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

OR SEARCH CITATIONS

My Activity
Publications
CONTENT TYPES

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. Lett. 2017, 4, 10, 421-426
RETURN TO ISSUEPREVLetterNEXT

Uranium(V) Incorporation Mechanisms and Stability in Fe(II)/Fe(III) (oxyhydr)Oxides

View Author Information
† Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom
‡ Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
§ Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
∥ The Rossendorf Beamline at ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France
⊥ Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden, Germany
*E-mail: [email protected]. Telephone: +44 (0)161 275 3826.
Cite this: Environ. Sci. Technol. Lett. 2017, 4, 10, 421–426
Publication Date (Web):September 8, 2017
https://doi.org/10.1021/acs.estlett.7b00348

Copyright © 2022 American Chemical Society. This publication is licensed under CC-BY.

  • Open Access

Article Views

4731

Altmetric

-

Citations

74
LEARN ABOUT THESE METRICS
PDF (2 MB)
Get e-Alerts
Supporting Info (1)»
SUBJECTS:

Abstract

High Resolution Image
Download MS PowerPoint Slide

Understanding interactions between radionuclides and mineral phases underpins site environmental cleanup and waste management in the nuclear industry. The transport and fate of radionuclides in many subsurface environments are controlled by adsorption, redox, and mineral incorporation processes. Interactions of iron (oxyhydr)oxides with uranium have been extensively studied because of the abundance of uranium as an environmental contaminant and the ubiquity of iron (oxyhydr)oxides in engineered and natural environments. Despite this, detailed mechanistic information regarding the incorporation of uranium into Fe(II)-bearing magnetite and green rust is sparse. Here, we present a co-precipitation study in which U(VI) was reacted with environmentally relevant iron(II/III) (oxyhydr)oxide mineral phases. On the basis of diffraction, microscopic, dissolution, and spectroscopic evidence, we show the reduction of U(VI) to U(V) and stabilization of the U(V) by incorporation within the near surface and bulk of the particles during co-precipitation with iron (oxyhydr)oxides. U(V) was stable in both magnetite and green rust structures and incorporated via substitution for octahedrally coordinated Fe in a uranate-like coordination environment. As the Fe(II)/Fe(III) ratio increased, a proportion of U(IV) was also precipitated as surface-associated UO2. These novel observations have significant implications for the behavior of uranium within engineered and natural environments.

Introduction

ARTICLE SECTIONS
Jump To
Uranium is a problematic contaminant at nuclear sites and is the dominant radionuclide by mass in radioactive wastes destined for geological disposal. Groundwater conditions under both scenarios range from mildly acidic to alkaline and from oxic to anoxic. (1-4) The oxidation state of uranium significantly controls its mobility. Under oxic conditions, soluble and environmentally mobile U(VI) dominates; under anaerobic conditions, uranium is typically reduced to poorly soluble U(IV). During biological and abiotic reduction of U(VI), U(V) reportedly forms as a transient species. (5-7) Recent work has also suggested that U(V) can be stabilized at mineral surfaces (8-12) and via incorporation into environmentally relevant iron (oxyhydr)oxide phases such as goethite (α-FeOOH) and magnetite (FeIIFeIII2O4). (13-21) Indeed, establishing the extent of U(V) stability upon interaction with Fe (oxyhydr)oxides is essential in underpinning predictive models for U behavior in environmental systems that currently do not recognize the presence of U(V). To achieve this, U speciation needs to be determined at a molecular scale, which is a key step in defining the significance of U(V) in environmental systems and in developing realistic models for predicting the environmental fate of uranium.
Fe(II)/Fe(III)-bearing (oxyhydr)oxide minerals such as magnetite and green rust (22) (e.g., [FeII3FeIII(OH)8]+[Cl,nH2O]−) are ubiquitous in anoxic subsurface environments (e.g., soils and sediments), forming via a variety of biogeochemical processes (23, 24) and during the anaerobic corrosion of steel, a significant component in contaminated, engineered environments and geological disposal facilities. (25-27) Recent studies have suggested possible pathways for how U(VI) reduction occurs at the magnetite surface. (8, 10, 11, 28) Some studies suggest U(VI) is reduced to directly form U(IV), (29) whereas other studies show U(VI) is reduced to U(V) via a one-electron transfer process and then U(V) disproportionates to form U(IV). (28, 30) Previous spectroscopic studies have suggested that U(V) can be stabilized via its incorporation into magnetite within the octahedral sites in a distorted uranate-like coordination, although the exact structural site has not been conclusively determined, and no information about U(V) stabilization in other Fe(II)/Fe(III) (oxyhydr)oxides (e.g., green rust) is currently available. (8, 16, 19) Theoretical simulations of incorporation of U into iron (oxyhydr)oxide minerals have provided information about the U(VI) and U(V) coordination environment when substituted for octahedrally coordinated Fe within the magnetite structure. (21, 31) Recently, advances in spectroscopic techniques have also demonstrated that U(IV), U(V), and U(VI) can be distinguished using high-energy resolution fluorescence-detected-X-ray absorption near edge structure (HERFD-XANES) techniques. (19) Ultimately, if U(V) is incorporated into the structure of Fe(II)/Fe(III) (oxyhydr)oxides after U(VI) reduction, this could prevent disproportionation and lead to long-term immobilization of U(V). However, the pathway and mechanism of U(V) incorporation into magnetite and green rust are either poorly defined or yet to be determined.
Here, we synthesized both magnetite and green rust with U(VI) via a co-precipitation process. We then gained detailed molecular scale insights into the speciation and atomic scale mechanisms of incorporation of U within the mineral structures using state-of-the-art HERFD-XANES spectroscopy in combination with extended X-ray absorption fine structure (EXAFS) spectroscopy. Synchrotron analysis unequivocally confirmed the reduction of U(VI) to stabilized, octahedrally coordinated U(V), which is incorporated within both magnetite and green rust. This facile stabilization of U(V) within these bulk mineral phases may have important implications for the fate of U in engineered and natural environments where U(V) has typically been considered transient.

Methods

ARTICLE SECTIONS
Jump To

Mineral Synthesis and Characterization

Uranium-bearing magnetite and green rust were synthesized using a direct co-precipitation method in experiments performed at room temperature in an anaerobic chamber. (32) In brief, solutions of 0.1 M FeCl2, 0.2 M FeCl3, 0.3 M HCl, and 0.0126 M U(VI)Cl6 were mixed for 24 h before mineral precipitation was induced by introduction of the Fe(II)/Fe(III) solution into a N2-sparged 28–30% (w/v) NH4OH solution (pH 11) that was being continuously stirred over 15 min to a final pH of 9. This led to the instantaneous co-precipitation of the uranium-doped minerals. Four different starting Fe(II)/Fe(III) ratios were used to form magnetite and green rust:
After reaction, the solid samples were analyzed by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize their structure, particle size, and morphology. The distribution of uranium within the iron (oxyhydr)oxides particles was determined using acid dissolution performed as a function of [H+] in solution. (33)

X-ray Absorption Spectroscopy (XAS)

Uranium L3 edge XAS spectra were recorded on wet mineral pastes at Diamond Light Source, beamline B18, (34) in a liquid N2 cryostat in fluorescent mode using a Ge detector. (35) Analysis of the EXAFS spectra was performed in Artemis and Athena with details given in the Supporting Information. (36-40) U M4 edge HERFD-XANES spectra were recorded at European Synchrotron Radiation Facility, beamline ID26, (41) through the use of an X-ray emission spectrometer (42, 43) and analyzed using iterative transformation factor analysis (12, 44) to determine the proportion of U(IV), U(V), and U(VI) in the samples.

Results and Discussion

ARTICLE SECTIONS
Jump To
Co-precipitation experiments were performed to determine the speciation of uranium following co-precipitation with either magnetite or green rust. The Fe(II)/Fe(III) (oxyhydr)oxides were co-precipitated with U(VI) at starting Fe(II)/Fe(III) ratios of 0.5/0.6 to synthesize magnetite and 0.8/2.0 to synthesize green rust (Figure S1). Additionally, transmission electron microscopy showed the magnetite was nanoparticulate, with particle sizes ranging from 1 to 20 nm (Figure S2). Green rust was present as pseudohexagonal plates of approximately 50–600 nm, and energy dispersive X-ray analysis showed chloride was present, indicating green rust chloride formed (Figure S3).

Reduction of U(VI) to Stable U(V)

Uranium M4 edge HERFD-XANES spectra were used to determine the oxidation state of U associated with the Fe(II)/Fe(III) (oxyhydr)oxide phases (Figure 1). (19, 45, 46) The energy of the XANES peak position showed a systematic decrease as the Fe(II)/Fe(III) ratio increased (Figure S4) from 3726.5 eV [at 0.5 Fe(II)/Fe(III)] to 3726.3 eV [at 2.0 Fe(II)/Fe(III)]. Comparison with the peak position of the U oxidation state standards [U(VI) = 3726.95 eV, U(V) = 3726.4 eV, and U(IV) = 3725.2 eV] suggests that U(V) dominated in all of the samples. Furthermore, there were no indications of the higher-energy peaks (3728.7 and 3732.0 eV) that are typical of U(VI). However, in the Fe(II)/Fe(III) = 2.0 spectra, the small shoulder on the low-energy side of the XANES spectrum confirms the presence of U(IV) (Figure 1). Iterative transformation factor analysis (ITFA) of the HERFD-XANES data identified the three main components present in the samples (Figure S5) and indicated that at Fe(II)/Fe(III) = 0.5–0.8, 87–96% of U was present as U(V), with the remainder being from U(VI) for Fe(II)/Fe(III) = 0.5 and U(IV) for Fe(II)/Fe(III) = 0.6 and 0.8 (Table S1). At Fe(II)/Fe(III) = 2.0, U(V) still dominated but the amount of U(IV) increased to approximately 28%. The U L3 edge XANES also supports stabilization of U(V) with XANES edge positions for all the samples (17169.6–17171.2 eV) between those of U(VI) (17173.4 eV) and U(IV) (17170.3 eV). Additionally, shifts in the U L3 edge XANES post-edge resonance features to a lower energy relative to that of the uranyl U(VI) standard indicate the formation of a uranate-like coordination (47) consistent with the reported U coordination within magnetite (Figure S6). (16, 19)

Figure 1

Figure 1. U M4 edge HERFD-XANES of U co-precipitated with magnetite [Fe(II)/Fe(III) = 0.5 and 0.6] and green rust [Fe(II)/Fe(III) = 0.8 and 2.0] with standards U(IV)O2, (46) U(IV)2U(V)2O9, (46) and U(VI) adsorbed to ferrihydrite. Gray arrows indicate characteristic U(VI) features.

High Resolution Image
Download MS PowerPoint Slide

Incorporation of U within Magnetite and Green Rust

U L3 edge EXAFS spectra (Figure S7 and Table S2) were analyzed to determine the molecular scale speciation of U associated within the magnetite and green rust mineral phases. For U associated with magnetite [Fe(II)/Fe(III) = 0.5 and 0.6], the best fits confirm 4–4.5 oxygen backscatterers at 2.17(1) Å, indicative of uranate-like coordination, (8, 13, 15, 16, 19, 47) which is consistent with our interpretation of the L3 edge XANES spectra. The U–O coordination number is lower than would be predicted for an octahedral site (i.e., <6) because of the presence of a proportion of either U(IV)O2 or U(VI) within the samples. The fitting of Fe shells to the EXAFS was then informed by assuming that incorporation of U into magnetite occurred by substituting U for Fe at an octahedrally coordinated Fe site. The fits confirmed the presence of two U–Fe shells at 3.20(2) and 3.72(2) Å for Fe(II)/Fe(III) = 0.5 and 3.15(2) and 3.69(3) Å for Fe(II)/Fe(III) = 0.6, showing a systematic and significant increase in the interatomic distance relative to the Fe–Fe distances in magnetite (2.97 and 3.48 Å, respectively (38)). At Fe(II)/Fe(III) = 0.6, the additional U–O and U–U backscattering shells observed at 2.42(2) and 3.89(2) Å, respectively, reflect the presence of U(IV) supporting the HERFD-XANES data, and assuming an error of ±1 on the coordination number, the proportions of U(IV) are within error [i.e., 4–20% U(IV)]. Finally, the presence of oxygen backscatterers at 1.81(2) and 2.43(2) Å in the fit for the Fe(II)/Fe(III) = 0.5 sample suggests a modest contribution from U(VI) in uranyl dioxygenyl coordination. This was confirmed by the ITFA analysis and has previously been attributed to U(VI) adsorbed to magnetite. (8, 15)
For Fe(II)/Fe(III) = 0.8 and 2.0 samples, the U–O coordination environment in green rust showed differences when compared to the magnetite system, with U–O distances at approximately 1.90(6) and 2.17(1) Å again indicative of uranate-like coordination. Similar to the magnetite systems, additional U–O and U–U shells at 2.46(2) and 3.89(1) Å confirm the presence of U(IV)O2, which is consistent with the HERFD-XANES analysis and previous studies. (25, 48) Similar to the magnetite system, fitting of additional Fe shells was informed by the green rust structure and assumes direct substitution of octahedrally coordinated Fe by U. The best fits include six Fe atoms at 3.09(1) and 3.28(2) Å with an additional shell of four Fe atoms at 5.24(3) Å. These fits are consistent with the Fe–Fe distances in green rust, which are 3.19 and 5.52 Å, respectively. The dissolution experiments for the Fe(II)/Fe(III) = 0.5, 0.6, and 0.8 samples (Figure S8) show an initial release of 35–40% of U with minimal Fe dissolution, followed by congruent dissolution of U and Fe. This suggests that 60–65% of the U is distributed within the magnetite and/or green rust particles, with the remaining U being discrete U phases (i.e., UO2) or near-surface-associated U(V)/U(VI).
Overall, the EXAFS and dissolution data confirm that U(V) is incorporated within octahedral sites in the Fe(II)/Fe(III) (oxyhydr)oxide phases in a uranate-like coordination environment. This is consistent with several recent experimental and theoretical reports showing U can directly substitute for octahedrally coordinated Fe in iron (oxyhydr)oxide mineral phases. (8, 15, 16, 19, 31) Our work extends these observations for the first time to systems in which U(V) is the dominant species during direct precipitation of both magnetite and green rust.

Mechanism of Incorporation of U(V) into Magnetite and Green Rust

Our results show that direct co-precipitation of U(VI) with magnetite and green rust leads to reduction of U(VI) to U(V) and subsequent stabilization within the bulk structure of both minerals. The stabilization of U(V) via incorporation into Fe(II)/Fe(III)-bearing iron (oxyhydr)oxides has been hypothesized in several systems, (8, 15, 16) with very recent work postulating U(V) stabilization via incorporation into magnetite. (19) For the current work, in both systems U(V) is incorporated into the mineral structures via direct substitution of U for octahedrally coordinated Fe. In magnetite, the average U(V)–O bond length is 2.17(1) Å [Fe(II)/Fe(III) = 0.5 and 0.6], consistent both with U(V) in uranate-like coordination (19, 47) and with recent atomistic simulations that predict a U–O distance of 2.08 Å for this system. (19, 31, 49) The U–Fe interatomic distances derived from the EXAFS data (i.e., 3.15–3.20 and 3.69–3.72 Å) are consistent with those previously published. (19) The U–Fe distances are ≈0.2 Å longer than the Fe–Fe distances in magnetite, but the distance between the two Fe shells matches that of pure magnetite [≈0.5 Å (Table S2)]. Again these values are consistent with U(V) incorporation simulations for the first Fe shell (3.15 Å) in magnetite. (31) The reason for the increased interatomic distances is unlikely to be the size of the incorporated U(V) [the octahedral crystal radius of U(V) is 0.9 Å, and the radii for Fe(II) and Fe(III) are 0.92 and 0.785 Å, respectively]; rather, strengthened repulsive electrostatic interactions between U(V) and the Fe(II/III) atoms pushed the iron out. (31) The low coordination numbers of the U–Fe shells (2) relative to that of pure magnetite (6) are likely due to the nanoparticulate nature of magnetite, which leads to a proportion of the U being near-surface-associated. (50) This is consistent with the dissolution data that shows  35–40% of U is released with minimal Fe dissolution (Figure S8), suggesting this fraction is near-surface-associated U(V)/U(VI) and UO2, with the remaining U distributed evenly throughout the particles. The presence of U(IV) at the (near) surface of the particles is likely due to the presence of Fe(II), which provides strong reducing conditions, resulting in the reduction of sorbed U to U(IV) surface complexes that can transform into UO2 particles.
The incorporation of U(V) into green rust [Fe(II)/Fe(III) = 0.8 and 2.0] again occurs via direct substitution for octahedrally coordinated Fe within the sheet structure of the layered double hydroxide. In addition, the dissolution data indicate that 35–40% of U is present as a discrete phase or is near-surface-associated, which is consistent with the presence of UO2 in the XAS, formed via the process stated above, and some near-surface-associated U(V). The EXAFS data indicate that the U(V) local coordination is different compared to that of magnetite (Figure S7). Indeed, the best fit for these samples confirmed two oxygens at ≈1.9 Å and a shell of four equatorial oxygens at 2.17 Å, again consistent with a uranate-like coordination environment (Table S2). This difference in U(V)–O coordination relative to that of magnetite is presumably due to the layered structure of the green rust and similar to that observed for incorporation of U(V) into other layered iron (oxyhydr)oxides (i.e., lepidocrocite). (51) Here, incorporation of U(V) within isolated octahedral sheets evidently provides significantly less steric constraint on the U(V)–O octahedron relative to U(V) in the highly constrained cubic spinel structure of magnetite. The variation in the axial and equatorial U–O bond lengths in the U(V) incorporated within green rust clearly leads to local distortion of the green rust octahedral sheet and splitting of U–Fe distances relative to the Fe–Fe distances in green rust (Table S2). Overall, the best fit indicates three or four Fe–O octahedra adjacent to the short (1.9 Å) U–O axial oxygens and approximately two Fe–O octahedra adjacent to the long (2.17 Å) U–O equatorial oxygen distances (Figure 2). This is consistent with the U(V) being present in a distorted octahedral environment and is presumably due to the enhanced flexibility of the octahedral sheet in green rust compared to octahedral sites within cubic magnetite.

Figure 2

Figure 2. (A) Magnetite structure showing Fe–Fe distances (38) and U–Fe distances obtained from EXAFS at Fe(II)/Fe(III) = 0.6. (B) Green rust structures showing Fe–Fe distances (40) and U–Fe distances obtained from EXAFS at Fe(II)/Fe(III) = 2.0. Yellow lines indicate shorter U–O distances (1.9 Å), and white lines indicate longer U–O distances (2.17 Å).

High Resolution Image
Download MS PowerPoint Slide
The novel incorporation of U(V) in green rust is in contrast to the results of previous sorption studies in which U(IV) surface complexes or UO2(s) was observed as the reaction end product. (25, 48, 52)
The observed energy shift of the U(V) M4 edge HERFD-XANES main peak position (Figure 1) for different Fe(II)/Fe(III) ratios (Figure S4) from 3726.5 eV [Fe(II)/Fe(III) = 0.5] to 3726.3 eV [Fe(II)/Fe(III) = 2.0] may relate to the different strengths of the covalent bond between the U and neighboring atoms. (53) Electronic structure calculations (Figure S9) show a clear difference in the distribution of density of states for U incorporated into the octahedral site of magnetite relative to green rust. The hybridization between U f states and Fe d states above the Fermi level is much stronger for U incorporated into green rust than for U incorporated into magnetite. This may be associated with a stronger, more covalent, U bond in green rust compared to the U bond in the magnetite structure.

Mechanism of U(V) Stabilization

Our results suggest that U(V) incorporation during magnetite and green rust formation occurs via a two-step process (abstract graphic). First, we suggest that U(VI) is adsorbed to the surface of the growing Fe(II)/Fe(III) (oxyhydr)oxide nanoparticles and undergoes reduction to U(V) via one-electron transfer. (8) Second, during rapid crystal growth, the U(V), which is compatible with the Fe octahedral site in both magnetite (19) and green rust, becomes incorporated within the structure. These steps are consistent with those proposed for U(V) incorporation during goethite formation; (14) however, further research is required to determine the exact nature of each step in the process. Recent work has highlighted that disproportion of U(V) can occur on the magnetite surface, implying that stabilization of structural U(V) may occur only during rapid crystal growth. (10) Under these conditions, isolation of U(V) within the mineral structure may prevent its disproportionation to U(IV) and U(VI). Indeed, U(V) is reportedly stable in magnetite for up to 550 days, suggesting that incorporated U(V) may be stable over extended time periods. (15) Furthermore, steric constraints seem likely to favor U(V) stabilization in these systems as U(IV) strongly prefers larger coordination environments (e.g., n = 8). (8, 13, 20) Indeed, steric constraints may be the most crucial factor in stabilizing U(V) as both magnetite and green rust are electrically conductive, (54) and therefore, physical isolation of U(V) alone seems unlikely to prevent disproportionation.

Implications for U Speciation and the Fate of U in the Environment

Here, we have shown the reduction of U(VI) to U(V) followed by incorporation into both magnetite and green rust is the dominant process during the direct precipitation of these mineral phases. The potential for U(V) incorporation processes to be dominant in these environmentally relevant phases is certainly highlighted in this and other very recent work (19) and has important implications, which have not been fully explored, for understanding and predicting U mobility in engineered and natural environments. Clearly, the extent of incorporation of U(V) into Fe(II)/Fe(III) (oxyhydr)oxides forming under contaminated land and geodisposal conditions needs to be fully quantified. Incorporation of U(V) into mineral phases commonly present in contaminated environments may offer a more resilient species for oxidative remobilization compared to uraninite and adsorbed U(IV), which are readily oxidized to soluble U(VI) in many environmental systems. (16, 55) The incorporation of U(V) into magnetite and green rust offers a promising prospect for optimizing its incorporation in a range of engineered settings, while the stability of U(V) in these systems clearly warrants further investigation.

