flat interfaces, with the corresponding cond. and phase stability properties.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Ols77I&md5=bf7e5bcfaf544b8dfa2af0030375e23e
    38. 38
      Moyer, B. A., Ed. Ion Exchange and Solvent Extraction: A Series of Advances; CRC Press: Boca Raton, FL, 2010; p 19.
      Google Scholar
      There is no corresponding record for this reference.
    39. 39
      Ellis, R. J. Critical exponents for solvent extraction resolved using SAXS. J. Phys. Chem. B 2014, 118, 315– 322,  DOI: 10.1021/jp408078v
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      39
      Critical Exponents for Solvent Extraction Resolved Using SAXS
      Ellis, Ross J.
      Journal of Physical Chemistry B (2014), 118 (1), 315-322CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
      The solvent extn. of an ionizable solute (H3PO4) from water into a water-in-oil microemulsion, and subsequent org. phase splitting (known as third phase formation), has been recast as a crit. phenomenon by linking system structure to solute concn. via a crit. exponent. The transuranic extn. (TRUEX) system was investigated by extg. increasing concns. of H3PO4 into a microemulsion - consisting of two extractant amphiphiles (CMPO and TBP) and water in n-dodecane - and taking small-angle X-ray scattering (SAXS) measurements from the resulting solns. The H3PO4 concn. at which phase splitting occurred was defined as the crit. concn. (XC), and this was related to the precrit. concns. (X) by the reduced parameter ε = (XC - X)/XC. The scattering intensity at the zero angle I(0), relating to the interaction between reverse micellar aggregates, conformed to the relation I(0) = I0ε-γ, with crit. exponent γ = 2.20. To check γ, SAXS measurements were taken from the org. phase in situ with variable temp. through the point at which third phase formation initiates (the crit. temp.), giving I(0) = I0t-γ, where t = (T - TC)/TC and TC and T are the crit. and precrit. temps., with crit. exponent γ = 2.55. These γ values suggest third phase formation is a universal phenomenon manifest from a crit. double point. Thus, solvent extn. is reduced to its fundamental phys. roots where the system is not defined by detailed anal. of metrical properties but by linking the fundamental order to thermodn. parameters via an exponent, working toward a more predictive understanding of third phase formation.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvFejur3N&md5=b585a55ca00fc242fb70bf8ddb65dac8
    40. 40
      Plaue, J.; Gelis, A.; Czerwinski, K.; Thiyagarajan, P.; Chiarizia, R. Small-angle neutron scattering study of plutonium third phase formation in 30% TBP/HNO3/alkane diluent systems. Solvent Extr. Solvent Extr. Ion Exch. 2006, 24, 283– 298,  DOI: 10.1080/07366290600646970
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    41. 41
      Chiarizia, R.; Jensen, M. P.; Rickert, P. G.; Kolarik, Z.; Borkowski, M.; Thiyagarajan, P. Extraction of zirconium nitrate by TBP in n-octane: Influence of cation type on third phase formation according to the ″sticky spheres″ model. Langmuir 2004, 20, 10798– 10808,  DOI: 10.1021/la0488957
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      41
      Extraction of zirconium nitrate by TBP in n-octane: influence of cation type on third phase formation according to the "sticky spheres" model
      Chiarizia, Renato; Jensen, Mark P.; Rickert, Paul G.; Kolarik, Zdenek; Borkowski, Marian; Thiyagarajan, Pappanan
      Langmuir (2004), 20 (25), 10798-10808CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      Small-angle neutron scattering (SANS) data for the tri-Bu phosphate (TBP)-n-octane, HNO3-Zr(NO3)4 solvent extn. system, obtained under a variety of exptl. conditions, have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in scattering intensity in the low Q range obsd. when increasing amts. of Zr(NO3)4 were extd. into the org. phase was interpreted as arising from interactions between small reverse micelle-like particles contg. two to three TBP mols. Upon extn. of Zr(NO3)4, the particles interact through attractive forces between their polar cores with a potential energy that exceeds 2 kBT. The interparticle attraction, under suitable conditions, leads to third phase formation. A linear relationship exists between the deriv. of the potential energy of attraction with respect to the concn. of nitrate ions in the org. phase and the ionization potential or the hydration enthalpy of the extd. metal cations.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXmvVeju7o%253D&md5=4ca5c19b8f5605770743ea5c344d4a2f
    42. 42
      Ivanov, P.; Mu, J.; Leay, L.; Chang, S. Y.; Sharrad, C. A.; Masters, A. J.; Schroeder, S. L. M. Organic and third phase in HNO3/TBP/n-dodecane system: No reverse micelles. Solvent Extr. Ion Exch. 2017, 35, 251– 265,  DOI: 10.1080/07366299.2017.1336048
      [Crossref], [CAS], Google Scholar
      42
      Organic and Third Phase in HNO3/TBP/n-Dodecane System: No Reverse Micelles
      Ivanov, P.; Mu, J.; Leay, L.; Chang, S.-Y.; Sharrad, C. A.; Masters, A. J.; Schroeder, S. L. M.