Supporting Information

ARTICLE SECTIONS
Jump To

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.estlett.7b00348.

  • Additional figures and tables showing XRD patterns, TEM images and EDS analyses, HERFD-XANES data and fitting results, EXAFS fitting parameters, dissolution data, and a description of the EXAFS fitting process (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 Author
    • Samuel Shaw - Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom;  Orcidhttp://orcid.org/0000-0002-6353-5454;  Email: [email protected]
  • Authors
    • Hannah E. Roberts - Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom
    • Katherine Morris - Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom;  Orcidhttp://orcid.org/0000-0002-0716-7589
    • Gareth T. W. Law - Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom;  Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom;  Orcidhttp://orcid.org/0000-0002-2320-6330
    • J. Frederick W. Mosselmans - Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom;  Orcidhttp://orcid.org/0000-0001-6473-2743
    • Pieter Bots - Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, United Kingdom
    • Kristina Kvashnina - The Rossendorf Beamline at ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France;  Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden, Germany
  • Notes
    The authors declare no competing financial interest.

Acknowledgment

ARTICLE SECTIONS
Jump To

This work was supported by the STFC (ST/L502534/1), Env Rad Net (ST/K001787/1 and ST/N002474/1), and BIGRAD (NE/H007768/1). We thank both Diamond Light Source (DLS) (SP9621-2, SP10163-1, and SP12767-1) and European Synchrotron Radiation Facility (ESRF) (EV/192) for beam time. We thank Dr. Giannantonio Cibin, Dr. Steve Parry, and Richard Doull for their help during beam time at DLS, Dr. Sara Lafuerza for help during beam time at ESRF, Dr. John Waters for help with XRD, Dr. Heath Bagshaw for help with TEM, Ellen Winstanley for providing U(VI) HERFD-XANES data, and Dr. Carolyn Pearce for help with the mineral synthesis method.

References

ARTICLE SECTIONS
Jump To

This article references 55 other publications.

  1. 1
    Newsome, L.; Morris, K.; Lloyd, J. R. The biogeochemistry and bioremediation of uranium and other priority radionuclides Chem. Geol. 2014, 363, 164– 184 DOI: 10.1016/j.chemgeo.2013.10.034
    [Crossref], [CAS], Google Scholar
    1
    The biogeochemistry and bioremediation of uranium and other priority radionuclides
    Newsome, Laura; Morris, Katherine; Lloyd, Jonathan R.
    Chemical Geology (2014), 363 (), 164-184CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
    Microbial metab. has the potential to alter the soly. of a broad range of priority radionuclides, including uranium, other actinides and fission products. Of notable interest has been the biostimulation of anaerobic microbial communities to remove redox-sensitive radionuclides such as uranium U(VI) from contaminated groundwaters at nuclear sites. Particularly promising are bioredn. processes, whereby bacteria enzymically reduce aq. U(VI) to insol. U(IV) coupled to oxidn. of an org. electron donor; and uranium phosphate biomineralization, in which bacterial phosphatase activity cleaves organophosphates, liberating inorg. phosphate that ppts. with aq. U(VI) as uranyl phosphate minerals. Here we review the mechanisms of uranium bioredn. and phosphate biomineralization and their suitability to facilitate long-term pptn. of uranium from groundwater, with particular focus on in situ trials at the US Department of Energy field sites. Redox interactions of other priority radionuclides (technetium, neptunium, plutonium, americium, iodine, strontium and caesium) are also reviewed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXksFOmtw%253D%253D&md5=082030dc4e6b69149b5fbdf1ade3f69d
  2. 2
    Moyce, E. B. A.; Rochelle, C.; Morris, K.; Milodowski, A. E.; Chen, X.; Thornton, S.; Small, J. S.; Shaw, S. Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste Appl. Geochem. 2014, 50, 91– 105 DOI: 10.1016/j.apgeochem.2014.08.003
    [Crossref], [CAS], Google Scholar
    2
    Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste
    Moyce, Elizabeth B. A.; Rochelle, Christopher; Morris, Katherine; Milodowski, Antoni E.; Chen, Xiaohui; Thornton, Steve; Small, Joe S.; Shaw, Samuel
    Applied Geochemistry (2014), 50 (), 91-105CODEN: APPGEY; ISSN:0883-2927. (Elsevier Ltd.)
    The interaction of groundwater with cement in a geol. disposal facility (GDF) for intermediate level radioactive waste will produce a high pH leachate plume. Such a plume may alter the phys. and chem. properties of the GDF host rock. However, the geochem. and mineralogical processes which may occur in such systems over timescales relevant for geol. disposal remain unclear. This study has extended the timescale for lab. expts. and shown that, after 15 years two distinct phases of reaction may occur during alteration of a dolomite-rich rock at high pH. In these expts. the dissoln. of primary silicate minerals and the formation of secondary calcium silicate hydrate (C-S-H) phases contg. varying amts. of aluminum and potassium (C-(A)-(K)-S-H) during the early stages of reaction (up to 15 mo) have been superseded as the systems have evolved. After 15 years significant dedolomitisation (MgCa(CO3)2 + 2OH- → Mg(OH)2 + CaCO3 + CO2-32-(aq)) has led to the formation of magnesium silicates, such as saponite and talc, contg. variable amts. of aluminum and potassium (Mg-(Al)-(K)-silicates), and calcite at the expense of the early-formed C-(A)-(K)-S-H phases. This occurred in high pH solns. representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a KOH and NaOH or a Ca(OH)2 dominated soln. but a greater extent of alteration in the higher pH KOH/NaOH leachate. The high pH alteration of the rock over 15 years also increased the rock's sorption capacity for U(VI). The results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite-rich rock in the geosphere. These processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geol. disposal.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFGlurjM&md5=97dc93a1126cf9534cd1fa4b102db878
  3. 3
    Gavrilescu, M.; Pavel, L. V.; Cretescu, I. Characterization and remediation of soils contaminated with uranium J. Hazard. Mater. 2009, 163 (2–3) 475– 510 DOI: 10.1016/j.jhazmat.2008.07.103
    [Crossref], [PubMed], [CAS], Google Scholar
    3
    Characterization and remediation of soils contaminated with uranium
    Gavrilescu, Maria; Pavel, Lucian Vasile; Cretescu, Igor
    Journal of Hazardous Materials (2009), 163 (2-3), 475-510CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
    A review. Environmental contamination caused by radionuclides, in particular by uranium and its decay products is a serious problem worldwide. The development of nuclear science and technol. has led to increasing nuclear waste contg. uranium being released and disposed in the environment. The objective of this paper is to develop a better understanding of the techniques for the remediation of soils polluted with radionuclides (uranium in particular), considering: the chem. forms of uranium, including depleted uranium (DU) in soil and other environmental media, their characteristics and concns., and some of the effects on environmental and human health; research issues concerning the remediation process, the benefits and results; a better understanding of the range of uses and situations for which each is most appropriate. The paper addresses the main features of the following techniques for uranium remediation: natural attenuation, phys. methods, chem. processes (chem. extn. methods from contaminated soils assisted by various suitable chelators (sodium bicarbonate, citric acid, two-stage acid leaching procedure), extn. using supercrit. fluids such as solvents, permeable reactive barriers), biol. processes (biomineralization and microbial redn., phytoremediation, biosorption), and electrokinetic methods. In addn., factors affecting uranium removal from soils are furthermore reviewed including soil characteristics, pH and reagent concn., retention time.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhvFait7s%253D&md5=513e376b91681948aae8fa59e27f6bf8
  4. 4
    Bone, S. E.; Dynes, J. J.; Cliff, J.; Bargar, J. R. Uranium(IV) adsorption by natural organic matter in anoxic sediments Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (4) 711 DOI: 10.1073/pnas.1611918114
    [Crossref], [PubMed], [CAS], Google Scholar
    4
    Uranium(IV) adsorption by natural organic matter in anoxic sediments
    Bone, Sharon E.; Dynes, James J.; Cliff, John; Bargar, John R.
    Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (4), 711-716CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temp. geochem. environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly sol. mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to org. carbon and org. carbon-coated clays dominate U(IV) speciation in an org.-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of redn. (i.e., whether redn. is mediated by microbes or by inorg. reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of redn. pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to org. matter within the sediment environment.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmslWrtg%253D%253D&md5=808b80c037df85cb10520fed03cfcb1e
  5. 5
    Ekstrom, A. Kinetics and Mechanism of the Disproportionation of Uranium(V) Inorg. Chem. 1974, 13 (9) 2237– 2241 DOI: 10.1021/ic50139a035
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    5
    Kinetics and mechanism of the disproportionation of uranium(V)
    Ekstrom, A.
    Inorganic Chemistry (1974), 13 (9), 2237-41CODEN: INOCAJ; ISSN:0020-1669.
    The kinetics and mechanism of the disproportionation of UO2+ [21294-41-7] were investigated. In agreement with a previous study (T. W. Newton; F. B. Baker, 1965), the rate of disproportionation was retarded by the presence of UO22+ [16637-16-4], the effect being attributed to the formation of a U(V).U(VI) complex whose absorption spectrum in the range 360-760 nm was measured. The effects of ionic strength, acid concn., and the presence of complex anions on the disproportionation rate were examd. The reaction was also studied in D2O soln. and reaction mechanisms are discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXkvVaku70%253D&md5=65107db2f141e134c429dec087883ebe
  6. 6
    Steele, H.; Taylor, R. J. A Theoretical Study of the Inner-Sphere Disproportionation Reaction Mechanism of the Pentavalent Actinyl Ions Inorg. Chem. 2007, 46 (16) 6311– 6318 DOI: 10.1021/ic070235c
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    6
    A theoretical study of the inner-sphere disproportionation reaction mechanism of the pentavalent actinyl ions
    Steele, Helen; Taylor, Robin J.
    Inorganic Chemistry (2007), 46 (16), 6311-6318CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    The inner-sphere mechanisms of the disproportionation reactions of U(V), Np(V), and Pu(V) ions have been studied using a quantum mech. approach. The U(V) disproportionation proceeds via the formation of a dimer (a cation-cation complex) followed by two successive protonations at the axial oxygens of the donor uranyl ion. Bond lengths and spin multiplicities indicate that electron transfer occurs after the first protonation. A solvent water mol. then breaks the complex into solvated U(OH)22+ and UO22+ ions. Pu(V) behaves similarly, but Np(V) appears not to follow this path. The observations from quantum modeling are consistent with existing exptl. data on actinyl(V) disproportionation reactions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXns1CktL4%253D&md5=56e8e4e1cd716169797c39487c14cedf
  7. 7
    Ikeda, A.; Hennig, C.; Tsushima, S.; Takao, K.; Ikeda, Y.; Scheinost, A. C.; Bernhard, G. Comparative study of uranyl(VI) and -(V) carbonato complexes in an aqueous solution Inorg. Chem. 2007, 46 (10) 4212– 4219 DOI: 10.1021/ic070051y
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    7
    Comparative Study of Uranyl(VI) and -(V) Carbonato Complexes in an Aqueous Solution
    Ikeda, Atsushi; Hennig, Christoph; Tsushima, Satoru; Takao, Koichiro; Ikeda, Yasuhisa; Scheinost, Andreas C.; Bernhard, Gert
    Inorganic Chemistry (2007), 46 (10), 4212-4219CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Electrochem., complexation, and electronic properties of uranyl(VI) and -(V) carbonato complexes in an aq. Na2CO3 soln. were studied to define the appropriate conditions for prepg. pure uranyl(V) samples and to understand the difference in coordination character between UO22+ and UO2+. Cyclic voltammetry using 3 different working electrodes of Pt, Au, and glassy C suggested that the electrochem. reaction of uranyl(VI) carbonate species proceeds quasi-reversibly. Electrolysis of UO22+ was performed in Na2CO3 solns. of >0.8 M with a limited pH range of 11.7 < pH < 12.0 using a Pt mesh electrode. It produces a high purity of the uranyl(V) carbonate soln., which is stable for at least 2 wk in a sealed glass cuvette. Extended x-ray absorption fine structure (EXAFS) measurements revealed the structural arrangement of uranyl(VI) and -(V) tricarbonato complexes, [UO2(CO3)3]n- [n = 4 for uranyl(VI), 5 for uranyl(V)]. The bond distances of U-Oax, U-Oeq, U-C, and U-Odist are 1.81, 2.44, 2.92, and 4.17 Å for the uranyl(VI) complex and 1.91, 2.50, 2.93, and 4.23 Å for the uranyl(V) complex, resp. The validity of the structural parameters obtained from EXAFS was supported by quantum chem. calcns. for the uranyl(VI) complex. The U L|- and L|||-edge x-ray absorption near-edge structure spectra were interpreted in terms of electron transitions and multiple-scattering features.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjvVOlsLs%253D&md5=aa3cc71c9c632e1db9faac798eea2f06
  8. 8
    Ilton, E. S.; Boily, J. F.; Buck, E. C.; Skomurski, F. N.; Rosso, K. M.; Cahill, C. L.; Bargar, J. R.; Felmy, A. R. Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface Environ. Sci. Technol. 2010, 44, 170– 176 DOI: 10.1021/es9014597
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    8
    Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface
    Ilton, Eugene S.; Boily, Jean-Francois; Buck, Edgar C.; Skomurski, Frances N.; Rosso, Kevin M.; Cahill, Christopher L.; Bargar, John R.; Felmy, Andrew R.
    Environmental Science & Technology (2010), 44 (1), 170-176CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    The heterogeneous redn. of UVI to UIV by ferrous iron is believed to be a key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. Published results from UVI-magnetite expts. have been variable, ranging from no redn. to clear evidence for the formation of UIV. In this contribution, we used XAS and high resoln. (±cryogenic) XPS to study the interaction of UVI with nanoparticulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UIV. However, thermodn. calcns. indicated that U phases with av. oxidn. states below (V) should have been stable, indicating that the system was not in redox equil. A reaction pathway that involves incorporation and stabilization of UV and UVI into secondary phases is invoked to explain the observations. The results suggest an important and previously unappreciated role of UV in the fate and transport of uranium in the environment.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtlagsbnN&md5=0565c8450d91f25cd92f8953133b8e4d
  9. 9
    Ilton, E. S.; Haiduc, A.; Cahill, C. L.; Felmy, A. R. Mica Surfaces Stabilize Pentavalent Uranium Inorg. Chem. 2005, 44 (9) 2986– 2988 DOI: 10.1021/ic0487272
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  10. 10
    Yuan, K.; Renock, D.; Ewing, R. C.; Becker, U. Uranium reduction on magnetite: Probing for pentavalent uranium using electrochemical methods Geochim. Cosmochim. Acta 2015, 156, 194– 206 DOI: 10.1016/j.gca.2015.02.014
    [Crossref], [CAS], Google Scholar
    10
    Uranium reduction on magnetite: Probing for pentavalent uranium using electrochemical methods
    Yuan, Ke; Renock, Devon; Ewing, Rodney C.; Becker, Udo
    Geochimica et Cosmochimica Acta (2015), 156 (), 194-206CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Pentavalent uranium is generally treated as an unstable intermediate when uranyl, U(VI)O2+2, is reduced to U4+. However, mineral surfaces have been shown to stabilize pentavalent uranium, thus hindering further redn. (Ilton et al., 2005, 2010). The subject of this study is to identify the kinetic pathways that lead to U(V)O+2 being a metastable species. Electrochem. methods provide an in situ approach for the investigation of the intermediate reaction of U(V)O+2 on the surfaces of magnetite. Redox reactions of uranyl ions on particulate (∼3 μm) and bulk magnetite surfaces were investigated using cyclic voltammetry and potential step chronoamperometry using cavity microelectrodes and bulk (planar) mineral electrodes. The estd. redox potentials are consistent with the std. redox potential of UO2+2/UO+2, indicating UO2+2 is first reduced to UO+2 on the surfaces of both powder and bulk magnetite. The one-electron redn. of UO2+2 to UO+2 was further confirmed by directly measuring the no. of electrons transferred during the redn. process on the bulk magnetite electrode. Based on the charge conservation anal. and the pos. correlation between the pH and the peak current for the UO+2 transformation to UO2+2, the peak corresponding to the oxidn. of U4+ to UO2+2 was assigned in the voltammograms of particulate magnetite. The presence of U4+ indicates that the disproportionation of UO+2 (2U(V) ↔ U(IV) + U(VI)) is occurring on the surface of particulate magnetite within the timeframe of the expt. The lack of a peak for U4+ in voltammograms for bulk magnetite suggests that the rate of the UO+2 disproportionation reaction is slower on bulk magnetite than that on particulate magnetite. The catalytic property of particulate magnetite surfaces on the disproportionation reaction is explained by its ability to adsorb and desorb protons, which could facilitate the proton-coupled disproportionation reaction of UO+2. This increased catalytic activity and related adsorption and desorption kinetics of protons may be related to the increased no. of under-coordinated surface sites near step edges on the magnetite powder.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsF2rt7w%253D&md5=2444be57fb4718c8270ad5c326122f78
  11. 11
    Yuan, K.; Ilton, E. S.; Antonio, M. R.; Li, Z.; Cook, P. J.; Becker, U. Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite Environ. Sci. Technol. 2015, 49 (10) 6206– 6213 DOI: 10.1021/acs.est.5b00025
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    11
    Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite
    Yuan, Ke; Ilton, Eugene S.; Antonio, Mark R.; Li, Zhongrui; Cook, Peter J.; Becker, Udo
    Environmental Science & Technology (2015), 49 (10), 6206-6213CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Redn. of U(VI) to U(IV) on mineral surfaces is often considered a one-step 2-electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies indicates U(VI) can undergo a 1-electron redn. to U(V) without further progression to U(IV). We studied redn. pathways of U by reducing U(VI) electrochem. on a magnetite electrode at pH 3.4. Cyclic voltammetry confirms the 1-electron redn. of U(VI) to U(V). Formation of nanosize U ppts. on the magnetite surface at reducing potentials and dissoln. of the solids at oxidizing potentials are obsd. by in situ electrochem. at. force microscopy. XPS anal. of the magnetite electrodes polarized in U solns. at voltages from -0.1 to -0.9 V (E0U(VI)/U(V)= -0.135 V vs. Ag/AgCl) show the presence of only U(V) and U(VI). The sample with the highest U(V)/U(VI) ratio was prepd. at -0.7 V, where the longest av. U-Oaxial distance of 2.05±0.01 Å was evident in the same sample revealed by extended x-ray absorption fine structure anal. The results demonstrate that the electrochem. redn. of U(VI) on magnetite only yields U(V), even at a potential of -0.9 V, which favors the 1-electron redn. mechanism. U(V) does not disproportionate but stabilizes on magnetite through pptn. of mixed-valence state U(V)/U(VI) solids.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmslChtLg%253D&md5=d2ec7b36018e5d6881447462ad135f76
  12. 12
    Tsarev, S.; Collins, R. N.; Fahy, A.; Waite, T. D. Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zerovalent Iron Environ. Sci. Technol. 2016, 50 (5) 2595– 2601 DOI: 10.1021/acs.est.5b06160
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    12
    Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zero Valent Iron
    Tsarev, Sergey; Collins, Richard N.; Fahy, Adam; Waite, T. David
    Environmental Science & Technology (2016), 50 (5), 2595-2601CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Nanoscale zero-valent Fe (nZVI) has demonstrated potential as an effective agent to remediate U-contaminated subsurface environments; however, the nature of and reaction product formation kinetics have not been fully elucidated at environmentally relevant conditions. This work examd. the O-free reaction of U6+ with varying quantities of nZVI at pH 7 in the presence of Ca and CO32- by x-ray absorption spectroscopy, x-ray diffraction, and transmission electron microscopy. The reduced U solid phase structure was time dependent and largely affected by system nZVI:U ratio. At the highest examd. U:Fe molar ratio, 1:4, nanoscale uraninite (UO2) was predominantly formed within 1 day of reaction. At lower U:Fe molar ratios, 1:21, evidence was obtained for formation of sorbed U4+ and U5+ surface complexes which slowly transformed to UO2 nanoparticles stable for up to 1 yr of anaerobic incubation. Following 8 days reaction at the lowest examd. U:Fe molar ratio, 1:110, sorbed U4+ was still the major U form assocd. with the solid phase. Regardless of the U:Fe molar ratio, anaerobic corrosion of nZVI resulted in the slow formation of micron-sized fibrous chukanovite (Fe2(OH)2CO3) particles.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvV2rs78%253D&md5=b50729fad63004af0d02f1dfe555b2c6
  13. 13
    Ilton, E. S.; Pacheco, J. S. L.; Bargar, J. R.; Shi, Z.; Liu, J.; Kovarik, L.; Engelhard, M. H.; Felmy, A. R. Reduction of U(VI) Incorporated in the Structure of Hematite Environ. Sci. Technol. 2012, 46, 9428– 9436 DOI: 10.1021/es3015502
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    13
    Reduction of U(VI) Incorporated in the Structure of Hematite
    Ilton, Eugene S.; Pacheco, Juan S. Lezama; Bargar, John R.; Shi, Zhi; Liu, Juan; Kovarik, Libor; Engelhard, Mark H.; Felmy, Andrew R.
    Environmental Science & Technology (2012), 46 (17), 9428-9436CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    U(VI) doped hematite was synthesized and exposed to two different org. reductants with E0 of 0.23 and 0.70 V. A combination of HAADF-TEM and EXAFS provided evidence that uranium was incorporated in hematite in uranate, likely octahedral coordination. XPS indicated that structurally incorporated U(VI) was reduced to U(V), whereas non-incorporated U(VI) was reduced to U(IV). Specifically, the expts. indicate that U(V) was the dominant oxidn. state of uranium in hematite around Eh -0.24 to -0.28 V and pH 7.7-8.6 for at least up to 5 wk of reaction time. U(V), but not U(IV), was also detected in hematite at Eh +0.21 V (pH 7.1-7.3). The results support the hypothesis, based on previous exptl. and theor. work, that the stability field of U(V) is widened relative to U(IV) and U(VI) in uranate coordination environments where the coordination no. of U is less than 8.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFSjurfN&md5=8205cc1c3a1027d8eb77d528a47faf5a
  14. 14
    Massey, M. S.; Lezama-Pacheco, J. S.; Jones, M. E.; Ilton, E. S.; Cerrato, J. M.; Bargar, J. R.; Fendorf, S. Competing retention pathways of uranium upon reaction with Fe(II) Geochim. Cosmochim. Acta 2014, 142 (1) 166– 185 DOI: 10.1016/j.gca.2014.07.016
    [Crossref], [CAS], Google Scholar
    14
    Competing retention pathways of uranium upon reaction with Fe(II)
    Massey, Michael S.; Lezama-Pacheco, Juan S.; Jones, Morris E.; Ilton, Eugene S.; Cerrato, Jose M.; Bargar, John R.; Fendorf, Scott
    Geochimica et Cosmochimica Acta (2014), 142 (), 166-185CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Biogeochem. retention processes, including adsorption, reductive pptn., and incorporation into host minerals, are important in contaminant transport, remediation, and geol. deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3·nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway's contribution to U retention, including: (i) the competitiveness of U incorporation vs. redn. to U(IV) and subsequent pptn. of UO2; (ii) the oxidn. state of incorporated U; (iii) the effects of uranyl aq. speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ∼7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM coupled with spectroscopic examn. of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended X-ray absorption fine structure (EXAFS) spectroscopy, X-ray powder diffraction, XPS, and transmission electron microscopy. Anal. of EXAFS spectra showed that 14-89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concns. ≤50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64-89% of total U. With increasing U(VI) and Fe(II) concns., U(VI) redn. to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron oxides as a retention process of U across a wide range of biogeochem. environments and the sensitivity of uranium retention processes to operative (bio)geochem. conditions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Gqu7vF&md5=694b78d5b684ed09757800937271ea50
  15. 15
    Huber, F.; Schild, D.; Vitova, T.; Rothe, J.; Kirsch, R.; Schäfer, T. U(VI) removal kinetics in presence of synthetic magnetite nanoparticles Geochim. Cosmochim. Acta 2012, 96, 154– 173 DOI: 10.1016/j.gca.2012.07.019
    [Crossref], [CAS], Google Scholar
    15
    U(VI) removal kinetics in presence of synthetic magnetite nanoparticles
    Huber, F.; Schild, D.; Vitova, T.; Rothe, J.; Kirsch, R.; Schaefer, T.
    Geochimica et Cosmochimica Acta (2012), 96 (), 154-173CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    The interaction of hexavalent U with a freshly synthesized nanoparticulate magnetite (FeIIFeIII2O4) (stoichiometric ratio x(Fe(II)/FeTOT) = 0.25-0.33), a partly oxidized synthetic nanoparticulate magnetite (x = 0.11-0.27) and maghemite nanoparticles (x = 0-1) under anoxic conditions and exclusion of CO2 as function of pH, contact time and total U concn. (3 × 10-5 M and 1 × 10-7 M) has been examd. Short term kinetic batch expts. (contact time of 90 d) for four different pH values have been conducted. Moreover, classical batch pH sorption edges have been prepd. for two different uranium concns. for a contact time of 550 d. Spectroscopic techniques (XPS, XAS) were applied to probe for the presence and amt. of reduced U on the magnetite surface. Batch kinetic studies revealed a fast initial U removal from aq. soln. with >90% magnetite assocd. U after 24 h within the pH range 5-11. Long-term contact time batch expts. (550 d) showed neither a U removal below pH < 3 nor a decrease in the magnetite assocd. U at pH ≥ 9. Redox speciation by XPS verifies the presence of reduced U (both U(IV) and U(V) were resolved if the satellite structures were used in the fitting procedure) at the near surface of magnetite up to a contact time of 550 d and a clear correlation of the amt. of available Fe(II) on the magnetite surface and the amt. of reduced U is obsd. XANES investigation supports presence of U(V)/U(VI) uranate and U(IV). Interpretation of the EXAFS for one sample is consistent with incorporation of U into an Fe oxide phase, after long reaction times. Thermodn. calcns. based on the exptl. detd. redox potentials corroborate the spectroscopic findings of U oxidn. states. Overall, the results reflect the importance of structurally bound Fe(II) as redox partner for uranyl redn.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsV2js73M&md5=8ed206c8574a8746b844f3fb8f905d89
  16. 16
    Marshall, T. A.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Roberts, H.; Shaw, S. Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste Mineral. Mag. 2015, 79 (6) 1265– 1274 DOI: 10.1180/minmag.2015.079.6.02
    [Crossref], [CAS], Google Scholar
    16
    Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste
    Marshall, Timothy A.; Morris, Katherine; Law, Gareth T. W.; Mosselmans, Frederick W.; Bots, Pieter; Roberts, Hannah; Shaw, Samuel
    Mineralogical Magazine (2015), 79 (6), 1265-1274CODEN: MNLMBB; ISSN:1471-8022. (Walter de Gruyter GmbH)