      Solvent Extraction and Ion Exchange (2017), 35 (4), 251-265CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
      The compn. and speciation of the org. and third phases in the system HNO3/TBP (tri-Bu phosphate)/n-dodecane have been examd. by a combination of gravimetric, Karl Fischer anal., chem. anal., FTIR, and 31P NMR spectroscopy, with particular emphasis on the transition from the two-phase to the three-phase region. Phase densities indicate that third-phase formation takes place for initial aq. HNO3 concns. above 15 M, while the results from the stoichiometric anal. imply that the org. and third phases are characterized by two distinct species, namely the mono-solvate TBP·HNO3 and the hemi-solvate TBP·2HNO3, resp. Furthermore, the 31P NMR spectra of org. and third phase show no significant chem. differences at the phosphorus centers, suggesting that the second HNO3 mol. in the third phase is bound to HNO3 rather than TBP. The third-phase FTIR spectra reveal stronger vibrational absorption bands at 1028, 1310, 1653, and 3200-3500 cm-1, reflecting higher concns. of H2O, HNO3, and TBP. The mol. dynamics simulation data predict structures in accord with the spectroscopically identified speciation, indicating inequivalent HNO3 mols. in the third phase. The predicted structures of the org. and third phases are more akin to microemulsion networks rather than the distinct, reverse micelles assumed in previous studies. H2O appears to be present as a disordered hydrogen-bonded solvate stabilizing the polar TBP/HNO3 aggregates in the org. matrix, and not as a strongly bound hydrate species in aggregates with defined stoichiometry.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFCltLnK&md5=1b55aa151fba0c853a95d2a42fbebecc
    43. 43
      Servis, M.; Wu, D.; Braley, J. Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate. Phys. Chem. Chem. Phys. 2017, 19, 11326– 11339,  DOI: 10.1039/C7CP01845B
      [Crossref], [PubMed], [CAS], Google Scholar
      43
      Network analysis and percolation transition in hydrogen bonded clusters: nitric acid and water extracted by tributyl phosphate
      Servis, Michael J.; Wu, David T.; Braley, Jenifer C.
      Physical Chemistry Chemical Physics (2017), 19 (18), 11326-11339CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Extn. of polar mols. by amphiphilic species results in a complex variety of clusters whose topologies and energetics control phase behavior and efficiency of liq.-liq. sepns. A computational approach including quantum mech. vibrational frequency calcns. and mol. dynamics simulation with intermol. network theory is used to provide a robust assessment of extractant and polar solute assocn. through hydrogen bonding in the tri-Bu phosphate (TBP)/HNO3/H2O/dodecane system for the first time. The distribution of local topologies of the TBP/HNO3/H2O hydrogen bonded clusters is shown to be consistent with an equil. binding model. Mixed TBP/HNO3/H2O clusters are predicted that have not been previously observable in expt. due to limitations in scattering and spectroscopic resoln. Vibrational frequency calcns. are compared with exptl. data to validate the exptl. obsd. TBP-HNO3-HNO3 Chain structure. At high nitric acid and water loading, large hydrogen-bonded clusters of 20 to 80 polar solutes formed. The cluster sizes were found to be exponentially distributed, consistent with a const. av. solute assocn. free energy in that size range. Due to the deficit of hydrogen bond donors in the predominantly TBP/HNO3 org. phase, increased water concns. lower the assocn. free energy and enable growth of larger cluster sizes. For sufficiently high water concns., changes in the cluster size distribution are found to be consistent with the formation of a percolating cluster rather than reverse micelles, as has been commonly assumed for the occurrence of an extractant-rich third phase in metal-free solvent extn. systems. Moreover, the compns. of the large clusters leading to percolation agrees with the 1:3TBP:HNO3 ratio reported in the exptl. literature for TBP/HNO3/H2O third phases. More generally, the network anal. of cluster formation from at. level interactions could allow for control of phase behavior in multi-component solns. of species with a variety of hydrogen bond types.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslCrtL8%253D&md5=6256e89964eff4664907fc5beefc0268
    44. 44
      Mu, J.; Motokawa, R.; Akutsu, K.; Nishitsuji, S.; Masters, A. J. A novel microemulsion phase transition: Toward the elucidation of third-phase formation in spent nuclear fuel reprocessing. J. Phys. Chem. B 2018, 122, 1439– 1452,  DOI: 10.1021/acs.jpcb.7b08515
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      44
      A Novel Microemulsion Phase Transition: Toward the Elucidation of Third-Phase Formation in Spent Nuclear Fuel Reprocessing
      Mu, Junju; Motokawa, Ryuhei; Akutsu, Kazuhiro; Nishitsuji, Shotaro; Masters, Andrew J.