    Uranium incorporation into magnetite and its behavior during subsequent oxidn. has been investigated at high pH to det. the uranium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to U(VI)aq contg. cement leachates (pH 10.5-13.1) and crystn. of magnetite was induced via addn. of Fe(II)aq. A combination of XRD, chem. extn. and XAS techniques provided direct evidence that U(VI) was reduced and incorporated into the magnetite structure, possibly as U(V), with a significant fraction recalcitrant to oxidative remobilization. Immobilization of U(VI) by redn. and incorporation into magnetite at high pH, and with significant stability upon reoxidn., has clear and important implications for limiting uranium migration in geol. disposal of radioactive wastes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWlt7nI&md5=6ed6719bd416be168de6d69d924c9ccc
  17. 17
    Boland, D. D.; Collins, R. N.; Payne, T. E.; Waite, T. D. Effect of Amorphous Fe(III) Oxide Transformation on the Fe(II)-Mediated Reduction of U(VI) Environ. Sci. Technol. 2011, 45, 1327– 1333 DOI: 10.1021/es101848a
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    17
    Effect of Amorphous Fe(III) Oxide Transformation on the Fe(II)-Mediated Reduction of U(VI)
    Boland, Daniel D.; Collins, Richard N.; Payne, Timothy E.; Waite, T. David
    Environmental Science & Technology (2011), 45 (4), 1327-1333CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    It has recently been reported that the Fe(II)-catalyzed crystn. of 2-line ferrihydrite to goethite and magnetite can result in the immobilization of uranium. Although it might be expected that interference of the crystn. process (for example, by the presence of silicate) would prevent uranium immobilization, this has not yet been demonstrated. Here we present results of an X-ray absorption spectroscopy study on the fate of hexavalent uranium (U(VI)) during the Fe(II)-catalyzed transformations of 2-line ferrihydrite and ferrihydrite copptd. with silicate (silicate-ferrihydrite). Two-line ferrihydrite transformed monotonically to goethite, whereas silicate-ferrihydrite transformed into a form similar to ferrihydrite synthesized in the absence of silicate. Modeling of U L(III)-edge EXAFS data indicated that both copptd. and adsorbed U(VI) were initially assocd. with ferrihydrite and silicate-ferrihydrite as a mononuclear bidentate surface complex. During the Fe(II)-catalyzed transformation process, U(VI) assocd. with 2-line ferrihydrite was reduced and partially incorporated into the newly formed goethite mineral structure, most likely as U(V), whereas U(VI) assocd. with silicate-ferrihydrite was not reduced and remained in a form similar to its initially adsorbed state. Uranium(VI) that was initially adsorbed to silicate-ferrihydrite did, however, become more resistant to reductive dissoln. indicating at least a partial redn. in mobility. These results suggest that when the Fe(II)-catalyzed transformation of ferrihydrite-like iron oxyhydroxides is inhibited, at least under conditions similar to those used in these expts., uranium redn. will not occur.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXit1Cmug%253D%253D&md5=5f279b5adec98f1f23df9db859ad236a
  18. 18
    Boland, D. D.; Collins, R. N.; Glover, C. J.; Payne, T. E.; Waite, T. D. Reduction of U(VI) by Fe(II) during the Fe(II)-Accelerated Transformation of Ferrihydrite Environ. Sci. Technol. 2014, 48 (16) 9086– 9093 DOI: 10.1021/es501750z
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    18
    Reduction of U(VI) by Fe(II) during the Fe(II)-accelerated transformation of ferrihydrite
    Boland, Daniel D.; Collins, Richard N.; Glover, Chris J.; Payne, Timothy E.; Waite, T. David
    Environmental Science & Technology (2014), 48 (16), 9086-9093CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    X-ray absorption spectroscopy has been used to study the redn. of adsorbed U(VI) during the Fe(II)-accelerated transformation of ferrihydrite to goethite. The fate of U(VI) was examd. across a variety of pH values and Fe(II) concns., with results suggesting that, in all cases, it was reduced over the course of the Fe(III) phase transformation to a U(V) species incorporated in goethite. A pos. correlation between U(VI) redn. and ferrihydrite transformation rate consts. implies that U(VI) redn. was driven by the prodn. of goethite under the conditions used in these studies. This interpretation was supported by addnl. exptl. evidence that demonstrated the (fast) redn. of U(VI) to U(V) by Fe(II) in the presence of goethite only. Theor. redox potential calcns. clearly indicate that the redn. of U(VI) by Fe(II) in the presence of goethite is thermodynamically favorable. In contrast, redn. of U(VI) by Fe(II) in the presence of ferrihydrite is largely thermodynamically unfavorable within the range of conditions examd. in this study.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFCitr7M&md5=c76320d8482b88dd04406a95594818cf
  19. 19
    Pidchenko, I.; Kvashnina, K. O.; Yokosawa, T.; Finck, N.; Bahl, S.; Schild, D.; Polly, R.; Bohnert, E.; Rossberg, A.; Göttlicher, J. Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles Environ. Sci. Technol. 2017, 51, 2217– 2225 DOI: 10.1021/acs.est.6b04035
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    19
    Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles
    Pidchenko, Ivan; Kvashnina, Kristina O.; Yokosawa, Tadahiro; Finck, Nicolas; Bahl, Sebastian; Schild, Dieter; Polly, Robert; Bohnert, Elke; Rossberg, Andre; Goettlicher, Joerg; Dardenne, Kathy; Rothe, Joerg; Schaefer, Thorsten; Geckeis, Horst; Vitova, Tonya
    Environmental Science & Technology (2017), 51 (4), 2217-2225CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Uranium redox states and speciation in magnetite nanoparticles copptd. with U(VI) for uranium loadings varying from 1000 to 10000 ppm are investigated by X-ray absorption spectroscopy (XAS). It is demonstrated that the U M4 high energy resoln. X-ray absorption near edge structure (HR-XANES) method is capable to clearly characterize U(IV), U(V), and U(VI) existing simultaneously in the same sample. The contributions of the three different uranium redox states are quantified with the iterative transformation factor anal. (ITFA) method. U L3 XAS and transmission electron microscopy (TEM) reveal that initially sorbed U(VI) species recrystallize to nonstoichiometric UO2+x nanoparticles within 147 days when stored under anoxic conditions. These U(IV) species oxidize again when exposed to air. U M4 HR-XANES data demonstrate strong contribution of U(V) at day 10 and that U(V) remains stable over 142 days under ambient conditions as shown for magnetite nanoparticles contg. 1000 ppm U. U L3 XAS indicates that this U(V) species is protected from oxidn. likely incorporated into octahedral magnetite sites. XAS results are supported by d. functional theory (DFT) calcns. Further characterization of the samples include powder X-ray diffraction (pXRD), SEM and Fe 2p XPS.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVKiu7w%253D&md5=9bea4b58876b52e93c98edb8cf680bc3
  20. 20
    Skomurski, F. N.; Ilton, E. S.; Engelhard, M. H.; Arey, B. W.; Rosso, K. M. Heterogeneous reduction of U6+ by structural Fe2+ from theory and experiment Geochim. Cosmochim. Acta 2011, 75 (22) 7277– 7290 DOI: 10.1016/j.gca.2011.08.006
    [Crossref], [CAS], Google Scholar
    20
    Heterogeneous reduction of U6+ by structural Fe2+ from theory and experiment
    Skomurski, F. N.; Ilton, E. S.; Engelhard, M. H.; Arey, B. W.; Rosso, K. M.
    Geochimica et Cosmochimica Acta (2011), 75 (22), 7277-7290CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    Computational and exptl. studies were performed to explore heterogeneous redn. of U6+ by structural Fe2+ at magnetite (Fe3O4) surfaces. Mol. Fe-Fe-U models representing a uranyl species adsorbed in a diat. bidentate fashion to an iron surface group were constructed. Various possible charge distributions in this model surface complex were evaluated in terms of their relative stabilities and electron exchange rates using ab initio MO methods. Freshly-cleaved, single crystals of magnetite with different initial Fe2+/Fe3+ ratios were exposed to uranyl-nitrate soln. (pH ∼ 4) for 90 h. XPS and electron microscopy indicated the presence of a mixed U6+/U5+ ppt. heterogeneously nucleated and grown on stoichiometric magnetite surfaces, but only the presence of sorbed U6+ and no ppt. on sub-stoichiometric magnetite surfaces. Calcd. electron transfer rates indicate that sequential multi-electron uranium redn. is not kinetically limited by conductive electron resupply to the adsorption site. Both theory and expt. point to structural Fe2+ d., taken as a measure of thermodn. reducing potential, and sterically accessible uranium coordination environments as key controls on uranium redn. extent and rate. Uranium incorporation in solid phases where its coordination is constrained to the uranate type should widen the stability field of U5+ relative to U6+. If uranium cannot acquire 8-fold coordination then redn. may proceed to U5+ but not necessarily U4+.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlyjt7zF&md5=9a42044a229e76a67d8d0f10fcb2898b
  21. 21
    Kerisit, S.; Bylaska, E. J.; Massey, M. S.; McBriarty, M. E.; Ilton, E. S. Ab initio molecular dynamics of uranium incorporated in goethite (α-FeOOH): Interpretation of X-ray absorption spectroscopy of trace polyvalent metals Inorg. Chem. 2016, 55 (22) 11736– 11746 DOI: 10.1021/acs.inorgchem.6b01773
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    21
    Ab Initio Molecular Dynamics of Uranium Incorporated in Goethite (α-FeOOH): Interpretation of X-ray Absorption Spectroscopy of Trace Polyvalent Metals
    Kerisit, Sebastien; Bylaska, Eric J.; Massey, Michael S.; McBriarty, Martin E.; Ilton, Eugene S.
    Inorganic Chemistry (2016), 55 (22), 11736-11746CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Incorporation of economically or environmentally consequential polyvalent metals into iron (oxyhydr)oxides has applications in environmental chem., remediation, and materials science. A primary tool for characterizing the local coordination environment of such metals, and therefore building models to predict their behavior, is extended X-ray absorption fine structure spectroscopy (EXAFS). Accurate structural information can be lacking yet is required to constrain and inform data interpretation. In this regard, ab initio mol. dynamics (AIMD) was used to calc. the local coordination environment of minor amts. of U incorporated in the structure of goethite (α-FeOOH). U oxidn. states (VI, V, and IV) and charge compensation schemes were varied. Simulated trajectories were used to calc. the U LIII-edge EXAFS function and fit exptl. EXAFS data for U incorporated into goethite under reducing conditions. Calcns. that closely matched the U EXAFS of the well-characterized mineral uraninite (UO2), and constrained the S02 parameter to be 0.909, validated the approach. The results for the U-goethite system indicated that U(V) substituted for structural Fe(III) in octahedral uranate coordination. Charge balance was achieved by the loss of one structural proton coupled to addn. of one electron into the solid (-1 H+, +1 e-). The ability of AIMD to model higher energy states thermally accessible at room temp. is particularly relevant for protonated systems such as goethite, where proton transfers between adjacent octahedra had a dramatic effect on the calcd. EXAFS. Vibrational effects as a function of temp. were also estd. using AIMD, allowing sep. quantification of thermal and configurational disorder. In summary, coupling AIMD structural modeling and EXAFS expts. enables modeling of the redox behavior of polyvalent metals that are incorporated in conductive materials such as iron (oxyhydr)oxides, with applications over a broad swath of chem. and materials science.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslOmu7fP&md5=2e90c05632b468be9197e24b96ff9a30
  22. 22
    Refait, P.; Genin, J. M. R. The oxidation of ferrous hydroxide in chloride-containing aqueous media and pourbaix diagrams of green rust one Corros. Sci. 1993, 34 (5) 797– 819 DOI: 10.1016/0010-938X(93)90101-L
    [Crossref], [CAS], Google Scholar
    22
    The oxidation of ferrous hydroxide in chloride-containing aqueous media and Pourbaix diagrams of green rust one
    Refait, P.; Genin, J. M. R.
    Corrosion Science (1993), 34 (5), 797-819CODEN: CRRSAA; ISSN:0010-938X.
    The oxidn. of a ferrous hydroxide pptd. by mixing solns. of ferrous chloride and caustic soda depends on the ratio R' = Cl-/OH- of the initial concns. of the reactants. The mechanisms of oxidn. for 1 < R' ≤ 3 are related to the existence of the ferrous-ferric compd. green rust 1 (GR1). The direct recording of the pH and the electrode potential allows the trigger value of R'c = 8/7 to be detd., which is found to correspond to the stoichiometric conditions of obtaining of GR1. By coupling this information with that obtained from the three iron sites R1, R2, R3 detected by Moessbauer spectroscopy, the formula of GR1 is set up at 3Fe(OH)2·Fe(OH)2Cl·nH2O. Thus GR1 contains an equal no. of Cl- and Fe3+ ions. The std. chem. potential μ0 is detd. to be -509,500 ± 500 cal mol-1 for n = 0. Eh/PH Pourbaix diagrams specific to the oxidn. of iron in chloride-contg. aq. media, including GR1, are drawn.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXis1WltLc%253D&md5=948a99d601df6edda1171b8ee7be92f9
  23. 23
    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens Nanotechnology 2011, 22 (45) 455709 DOI: 10.1088/0957-4484/22/45/455709
    [Crossref], [PubMed], [CAS], Google Scholar
    23
    Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens
    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R.
    Nanotechnology (2011), 22 (45), 455709/1-455709/9CODEN: NNOTER; ISSN:1361-6528. (Institute of Physics Publishing)
    The bioprodn. of nanoscale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction anal. indicates that controlled prodn. of a no. of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) redn. and total concn. and rate of Fe(II) produced by the bacteria during the redn. process. Relative cation distributions within the structure of the nanoparticles have been investigated by x-ray magnetic CD and indicate the presence of a highly reduced surface layer which is not obsd. when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of orgs., radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimized biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently to the less harmful trivalent form.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1ersrfL&md5=7e225721583b64cc736519a9e44522ae
  24. 24
    O’Loughlin, E. J.; Larese-Casanova, P.; Scherer, M.; Cook, R. Green Rust Formation from the Bioreduction of γ–FeOOH (Lepidocrocite): Comparison of Several Shewanella Species Geomicrobiol. J. 2007, 24 (Ii) 211– 230 DOI: 10.1080/01490450701459333
    [Crossref], [CAS], Google Scholar
    24
    Green rust formation from the bioreduction of γ -FeOOH (lepidocrocite): Comparison of several Shewanella species
    O'Loughlin, Edward J.; Larese-Casanova, Phil; Scherer, Michelle; Cook, Russell
    Geomicrobiology Journal (2007), 24 (3-4), 211-230CODEN: GEJODG; ISSN:0149-0451. (Taylor & Francis, Inc.)
    Green rusts are mixed ferrous/ferric hydroxides that typically form under weakly acidic to alk. conditions in suboxic environments. The recent identification of green rusts as products of the redn. of Fe(III) oxides and oxyhydroxides by Shewanella putrefaciens, a dissimilatory iron-reducing bacterium (DIRB), suggests that green rusts may play a role in the redox cycling of Fe in many aquatic and terrestrial environments. We examd. the potential for green rust formation resulting from the bioredn. of lepidocrocite(γ -FeOOH) by a series of Shewanella species (S. alga BrY, S. amazonensis SB2B, S. baltica OS155, S. denitrificans OS217T, S. loihica PV-4, S. oneidensis MR-1, S. putrefaciens ATCC 8071, S. putrefaciens CN32, S. saccharophilia, and Shewanella sp. ANA-3). All Shewanella species, with the exception of S. denitrificans OS217T, were able to couple the oxidn. of formate to the redn. of Fe(III) in lepidocrocite; however there were significant differences among species with respect to the rate and extent of Fe(II) prodn. Despite these differences, green rust was the only Fe(II)-bearing solid phase formed under our exptl. conditions, as indicated by X-ray diffraction, Moessbauer spectroscopy, and SEM. The formation of green rust by Shewanella species isolated from a wide range of habitats and possessing varied metabolic capabilities suggests that under favorable conditions biogenic green rusts may be formed by a diverse array of DIRB.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXotV2rtLs%253D&md5=b5fdc2533e0a0b48fd09e760d21ffab0
  25. 25
    Dodge, C. J.; Francis, A. J.; Gillow, J. B.; Halada, G. P.; Eng, C.; Clayton, C. R. Association of uranium with iron oxides typically formed on corroding steel surfaces Environ. Sci. Technol. 2002, 36 (16) 3504– 3511 DOI: 10.1021/es011450+
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    25
    Association of Uranium with Iron Oxides Typically Formed on Corroding Steel Surfaces
    Dodge, C. J.; Francis, A. J.; Gillow, J. B.; Halada, G. P.; Eng, C.; Clayton, C. R.
    Environmental Science and Technology (2002), 36 (16), 3504-3511CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Decontamination of metal surfaces contaminated with low levels of radionuclides is a major concern at Department of Energy facilities. The development of an environmentally friendly and cost-effective decontamination process requires an understanding of their assocn. with the corroding surfaces. We investigated the assocn. of uranium with the amorphous and cryst. forms of iron oxides commonly formed on corroding steel surfaces. Uranium was incorporated with the oxide by addn. during the formation of ferrihydrite, goethite, green rust II, lepidocrocite, maghemite, and magnetite. x-ray diffraction confirmed the mineralogical form of the oxide. EXAFS anal. at the U LIII edge showed that uranium was present in hexavalent form as a uranyl oxyhydroxide species with goethite, maghemite, and magnetite and as a bidentate inner-sphere complex with ferrihydrite and lepidocrocite. Iron was present in the ferric form with ferrihydrite, goethite, lepidocrocite, and maghemite; whereas with magnetite and green rust II, both ferrous and ferric forms were present with characteristic ferrous:total iron ratios of 0.65 and 0.73, resp. In the presence of the uranyl ion, green rust II was converted to magnetite with concomitant redn. of uranium to its tetravalent form. The rate and extent of uranium dissoln. in dil. HCl depended on its assocn. with the oxide: uranium present as oxyhydroxide species underwent rapid dissoln. followed by a slow dissoln. of iron; whereas uranium present as an inner-sphere complex with iron resulted in concomitant dissoln. of the uranium and iron.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xlt1equ7o%253D&md5=62f6b12a6e9e7b3e712cc0e972057171
  26. 26
    Tremaine, P. R.; LeBlanc, J. C. The solubility of magnetite and the hydrolysis and oxidation of Fe2+ in water to 300°C J. Solution Chem. 1980, 9 (6) 415– 442 DOI: 10.1007/BF00645517
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  27. 27
    Musić, S.; Ristić, M. Adsorption of trace elements or radionuclides on hydrous iron oxides J. Radioanal. Nucl. Chem. 1988, 120 (2) 289– 304 DOI: 10.1007/BF02037344
    [Crossref], [CAS], Google Scholar
    27
    Adsorption of trace elements or radionuclides on hydrous iron oxides
    Music, S.; Ristic, M.
    Journal of Radioanalytical and Nuclear Chemistry (1988), 120 (2), 289-304CODEN: JRNCDM; ISSN:0236-5731.
    Factors which influence the adsorption of trace elements or radionuclides on hydrous Fe oxides were investigated. The adsorption of monovalent cations (Cs+, Rb+) on hydrous Fe oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, the adsorption of Ag+, divalent cations (Zn2+, Cd2+, Mn2+, Sr2+) or trivalent cations (Cr3+, La3+, Ce3+, Eu3+, Gd3+, Er3+, Yb3+) strongly depends on the pH. The regularities of the adsorption of these cations on hydrous Fe oxides are discussed. Also, the differences in the adsorption behavior of some divalent and trivalent cations are explained. Freshly pptd. Fe(OH)3 can be used for the decontamination of radionuclides from low-level waste solns. However, the efficacy of decontamination depends on the oxidn. state and the chem. properties of the radionuclides.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXhtl2nur4%253D&md5=ff343da942b2652bb28d7ed0013ee16b
  28. 28
    Latta, D. E.; Mishra, B.; Cook, R. E.; Kemner, K. M.; Boyanov, M. I. Stable U(IV) complexes form at high-affinity mineral surface sites Environ. Sci. Technol. 2014, 48 (3) 1683– 1691 DOI: 10.1021/es4047389
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    28
    Stable U(IV) complexes form at high-affinity mineral surface sites
    Latta, Drew E.; Mishra, Bhoopesh; Cook, Russell E.; Kemner, Kenneth M.; Boyanov, Maxim I.
    Environmental Science & Technology (2014), 48 (3), 1683-1691CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due to its extensive use for energy prodn. Despite advances in modeling the risks of this toxic and radioactive element, lack of information about the mechanisms controlling U transport hinders further improvements, particularly in reducing environments where UIV predominates. Here we establish that mineral surfaces can stabilize the majority of U as adsorbed UIV species following redn. of UVI. Using X-ray absorption spectroscopy and electron imaging anal., we find that at low surface loading, UIV forms inner-sphere complexes with two metal oxides, TiO2 (rutile) and Fe3O4 (magnetite) (at <1.3 U nm-2 and <0.037 U nm-2, resp.). The uraninite (UO2) form of UIV predominates only at higher surface loading. UIV-TiO2 complexes remain stable for at least 12 mo, and UIV-Fe3O4 complexes remain stable for at least 4 mo, under anoxic conditions. Adsorbed UIV results from UVI redn. by FeII or by the reduced electron shuttle AH2QDS, suggesting that both abiotic and biotic redn. pathways can produce stable UIV-mineral complexes in the subsurface. The obsd. control of high-affinity mineral surface sites on UIV speciation helps explain the presence of nonuraninite UIV in sediments and has important implications for U transport modeling.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXltFehtg%253D%253D&md5=89902e5b02f6b1e65a5bc5293deb1f2f
  29. 29
    Scott, T. B.; Allen, G. C.; Heard, P. J.; Randell, M. G. Reduction of U(VI) to U(IV) on the surface of magnetite Geochim. Cosmochim. Acta 2005, 69 (24) 5639– 5646 DOI: 10.1016/j.gca.2005.07.003
    [Crossref], [CAS], Google Scholar
    29
    Reduction of U(VI) to U(IV) on the surface of magnetite
    Scott, T. B.; Allen, G. C.; Heard, P. J.; Randell, M. G.
    Geochimica et Cosmochimica Acta (2005), 69 (24), 5639-5646CODEN: GCACAK; ISSN:0016-7037. (Elsevier)
    To increase the understanding of uranium transport in the environment and in the presence of steel corrosion products, the interaction of U(VI) with natural magnetite has been studied. Sorption studies have been carried out using XPS and secondary ion mass spectrometry (SIMS). The XPS results clearly indicate the redn. of U(VI) to U(IV) on the surface of magnetite facilitated by electron transfer between the Fe and U, leading to a coupled oxidn. of Fe(II) to Fe(III).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtlerur%252FJ&md5=d02a97e0191634f5e9485f938c1bc779
  30. 30
    Wang, Z.; Ulrich, K.-U.; Pan, C.; Giammar, D. E. Measurement and Modeling of U(IV) Adsorption to Metal Oxide Minerals Environ. Sci. Technol. Lett. 2015, 2 (8) 227– 232 DOI: 10.1021/acs.estlett.5b00156
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    30
    Measurement and Modeling of U(IV) Adsorption to Metal Oxide Minerals
    Wang, Zimeng; Ulrich, Kai-Uwe; Pan, Chao; Giammar, Daniel E.
    Environmental Science & Technology Letters (2015), 2 (8), 227-232CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
    Chem. or biol. redn. of U(VI) produces a variety of poorly sol. U(IV) species. In addn. to uraninite (UO2) and biomass-assocd. noncryst. U(IV), recent research has found adsorbed U(IV) species on mineral surfaces. To build on these observations, we evaluated equil. adsorption of U(IV) to magnetite and rutile as a function of pH and total U(IV) loading. Surface complexation models that could simulate the uptake of U(IV) by accounting for UO2 pptn. and adsorption of U(IV) to both the minerals and the reactor surfaces were developed. Application of the models could det. the conditions under which adsorption as opposed to pptn. would dominate U(IV) uptake with solids. The model-predicted U(IV) surface coverages of the minerals were consistent with a recent spectroscopic study. Such models advance our ability to predict the equil. speciation of U(IV) in the subsurface.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFWmtrrF&md5=0150b6d8052c172f00f7f9d7fdbeab54
  31. 31
    Kerisit, S.; Felmy, A. R.; Ilton, E. S. Atomistic simulations of uranium incorporation into iron (hydr)oxides Environ. Sci. Technol. 2011, 45 (7) 2770– 2776 DOI: 10.1021/es1037639
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    31
    Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides
    Kerisit, Sebastien; Felmy, Andrew R.; Ilton, Eugene S.
    Environmental Science & Technology (2011), 45 (7), 2770-2776CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination nos., and lattice distortion for U incorporated in different sites (e.g., unoccupied vs. occupied sites, octahedral vs. tetrahedral) as a function of the oxidn. state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or redn. of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amt. of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidn. states and charge compensation mechanisms. Importantly, U-Fe distances of ∼3.6 Å were assocd. with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available exptl. data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXivFyhsbk%253D&md5=5fa577bda6deb2459d67357af879e308
  32. 32
    Pearce, C. I.; Qafoku, O.; Liu, J.; Arenholz, E.; Heald, S. M.; Kukkadapu, R. K.; Gorski, C. A.; Henderson, C. M. B.; Rosso, K. M. Synthesis and properties of titanomagnetite (Fe 3-xTi xO 4) nanoparticles: A tunable solid-state Fe(II/III) redox system J. Colloid Interface Sci. 2012, 387 (1) 24– 38 DOI: 10.1016/j.jcis.2012.06.092
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  33. 33
    Doornbusch, B.; Bunney, K.; Gan, B. K.; Jones, F.; Gräfe, M. Iron oxide formation from FeCl2 solutions in the presence of uranyl (UO22+) cations and carbonate rich media Geochim. Cosmochim. Acta 2015, 158, 22– 47 DOI: 10.1016/j.gca.2015.02.038