      Journal of Physical Chemistry B (2018), 122 (4), 1439-1452CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
      We present evidence that the transition between org. and third phases, which can be obsd. in the plutonium uranium redn. extn. (PUREX) process at high metal loading, is an unusual transition between two isotropic bicontinuous microemulsion phases. As this system contains so many components, however, we have been seeking first to investigate the properties of a simpler system, namely, the related metal-free, quaternary water/n-dodecane/nitric acid/tributyl phosphate (TBP) system. This quaternary system has been shown to exhibit, under appropriate conditions, three coexisting phases: a light org. phase, an aq. phase, and the so-called third phase. In the current work, we focused on the coexistence of the light org. phase with the third phase. Using Gibbs ensemble Monte Carlo (GEMC) simulations, we found coexistence of a phase rich in nitric acid and dil. in n-dodecane (the third phase) with a phase more dil. in nitric acid but rich in n-dodecane (the light org. phase). The compns. and densities of these two coexisting phases detd. using the simulations were in good agreement with those detd. exptl. Because such systems are generally dense and the mols. involved are not simple, the particle exchange rate in their GEMC simulations can be rather low. To test whether a system having a compn. between those of the obsd. third and org. phases is indeed unstable with respect to phase sepn., we used the Bennett acceptance ratio method to calc. the Gibbs energies of the homogeneous phase and the weighted av. of the two coexisting phases, where the compns. of these phases were taken both from exptl. results and from the results of the GEMC simulations. Both demixed states were detd. to have statistically significant lower Gibbs energies than the uniform, mixed phase, providing confirmation that the GEMC simulations correctly predicted the phase sepn. Snapshots from the simulations and a cluster anal. of the org. and third phases revealed structures akin to bicontinuous microemulsion phases, with the polar species residing within a mesh and with the surface of the mesh formed by amphiphilic TBP mols. The nonpolar n-dodecane mols. were obsd. in these snapshots to be outside this mesh. The only large-scale structural differences obsd. between the two phases were the dimensions of the mesh. Evidence for the correctness of these structures was provided by the results of small-angle X-ray scattering (SAXS) studies, where the profiles obtained for both the org. and third phases agreed well with those calcd. from simulations. Finally, we looked at the microscopic structures of the two phases. In the org. phase, the basic motif was obsd. to be one nitric acid mol. hydrogen-bonded to a TBP mol. In the third phase, the most common structure was that of the hydrogen-bonded TBP-HNO3-HNO3 chain. A cluster anal. provided evidence for TBP forming an extended, connected network in both phases. Studies of the effects of metal ions on these systems will be presented elsewhere.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFGjtL7K&md5=d7ddd4cca1561bf5eb06056a3400cb1f
    45. 45
      Baldwin, A. G.; Servis, M. J.; Yang, Y.; Bridges, N. J.; Wu, D. T.; Shafer, J. C. The structure of tributyl phosphate solutions: Nitric acid, uranium(VI), and zirconium(IV). J. Mol. Liq. 2017, 246, 225– 235,  DOI: 10.1016/j.molliq.2017.09.032
      [Crossref], [CAS], Google Scholar
      45
      The structure of tributyl phosphate solutions: Nitric acid, uranium (VI), and zirconium (IV)
      Baldwin, Anna G.; Servis, Michael J.; Yang, Yuan; Bridges, Nicholas J.; Wu, David T.; Shafer, Jenifer C.
      Journal of Molecular Liquids (2017), 246 (), 225-235CODEN: JMLIDT; ISSN:0167-7322. (Elsevier B.V.)
      Diffusion, rheol., and small angle neutron scattering (SANS) data for org. phase 30 vol./vol.% tri-Bu phosphate (TBP) samples contg. varying amts. of water, nitric acid, and uranium or zirconium nitrate were interpreted from a colloidal perspective to give information on the types of structures formed by TBP under different conditions. Taken as a whole, the results of the different analyses were contradictory, suggesting that these samples should be treated as mol. solns. rather than colloids. This conclusion is supported by mol. dynamics (MD) simulations showing the existence of small, mol. aggregates in TBP samples contg. water and nitric acid. Interpretation of TBP and nitric acid diffusion measurements from a mol. perspective suggest that nitric acid and metal species formed are consistent with the stoichiometric solvates that have traditionally been considered to exist in soln.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFGntb3E&md5=7c78e6805279827ebbdb82367a775dd0
    46. 46
      Borkowski, M.; Chiarizia, R.; Jensen, M. P.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C. SANS study of third phase formation in the Th(IV)-HNO3/TBP-n-octane system. Sep. Sci. Technol. 2003, 38, 3333– 3351,  DOI: 10.1081/SS-120022600
      [Crossref], [CAS], Google Scholar
      46
      SANS Study of Third Phase Formation in the Th(IV)-HNO3/TBP-n-Octane System
      Borkowski, M.; Chiarizia, R.; Jensen, M. P.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C.
      Separation Science and Technology (2003), 38 (12 & 13), 3333-3351CODEN: SSTEDS; ISSN:0149-6395. (Marcel Dekker, Inc.)