    [Crossref], [CAS], Google Scholar
    33
    Iron oxide formation from FeCl2 solutions in the presence of uranyl (UO2+2) cations and carbonate rich media
    Doornbusch, Brodie; Bunney, Karl; Gan, Bee K.; Jones, Franca; Grafe, Markus
    Geochimica et Cosmochimica Acta (2015), 158 (), 22-47CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
    The mineral goethite (α-FeOOH) has previously been investigated as a thermodynamically stable repository for many potentially toxic metals (e.g., Cd, Pb, Cu). The substitution of uranium (U as uranyl, UO2+2) for Fe, however, has been studied sparingly, and conclusive uranium incorporation into the goethite structure has been obscured by formation of polymineralic Fe systems that all appeared involved in U's sequestration. In this study, we investigated the formation of goethite from FeCl2 in the presence of seven nominal uranyl concns. (0.2-4 mol percent, U/(U + Fe) × 100) and characterized the solids using quant. X-ray diffraction (QXRD), X-ray absorption fine structure (XAFS) spectroscopy at the U LIII edge (17,166 eV), diffuse reflectance IR Fourier Transform (DRIFT) spectrometry and congruency of acid dissoln. Our findings show that U does indeed, however sparingly, incorporate into the goethite structure. The unit cell vol., ascertained from Rietveld models of XRD patterns, increased linearly as a function of U content, which could be ascribed to a linear increase of the unit cell length a and c. The highest U-for-Fe substitution was 0.48 mol percent, however, most U-contg. goethite samples showed substitution levels around 0.2 mol percent, which was in good agreement with previous findings. DRIFT spectra showed a shift of the sym. Fe-O and asym. Fe-OH stretch modes (τ-O and τ-OH bands, resp.) to lower frequency, which by Hooks analogy, can only occur if a heavier atom substitutes for Fe, i.e., U. The congruency of acid dissoln. results showed that fractional U release was greater than the corresponding fractional Fe release into soln., suggesting that U was overall more sol. In two of the synthates, however, (initial U mole percent of 2 and 4), the dissoln. was congruent. XAFS data collected on a selected subset of samples showed the disappearance of the uranyl moiety with higher levels of U incorporation and acid extn. In sample S6, non-linear least-square fits of the extended XAFS data demonstrated that the coordination environment around U atoms was sixfold occupied by O/OH atoms and was further coordinated by next nearest Fe neighbors that are 1.063 ± 0.008 times inflated in distance to the normal Fe-Fe distances in goethite without U substitution. Despite low levels of incorporation, U bound by goethite was recalcitrant to desorption/dissoln. in increasingly acidic solns. thus warranting further research into the possibility of using iron oxides as a sink for U.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkvVKrt7w%253D&md5=9a922f272a7bde6a0a28f95c36226270
  34. 34
    Burke, I. T.; Mosselmans, J. F. W.; Shaw, S.; Peacock, C. L.; Benning, L. G.; Coker, V. S. Impact of the Diamond Light Source on Research in Earth and Environmental Sciences: Current Work and Future Perspectives Philos. Trans. R. Soc., A 2015, 373, 20130151 DOI: 10.1098/rsta.2013.0151
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Dent, A. J.; Cibin, G.; Ramos, S.; Smith, A. D.; Scott, S. M.; Varandas, L.; Pearson, M. R.; Krumpa, N. A.; Jones, C. P.; Robbins, P. E. B18: A core XAS spectroscopy beamline for Diamond J. Phys.: Conf. Ser. 2009, 190 (1) 012039 DOI: 10.1088/1742-6596/190/1/012039
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray absorption spectroscopy using IFEFFIT J. Synchrotron Radiat. 2005, 12, 537– 541 DOI: 10.1107/S0909049505012719
    [Crossref], [PubMed], [CAS], Google Scholar
    36
    ATHENA, ARTEMIS, HEPHAESTUS: data analysis for x-ray absorption spectroscopy using IFEFFIT
    Ravel, B.; Newville, M.
    Journal of Synchrotron Radiation (2005), 12 (4), 537-541CODEN: JSYRES; ISSN:0909-0495. (Blackwell Publishing Ltd.)
    A software package for the anal. of x-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data anal. using theor. stds. from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of at. absorption data. These programs enable high-quality data anal. that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXltlCntLo%253D&md5=a35c32b41de3dc234b101b63927fca73
  37. 37
    Bannister, M. J.; Taylor, J. C. The crystal structure and anisotropic thermal expansion of β-uranyl dihydroxide, UO 2 (OH) 2 Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1970, 26 (11) 1775– 1781 DOI: 10.1107/S0567740870004879
    [Crossref], [CAS], Google Scholar
    37
    Crystal structure and anisotropic thermal expansion of β-uranyl dihydroxide, UO2(OH)2
    Bannister, M. J.; Taylor, John C.
    Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1970), 26 (11), 1775-81CODEN: ACBCAR; ISSN:0567-7408.
    Single-crystal and powder x-ray diffraction techniques were used to det. improved positional, thermal vibration, and lattice parameters for the orthorhombic β-UO2(OH)2. Values obtained for lattice parameters at 21° are: a = 5.6438 ± 0.0001, b = 6.2867 ± 0.0001, c = 9.9372 ± 0.0002 Å. Thermal expansion of this material was studied by elevated temp. x-ray diffraction and hot-stage optical microscopy. Thermal expansion up to 260° was strongly anisotropic, with large contractions in a, large expansions in b, and a smaller cyclic change in c. Expansion at higher temps. was almost isotropic. By using the structural and vibrational data, the anisotropic thermal expansion is interpreted in terms of a thermally induced rotation of the O octahedra surrounding all U atoms.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3MXjsFOnsg%253D%253D&md5=c76a69f4507d0c0ad04bdc93032377ea
  38. 38
    Fleet, M. E. The structure of magnetite Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1981, 37 (4) 917– 920 DOI: 10.1107/S0567740881004597
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  39. 39
    Barrett, S.; Jacobson, A. J.; Tofield, B. C.; Fender, B. E. F. The Preparation and Structure of Barium Uranium Oxide BaUO3+X Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1982, 38, 2775– 2781 DOI: 10.1107/S0567740882009935
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Simon, L.; François, M.; Refait, P.; Renaudin, G.; Lelaurain, M.; Génin, J. M. R. Structure of the Fe(II-III) layered double hydroxysulphate green rust two from Rietveld analysis Solid State Sci. 2003, 5 (2) 327– 334 DOI: 10.1016/S1293-2558(02)00019-5
    [Crossref], [CAS], Google Scholar
    40
    Structure of the Fe(II-III) layered double hydroxysulphate green rust two from Rietveld analysis
    Simon, Lilian; Francois, Michel; Refait, Philippe; Renaudin, Guillaume; Lelaurain, Michele; Genin, Jean-Marie R.
    Solid State Sciences (2003), 5 (2), 327-334CODEN: SSSCFJ; ISSN:1293-2558. (Editions Scientifiques et Medicales Elsevier)
    Synthetic samples of the Fe(II-III) hydroxysulfate known as green rust two were obtained by aerial oxidn. of Fe(II) hydroxide ppts. and studied using chem. and thermal analyses, transmission Mossbauer spectroscopy and powder x-ray diffraction. The ideal formula is FeII4FeIII2(OH)12SO4·∼8H2O. The structure is trigonal, space group P‾3m1 with a = 0.5524(1) nm, c 1.1011(3) nm and Z = 1/2. It is characterized by the succession of pos. charged hydroxide sheets [FeII4 FeIII2(OH)12]2+ and neg. charged interlayers composed of the sulfate anions and H2O mols., [SO4·∼8H2O]2-. These interlayers are made of two planes of H2O and SO42-, in contrast with those found in the rhombohedral green rust one compds., which are made of a single plane. A superstructure (a = a0√3) is found along the [110] direction of the parent hexagonal unit cell, where a0 is the lattice parameter of Fe(OH)2, and due to an ordering of the sulfate anions in the interlayers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXit1Kgu7c%253D&md5=b5c4fa60921b88b27850206f67d53672
  41. 41
    Gauthier, C.; Solé, V. A.; Signorato, R.; Goulon, J.; Moguiline, E. The ESRF beamline ID26: X-ray absorption on ultra dilute sample J. Synchrotron Radiat. 1999, 6, 164– 166 DOI: 10.1107/S0909049598016835
    [Crossref], [PubMed], [CAS], Google Scholar
    41
    The ESRF beamline ID26: X-ray absorption on ultra dilute sample
    Gauthier, Christophe; Sole, Vicente Armando; Signorato, Riccardo; Goulon, Jose; Moguiline, Eric
    Journal of Synchrotron Radiation (1999), 6 (3), 164-166CODEN: JSYRES; ISSN:0909-0495. (Munksgaard International Publishers Ltd.)
    The ESRF beamline ID26 is dedicated to x-ray absorption spectroscopy on Ultra dil. samples. Tech. characteristics are briefly described : optics, monochromator, detectors and sample environment. Recent results are reported to illustrate present performance of the beamline.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXksFCgsb4%253D&md5=4c8619f6e908f4b7633447962ee24990
  42. 42
    Glatzel, P.; Bergmann, U. High resolution 1s core hole X-ray spectroscopy in 3d transition metal complexes - Electronic and structural information Coord. Chem. Rev. 2005, 249 (1–2) 65– 95 DOI: 10.1016/j.ccr.2004.04.011
    [Crossref], [CAS], Google Scholar
    42
    High resolution 1s core hole X-ray spectroscopy in 3d transition metal complexes-electronic and structural information
    Glatzel, Pieter; Bergmann, Uwe
    Coordination Chemistry Reviews (2005), 249 (1-2), 65-95CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. The creation of a 1s core hole in a 3d transition metal ion gives rise to an emission spectrum that can be recorded using a crystal analyzer. K shell x-ray spectroscopy using an analyzer energy bandwidth of ∼1 eV is sensitive to electron-electron interactions and orbital splittings and preserves the advantages of the hard x-ray probe. The authors review recent developments in Kα and Kβ spectroscopy and show how the chem. sensitivity of the fluorescence lines can be exploited for selective x-ray absorption studies. When the photo excitation energy is tuned close to the K edge threshold, the phenomenon known as x-ray resonant Raman or resonant inelastic x-ray scattering (RIXS) occurs. RIXS spectroscopy on 3d transition metals at the 1s resonances with lowest incident energies (K pre-edge) is a very recent technique. The authors discuss basic aspects and demonstrate with several examples its potential as a future routine spectroscopic tool.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFejs7zP&md5=f9d1247588b31237b4a47a9378ae1dd2
  43. 43
    Kvashnina, K. O.; Scheinost, A. C. A Johann-type X-ray emission spectrometer at the Rossendorf beamline J. Synchrotron Radiat. 2016, 23 (3) 836– 841 DOI: 10.1107/S1600577516004483
    [Crossref], [PubMed], [CAS], Google Scholar
    43
    A Johann-type X-ray emission spectrometer at the Rossendorf beamline
    Kvashnina, Kristina O.; Scheinost, Andreas C.
    Journal of Synchrotron Radiation (2016), 23 (3), 836-841CODEN: JSYRES; ISSN:1600-5775. (International Union of Crystallography)
    This paper gives a detailed description, including equations, of the Johann-type X-ray emission spectrometer which has been recently installed and tested at the Rossendorf beamline (ROBL) of the European Synchrotron Radiation Facility. The spectrometer consists of a single spherically bent crystal analyzer and an avalanche photodiode detector positioned on the vertical Rowland cycle of 1 m diam. The hard X-ray emission spectrometer (∼3.5-25 keV) operates at atm. pressure and covers the Bragg angles of 65°-89°. The instrument has been tested at high and intermediate incident energies, i.e. at the Zr K-edge and at the Au L3-edge, in the second exptl. hutch of ROBL. The spectrometer is dedicated for studying actinides in materials and environmental samples by high-energy-resoln. X-ray absorption and X-ray emission spectroscopies.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xntlyjur4%253D&md5=1272cd53368cf43de4696816278ae72b
  44. 44
    Rossberg, A.; Ulrich, K. U.; Weiss, S.; Tsushima, S.; Hiemstra, T.; Scheinost, A. C. SI: Identification of uranyl surface complexes on ferrihydrite: Advanced EXAFS data analysis and CD-music modeling Environ. Sci. Technol. 2009, 43 (5) 1400– 1406 DOI: 10.1021/es801727w
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  45. 45
    Vitova, T.; Kvashnina, K. O.; Nocton, G.; Sukharina, G.; Denecke, M. A.; Butorin, S. M.; Mazzanti, M.; Caciuffo, R.; Soldatov, A.; Behrends, T.; Geckeis, H. High energy resolution x-ray absorption spectroscopy study of uranium in varying valence states Phys. Rev. B: Condens. Matter Mater. Phys. 2010, 82 (23) 235118 DOI: 10.1103/PhysRevB.82.235118
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Kvashnina, K. O.; Butorin, S. M.; Martin, P.; Glatzel, P. Chemical state of complex uranium oxides Phys. Rev. Lett. 2013, 111, 25 DOI: 10.1103/PhysRevLett.111.253002
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Soldatov, A. V.; Lamoen, D.; Konstantinović, M. J.; Van den Berghe, S.; Scheinost, A. C.; Verwerft, M. Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis J. Solid State Chem. 2007, 180 (1) 54– 61 DOI: 10.1016/j.jssc.2006.08.038
    [Crossref], [CAS], Google Scholar
    47
    Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis
    Soldatov, A. V.; Lamoen, D.; Konstantinovic, M. J.; Van den Berghe, S.; Scheinost, A. C.; Verwerft, M.
    Journal of Solid State Chemistry (2007), 180 (1), 54-61CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
    The authors studied the local at. and electronic structures of two related systematic sets of ternary U oxides, NaUO3-KUO3-RbUO3 and BaUO3-Ba2U2O7-BaUO4, by measuring the x-ray absorption near edge structure (XANES). The results are compared with calcns. based on a self-consistent real space full multiple scattering anal. The authors found a very good agreement between measured and calcd. spectra, which indicates that the U ions are in a pure U5+ oxidn. state in these compds. The low energy shoulder obsd. in the U L3 edge XANES is an intrinsic feature of the U unoccupied 6d electronic states of the U5+ ions within the studied materials. Specific double shoulder features in the higher energy range of the U L3 edge XANES can be interpreted as indicative of the pure cubic perovskite structure.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnt1Cltg%253D%253D&md5=a79106e07d54ccf7b2284648634486fc
  48. 48
    O’Loughlin, E. J.; Kelly, S. D.; Cook, R. E.; Csencsits, R.; Kemner, K. M. Reduction of uranium(VI) by mixed iron(II)/iron(III) hydroxide (green rust): formation of UO2 nanoparticles Environ. Sci. Technol. 2003, 37 (4) 721– 727 DOI: 10.1021/es0208409
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    48
    Reduction of Uranium(VI) by Mixed Iron(II)/Iron(III) Hydroxide (Green Rust): Formation of UO2 Nanoparticles
    O'Loughlin, Edward J.; Kelly, Shelly D.; Cook, Russell E.; Csencsits, Roseann; Kemner, Kenneth M.
    Environmental Science and Technology (2003), 37 (4), 721-727CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Green rusts, which are mixed ferrous/ferric hydroxides, are found in many suboxic environments and are believed to play a central role in the biogeochem. of Fe. Anal. by U LIII-edge x-ray absorption near edge spectroscopy of aq. green rust suspensions spiked with uranyl (UVI) showed that UVI was readily reduced to UIV by green rust. The extended x-ray absorption fine structure (EXAFS) data for U reduced by green rust indicate the formation of a UO2 phase. A theor. model based on the crystal structure of UO2 was generated by using FEFF7 and fitted to the data for the UO2 std. and the U in the green rust samples. The model fits indicate that the no. of nearest-neighbor U atoms decreases from 12 for the UO2 structure to 5.4 for the U-green rust sample. With an assumed 4 near-neighbor U atoms per U atom on the surface of UO2, the best-fit value for the av. no. of U atoms indicates UO2 particles with an av. diam. of 1.7 ± 0.6 nm. The formation of nanometer-scale particles of UO2, suggested by the modeling of the EXAFS data, was confirmed by high-resoln. TEM, which showed discrete particles (∼2-9 nm in diam.) of cryst. UO2. UVI (as sol. uranyl ion) is readily reduced by green rust to UIV as relatively insol. UO2 nanoparticles, suggesting that the presence of green rusts in the subsurface may have significant effects on the mobility of U, particularly under Fe-reducing conditions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXivF2ksQ%253D%253D&md5=3d5b47f2e0ed6891772214c97a2bbca4
  49. 49
    Shuller-Nickles, L.; Bender, W.; Walker, S.; Becker, U. Quantum-Mechanical Methods for Quantifying Incorporation of Contaminants in Proximal Minerals Minerals 2014, 4 (3) 690– 715 DOI: 10.3390/min4030690
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  50. 50
    Marshall, T. A.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Parry, S. A.; Shaw, S. Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions Environ. Sci. Technol. 2014, 48 (20) 11853– 11862 DOI: 10.1021/es503438e
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    50
    Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions
    Marshall, Timothy A.; Morris, Katherine; Law, Gareth T. W.; Mosselmans, J. Frederick W.; Bots, Pieter; Parry, Stephen A.; Shaw, Samuel
    Environmental Science & Technology (2014), 48 (20), 11853-11862CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Technetium incorporation into magnetite and its behavior during subsequent oxidn. has been investigated at high pH to det. the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) contg. cement leachates (pH 10.5-13.1), and crystn. of magnetite was induced via addn. of Fe(II)aq. A combination of X-ray diffraction (XRD), chem. extn., and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidn. of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Anal. of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidn. in air, the incorporated Tc(IV) was recalcitrant to oxidative dissoln. with less than 40% remobilization to soln. despite significant oxidn. of the magnetite to maghemite/goethite: All solid assocd. Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissoln. Immobilization of Tc(VII) by redn. and incorporation into magnetite at high pH and with significant stability upon reoxidn. has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geol. disposal of radioactive wastes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFKrsb7O&md5=c7f4658634192fd58ef1a0f805afdb14
  51. 51
    McBriarty, M. E.; Soltis, J. A.; Kerisit, S.; Qafoku, O.; Bowden, M. E.; Bylaska, E. J.; De Yoreo, J. J.; Ilton, E. S. Trace Uranium Partitioning in a Multiphase Nano-FeOOH System Environ. Sci. Technol. 2017, 51 (9) 4970– 4977 DOI: 10.1021/acs.est.7b00432
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    51
    Trace Uranium Partitioning in a Multiphase Nano-FeOOH System
    McBriarty, Martin E.; Soltis, Jennifer A.; Kerisit, Sebastien; Qafoku, Odeta; Bowden, Mark E.; Bylaska, Eric J.; De Yoreo, James J.; Ilton, Eugene S.
    Environmental Science & Technology (2017), 51 (9), 4970-4977CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    The characterization of trace elements in minerals using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities and contaminants interact with the host phase and the environment. However, limitations to EXAFS interpretation complicate the anal. of trace concns. of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio mol. dynamics (AIMD)-informed EXAFS anal. was employed to investigate the immobilization of trace uranium assocd. with nanophase iron (oxyhydr)oxides, a model system for the geochem. sequestration of radiotoxic actinides. The reductive transformation of ferrihydrite [Fe(OH)3] to nanoparticulate iron oxyhydroxide minerals in the presence of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (α-FeOOH) over lepidocrocite (γ-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is supported by atomically resolved transmission electron microscopy. We demonstrate how AIMD-informed EXAFS anal. lifts the strict statistical limitations and uncertainty of traditional shell-by-shell EXAFS fitting, enabling the detailed characterization of the local bonding environment, charge compensation mechanisms, and oxidn. states of polyvalent impurities in complex multiphase mineral systems.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmtVCmt7s%253D&md5=2a59124a8b68edb010d6049c4c224923
  52. 52
    Latta, D. E.; Boyanov, M. I.; Kemner, K. M.; O’Loughlin, E. J.; Scherer, M. Reaction of Uranium(VI) with Green Rusts: Effect of Interlayer Anion Curr. Inorg. Chem. 2015, 5, 156– 168 DOI: 10.2174/1877944105666150420235350
    [Crossref], [CAS], Google Scholar
    52
    Reaction of Uranium(VI) with Green Rusts: Effect of Interlayer Anion
    Latta, Drew E.; Boyanov, Maxim I.; Kemner, Kenneth M.; O'Loughlin, Edward J.; Scherer, Michelle
    Current Inorganic Chemistry (2015), 5 (3), 156-168CODEN: CICUBF; ISSN:1877-9441. (Bentham Science Publishers Ltd.)
    Green rusts are widely recognized as an important metastable intermediate phase in Fe biogeochem. cycling and Fe metal corrosion and are strong reductants capable of reducing a widerange of contaminants. Here we investigate the effect of interlayer anion on the reaction of green rusts with hexavalent uranium (U(VI)). We react three synthetic green rusts, including carbonate, sulfate, and chloride green rust, as well as pyroaurite, a redox-inactive Mg(II)-Fe(III) structural analog of carbonate green rust with U(VI). The majority of U(VI) (> 80%) was removed from soln. in about an hour at pH 8.0 in 0.1 M N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS) buffer. Similar kinetics of U(VI) uptake on green rusts and pyroaurite suggest that the obsd. uptake kinetics reflect an adsorption step rather than redn. of U(VI) by structural Fe(II) in the green rusts. X-ray absorption spectroscopy (XAS) of the green rust solids indicates significant redn. of U(VI) to U(IV) for all three green rusts, with complete redn. obsd. for sulfate and chloride green rust and varied extents of redn. (34 to 100%) obsd. for carbonate green rust depending on the soln. conditions. No redn. of U(VI) was obsd. in the presence of pyroaurite, consistent with the absence of Fe(II) in the pyroaurite structure. The decreased extent of U(VI) redn. obsd. with carbonate green rust in TAPS buffer may be due to modification of the redox reactivity of U(VI) or green rust due to interaction with the TAPS buffer mols. XAS results indicate that U(VI) was reduced to U(IV) and was present as a monomeric-type U(IV) species in the presence of TAPS buffer. In deionized water, however, carbonate green rust reduced U(VI) to nanoparticulate UO2. Green rusts may be an important phase in the fate and transport of U(VI) in the contaminated subsurface, or under conditions where it forms on corroding U-bearing waste containers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1OmsLrP&md5=ef893a596df35f65bc17b403078649c4
  53. 53
    Neidig, M. L.; Clark, D. L.; Martin, R. L. Covalency in f-element complexes Coord. Chem. Rev. 2013, 257 (2) 394– 406 DOI: 10.1016/j.ccr.2012.04.029
    [Crossref], [CAS], Google Scholar
    53
    Covalency in f-element complexes
    Neidig, Michael L.; Clark, David L.; Martin, Richard L.
    Coordination Chemistry Reviews (2013), 257 (2), 394-406CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. The presence of covalency in complexes of the 4f and 5f elements has been a source of intense research and controversy. In addn. to academic interest in this debate, there is an industrial motivation for better understanding of bonding in f-element complexes due to the need to sep. trivalent trans-plutonium elements from trivalent lanthanide fission products in advanced nuclear fuel cycles. This review discusses the key evidence for covalency in f-element bonds derived from structural, spectroscopic and theor. studies of some selected classes of mols., including octahedral hexahalides, linear actinyl and organometallic sandwich complexes. This evidence is supplemented by a discussion of covalency, including the possibility of both overlap and near-degeneracy driven covalency and the need to quantify their relative contributions in actinide metal-ligand bonds.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVekurrE&md5=e0a768f5c3c99b19283f5dc76d74c41c
  54. 54
    Hubbard, C. G.; West, L. J.; Rodriguez-Blanco, J. D.; Shaw, S. Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media Geophysics 2014, 79 (1) D21– D30 DOI: 10.1190/geo2013-0079.1
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  55. 55
    Finch, R. J.; Ewing, R. C. The corrosion of uraninite under oxidizing conditions J. Nucl. Mater. 1992, 190 (C) 133– 156 DOI: 10.1016/0022-3115(92)90083-W
    [Crossref], [CAS], Google Scholar
    55
    The corrosion of uraninite under oxidizing conditions
    Finch, Robert J.; Ewing, Rodney C.
    Journal of Nuclear Materials (1992), 190 (), 133-56CODEN: JNUMAM; ISSN:0022-3115.
    Uraninite contains "impurities" such as Pb, Ca, Si, U6+, Th, Zr, and lanthanides. These affect the thermodn. properties of uraninite, the rate of uraninite alteration, and the compn. of the corrosion products. Uraninite can contain a significant amt. of radiogenic Pb, and the Pb-uranyl oxide hydrates (Pb-UOH) are the most common corrosion products formed by the oxidative alteration of Pb-bearing uraninites. Incongruent alteration of the Pb-UOHs in natural waters produces increasingly Pb-enriched uranyl phases, effectively reducing the amt. of U lost from the corrosion rind. This is not true of other uranyl oxide hydrates, such as schoepite, UO3·2H2O, or becquerelite, CaU6O19·11H2O, which can dissolve completely under similar geochem. conditions. The most common end product of Pb-UOH alteration is curite. Curite may provide surface nucleation sites for certain uranyl phosphates, thereby enhancing their formation. Uranyl phosphates are generally less sol. than other uranyl phases. In the absence of Pb, schoepite and becquerelite are the common initial corrosion products. The reaction path for the alteration of Pb-free uraninite results in the formation of uranyl silicates, which are generally more sol. than the uranyl phosphates. Thus, the long-term oxidn. behavior for ancient, Pb-bearing uraninite is different from young, Pb-free uraninite. Because the presence of Pb effectively reduces the mobility of uranium in oxidizing waters, the concn. of uranium in groundwaters assocd. with oxidized uranium ore deposits will depend in part on the age of the primary uraninite.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XmtlOhtLs%253D&md5=b6a3c857c5246e7038d7b52696244f6a