      Formation of a third org. phase at high metal loading in the extn. of tetravalent actinides by TBP in aliph. diluents has been investigated mostly from the standpoint of the compn. of the org. phase species before and after phase splitting. Very little is known of the structure and morphol. of the org. phase species. In this work, a study of third phase formation upon either dissoln. of Th(NO3)4 in 20 % TBP in n-octane or Th(NO3)4 extn. from 1 M HNO3 by 20% TBP in n-octane is reported. Chem. analyses have shown that, under the conditions of this work, Th(IV) exists in the org. phase mainly as the trisolvate Th(NO3)4·(TBP)3. The third phase species also contains a small amt. of HNO3, presumably hydrogen-bonded to the trisolvate complex. Small-angle neutron scattering measurements on Th(IV) revealed the presence, before phase splitting, of large ellipsoidal aggregates with the parallel and perpendicular axes having lengths up to about 230 and 24 Å, resp. Although the formation of these aggregates is obsd. in all cases, i.e., when only HNO3, only Th(NO3)4, or both HNO3 and Th(NO3)4 are extd. by the TBP soln., the size of the aggregates is largest in the latter case. Formation of these aggregates is probably the main reason for phase splitting.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXltlOntr0%253D&md5=0daf9f2391aa764d7bbab7e72c811051
    47. 47
      Chiarizia, R.; Jensen, M. P.; Borkowski, M.; Ferraro, J. R.; Thiyagarajan, P.; Littrell, K. C. Third phase formation revisited: The U(VI), HNO3-TBP, n-dodecane system. Solvent Extr. Ion Exch. 2003, 21, 1– 27,  DOI: 10.1081/SEI-120017545
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    48. 48
      Motokawa, R.; Endo, H.; Nagao, M.; Heller, W. T. Neutron polarization analysis for biphasic solvent extraction systems. Solvent Extr. Ion Exch. 2016, 34, 399– 406,  DOI: 10.1080/07366299.2016.1201980
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    49. 49
      Koga, T.; Tanaka, F.; Motokawa, R.; Koizumi, S.; Winnik, F. M. Theoretical modeling of associated structures in aqueous solutions of hydrophobically modified telechelic PNIPAM based on a neutron scattering study. Macromolecules 2008, 41, 9413– 9422,  DOI: 10.1021/ma800957z
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      49
      Theoretical Modeling of Associated Structures in Aqueous Solutions of Hydrophobically Modified Telechelic PNIPAM Based on a Neutron Scattering Study
      Koga, Tsuyoshi; Tanaka, Fumihiko; Motokawa, Ryuhei; Koizumi, Satoshi; Winnik, Francoise M.
      Macromolecules (Washington, DC, United States) (2008), 41 (23), 9413-9422CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      On the basis of results from a small-angle neutron scattering (SANS) study of aq. solns. of a telechelic PNIPAM with octadecyl end groups, we developed a theor. model of the self-assembly of this polymer in water as a function of temp. and concn. This model leads us to the following description. In solns. of concn. 10 g L-1 kept between 10 and 20°, telechelic PNIPAMs (Mn=22,200 g mol-1) assoc. in the form of flower micelles, contg. about 12 polymer chains, assembled in a three-layered core-shell morphol. with an inner core consisting of the octadecyl units, a dense inner shell consisting of partly collapsed PNIPAM chains, and an outer shell of swollen hydrated chains. Drastic changes in the scattering profile of the soln. heated above 31° are attributed to the formation of mesoglobules (diam. of ∼40 nm) consisting of about 1000 polymer chains. On further heating, the aggregation no. of the mesoglobules increases. It reaches a value of ∼9000 at 34° and stays const. upon further heating. In solns. of lower concn. (1 g L-1), assocn. of flower micelles and mesoglobules does not occur; however, the structure of individual flower micelles and mesoglobules is not affected by the change in concn. In solns. of 50 g L-1 in which flower micelles are expected to be partially connected by bridge chains, a peak attributed to correlation between flower micelles appears in the scattering profiles recorded at low temp. (10-20°). In spite of the intermicellar bridging connection, the overall temp. dependence of the scattering profile at 50 g L-1 remains similar to that at 10 g L-1. Distinct features of the self-assembled structures formed in aq. telechelic PNIPAM solns. are discussed in terms of the interactions between water and the polymer main chains.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtlemt7%252FM&md5=12c3a7bed1ecd018fb337e4ab78c151b
    50. 50
      Debye, P. Zerstreuung von röntgenstrahlen. Ann. Phys. (Berlin, Ger.) 1915, 351, 809– 823,  DOI: 10.1002/andp.19153510606
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    51. 51
      Svergun, D.; Barberato, C.; Koch, M. H. J. J. CRYSOL– a program to evaluate X-ray solution scattering of biological macromolecules from atomic coordinates. J. Appl. Crystallogr. 1995, 28, 768– 773,  DOI: 10.1107/S0021889895007047
      [Crossref], [CAS], Google Scholar
      51
      CRYSOL - a program to evaluate x-ray solution scattering of biological macromolecules from atomic coordinates
      Svergun, D.; Barberato, C.; Koch, M. H. J.
      Journal of Applied Crystallography (1995), 28 (6), 768-73CODEN: JACGAR; ISSN:0021-8898. (Munksgaard)
      A program for evaluating the soln. scattering from macromols. with known at. structure is presented. The program uses multiple expansion for fast calcn. of the spherically averaged scattering pattern and takes into account the hydration shell. Given the at. coordinates (e.g., from the Brookhaven Protein Data Bank) it can either predict the soln. scattering curve or fit the exptl. scattering curve using only 2 free parameters, the av. displaced solvent vol. per at. group and the contrast of the hydration layer. The program runs on IBM PCs and on the major UNIX platforms.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XksFektg%253D%253D&md5=ebcc992d5c7af97987ea4f5e1b014d02
    52. 52
      Antonio, M. R.; Demars, T. J.; Audras, M.; Ellis, R. J. Third phase inversion, red oil formation, and multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system. Sep. Sci. Technol. 2018, 53, 1834– 1847,  DOI: 10.1080/01496395.2017.1281303
      [Crossref], [CAS], Google Scholar
      52
      Third phase inversion, red oil formation, and multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system
      Antonio, Mark R.; Demars, Thomas J.; Audras, Matthieu; Ellis, Ross J.
      Separation Science and Technology (Philadelphia, PA, United States) (2018), 53 (12), 1834-1847CODEN: SSTEDS; ISSN:0149-6395. (Taylor & Francis, Inc.)
      The extn. of tetravalent cerium, Ce(IV), from aq. nitric acid with tri-Bu phosphate (TBP) in n-dodecane was studied by varying the aq., initial cerium(IV) concn., [Ce4+]aq,init, up to and beyond the point of third phase formation, defined by the crit. aq. concn. (or CAC) and the limiting org. concn. (or LOC). The new chem., elaborated here for the nearly-century-old Ce(IV)-20% TBP system, focuses on the phenomena of third phase inversion and the distribution of four solutes-Ce(IV), HNO3, H2O, and TBP-between the aq. and org. phases, which are of direct relevance to the PUREX process. We demonstrate that multinuclear Ce(IV) entities are present in the org. phases.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjt1agu7c%253D&md5=26976b1ec8534a9885033e0fd5c4ece0
    53. 53
      Antonio, M. R.; Ellis, R. J.; Estes, S. L.; Bera, M. K. Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system. Phys. Chem. Chem. Phys. 2017, 19, 21304– 21316,  DOI: 10.1039/C7CP03350H
      [Crossref], [PubMed], [CAS], Google Scholar
      53
      Structural insights into the multinuclear speciation of tetravalent cerium in the tri-n-butyl phosphate-n-dodecane solvent extraction system
      Antonio, Mark R.; Ellis, Ross J.; Estes, Shanna L.; Bera, Mrinal K.
      Physical Chemistry Chemical Physics (2017), 19 (32), 21304-21316CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      X-ray and electrochem. studies of org. phases obtained by the extn. of tetravalent cerium, Ce(IV), from aq. nitric acid (3 M) with tri-Bu phosphate (TBP) in n-dodecane reveal a tetranuclear Ce(IV) structural motif. This finding is consistent with the results of previous liq.-liq. extn. (LLE) studies that implicate the aggregation of (Ce-O-Ce)6+ dimers into multinuclear Ce(IV)·TBP solvates. The org. soln. structures elaborated here for the Ce(IV)-HNO3-20% TBP-n-C12H26 system are correlated with multiscale phenomena-from the at. level of the cerium coordination environment to the supramol. scale of solute aggregates-in the org. phases, which are of relevance to the PUREX (Plutonium Uranium Redn. Extn.) process. The combination of XANES, EXAFS, and SAXS results indicate the presence of tetranuclear cerium(IV)-oxo core structures in each of the org. phases investigated. In addn. to the use of X-ray spectroscopy and scattering for direct metrical details about the org. phase solute speciation, three-phase-electrode differential pulse voltammetry (DPV) of the third phase reveals a wave attributable to Ce(IV) redn. The electrode potential is consistent with values for the redn. of Ce(IV) in (Ce-O-Ce)6+ dimers in aq. electrolytes. The Ce(IV) coordination chem. of the org. solvates is independent of the bulk phenomenon of phase splitting, namely third phase formation. The local, mol. environment of Ce in the org. phase before splitting is identical to those in the two org. phases (the dense third phase and the light phase) after splitting. SAXS data are consistent with the formation of small spherical reverse micelles with core diams. (approx. 6 Å) that can accommodate a tetranuclear Ce(IV) oxo-cluster solvate of TBP. Sticky sphere modeling of the SAXS data for the org. phases with low cerium concns. ( < 0.14 M) is consistent with the presence of randomly- and homogeneously-dispersed micelles in combination with short-range percolated, assocd. micelles. At high cerium concns. (approx. 1.5 M) in the third phase, the SAXS modeling is consistent with correlated, long-range percolated micellar aggregates. The presence of strong inter-micellar interactions (-3 to -5kBT) in all org. phases of the Ce(IV)-HNO3-TBP-n-C12H26 LLE system suggests that the phenomena of phase splitting and third phase inversion are due to liq. pptn. that is dependent solely on the concn. of the tetranuclear Ce solvate.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFamsLfJ&md5=3acbf6dd8741f9e9998e4211abc87a65
    54. 54
      Ankudinov, A. L.; Ravel, B.; Rehr, J. J.; Conradson, S. D. Real-space multiple-scattering calculation and interpretation of X-ray-absorption near-edge structure. Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 58, 7565– 7576,  DOI: 10.1103/PhysRevB.58.7565
      [Crossref], [CAS], Google Scholar
      54
      Real-space multiple-scattering calculation and interpretation of x-ray-absorption near-edge structure
      Ankudinov, A. L.; Ravel, B.; Rehr, J. J.; Conradson, S. D.
      Physical Review B: Condensed Matter and Materials Physics (1998), 58 (12), 7565-7576CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      A self-consistent real-space multiple-scattering (RSMS) approach for calcns. of x-ray-absorption near-edge structure (XANES) is presented and implemented in an ab initio code applicable to arbitrary aperiodic or periodic systems. This approach yields a quant. interpretation of XANES based on simultaneous, SCF calcns. of local electronic structure and x-ray absorption spectra, which include full multiple scattering from atoms within a small cluster and the contributions of high-order MS from scatterers outside that cluster. The code includes a SCF est. of the Fermi energy and an account of orbital occupancy and charge transfer. The authors also present a qual., scattering-theoretic interpretation of XANES. Sample applications are presented for cubic BN, UF6, Pu hydrates, and distorted PbTiO3. Limitations and various extensions are also discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmtVCgu78%253D&md5=b7b8ea5b5d5798475d65c324de1b0849
    55. 55
      Roe, R.-J. Methods of X-ray and Neutron Scattering in Polymer Science, 1st ed.; Oxford University Press: NY, 2000.