Cited By

This article is cited by 74 publications.

  1. Yuge Bai, Tianran Sun, Muammar Mansor, Prachi Joshi, Yiling Zhuang, Stefan B. Haderlein, Stefan Fischer, Kurt O. Konhauser, Daniel S. Alessi, Andreas Kappler. Networks of Dissolved Organic Matter and Organo-Mineral Associations Stimulate Electron Transfer over Centimeter Distances. Environmental Science & Technology Letters 2023, 10 (6) , 493-498. https://doi.org/10.1021/acs.estlett.3c00172
  2. Margaux Molinas, Karin Lederballe Meibom, Radmila Faizova, Marinella Mazzanti, Rizlan Bernier-Latmani. Mechanism of Reduction of Aqueous U(V)-dpaea and Solid-Phase U(VI)-dpaea Complexes: The Role of Multiheme c-Type Cytochromes. Environmental Science & Technology 2023, 57 (19) , 7537-7546. https://doi.org/10.1021/acs.est.3c00666
  3. Olwen Stagg, Katherine Morris, Luke Thomas Townsend, Kristina O. Kvashnina, Michael L. Baker, Ryan L. Dempsey, Liam Abrahamsen-Mills, Samuel Shaw. Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling. Environmental Science & Technology 2022, 56 (24) , 17643-17652. https://doi.org/10.1021/acs.est.2c05314
  4. Takumi Yomogida, Daisuke Akiyama, Kazuki Ouchi, Yuta Kumagai, Kotaro Higashi, Yoshihiro Kitatsuji, Akira Kirishima, Naomi Kawamura, Yoshio Takahashi. Application of High-Energy-Resolution X-ray Absorption Spectroscopy at the U L3-Edge to Assess the U(V) Electronic Structure in FeUO4. Inorganic Chemistry 2022, 61 (50) , 20206-20210. https://doi.org/10.1021/acs.inorgchem.2c03208
  5. Eugene S. Ilton, Richard N. Collins, Cristiana L. Ciobanu, Nigel J. Cook, Max Verdugo-Ihl, Ashley D. Slattery, David J. Paterson, Sebastian T. Mergelsberg, Eric J. Bylaska, Kathy Ehrig. Pentavalent Uranium Incorporated in the Structure of Proterozoic Hematite. Environmental Science & Technology 2022, 56 (16) , 11857-11864. https://doi.org/10.1021/acs.est.2c02113
  6. Ke Yuan, Mark R. Antonio, Eugene S. Ilton, Zhongrui Li, Udo Becker. Pentavalent Uranium Enriched Mineral Surface under Electrochemically Controlled Reducing Environments. ACS Earth and Space Chemistry 2022, 6 (5) , 1204-1212. https://doi.org/10.1021/acsearthspacechem.1c00413
  7. Yingwei Wang, Sooyeon Kim, Maria C. Marcano, Yijun Cao, Udo Becker. Effect of EDTA Complexation on the Kinetics and Thermodynamics of Uranium Redox Reactions Catalyzed by Pyrite: A Combined Electrochemical and Quantum-Mechanical Approach. ACS Earth and Space Chemistry 2022, 6 (4) , 830-846. https://doi.org/10.1021/acsearthspacechem.1c00417
  8. Chris Foster, Samuel Shaw, Thomas S. Neill, Nick Bryan, Nick Sherriff, Louise S. Natrajan, Hannah Wilson, Laura Lopez-Odriozola, Bruce Rigby, Sarah J. Haigh, Yi-Chao Zou, Robert Harrison, Katherine Morris. Hydrotalcite Colloidal Stability and Interactions with Uranium(VI) at Neutral to Alkaline pH. Langmuir 2022, 38 (8) , 2576-2589. https://doi.org/10.1021/acs.langmuir.1c03179
  9. Zezhen Pan, Yvonne Roebbert, Aaron Beck, Barbora Bartova, Tonya Vitova, Stefan Weyer, Rizlan Bernier-Latmani. Persistence of the Isotopic Signature of Pentavalent Uranium in Magnetite. Environmental Science & Technology 2022, 56 (3) , 1753-1762. https://doi.org/10.1021/acs.est.1c06865
  10. Olwen Stagg, Katherine Morris, Andy Lam, Alexandra Navrotsky, Jesús M. Velázquez, Bianca Schacherl, Tonya Vitova, Jörg Rothe, Jurij Galanzew, Anke Neumann, Paul Lythgoe, Liam Abrahamsen-Mills, Samuel Shaw. Fe(II) Induced Reduction of Incorporated U(VI) to U(V) in Goethite. Environmental Science & Technology 2021, 55 (24) , 16445-16454. https://doi.org/10.1021/acs.est.1c06197
  11. Luke T. Townsend, Gina Kuippers, Jonathan R. Lloyd, Louise S. Natrajan, Christopher Boothman, J. Frederick W. Mosselmans, Samuel Shaw, Katherine Morris. Biogenic Sulfidation of U(VI) and Ferrihydrite Mediated by Sulfate-Reducing Bacteria at Elevated pH. ACS Earth and Space Chemistry 2021, 5 (11) , 3075-3086. https://doi.org/10.1021/acsearthspacechem.1c00126
  12. Fabrizio Ortu, Simon Randall, David J. Moulding, Adam W. Woodward, Andrew Kerridge, Karsten Meyer, Henry S. La Pierre, Louise S. Natrajan. Photoluminescence of Pentavalent Uranyl Amide Complexes. Journal of the American Chemical Society 2021, 143 (33) , 13184-13194. https://doi.org/10.1021/jacs.1c05184
  13. Margaux Molinas, Radmila Faizova, Ashley Brown, Jurij Galanzew, Bianca Schacherl, Barbora Bartova, Karin L. Meibom, Tonya Vitova, Marinella Mazzanti, Rizlan Bernier-Latmani. Biological Reduction of a U(V)–Organic Ligand Complex. Environmental Science & Technology 2021, 55 (8) , 4753-4761. https://doi.org/10.1021/acs.est.0c06633
  14. Alandra M. Lopez, Arden Wells, Scott Fendorf. Soil and Aquifer Properties Combine as Predictors of Groundwater Uranium Concentrations within the Central Valley, California. Environmental Science & Technology 2021, 55 (1) , 352-361. https://doi.org/10.1021/acs.est.0c05591
  15. Bin Ma, Alejandro Fernandez-Martinez, Mingliang Kang, Kaifeng Wang, Aled R. Lewis, Thierry G. G. Maffeis, Nathaniel Findling, Eduardo Salas-Colera, Delphine Tisserand, Sarah Bureau, Laurent Charlet. Influence of Surface Compositions on the Reactivity of Pyrite toward Aqueous U(VI). Environmental Science & Technology 2020, 54 (13) , 8104-8114. https://doi.org/10.1021/acs.est.0c01854
  16. Christian Dewey, Dimosthenis Sokaras, Thomas Kroll, John R. Bargar, Scott Fendorf. Calcium-Uranyl-Carbonato Species Kinetically Limit U(VI) Reduction by Fe(II) and Lead to U(V)-Bearing Ferrihydrite. Environmental Science & Technology 2020, 54 (10) , 6021-6030. https://doi.org/10.1021/acs.est.9b05870
  17. Gianni F. Vettese, Katherine Morris, Louise S. Natrajan, Samuel Shaw, Tonya Vitova, Jurij Galanzew, Debbie L. Jones, Jonathan R. Lloyd. Multiple Lines of Evidence Identify U(V) as a Key Intermediate during U(VI) Reduction by Shewanella oneidensis MR1. Environmental Science & Technology 2020, 54 (4) , 2268-2276. https://doi.org/10.1021/acs.est.9b05285
  18. William R. Bower, Katherine Morris, Francis R. Livens, J. Frederick W. Mosselmans, Connaugh M. Fallon, Adam J. Fuller, Louise Natrajan, Christopher Boothman, Jonathan R. Lloyd, Satoshi Utsunomiya, Daniel Grolimund, Dario Ferreira Sanchez, Tom Jilbert, Julia Parker, Thomas S. Neill, Gareth T. W. Law. Metaschoepite Dissolution in Sediment Column Systems—Implications for Uranium Speciation and Transport. Environmental Science & Technology 2019, 53 (16) , 9915-9925. https://doi.org/10.1021/acs.est.9b02292
  19. Will M. Bender, Udo Becker. Quantum-Mechanical Investigation of the Structures and Energetics of Uranium and Plutonium Incorporated into the Magnetite (Fe3O4) Lattice. ACS Earth and Space Chemistry 2019, 3 (4) , 637-651. https://doi.org/10.1021/acsearthspacechem.8b00167
  20. Radmila Faizova, Rosario Scopelliti, Anne-Sophie Chauvin, Marinella Mazzanti. Synthesis and Characterization of a Water Stable Uranyl(V) Complex. Journal of the American Chemical Society 2018, 140 (42) , 13554-13557. https://doi.org/10.1021/jacs.8b07885
  21. Huiyang Mei, Xiaoli Tan, Liqiang Tan, Yuedong Meng, Changlun Chen, Ming Fang, Xiangke Wang. Retention of U(VI) by the Formation of Fe Precipitates from Oxidation of Fe(II). ACS Earth and Space Chemistry 2018, 2 (10) , 968-976. https://doi.org/10.1021/acsearthspacechem.8b00055
  22. Lin Wang, Huan Song, Liyong Yuan, Zijie Li, Yujuan Zhang, John K. Gibson, Lirong Zheng, Zhifang Chai, Weiqun Shi. Efficient U(VI) Reduction and Sequestration by Ti2CTx MXene. Environmental Science & Technology 2018, 52 (18) , 10748-10756. https://doi.org/10.1021/acs.est.8b03711
  23. Martin E. McBriarty, Sebastien Kerisit, Eric J. Bylaska, Samuel Shaw, Katherine Morris, Eugene S. Ilton. Iron Vacancies Accommodate Uranyl Incorporation into Hematite. Environmental Science & Technology 2018, 52 (11) , 6282-6290. https://doi.org/10.1021/acs.est.8b00297
  24. Malin C. Dixon Wilkins, Luke T. Townsend, Martin C. Stennett, Kristina O. Kvashnina, Claire L. Corkhill, Neil C. Hyatt. A multimodal X-ray spectroscopy investigation of uranium speciation in ThTi2O6 compounds with the brannerite structure. Scientific Reports 2023, 13 (1) https://doi.org/10.1038/s41598-023-38912-1
  25. Mi Li, Wanqin Xu, Xiaoyan Wu, Xiaowen Zhang, Qi Fang, Tao Cai, Jianping Yang, Yilong Hua. Enhanced mechanism of calcium towards uranium incorporation and stability in magnetite during electromineralization. Journal of Hazardous Materials 2023, 457 , 131641. https://doi.org/10.1016/j.jhazmat.2023.131641
  26. Qian-Qian Jia, Xuejie Zhang, Jia Deng, Li-Zhi Huang. Labile Fe(III) phase mediates the electron transfer from Fe(II,III) (oxyhydr)oxides to carbon tetrachloride. Water Research 2023, 115 , 120636. https://doi.org/10.1016/j.watres.2023.120636
  27. Stephan Hilpmann, André Rossberg, Robin Steudtner, Björn Drobot, René Hübner, Frank Bok, Damien Prieur, Stephen Bauters, Kristina O. Kvashnina, Thorsten Stumpf, Andrea Cherkouk. Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T. Science of The Total Environment 2023, 875 , 162593. https://doi.org/10.1016/j.scitotenv.2023.162593
  28. Ryoji Kusaka, Yuta Kumagai, Masayuki Watanabe, Takayuki Sasaki, Daisuke Akiyama, Nobuaki Sato, Akira Kirishima. Raman identification and characterization of chemical components included in simulated nuclear fuel debris synthesized from uranium, stainless steel, and zirconium. Journal of Nuclear Science and Technology 2023, 60 (5) , 603-613. https://doi.org/10.1080/00223131.2022.2128460
  29. Connaugh M. Fallon, William R. Bower, Brian A. Powell, Francis R. Livens, Ian C. Lyon, Alana E. McNulty, Kathryn Peruski, J. Frederick W. Mosselmans, Daniel I. Kaplan, Daniel Grolimund, Peter Warnicke, Dario Ferreira-Sanchez, Marja Siitari Kauppi, Gianni F. Vettese, Samuel Shaw, Katherine Morris, Gareth T.W. Law. Vadose-zone alteration of metaschoepite and ceramic UO2 in Savannah River Site field lysimeters. Science of The Total Environment 2023, 862 , 160862. https://doi.org/10.1016/j.scitotenv.2022.160862
  30. Laura Lopez-Odriozola, Lauren Walker, Louise S. Natrajan. Luminescence properties of the actinides and actinyls. 2023, 789-807. https://doi.org/10.1016/B978-0-12-823144-9.00191-6
  31. Gianni F. Vettese, Katherine Morris, Matthew White-Pettigrew, Luke T. Townsend, Samuel Shaw, Christopher Boothman, Jonathan R. Lloyd. In situ (bio)remediation treatment options for U and Sr contaminated land: a comparison of radionuclide retention and remobilisation. Environmental Science: Advances 2023, 36 https://doi.org/10.1039/D3VA00104K
  32. Zhenpeng Cui, Shuyang Li, Xiaoyan Wei, Jingjing Wang, Yang Xu, Min Zhao, Duoqiang Pan, Wangsuo Wu. Photoreduction as an efficient approach for the rapid removal of U(VI) from the aqueous solution. Journal of Radioanalytical and Nuclear Chemistry 2022, 331 (10) , 4159-4168. https://doi.org/10.1007/s10967-022-08508-6
  33. Maengkyo Oh, Keunyoung Lee, Kwang-Wook Kim, Richard I. Foster, Chang-Ha Lee. Uranyl peroxide ((UO2)(O2)·4H2O; UO4) precipitation for uranium sequestering: formation and physicochemical characterization. Journal of Radioanalytical and Nuclear Chemistry 2022, 331 (6) , 2495-2501. https://doi.org/10.1007/s10967-022-08299-w
  34. Franky Barton, Samuel Shaw, Katherine Morris, James Graham, Jonathan R. Lloyd. Impact and control of fouling in radioactive environments. Progress in Nuclear Energy 2022, 148 , 104215. https://doi.org/10.1016/j.pnucene.2022.104215
  35. Ding-mi Fu, Mi Li, Yi-long Hua, Fang-ying Gao, Xiao-yan Wu, Xiao-wen Zhang, Qi Fang, Lei Bi, Tao Cai. Evidence for in-situ electric-induced uranium incorporation into magnetite crystal in acidic wastewater. Separation and Purification Technology 2022, 291 , 120957. https://doi.org/10.1016/j.seppur.2022.120957
  36. Luisa Köhler, Michael Patzschke, Stephen Bauters, Tonya Vitova, Sergei M. Butorin, Kristina O. Kvashnina, Moritz Schmidt, Thorsten Stumpf, Juliane März. Insights into the Electronic Structure of a U(IV) Amido and U(V) Imido Complex. Chemistry – A European Journal 2022, 28 (21) https://doi.org/10.1002/chem.202200119
  37. Rongyue Geng, Longmiao Yuan, Leiping Shi, Shirong Qiang, Yuqiang Li, Jianjun Liang, Ping Li, Guodong Zheng, Qiaohui Fan. New insights into the sorption of U(VI) on kaolinite and illite in the presence of Aspergillus niger. Chemosphere 2022, 288 , 132497. https://doi.org/10.1016/j.chemosphere.2021.132497
  38. Yuling Zhu, Yating Sheng, Yuxin Liu, Jiemin Chen, Xiaoyun He, Wenzhong Wang, Baowei Hu. Stable immobilization of uranium in iron containing environments with microbial consortia enriched via two steps accumulation method. Environmental Pollution 2022, 294 , 118591. https://doi.org/10.1016/j.envpol.2021.118591
  39. Kristina O. Kvashnina, Sergei M. Butorin. High-energy resolution X-ray spectroscopy at actinide M 4,5 and ligand K edges: what we know, what we want to know, and what we can know. Chemical Communications 2022, 58 (3) , 327-342. https://doi.org/10.1039/D1CC04851A
  40. D.H. Dang, W. Wang, T.M. Gibson, M. Kunzmann, M.B. Andersen, G.P. Halverson, R.D. Evans. Authigenic uranium isotopes of late Proterozoic black shale. Chemical Geology 2022, 588 , 120644. https://doi.org/10.1016/j.chemgeo.2021.120644
  41. Wenbo You, Wanting Peng, Zhichao Tian, Maosheng Zheng. Uranium bioremediation with U(VI)-reducing bacteria. Science of The Total Environment 2021, 798 , 149107. https://doi.org/10.1016/j.scitotenv.2021.149107
  42. Simon Pontér, Ilia Rodushkin, Emma Engström, Katerina Rodushkina, Cora Paulukat, Elsa Peinerud, Anders Widerlund. Early diagenesis of anthropogenic uranium in lakes receiving deep groundwater from the Kiruna mine, northern Sweden. Science of The Total Environment 2021, 793 , 148441. https://doi.org/10.1016/j.scitotenv.2021.148441
  43. Shao-yan Lv, Mi Li, Xiao-yan Wu, Xiao-wen Zhang, Yi-long Hua, Lei Bi, Qi Fang, Tao Cai. A non-polluting method for rapidly purifying uranium-containing wastewater and efficiently recovering uranium through electrochemical mineralization and oxidative roasting. Journal of Hazardous Materials 2021, 416 , 125885. https://doi.org/10.1016/j.jhazmat.2021.125885
  44. Luke T. Townsend, Katherine Morris, Robert Harrison, Bianca Schacherl, Tonya Vitova, Libor Kovarik, Carolyn I. Pearce, J. Frederick W. Mosselmans, Samuel Shaw. Sulfidation of magnetite with incorporated uranium. Chemosphere 2021, 276 , 130117. https://doi.org/10.1016/j.chemosphere.2021.130117
  45. Jingjing Wang, Shirong Qiang, Yun Wang, Wangsuo Wu, Ping Li, Haibo Qin, Qiaohui Fan. Adsorption of U(VI) on the natural soil around a very low-level waste repository. Journal of Environmental Radioactivity 2021, 233 , 106619. https://doi.org/10.1016/j.jenvrad.2021.106619
  46. Susan A Cumberland, Katy Evans, Grant Douglas, Martin de Jonge, Louise Fisher, Daryl Howard, John W Moreau. Characterisation of uranium-pyrite associations within organic-rich Eocene sediments using EM, XFM-µXANES and µXRD. Ore Geology Reviews 2021, 133 , 104051. https://doi.org/10.1016/j.oregeorev.2021.104051
  47. Natalie Byrd, Jonathan R. Lloyd, Joe S. Small, Frank Taylor, Heath Bagshaw, Christopher Boothman, Katherine Morris. Microbial Degradation of Citric Acid in Low Level Radioactive Waste Disposal: Impact on Biomineralization Reactions. Frontiers in Microbiology 2021, 12 https://doi.org/10.3389/fmicb.2021.565855
  48. Sheida Makvandi, Xiaowen Huang, Georges Beaudoin, David Quirt, Patrick Ledru, Mostafa Fayek. Trace element signatures in hematite and goethite associated with the Kiggavik–Andrew Lake structural trend U deposits (Nunavut, Canada). Mineralium Deposita 2021, 56 (3) , 509-535. https://doi.org/10.1007/s00126-020-00980-y
  49. Luke T. Townsend, Katherine Morris, Jonathan R. Lloyd. Microbial transformations of radionuclides in geodisposal systems. 2021, 245-265. https://doi.org/10.1016/B978-0-12-818695-4.00011-3
  50. Yuling Zhu, Xiaoyun He, Jiali Xu, Zheng Fu, Siying Wu, Jian Ni, Baowei Hu. Insight into efficient removal of Cr(VI) by magnetite immobilized with Lysinibacillus sp. JLT12: Mechanism and performance. Chemosphere 2021, 262 , 127901. https://doi.org/10.1016/j.chemosphere.2020.127901
  51. Yilong Hua, Donghan Li, Tianhang Gu, Wei Wang, Ruofan Li, Jianping Yang, Wei-xian Zhang. Enrichment of Uranium from Aqueous Solutions with Nanoscale Zero-valent Iron: Surface Chemistry and Application Prospect. Acta Chimica Sinica 2021, 79 (8) , 1008. https://doi.org/10.6023/A21040160
  52. Michael S. Massey. Investigating the Quantity and Form of Heavy Metal Contaminants for Improved Risk Analysis and Mitigation. 2021, 169-191. https://doi.org/10.1007/978-3-030-53893-4_5
  53. Zezhen Pan, Barbora Bártová, Thomas LaGrange, Sergei M. Butorin, Neil C. Hyatt, Martin C. Stennett, Kristina O. Kvashnina, Rizlan Bernier-Latmani. Nanoscale mechanism of UO2 formation through uranium reduction by magnetite. Nature Communications 2020, 11 (1) https://doi.org/10.1038/s41467-020-17795-0
  54. Pierre Le Pape, Lucie Stetten, Myrtille O.J.Y. Hunault, Arnaud Mangeret, Jessica Brest, Jean-Claude Boulliard, Guillaume Morin. HERFD-XANES spectroscopy at the U M-edge applied to the analysis of U oxidation state in a heavily contaminated wetland soil. Applied Geochemistry 2020, 122 , 104714. https://doi.org/10.1016/j.apgeochem.2020.104714
  55. Wanqiang Zhou, Dongfan Xian, Xuebin Su, Yao Li, Weimin Que, Yanlin Shi, Jingyi Wang, Chunli Liu. Macroscopic and spectroscopic characterization of U(VI) sorption on biotite. Chemosphere 2020, 255 , 126942. https://doi.org/10.1016/j.chemosphere.2020.126942
  56. Anna Yu. Romanchuk, Irina E. Vlasova, Stepan N. Kalmykov. Speciation of Uranium and Plutonium From Nuclear Legacy Sites to the Environment: A Mini Review. Frontiers in Chemistry 2020, 8 https://doi.org/10.3389/fchem.2020.00630
  57. S. Rohith, K. Kishore Ramanan, N. Santosh Srinivas, Gautham B. Jegadeesan. Fe-Ni-Doped Graphene Oxide for Uranium Removal—Kinetics and Equilibrium Studies. Water, Air, & Soil Pollution 2020, 231 (8) https://doi.org/10.1007/s11270-020-04804-7
  58. Yanpei Xie, Qi Fang, Mi Li, Sainan Wang, Yingfeng Luo, Xiaoyan Wu, Junwen Lv, Wenfa Tan, Hongqiang Wang, Kaixuan Tan. Low concentration of Fe(II) to enhance the precipitation of U(VI) under neutral oxygen-rich conditions. Science of The Total Environment 2020, 711 , 134827. https://doi.org/10.1016/j.scitotenv.2019.134827
  59. Chen Jing, Quan Li, Zhi Tang, Jiali Xu, Yilian Li. Removal of soluble uranium by illite supported nanoscale zero-valent iron: electron transfer processes and incorporation mechanisms. Journal of Radioanalytical and Nuclear Chemistry 2020, 323 (1) , 581-593. https://doi.org/10.1007/s10967-019-06959-y
  60. Christian Siebert, Peter Möller, Fabien Magri, Eyal Shalev, Eliahu Rosenthal, Marwan Al-Raggad, Tino Rödiger. Applying Rare Earth Elements, Uranium, and 87 Sr/ 86 Sr to Disentangle Structurally Forced Confluence of Regional Groundwater Resources: The Case of the Lower Yarmouk Gorge. Geofluids 2019, 2019 , 1-21. https://doi.org/10.1155/2019/6727681
  61. Liang Li, Mei Yang, Qian Lu, Wenkun Zhu, Hanqing Ma, Lichun Dai. Oxygen-rich biochar from torrefaction: A versatile adsorbent for water pollution control. Bioresource Technology 2019, 294 , 122142. https://doi.org/10.1016/j.biortech.2019.122142
  62. Thomas S. Neill, Katherine Morris, Carolyn I. Pearce, Liam Abrahamsen-Mills, Libor Kovarik, Simon Kellet, Bruce Rigby, Tonya Vitova, Bianca Schacherl, Samuel Shaw. Silicate stabilisation of colloidal UO2 produced by uranium metal corrosion. Journal of Nuclear Materials 2019, 526 , 151751. https://doi.org/10.1016/j.jnucmat.2019.151751
  63. Bin Zheng, Yizi Ye, Baowei Hu, Chunhui Luo, Yuling Zhu. Enhanced removal of chromium( vi ) by Fe( iii )-reducing bacterium coated ZVI for wastewater treatment: batch and column experiments. RSC Advances 2019, 9 (62) , 36144-36153. https://doi.org/10.1039/C9RA06516D
  64. Manuel Eibl, Sinikka Virtanen, Felix Pischel, Frank Bok, Satu Lönnrot, Samuel Shaw, Nina Huittinen. A spectroscopic study of trivalent cation (Cm3+ and Eu3+) sorption on monoclinic zirconia (ZrO2). Applied Surface Science 2019, 487 , 1316-1328. https://doi.org/10.1016/j.apsusc.2019.05.012
  65. Yi Xie, Changlun Chen, Xuemei Ren, Xiangxue Wang, Haiyan Wang, Xiangke Wang. Emerging natural and tailored materials for uranium-contaminated water treatment and environmental remediation. Progress in Materials Science 2019, 103 , 180-234. https://doi.org/10.1016/j.pmatsci.2019.01.005
  66. Ellen H. Winstanley, Katherine Morris, Liam G. Abrahamsen-Mills, Richard Blackham, Samuel Shaw. U(VI) sorption during ferrihydrite formation: Underpinning radioactive effluent treatment. Journal of Hazardous Materials 2019, 366 , 98-104. https://doi.org/10.1016/j.jhazmat.2018.11.077
  67. Pieter Bots, Arjen van Veelen, J. Frederick W. Mosselmans, Christopher Muryn, Roy A. Wogelius, Katherine Morris. Neptunium(V) and Uranium(VI) Reactions at the Magnetite (111) Surface. Geosciences 2019, 9 (2) , 81. https://doi.org/10.3390/geosciences9020081
  68. Hannah E. Roberts, Katherine Morris, J. Frederick W. Mosselmans, Gareth T. W. Law, Samuel Shaw. Neptunium Reactivity During Co-Precipitation and Oxidation of Fe(II)/Fe(III) (Oxyhydr)oxides. Geosciences 2019, 9 (1) , 27. https://doi.org/10.3390/geosciences9010027
  69. Saurav K. Guin, Arvind S. Ambolikar, Jhimli Paul Guin, Suman Neogy. Exploring the excellent photophysical and electrochemical properties of graphene quantum dots for complementary sensing of uranium. Sensors and Actuators B: Chemical 2018, 272 , 559-573. https://doi.org/10.1016/j.snb.2018.05.176
  70. Xiaoyan Sun, Zhongwu Liu, Zhigang Zheng, Hongya Yu, Dechang Zeng. Improved adsorption of Congo red by nanostructured flower-like Fe(II)–Fe(III) hydroxy complex. Water Science and Technology 2018, 78 (3) , 506-514. https://doi.org/10.2166/wst.2018.303
  71. Yubing Sun, Jianhui Lan, Mengxue Li, Wei Hu, Haibo Liu, Gang Song, Diyun Chen, Weiqun Shi, Xiangke Wang. Retracted Article: Influence of aqueous sulfide on speciation of U( vi ) adsorbed to nanomagnetite. Environmental Science: Nano 2018, 5 (8) , 1981-1989. https://doi.org/10.1039/C8EN00511G
  72. Keaton M. Belli, Martial Taillefert. Geochemical controls of the microbially mediated redox cycling of uranium and iron. Geochimica et Cosmochimica Acta 2018, 235 , 431-449. https://doi.org/10.1016/j.gca.2018.05.027
  73. Radmila Faizova, Sarah White, Rosario Scopelliti, Marinella Mazzanti. The effect of iron binding on uranyl( v ) stability. Chemical Science 2018, 9 (38) , 7520-7527. https://doi.org/10.1039/C8SC02099J
  74. Eugene S. Ilton, Yingge Du, Joanne E. Stubbs, Peter J. Eng, Anne M. Chaka, John R. Bargar, Connie J. Nelin, Paul S. Bagus. Quantifying small changes in uranium oxidation states using XPS of a shallow core level. Physical Chemistry Chemical Physics 2017, 19 (45) , 30473-30480. https://doi.org/10.1039/C7CP05805E
Download PDF

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. U M4 edge HERFD-XANES of U co-precipitated with magnetite [Fe(II)/Fe(III) = 0.5 and 0.6] and green rust [Fe(II)/Fe(III) = 0.8 and 2.0] with standards U(IV)O2, (46) U(IV)2U(V)2O9, (46) and U(VI) adsorbed to ferrihydrite. Gray arrows indicate characteristic U(VI) features.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. (A) Magnetite structure showing Fe–Fe distances (38) and U–Fe distances obtained from EXAFS at Fe(II)/Fe(III) = 0.6. (B) Green rust structures showing Fe–Fe distances (40) and U–Fe distances obtained from EXAFS at Fe(II)/Fe(III) = 2.0. Yellow lines indicate shorter U–O distances (1.9 Å), and white lines indicate longer U–O distances (2.17 Å).