      Google Scholar
      There is no corresponding record for this reference.
    56. 56
      Okuhara, T.; Mizuno, N.; Misono, M. In Adv. Catal.; Eley, D. D., Haag, W. O., Gates, B., Eds.; 1996; Vol. 41, pp 113– 252.
      Google Scholar
      There is no corresponding record for this reference.
    57. 57
      Bartlett, P.; Ottewill, R. H. A neutron scattering study of the structure of a bimodal colloidal crystal. J. Chem. Phys. 1992, 96, 3306– 3318,  DOI: 10.1063/1.461926
      [Crossref], [CAS], Google Scholar
      57
      A neutron-scattering study of the structure of a bimodal colloidal crystal
      Bartlett, P.; Ottewill, R. H.
      Journal of Chemical Physics (1992), 96 (4), 3306-18CODEN: JCPSA6; ISSN:0021-9606.
      The authors have studied the freezing of a binary mixt. of colloidal poly(Me methacrylate) spheres of size ratio 0.31 and compn. AB4 (here A refers to the larger spheres). When suspended in a suitable liq. these particles interact via a steeply repulsive (approx. hard sphere) potential. The structure of the colloidal crystals formed in this binary system was established from a combination of small-angle neutron and light scattering measurements. There is an almost complete size sepn. on freezing. The cryst. phase contains almost exclusively large spheres while the smaller spheres are excluded from the crystal into a coexisting binary fluid. This observation is in agreement with recent d. functional calcns. for the freezing of hard sphere mixts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XhvVaisrc%253D&md5=3b1e72a4b407519300de657c9f5b70e7
    58. 58
      Qiao, B.; Demars, T.; Olvela de la Cruz, M.; Ellis, R. J. How hydrogen bonds affect the growth of reverse micelles around coordinating metal ions. J. Phys. Chem. Lett. 2014, 5, 1440– 1444,  DOI: 10.1021/jz500495p
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      58
      How Hydrogen Bonds Affect the Growth of Reverse Micelles around Coordinating Metal Ions
      Qiao, Baofu; Demars, Thomas; Olvera de la Cruz, Monica; Ellis, Ross J.
      Journal of Physical Chemistry Letters (2014), 5 (8), 1440-1444CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      The role of hydrogen bonds on the hierarchical structure of an aggregating amphiphile-oil soln. contg. a coordinating metal complex has been studied by means of atomistic mol. dynamics simulations and X-ray techniques. Hydrogen bonds not only stabilize the metal complex in the hydrophobic environment by coordinating between the Eu(NO3)3 outer-sphere and aggregating amphiphiles, but also affect the growth of such reverse micellar aggregates. The formation of swollen, elongated reverse micelles elevates the extn. of metal ions with increased H-bonds under acidic condition. These new insights into H-bonds are of broad interest to nanosynthesis and biol. applications, in addn. to metal ion sepns.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXltF2kur0%253D&md5=dbc5a6098b8716bf3fb98b9ea7bc760d
    59. 59
      Ellis, R. J.; Meridiano, Y.; Muller, J.; Berthon, L.; Guilbaud, P.; Zorz, N.; Antonio, M. R.; Demars, T.; Zemb, T. Complexation-induced supramolecular assembly drives metal-ion extraction. Chem. - Eur. J. 2014, 20, 12796– 12807,  DOI: 10.1002/chem.201403859
      [Crossref], [PubMed], [CAS], Google Scholar
      59
      Complexation-Induced Supramolecular Assembly Drives Metal-Ion Extraction
      Ellis, Ross J.; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R.; Demars, Thomas; Zemb, Thomas
      Chemistry - A European Journal (2014), 20 (40), 12796-12807CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Combining expt. with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extd. from water into oil by a lipophilic neutral amphiphile. Mol. dynamics simulations were coupled to exptl. spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the org. phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extn. of the Eu3+-3(NO3-) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear EuIII-contg. aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, contg. high densities of O-donor ligands and anions, provide improved EuIII solvation environments that help drive interfacial transfer, as is reflected by the increasing EuIII partitioning ratios (oil/aq.) despite the org. phase approaching satn. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsVGgur7F&md5=07308486b263267f7a2041db86e0bc11
    60. 60
      Qiao, B. F.; Ferru, G.; Olvela de la Cruz, M.; Ellis, R. J. Molecular origins of mesoscale ordering in a metalloamphiphile phase. ACS Cent. Sci. 2015, 1, 493– 503,  DOI: 10.1021/acscentsci.5b00306
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      60
      Molecular Origins of Mesoscale Ordering in a Metalloamphiphile Phase
      Qiao, Baofu; Ferru, Geoffroy; Olvera de la Cruz, Monica; Ellis, Ross J.