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    ARTICLE SECTIONS
    Jump To

    This article references 55 other publications.

    1. 1
      Newsome, L.; Morris, K.; Lloyd, J. R. The biogeochemistry and bioremediation of uranium and other priority radionuclides Chem. Geol. 2014, 363, 164– 184 DOI: 10.1016/j.chemgeo.2013.10.034
      [Crossref], [CAS], Google Scholar
      1
      The biogeochemistry and bioremediation of uranium and other priority radionuclides
      Newsome, Laura; Morris, Katherine; Lloyd, Jonathan R.
      Chemical Geology (2014), 363 (), 164-184CODEN: CHGEAD; ISSN:0009-2541. (Elsevier B.V.)
      Microbial metab. has the potential to alter the soly. of a broad range of priority radionuclides, including uranium, other actinides and fission products. Of notable interest has been the biostimulation of anaerobic microbial communities to remove redox-sensitive radionuclides such as uranium U(VI) from contaminated groundwaters at nuclear sites. Particularly promising are bioredn. processes, whereby bacteria enzymically reduce aq. U(VI) to insol. U(IV) coupled to oxidn. of an org. electron donor; and uranium phosphate biomineralization, in which bacterial phosphatase activity cleaves organophosphates, liberating inorg. phosphate that ppts. with aq. U(VI) as uranyl phosphate minerals. Here we review the mechanisms of uranium bioredn. and phosphate biomineralization and their suitability to facilitate long-term pptn. of uranium from groundwater, with particular focus on in situ trials at the US Department of Energy field sites. Redox interactions of other priority radionuclides (technetium, neptunium, plutonium, americium, iodine, strontium and caesium) are also reviewed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXksFOmtw%253D%253D&md5=082030dc4e6b69149b5fbdf1ade3f69d
    2. 2
      Moyce, E. B. A.; Rochelle, C.; Morris, K.; Milodowski, A. E.; Chen, X.; Thornton, S.; Small, J. S.; Shaw, S. Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste Appl. Geochem. 2014, 50, 91– 105 DOI: 10.1016/j.apgeochem.2014.08.003
      [Crossref], [CAS], Google Scholar
      2
      Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste
      Moyce, Elizabeth B. A.; Rochelle, Christopher; Morris, Katherine; Milodowski, Antoni E.; Chen, Xiaohui; Thornton, Steve; Small, Joe S.; Shaw, Samuel
      Applied Geochemistry (2014), 50 (), 91-105CODEN: APPGEY; ISSN:0883-2927. (Elsevier Ltd.)
      The interaction of groundwater with cement in a geol. disposal facility (GDF) for intermediate level radioactive waste will produce a high pH leachate plume. Such a plume may alter the phys. and chem. properties of the GDF host rock. However, the geochem. and mineralogical processes which may occur in such systems over timescales relevant for geol. disposal remain unclear. This study has extended the timescale for lab. expts. and shown that, after 15 years two distinct phases of reaction may occur during alteration of a dolomite-rich rock at high pH. In these expts. the dissoln. of primary silicate minerals and the formation of secondary calcium silicate hydrate (C-S-H) phases contg. varying amts. of aluminum and potassium (C-(A)-(K)-S-H) during the early stages of reaction (up to 15 mo) have been superseded as the systems have evolved. After 15 years significant dedolomitisation (MgCa(CO3)2 + 2OH- → Mg(OH)2 + CaCO3 + CO2-32-(aq)) has led to the formation of magnesium silicates, such as saponite and talc, contg. variable amts. of aluminum and potassium (Mg-(Al)-(K)-silicates), and calcite at the expense of the early-formed C-(A)-(K)-S-H phases. This occurred in high pH solns. representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a KOH and NaOH or a Ca(OH)2 dominated soln. but a greater extent of alteration in the higher pH KOH/NaOH leachate. The high pH alteration of the rock over 15 years also increased the rock's sorption capacity for U(VI). The results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite-rich rock in the geosphere. These processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geol. disposal.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFGlurjM&md5=97dc93a1126cf9534cd1fa4b102db878
    3. 3
      Gavrilescu, M.; Pavel, L. V.; Cretescu, I. Characterization and remediation of soils contaminated with uranium J. Hazard. Mater. 2009, 163 (2–3) 475– 510 DOI: 10.1016/j.jhazmat.2008.07.103
      [Crossref], [PubMed], [CAS], Google Scholar
      3
      Characterization and remediation of soils contaminated with uranium
      Gavrilescu, Maria; Pavel, Lucian Vasile; Cretescu, Igor
      Journal of Hazardous Materials (2009), 163 (2-3), 475-510CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
      A review. Environmental contamination caused by radionuclides, in particular by uranium and its decay products is a serious problem worldwide. The development of nuclear science and technol. has led to increasing nuclear waste contg. uranium being released and disposed in the environment. The objective of this paper is to develop a better understanding of the techniques for the remediation of soils polluted with radionuclides (uranium in particular), considering: the chem. forms of uranium, including depleted uranium (DU) in soil and other environmental media, their characteristics and concns., and some of the effects on environmental and human health; research issues concerning the remediation process, the benefits and results; a better understanding of the range of uses and situations for which each is most appropriate. The paper addresses the main features of the following techniques for uranium remediation: natural attenuation, phys. methods, chem. processes (chem. extn. methods from contaminated soils assisted by various suitable chelators (sodium bicarbonate, citric acid, two-stage acid leaching procedure), extn. using supercrit. fluids such as solvents, permeable reactive barriers), biol. processes (biomineralization and microbial redn., phytoremediation, biosorption), and electrokinetic methods. In addn., factors affecting uranium removal from soils are furthermore reviewed including soil characteristics, pH and reagent concn., retention time.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhvFait7s%253D&md5=513e376b91681948aae8fa59e27f6bf8
    4. 4
      Bone, S. E.; Dynes, J. J.; Cliff, J.; Bargar, J. R. Uranium(IV) adsorption by natural organic matter in anoxic sediments Proc. Natl. Acad. Sci. U. S. A. 2017, 114 (4) 711 DOI: 10.1073/pnas.1611918114
      [Crossref], [PubMed], [CAS], Google Scholar
      4
      Uranium(IV) adsorption by natural organic matter in anoxic sediments
      Bone, Sharon E.; Dynes, James J.; Cliff, John; Bargar, John R.
      Proceedings of the National Academy of Sciences of the United States of America (2017), 114 (4), 711-716CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temp. geochem. environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly sol. mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to org. carbon and org. carbon-coated clays dominate U(IV) speciation in an org.-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of redn. (i.e., whether redn. is mediated by microbes or by inorg. reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of redn. pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to org. matter within the sediment environment.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmslWrtg%253D%253D&md5=808b80c037df85cb10520fed03cfcb1e
    5. 5
      Ekstrom, A. Kinetics and Mechanism of the Disproportionation of Uranium(V) Inorg. Chem. 1974, 13 (9) 2237– 2241 DOI: 10.1021/ic50139a035
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      5
      Kinetics and mechanism of the disproportionation of uranium(V)
      Ekstrom, A.
      Inorganic Chemistry (1974), 13 (9), 2237-41CODEN: INOCAJ; ISSN:0020-1669.
      The kinetics and mechanism of the disproportionation of UO2+ [21294-41-7] were investigated. In agreement with a previous study (T. W. Newton; F. B. Baker, 1965), the rate of disproportionation was retarded by the presence of UO22+ [16637-16-4], the effect being attributed to the formation of a U(V).U(VI) complex whose absorption spectrum in the range 360-760 nm was measured. The effects of ionic strength, acid concn., and the presence of complex anions on the disproportionation rate were examd. The reaction was also studied in D2O soln. and reaction mechanisms are discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXkvVaku70%253D&md5=65107db2f141e134c429dec087883ebe
    6. 6
      Steele, H.; Taylor, R. J. A Theoretical Study of the Inner-Sphere Disproportionation Reaction Mechanism of the Pentavalent Actinyl Ions Inorg. Chem. 2007, 46 (16) 6311– 6318 DOI: 10.1021/ic070235c
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      6
      A theoretical study of the inner-sphere disproportionation reaction mechanism of the pentavalent actinyl ions
      Steele, Helen; Taylor, Robin J.
      Inorganic Chemistry (2007), 46 (16), 6311-6318CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      The inner-sphere mechanisms of the disproportionation reactions of U(V), Np(V), and Pu(V) ions have been studied using a quantum mech. approach. The U(V) disproportionation proceeds via the formation of a dimer (a cation-cation complex) followed by two successive protonations at the axial oxygens of the donor uranyl ion. Bond lengths and spin multiplicities indicate that electron transfer occurs after the first protonation. A solvent water mol. then breaks the complex into solvated U(OH)22+ and UO22+ ions. Pu(V) behaves similarly, but Np(V) appears not to follow this path. The observations from quantum modeling are consistent with existing exptl. data on actinyl(V) disproportionation reactions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXns1CktL4%253D&md5=56e8e4e1cd716169797c39487c14cedf
    7. 7
      Ikeda, A.; Hennig, C.; Tsushima, S.; Takao, K.; Ikeda, Y.; Scheinost, A. C.; Bernhard, G. Comparative study of uranyl(VI) and -(V) carbonato complexes in an aqueous solution Inorg. Chem. 2007, 46 (10) 4212– 4219 DOI: 10.1021/ic070051y
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      7
      Comparative Study of Uranyl(VI) and -(V) Carbonato Complexes in an Aqueous Solution
      Ikeda, Atsushi; Hennig, Christoph; Tsushima, Satoru; Takao, Koichiro; Ikeda, Yasuhisa; Scheinost, Andreas C.; Bernhard, Gert
      Inorganic Chemistry (2007), 46 (10), 4212-4219CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Electrochem., complexation, and electronic properties of uranyl(VI) and -(V) carbonato complexes in an aq. Na2CO3 soln. were studied to define the appropriate conditions for prepg. pure uranyl(V) samples and to understand the difference in coordination character between UO22+ and UO2+. Cyclic voltammetry using 3 different working electrodes of Pt, Au, and glassy C suggested that the electrochem. reaction of uranyl(VI) carbonate species proceeds quasi-reversibly. Electrolysis of UO22+ was performed in Na2CO3 solns. of >0.8 M with a limited pH range of 11.7 < pH < 12.0 using a Pt mesh electrode. It produces a high purity of the uranyl(V) carbonate soln., which is stable for at least 2 wk in a sealed glass cuvette. Extended x-ray absorption fine structure (EXAFS) measurements revealed the structural arrangement of uranyl(VI) and -(V) tricarbonato complexes, [UO2(CO3)3]n- [n = 4 for uranyl(VI), 5 for uranyl(V)]. The bond distances of U-Oax, U-Oeq, U-C, and U-Odist are 1.81, 2.44, 2.92, and 4.17 Å for the uranyl(VI) complex and 1.91, 2.50, 2.93, and 4.23 Å for the uranyl(V) complex, resp. The validity of the structural parameters obtained from EXAFS was supported by quantum chem. calcns. for the uranyl(VI) complex. The U L|- and L|||-edge x-ray absorption near-edge structure spectra were interpreted in terms of electron transitions and multiple-scattering features.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjvVOlsLs%253D&md5=aa3cc71c9c632e1db9faac798eea2f06
    8. 8
      Ilton, E. S.; Boily, J. F.; Buck, E. C.; Skomurski, F. N.; Rosso, K. M.; Cahill, C. L.; Bargar, J. R.; Felmy, A. R. Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface Environ. Sci. Technol. 2010, 44, 170– 176 DOI: 10.1021/es9014597
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      8
      Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface
      Ilton, Eugene S.; Boily, Jean-Francois; Buck, Edgar C.; Skomurski, Frances N.; Rosso, Kevin M.; Cahill, Christopher L.; Bargar, John R.; Felmy, Andrew R.
      Environmental Science & Technology (2010), 44 (1), 170-176CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      The heterogeneous redn. of UVI to UIV by ferrous iron is believed to be a key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. Published results from UVI-magnetite expts. have been variable, ranging from no redn. to clear evidence for the formation of UIV. In this contribution, we used XAS and high resoln. (±cryogenic) XPS to study the interaction of UVI with nanoparticulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UIV. However, thermodn. calcns. indicated that U phases with av. oxidn. states below (V) should have been stable, indicating that the system was not in redox equil. A reaction pathway that involves incorporation and stabilization of UV and UVI into secondary phases is invoked to explain the observations. The results suggest an important and previously unappreciated role of UV in the fate and transport of uranium in the environment.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtlagsbnN&md5=0565c8450d91f25cd92f8953133b8e4d
    9. 9
      Ilton, E. S.; Haiduc, A.; Cahill, C. L.; Felmy, A. R. Mica Surfaces Stabilize Pentavalent Uranium Inorg. Chem. 2005, 44 (9) 2986– 2988 DOI: 10.1021/ic0487272
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    10. 10
      Yuan, K.; Renock, D.; Ewing, R. C.; Becker, U. Uranium reduction on magnetite: Probing for pentavalent uranium using electrochemical methods Geochim. Cosmochim. Acta 2015, 156, 194– 206 DOI: 10.1016/j.gca.2015.02.014
      [Crossref], [CAS], Google Scholar
      10
      Uranium reduction on magnetite: Probing for pentavalent uranium using electrochemical methods
      Yuan, Ke; Renock, Devon; Ewing, Rodney C.; Becker, Udo
      Geochimica et Cosmochimica Acta (2015), 156 (), 194-206CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Pentavalent uranium is generally treated as an unstable intermediate when uranyl, U(VI)O2+2, is reduced to U4+. However, mineral surfaces have been shown to stabilize pentavalent uranium, thus hindering further redn. (Ilton et al., 2005, 2010). The subject of this study is to identify the kinetic pathways that lead to U(V)O+2 being a metastable species. Electrochem. methods provide an in situ approach for the investigation of the intermediate reaction of U(V)O+2 on the surfaces of magnetite. Redox reactions of uranyl ions on particulate (∼3 μm) and bulk magnetite surfaces were investigated using cyclic voltammetry and potential step chronoamperometry using cavity microelectrodes and bulk (planar) mineral electrodes. The estd. redox potentials are consistent with the std. redox potential of UO2+2/UO+2, indicating UO2+2 is first reduced to UO+2 on the surfaces of both powder and bulk magnetite. The one-electron redn. of UO2+2 to UO+2 was further confirmed by directly measuring the no. of electrons transferred during the redn. process on the bulk magnetite electrode. Based on the charge conservation anal. and the pos. correlation between the pH and the peak current for the UO+2 transformation to UO2+2, the peak corresponding to the oxidn. of U4+ to UO2+2 was assigned in the voltammograms of particulate magnetite. The presence of U4+ indicates that the disproportionation of UO+2 (2U(V) ↔ U(IV) + U(VI)) is occurring on the surface of particulate magnetite within the timeframe of the expt. The lack of a peak for U4+ in voltammograms for bulk magnetite suggests that the rate of the UO+2 disproportionation reaction is slower on bulk magnetite than that on particulate magnetite. The catalytic property of particulate magnetite surfaces on the disproportionation reaction is explained by its ability to adsorb and desorb protons, which could facilitate the proton-coupled disproportionation reaction of UO+2. This increased catalytic activity and related adsorption and desorption kinetics of protons may be related to the increased no. of under-coordinated surface sites near step edges on the magnetite powder.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsF2rt7w%253D&md5=2444be57fb4718c8270ad5c326122f78
    11. 11
      Yuan, K.; Ilton, E. S.; Antonio, M. R.; Li, Z.; Cook, P. J.; Becker, U. Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite Environ. Sci. Technol. 2015, 49 (10) 6206– 6213 DOI: 10.1021/acs.est.5b00025
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      11
      Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite
      Yuan, Ke; Ilton, Eugene S.; Antonio, Mark R.; Li, Zhongrui; Cook, Peter J.; Becker, Udo
      Environmental Science & Technology (2015), 49 (10), 6206-6213CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Redn. of U(VI) to U(IV) on mineral surfaces is often considered a one-step 2-electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies indicates U(VI) can undergo a 1-electron redn. to U(V) without further progression to U(IV). We studied redn. pathways of U by reducing U(VI) electrochem. on a magnetite electrode at pH 3.4. Cyclic voltammetry confirms the 1-electron redn. of U(VI) to U(V). Formation of nanosize U ppts. on the magnetite surface at reducing potentials and dissoln. of the solids at oxidizing potentials are obsd. by in situ electrochem. at. force microscopy. XPS anal. of the magnetite electrodes polarized in U solns. at voltages from -0.1 to -0.9 V (E0U(VI)/U(V)= -0.135 V vs. Ag/AgCl) show the presence of only U(V) and U(VI). The sample with the highest U(V)/U(VI) ratio was prepd. at -0.7 V, where the longest av. U-Oaxial distance of 2.05±0.01 Å was evident in the same sample revealed by extended x-ray absorption fine structure anal. The results demonstrate that the electrochem. redn. of U(VI) on magnetite only yields U(V), even at a potential of -0.9 V, which favors the 1-electron redn. mechanism. U(V) does not disproportionate but stabilizes on magnetite through pptn. of mixed-valence state U(V)/U(VI) solids.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmslChtLg%253D&md5=d2ec7b36018e5d6881447462ad135f76
    12. 12
      Tsarev, S.; Collins, R. N.; Fahy, A.; Waite, T. D. Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zerovalent Iron Environ. Sci. Technol. 2016, 50 (5) 2595– 2601 DOI: 10.1021/acs.est.5b06160
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      12
      Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zero Valent Iron
      Tsarev, Sergey; Collins, Richard N.; Fahy, Adam; Waite, T. David
      Environmental Science & Technology (2016), 50 (5), 2595-2601CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Nanoscale zero-valent Fe (nZVI) has demonstrated potential as an effective agent to remediate U-contaminated subsurface environments; however, the nature of and reaction product formation kinetics have not been fully elucidated at environmentally relevant conditions. This work examd. the O-free reaction of U6+ with varying quantities of nZVI at pH 7 in the presence of Ca and CO32- by x-ray absorption spectroscopy, x-ray diffraction, and transmission electron microscopy. The reduced U solid phase structure was time dependent and largely affected by system nZVI:U ratio. At the highest examd. U:Fe molar ratio, 1:4, nanoscale uraninite (UO2) was predominantly formed within 1 day of reaction. At lower U:Fe molar ratios, 1:21, evidence was obtained for formation of sorbed U4+ and U5+ surface complexes which slowly transformed to UO2 nanoparticles stable for up to 1 yr of anaerobic incubation. Following 8 days reaction at the lowest examd. U:Fe molar ratio, 1:110, sorbed U4+ was still the major U form assocd. with the solid phase. Regardless of the U:Fe molar ratio, anaerobic corrosion of nZVI resulted in the slow formation of micron-sized fibrous chukanovite (Fe2(OH)2CO3) particles.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvV2rs78%253D&md5=b50729fad63004af0d02f1dfe555b2c6
    13. 13
      Ilton, E. S.; Pacheco, J. S. L.; Bargar, J. R.; Shi, Z.; Liu, J.; Kovarik, L.; Engelhard, M. H.; Felmy, A. R. Reduction of U(VI) Incorporated in the Structure of Hematite Environ. Sci. Technol. 2012, 46, 9428– 9436 DOI: 10.1021/es3015502
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      13
      Reduction of U(VI) Incorporated in the Structure of Hematite
      Ilton, Eugene S.; Pacheco, Juan S. Lezama; Bargar, John R.; Shi, Zhi; Liu, Juan; Kovarik, Libor; Engelhard, Mark H.; Felmy, Andrew R.
      Environmental Science & Technology (2012), 46 (17), 9428-9436CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      U(VI) doped hematite was synthesized and exposed to two different org. reductants with E0 of 0.23 and 0.70 V. A combination of HAADF-TEM and EXAFS provided evidence that uranium was incorporated in hematite in uranate, likely octahedral coordination. XPS indicated that structurally incorporated U(VI) was reduced to U(V), whereas non-incorporated U(VI) was reduced to U(IV). Specifically, the expts. indicate that U(V) was the dominant oxidn. state of uranium in hematite around Eh -0.24 to -0.28 V and pH 7.7-8.6 for at least up to 5 wk of reaction time. U(V), but not U(IV), was also detected in hematite at Eh +0.21 V (pH 7.1-7.3). The results support the hypothesis, based on previous exptl. and theor. work, that the stability field of U(V) is widened relative to U(IV) and U(VI) in uranate coordination environments where the coordination no. of U is less than 8.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFSjurfN&md5=8205cc1c3a1027d8eb77d528a47faf5a
    14. 14
      Massey, M. S.; Lezama-Pacheco, J. S.; Jones, M. E.; Ilton, E. S.; Cerrato, J. M.; Bargar, J. R.; Fendorf, S. Competing retention pathways of uranium upon reaction with Fe(II) Geochim. Cosmochim. Acta 2014, 142 (1) 166– 185 DOI: 10.1016/j.gca.2014.07.016