      ACS Central Science (2015), 1 (9), 493-503CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
      A metalloamphiphile-oil soln. that organizes on multiple length scales has been studied using d synchrotron small- and wide-angle X-ray scattering combined with large-scale atomistic mol. dynamics simulations. The mols. assoc. into aggregates, and aggregates flocculate into meso-ordered phases. The dipolar interactions, centered on the amphiphile headgroup, bridge ionic aggregate cores and drive aggregate flocculation. By identifying specific intermol. interactions that drive mesoscale ordering in soln., the authors bridge two different length scales that are classically addressed sep. These results highlight the importance of individual intermol. interactions in driving mesoscale ordering.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVanurfK&md5=50faee10cf0a6440d18903d8543c429b
    61. 61
      Sevick, E.; Monson, P.; Ottino, J. Monte-carlo calculations of cluster statistics in continuum models of composite morphology. J. Chem. Phys. 1988, 88, 1198– 1206,  DOI: 10.1063/1.454720
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    62. 62
      Servis, M.; Wu, D.; Jenifer, S.; Clark, A. Square supramolecular assemblies of uranyl complexes in organic solvents. Chem. Commun. 2018, 54, 10064– 10067,  DOI: 10.1039/C8CC05277H
      [Crossref], [PubMed], [CAS], Google Scholar
      62
      Square supramolecular assemblies of uranyl complexes in organic solvents
      Servis, Michael J.; Wu, David T.; Shafer, Jenifer C.; Clark, Aurora E.
      Chemical Communications (Cambridge, United Kingdom) (2018), 54 (72), 10064-10067CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Uranyl nitrate/extractant complexes form long-range isotropic pairs and short-range ordered dimeric assemblies with a unique square configuration comprised of noncovalent ligand and acid anion mediated interactions, further stabilized by org. phase solvation.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVyns73J&md5=1dc4065e6badb22c4cb792b74bf80cc4
    63. 63
      Hill, T. L. An Introduction to Statistical Thermodynamics; Addison-Wesley: Reading, MA, 1960.
      Google Scholar
      There is no corresponding record for this reference.
    64. 64
      Higgins, J. S.; Benoît, H. C. Polymers and Neutron Scattering; Oxford University Press: Oxford, 1994.
      Google Scholar
      There is no corresponding record for this reference.
    65. 65
      Berthon, L.; Martinet, L.; Testard, F.; Madic, C.; Zemb, T. Solvent penetration and sterical stabilization of reverse aggregates based on the DIAMEX process extracting molecules: Consequences for the third phase formation. Solvent Extr. Ion Exch. 2007, 25, 545– 576,  DOI: 10.1080/07366290701512576
      [Crossref], [CAS], Google Scholar
      65
      Solvent Penetration and Sterical Stabilization of Reverse Aggregates based on the DIAMEX Process Extracting Molecules: Consequences for the Third Phase Formation
      Berthon, L.; Martinet, L.; Testard, F.; Madic, C.; Zemb, Th.
      Solvent Extraction and Ion Exchange (2007), 25 (5), 545-576CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
      Studies on third phase formation during the extn. of nitric acid by malonamide extractants in various diluents are investigated. This "third phase transition" is studied from a fundamental point of view, combining vapor pressure osmometry, phase diagram, and scattering studies. The organization of the org. phases of the "malonamides/alkane/water/nitric acid" systems was studied at three "scales" enumerated below. 1. At a mol. scale by detg. the compns. of the extd. complexes. 2. At a macroscopic scale by detg. the phase transition boundaries quantified by the limiting org. concn. (LOC) of solutes. 3. At a supramol. scale by analyzing the organization of the species in the org. phases (i.e. measuring the crit. micellization concn., the aggregation no., and the interactions between the aggregates). The instability (third phase apparition) has a supramol. origin: It is a "long range" attraction between polar cores of the reverse micelles formed by the extg. agent. Water and nitric acid extn. are decoupled from these interactions. The alkyl chains of the extractant and the diluent play a sym. role in the phys. stability of the org. phase: Decreasing the diluent chain length or increasing the chain length of the complexing agent both promotes phase stability, i.e., they increase the LOC. The authors demonstrate here that this effect is the same as the effect obsd. and known for all other w/o "reverse" micelles: Chains protruding from any aggregate stabilize polar solute in oil and shorts oil penetrate and swells the reverse micelles apolar layer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXptlSrtLY%253D&md5=686cce21070ffa366b5d2bdab276aa57
    66. 66
      Zemb, T.; Bauer, C.; Bauduin, P.; Belloni, L.; Dejugnat, C.; Diat, O.; Dubois, V.; Dufreche, J. F.; Dourdain, S.; Duvail, M.; Larpent, C.; Testard, F.; Pellet-Rostaing, S. Recycling metals by controlled transfer of ionic species between complex fluids: en route to ″ienaics″. Colloid Polym. Sci. 2015, 293, 1– 22,  DOI: 10.1007/s00396-014-3447-x
      [Crossref], [CAS], Google Scholar
      66
      Recycling metals by controlled transfer of ionic species between complex fluids. En route to "ienaics"
      Zemb, Thomas; Bauer, Caroline; Bauduin, Pierre; Belloni, Luc; Dejugnat, Christophe; Diat, Olivier; Dubois, Veronique; Dufreche, Jean-Francois; Dourdain, Sandrine; Duvail, Magali; Larpent, Chantal; Testard, Fabienne; Pellet-Rostaing, Stephane
      Colloid and Polymer Science (2015), 293 (1), 1-22CODEN: CPMSB6; ISSN:0303-402X. (Springer)
      A review. Recycling chem. of metals and oxides relies on 3 steps: dissoln., sepn. and material reformation. We review in this work the colloidal approach of the transfer of ions between 2 complex fluids, i.e. the mechanism at the basis of the liq.-liq. extn. technol. This approach allows for rationalizing in a unified model transformation such as accidently splitting from 2 to 3 phases, or uncontrolled viscosity variations, as linked to the transformation in the phase diagram due to ion transfer. Moreover, differences in free energies assocd. to ion transfer between phases that are the origin of the selectivity need to be considered at the meso-scale beyond parameterization of an arbitrary no. of competing "complexes". Entropy and electrostatics are taken into account in relation to solvent formulation. By analogy with electronics dealing about electrons transported in conductors and semi-conductors, this "ienaic" approach deals with ions transported between nanostructures present in colloidal fluids under the influence of chem. potential gradients between nanostructures coexisting in colloidal fluids. We show in this review how this colloidal approach generalizes the multiple chem. equil. models used in supra-mol. chem. Statistical thermodn. applied to self-assembled fluids requires only a few measurable parameters to predict liq.-liq. extn. isotherms and selectivity in multi-phase chem. systems contg. at least one concd. emulsified water in oil (w/o) or oil in water (o/w) microemulsion.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvFOhtb%252FO&md5=a223fd32d4f7ea6b53e11cf6c3e0f3b2
    67. 67
      Abécassis, B.; Testard, F.; Zemb, T.; Berthon, L.; Madic, C. Effect of n-octanol on the structure at the supramolecular scale of concentrated dimethyldioctylhexylethoxymalonamide extractant solutions. Langmuir 2003, 19, 6638– 6644,  DOI: 10.1021/la034088g
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      67
      Effect of n-Octanol on the Structure at the Supramolecular Scale of Concentrated Dimethyldioctylhexylethoxymalonamide Extractant Solutions
      Abecassis, B.; Testard, F.; Zemb, Th.; Berthon, L.; Madic, C.
      Langmuir (2003), 19 (17), 6638-6644CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      Using small-angle X-ray scattering (SAXS) and interfacial tension measurements, we show that concd. solns. of dimethyldioctylhexyloxyethylmalonamide dild. in dodecane are organized in reverse aggregates that have many features in common with reverse micelles. The crit. micellar concn. is detd. from interfacial tension measurements using the pendant-drop technique, and the aggregation no. is given by fitting SAXS data on the abs. scale. The effect of the addn. of n-octanol, a modifier widely used in liq./liq. extn., is studied by SAXS. It is shown that, for small amts. of alc., the modifier acts as a cosurfactant; it swells the reverse micelles by adsorbing onto the aggregates and increases the surface per extractant polar head. When n-octanol is added in larger quantities, a new microstructure appears, and the amt. of octanol required for this transition depends on the amt. of diamide in soln. (for example, octanol concn. ≥ 1 M for 0.7 M diamide). Therefore, a hydrogen-bond network is present in soln., and the presence of areas of high electronic d. sepd. by a distance varying from 15 to 20 Å is found to explain the scattering patterns.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvFWlsb8%253D&md5=2c98ea122bcc228051291287efa2a7c7
    68. 68
      Whittaker, D.; Geist, A.; Modolo, G.; Taylor, R.; Sarsfield, M.; Wilden, A. Applications of diglycolamide based solvent extraction processes in spent nuclear fuel reprocessing, Part 1: TODGA. Solvent Extr. Ion Exch. 2018, 36, 223– 256,  DOI: 10.1080/07366299.2018.1464269
      [Crossref], [CAS], Google Scholar
      68
      Applications of Diglycolamide Based Solvent Extraction Processes in Spent Nuclear Fuel Reprocessing, Part 1: TODGA
      Whittaker, Daniel; Geist, Andreas; Modolo, Giuseppe; Taylor, Robin; Sarsfield, Mark; Wilden, Andreas
      Solvent Extraction and Ion Exchange (2018), 36 (3), 223-256CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)
      Over the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extn. of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N',N'-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A no. of new actinide sepn. processes have been proposed based on extn. with TODGA. This review covers TODGA-based processes and extn. data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the org. phase speciation are reviewed in this context. Relevant aspects of the extn. chem. of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide sepn. processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chem. occurring in the org. phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGA-based flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVSkur7M&md5=f02d4fa90a5a05427d0503412ed99688

  • Supporting Information

    Supporting Information

    ARTICLE SECTIONS
    Jump To

    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscentsci.8b00669.

    • Method section and additional data and figures including cluster probabilities, configurations, radial distribution function, chemical structure, EXAFS data, Guinier plots, theoretical modeling of the hierarchical aggregates for SANS data analysis, simulated SANS profiles, and coordination structure of zirconium nitrate complex in initial aqueous phase (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

PDF [ 3MB]

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

You’ve supercharged your research process with ACS and Mendeley!

STEP 1:
Click to create an ACS ID

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

MENDELEY PAIRING EXPIRED
Your Mendeley pairing has expired. Please reconnect

This website uses cookies to improve your user experience. By continuing to use the site, you are accepting our use of cookies. Read the ACS privacy policy.

CONTINUE