      [Crossref], [CAS], Google Scholar
      14
      Competing retention pathways of uranium upon reaction with Fe(II)
      Massey, Michael S.; Lezama-Pacheco, Juan S.; Jones, Morris E.; Ilton, Eugene S.; Cerrato, Jose M.; Bargar, John R.; Fendorf, Scott
      Geochimica et Cosmochimica Acta (2014), 142 (), 166-185CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Biogeochem. retention processes, including adsorption, reductive pptn., and incorporation into host minerals, are important in contaminant transport, remediation, and geol. deposition of uranium. Recent work has shown that U can become incorporated into iron (hydr)oxide minerals, with a key pathway arising from Fe(II)-induced transformation of ferrihydrite, (Fe(OH)3·nH2O) to goethite (α-FeO(OH)); this is a possible U retention mechanism in soils and sediments. Several key questions, however, remain unanswered regarding U incorporation into iron (hydr)oxides and this pathway's contribution to U retention, including: (i) the competitiveness of U incorporation vs. redn. to U(IV) and subsequent pptn. of UO2; (ii) the oxidn. state of incorporated U; (iii) the effects of uranyl aq. speciation on U incorporation; and, (iv) the mechanism of U incorporation. Here we use a series of batch reactions conducted at pH ∼7, [U(VI)] from 1 to 170 μM, [Fe(II)] from 0 to 3 mM, and [Ca] at 0 or 4 mM coupled with spectroscopic examn. of reaction products of Fe(II)-induced ferrihydrite transformation to address these outstanding questions. Uranium retention pathways were identified and quantified using extended X-ray absorption fine structure (EXAFS) spectroscopy, X-ray powder diffraction, XPS, and transmission electron microscopy. Anal. of EXAFS spectra showed that 14-89% of total U was incorporated into goethite, upon reaction with Fe(II) and ferrihydrite. Uranium incorporation was a particularly dominant retention pathway at U concns. ≤50 μM when either uranyl-carbonato or calcium-uranyl-carbonato complexes were dominant, accounting for 64-89% of total U. With increasing U(VI) and Fe(II) concns., U(VI) redn. to U(IV) became more prevalent, but U incorporation remained a functioning retention pathway. These findings highlight the potential importance of U(V) incorporation within iron oxides as a retention process of U across a wide range of biogeochem. environments and the sensitivity of uranium retention processes to operative (bio)geochem. conditions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Gqu7vF&md5=694b78d5b684ed09757800937271ea50
    15. 15
      Huber, F.; Schild, D.; Vitova, T.; Rothe, J.; Kirsch, R.; Schäfer, T. U(VI) removal kinetics in presence of synthetic magnetite nanoparticles Geochim. Cosmochim. Acta 2012, 96, 154– 173 DOI: 10.1016/j.gca.2012.07.019
      [Crossref], [CAS], Google Scholar
      15
      U(VI) removal kinetics in presence of synthetic magnetite nanoparticles
      Huber, F.; Schild, D.; Vitova, T.; Rothe, J.; Kirsch, R.; Schaefer, T.
      Geochimica et Cosmochimica Acta (2012), 96 (), 154-173CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      The interaction of hexavalent U with a freshly synthesized nanoparticulate magnetite (FeIIFeIII2O4) (stoichiometric ratio x(Fe(II)/FeTOT) = 0.25-0.33), a partly oxidized synthetic nanoparticulate magnetite (x = 0.11-0.27) and maghemite nanoparticles (x = 0-1) under anoxic conditions and exclusion of CO2 as function of pH, contact time and total U concn. (3 × 10-5 M and 1 × 10-7 M) has been examd. Short term kinetic batch expts. (contact time of 90 d) for four different pH values have been conducted. Moreover, classical batch pH sorption edges have been prepd. for two different uranium concns. for a contact time of 550 d. Spectroscopic techniques (XPS, XAS) were applied to probe for the presence and amt. of reduced U on the magnetite surface. Batch kinetic studies revealed a fast initial U removal from aq. soln. with >90% magnetite assocd. U after 24 h within the pH range 5-11. Long-term contact time batch expts. (550 d) showed neither a U removal below pH < 3 nor a decrease in the magnetite assocd. U at pH ≥ 9. Redox speciation by XPS verifies the presence of reduced U (both U(IV) and U(V) were resolved if the satellite structures were used in the fitting procedure) at the near surface of magnetite up to a contact time of 550 d and a clear correlation of the amt. of available Fe(II) on the magnetite surface and the amt. of reduced U is obsd. XANES investigation supports presence of U(V)/U(VI) uranate and U(IV). Interpretation of the EXAFS for one sample is consistent with incorporation of U into an Fe oxide phase, after long reaction times. Thermodn. calcns. based on the exptl. detd. redox potentials corroborate the spectroscopic findings of U oxidn. states. Overall, the results reflect the importance of structurally bound Fe(II) as redox partner for uranyl redn.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsV2js73M&md5=8ed206c8574a8746b844f3fb8f905d89
    16. 16
      Marshall, T. A.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Roberts, H.; Shaw, S. Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste Mineral. Mag. 2015, 79 (6) 1265– 1274 DOI: 10.1180/minmag.2015.079.6.02
      [Crossref], [CAS], Google Scholar
      16
      Uranium fate during crystallization of magnetite from ferrihydrite in conditions relevant to the disposal of radioactive waste
      Marshall, Timothy A.; Morris, Katherine; Law, Gareth T. W.; Mosselmans, Frederick W.; Bots, Pieter; Roberts, Hannah; Shaw, Samuel
      Mineralogical Magazine (2015), 79 (6), 1265-1274CODEN: MNLMBB; ISSN:1471-8022. (Walter de Gruyter GmbH)
      Uranium incorporation into magnetite and its behavior during subsequent oxidn. has been investigated at high pH to det. the uranium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to U(VI)aq contg. cement leachates (pH 10.5-13.1) and crystn. of magnetite was induced via addn. of Fe(II)aq. A combination of XRD, chem. extn. and XAS techniques provided direct evidence that U(VI) was reduced and incorporated into the magnetite structure, possibly as U(V), with a significant fraction recalcitrant to oxidative remobilization. Immobilization of U(VI) by redn. and incorporation into magnetite at high pH, and with significant stability upon reoxidn., has clear and important implications for limiting uranium migration in geol. disposal of radioactive wastes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsVWlt7nI&md5=6ed6719bd416be168de6d69d924c9ccc
    17. 17
      Boland, D. D.; Collins, R. N.; Payne, T. E.; Waite, T. D. Effect of Amorphous Fe(III) Oxide Transformation on the Fe(II)-Mediated Reduction of U(VI) Environ. Sci. Technol. 2011, 45, 1327– 1333 DOI: 10.1021/es101848a
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      17
      Effect of Amorphous Fe(III) Oxide Transformation on the Fe(II)-Mediated Reduction of U(VI)
      Boland, Daniel D.; Collins, Richard N.; Payne, Timothy E.; Waite, T. David
      Environmental Science & Technology (2011), 45 (4), 1327-1333CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      It has recently been reported that the Fe(II)-catalyzed crystn. of 2-line ferrihydrite to goethite and magnetite can result in the immobilization of uranium. Although it might be expected that interference of the crystn. process (for example, by the presence of silicate) would prevent uranium immobilization, this has not yet been demonstrated. Here we present results of an X-ray absorption spectroscopy study on the fate of hexavalent uranium (U(VI)) during the Fe(II)-catalyzed transformations of 2-line ferrihydrite and ferrihydrite copptd. with silicate (silicate-ferrihydrite). Two-line ferrihydrite transformed monotonically to goethite, whereas silicate-ferrihydrite transformed into a form similar to ferrihydrite synthesized in the absence of silicate. Modeling of U L(III)-edge EXAFS data indicated that both copptd. and adsorbed U(VI) were initially assocd. with ferrihydrite and silicate-ferrihydrite as a mononuclear bidentate surface complex. During the Fe(II)-catalyzed transformation process, U(VI) assocd. with 2-line ferrihydrite was reduced and partially incorporated into the newly formed goethite mineral structure, most likely as U(V), whereas U(VI) assocd. with silicate-ferrihydrite was not reduced and remained in a form similar to its initially adsorbed state. Uranium(VI) that was initially adsorbed to silicate-ferrihydrite did, however, become more resistant to reductive dissoln. indicating at least a partial redn. in mobility. These results suggest that when the Fe(II)-catalyzed transformation of ferrihydrite-like iron oxyhydroxides is inhibited, at least under conditions similar to those used in these expts., uranium redn. will not occur.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXit1Cmug%253D%253D&md5=5f279b5adec98f1f23df9db859ad236a
    18. 18
      Boland, D. D.; Collins, R. N.; Glover, C. J.; Payne, T. E.; Waite, T. D. Reduction of U(VI) by Fe(II) during the Fe(II)-Accelerated Transformation of Ferrihydrite Environ. Sci. Technol. 2014, 48 (16) 9086– 9093 DOI: 10.1021/es501750z
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      18
      Reduction of U(VI) by Fe(II) during the Fe(II)-accelerated transformation of ferrihydrite
      Boland, Daniel D.; Collins, Richard N.; Glover, Chris J.; Payne, Timothy E.; Waite, T. David
      Environmental Science & Technology (2014), 48 (16), 9086-9093CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      X-ray absorption spectroscopy has been used to study the redn. of adsorbed U(VI) during the Fe(II)-accelerated transformation of ferrihydrite to goethite. The fate of U(VI) was examd. across a variety of pH values and Fe(II) concns., with results suggesting that, in all cases, it was reduced over the course of the Fe(III) phase transformation to a U(V) species incorporated in goethite. A pos. correlation between U(VI) redn. and ferrihydrite transformation rate consts. implies that U(VI) redn. was driven by the prodn. of goethite under the conditions used in these studies. This interpretation was supported by addnl. exptl. evidence that demonstrated the (fast) redn. of U(VI) to U(V) by Fe(II) in the presence of goethite only. Theor. redox potential calcns. clearly indicate that the redn. of U(VI) by Fe(II) in the presence of goethite is thermodynamically favorable. In contrast, redn. of U(VI) by Fe(II) in the presence of ferrihydrite is largely thermodynamically unfavorable within the range of conditions examd. in this study.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFCitr7M&md5=c76320d8482b88dd04406a95594818cf
    19. 19
      Pidchenko, I.; Kvashnina, K. O.; Yokosawa, T.; Finck, N.; Bahl, S.; Schild, D.; Polly, R.; Bohnert, E.; Rossberg, A.; Göttlicher, J. Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles Environ. Sci. Technol. 2017, 51, 2217– 2225 DOI: 10.1021/acs.est.6b04035
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      19
      Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles
      Pidchenko, Ivan; Kvashnina, Kristina O.; Yokosawa, Tadahiro; Finck, Nicolas; Bahl, Sebastian; Schild, Dieter; Polly, Robert; Bohnert, Elke; Rossberg, Andre; Goettlicher, Joerg; Dardenne, Kathy; Rothe, Joerg; Schaefer, Thorsten; Geckeis, Horst; Vitova, Tonya
      Environmental Science & Technology (2017), 51 (4), 2217-2225CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Uranium redox states and speciation in magnetite nanoparticles copptd. with U(VI) for uranium loadings varying from 1000 to 10000 ppm are investigated by X-ray absorption spectroscopy (XAS). It is demonstrated that the U M4 high energy resoln. X-ray absorption near edge structure (HR-XANES) method is capable to clearly characterize U(IV), U(V), and U(VI) existing simultaneously in the same sample. The contributions of the three different uranium redox states are quantified with the iterative transformation factor anal. (ITFA) method. U L3 XAS and transmission electron microscopy (TEM) reveal that initially sorbed U(VI) species recrystallize to nonstoichiometric UO2+x nanoparticles within 147 days when stored under anoxic conditions. These U(IV) species oxidize again when exposed to air. U M4 HR-XANES data demonstrate strong contribution of U(V) at day 10 and that U(V) remains stable over 142 days under ambient conditions as shown for magnetite nanoparticles contg. 1000 ppm U. U L3 XAS indicates that this U(V) species is protected from oxidn. likely incorporated into octahedral magnetite sites. XAS results are supported by d. functional theory (DFT) calcns. Further characterization of the samples include powder X-ray diffraction (pXRD), SEM and Fe 2p XPS.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtVKiu7w%253D&md5=9bea4b58876b52e93c98edb8cf680bc3
    20. 20
      Skomurski, F. N.; Ilton, E. S.; Engelhard, M. H.; Arey, B. W.; Rosso, K. M. Heterogeneous reduction of U6+ by structural Fe2+ from theory and experiment Geochim. Cosmochim. Acta 2011, 75 (22) 7277– 7290 DOI: 10.1016/j.gca.2011.08.006
      [Crossref], [CAS], Google Scholar
      20
      Heterogeneous reduction of U6+ by structural Fe2+ from theory and experiment
      Skomurski, F. N.; Ilton, E. S.; Engelhard, M. H.; Arey, B. W.; Rosso, K. M.
      Geochimica et Cosmochimica Acta (2011), 75 (22), 7277-7290CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      Computational and exptl. studies were performed to explore heterogeneous redn. of U6+ by structural Fe2+ at magnetite (Fe3O4) surfaces. Mol. Fe-Fe-U models representing a uranyl species adsorbed in a diat. bidentate fashion to an iron surface group were constructed. Various possible charge distributions in this model surface complex were evaluated in terms of their relative stabilities and electron exchange rates using ab initio MO methods. Freshly-cleaved, single crystals of magnetite with different initial Fe2+/Fe3+ ratios were exposed to uranyl-nitrate soln. (pH ∼ 4) for 90 h. XPS and electron microscopy indicated the presence of a mixed U6+/U5+ ppt. heterogeneously nucleated and grown on stoichiometric magnetite surfaces, but only the presence of sorbed U6+ and no ppt. on sub-stoichiometric magnetite surfaces. Calcd. electron transfer rates indicate that sequential multi-electron uranium redn. is not kinetically limited by conductive electron resupply to the adsorption site. Both theory and expt. point to structural Fe2+ d., taken as a measure of thermodn. reducing potential, and sterically accessible uranium coordination environments as key controls on uranium redn. extent and rate. Uranium incorporation in solid phases where its coordination is constrained to the uranate type should widen the stability field of U5+ relative to U6+. If uranium cannot acquire 8-fold coordination then redn. may proceed to U5+ but not necessarily U4+.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlyjt7zF&md5=9a42044a229e76a67d8d0f10fcb2898b
    21. 21
      Kerisit, S.; Bylaska, E. J.; Massey, M. S.; McBriarty, M. E.; Ilton, E. S. Ab initio molecular dynamics of uranium incorporated in goethite (α-FeOOH): Interpretation of X-ray absorption spectroscopy of trace polyvalent metals Inorg. Chem. 2016, 55 (22) 11736– 11746 DOI: 10.1021/acs.inorgchem.6b01773
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      21
      Ab Initio Molecular Dynamics of Uranium Incorporated in Goethite (α-FeOOH): Interpretation of X-ray Absorption Spectroscopy of Trace Polyvalent Metals
      Kerisit, Sebastien; Bylaska, Eric J.; Massey, Michael S.; McBriarty, Martin E.; Ilton, Eugene S.
      Inorganic Chemistry (2016), 55 (22), 11736-11746CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Incorporation of economically or environmentally consequential polyvalent metals into iron (oxyhydr)oxides has applications in environmental chem., remediation, and materials science. A primary tool for characterizing the local coordination environment of such metals, and therefore building models to predict their behavior, is extended X-ray absorption fine structure spectroscopy (EXAFS). Accurate structural information can be lacking yet is required to constrain and inform data interpretation. In this regard, ab initio mol. dynamics (AIMD) was used to calc. the local coordination environment of minor amts. of U incorporated in the structure of goethite (α-FeOOH). U oxidn. states (VI, V, and IV) and charge compensation schemes were varied. Simulated trajectories were used to calc. the U LIII-edge EXAFS function and fit exptl. EXAFS data for U incorporated into goethite under reducing conditions. Calcns. that closely matched the U EXAFS of the well-characterized mineral uraninite (UO2), and constrained the S02 parameter to be 0.909, validated the approach. The results for the U-goethite system indicated that U(V) substituted for structural Fe(III) in octahedral uranate coordination. Charge balance was achieved by the loss of one structural proton coupled to addn. of one electron into the solid (-1 H+, +1 e-). The ability of AIMD to model higher energy states thermally accessible at room temp. is particularly relevant for protonated systems such as goethite, where proton transfers between adjacent octahedra had a dramatic effect on the calcd. EXAFS. Vibrational effects as a function of temp. were also estd. using AIMD, allowing sep. quantification of thermal and configurational disorder. In summary, coupling AIMD structural modeling and EXAFS expts. enables modeling of the redox behavior of polyvalent metals that are incorporated in conductive materials such as iron (oxyhydr)oxides, with applications over a broad swath of chem. and materials science.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslOmu7fP&md5=2e90c05632b468be9197e24b96ff9a30
    22. 22
      Refait, P.; Genin, J. M. R. The oxidation of ferrous hydroxide in chloride-containing aqueous media and pourbaix diagrams of green rust one Corros. Sci. 1993, 34 (5) 797– 819 DOI: 10.1016/0010-938X(93)90101-L
      [Crossref], [CAS], Google Scholar
      22
      The oxidation of ferrous hydroxide in chloride-containing aqueous media and Pourbaix diagrams of green rust one
      Refait, P.; Genin, J. M. R.
      Corrosion Science (1993), 34 (5), 797-819CODEN: CRRSAA; ISSN:0010-938X.
      The oxidn. of a ferrous hydroxide pptd. by mixing solns. of ferrous chloride and caustic soda depends on the ratio R' = Cl-/OH- of the initial concns. of the reactants. The mechanisms of oxidn. for 1 < R' ≤ 3 are related to the existence of the ferrous-ferric compd. green rust 1 (GR1). The direct recording of the pH and the electrode potential allows the trigger value of R'c = 8/7 to be detd., which is found to correspond to the stoichiometric conditions of obtaining of GR1. By coupling this information with that obtained from the three iron sites R1, R2, R3 detected by Moessbauer spectroscopy, the formula of GR1 is set up at 3Fe(OH)2·Fe(OH)2Cl·nH2O. Thus GR1 contains an equal no. of Cl- and Fe3+ ions. The std. chem. potential μ0 is detd. to be -509,500 ± 500 cal mol-1 for n = 0. Eh/PH Pourbaix diagrams specific to the oxidn. of iron in chloride-contg. aq. media, including GR1, are drawn.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXis1WltLc%253D&md5=948a99d601df6edda1171b8ee7be92f9
    23. 23
      Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens Nanotechnology 2011, 22 (45) 455709 DOI: 10.1088/0957-4484/22/45/455709
      [Crossref], [PubMed], [CAS], Google Scholar
      23
      Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens
      Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; van der Laan, G.; Arenholz, E.; Tuna, F.; Lloyd, J. R.
      Nanotechnology (2011), 22 (45), 455709/1-455709/9CODEN: NNOTER; ISSN:1361-6528. (Institute of Physics Publishing)
      The bioprodn. of nanoscale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction anal. indicates that controlled prodn. of a no. of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) redn. and total concn. and rate of Fe(II) produced by the bacteria during the redn. process. Relative cation distributions within the structure of the nanoparticles have been investigated by x-ray magnetic CD and indicate the presence of a highly reduced surface layer which is not obsd. when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of orgs., radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimized biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently to the less harmful trivalent form.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1ersrfL&md5=7e225721583b64cc736519a9e44522ae
    24. 24
      O’Loughlin, E. J.; Larese-Casanova, P.; Scherer, M.; Cook, R. Green Rust Formation from the Bioreduction of γ–FeOOH (Lepidocrocite): Comparison of Several Shewanella Species Geomicrobiol. J. 2007, 24 (Ii) 211– 230 DOI: 10.1080/01490450701459333
      [Crossref], [CAS], Google Scholar
      24
      Green rust formation from the bioreduction of γ -FeOOH (lepidocrocite): Comparison of several Shewanella species
      O'Loughlin, Edward J.; Larese-Casanova, Phil; Scherer, Michelle; Cook, Russell
      Geomicrobiology Journal (2007), 24 (3-4), 211-230CODEN: GEJODG; ISSN:0149-0451. (Taylor & Francis, Inc.)
      Green rusts are mixed ferrous/ferric hydroxides that typically form under weakly acidic to alk. conditions in suboxic environments. The recent identification of green rusts as products of the redn. of Fe(III) oxides and oxyhydroxides by Shewanella putrefaciens, a dissimilatory iron-reducing bacterium (DIRB), suggests that green rusts may play a role in the redox cycling of Fe in many aquatic and terrestrial environments. We examd. the potential for green rust formation resulting from the bioredn. of lepidocrocite(γ -FeOOH) by a series of Shewanella species (S. alga BrY, S. amazonensis SB2B, S. baltica OS155, S. denitrificans OS217T, S. loihica PV-4, S. oneidensis MR-1, S. putrefaciens ATCC 8071, S. putrefaciens CN32, S. saccharophilia, and Shewanella sp. ANA-3). All Shewanella species, with the exception of S. denitrificans OS217T, were able to couple the oxidn. of formate to the redn. of Fe(III) in lepidocrocite; however there were significant differences among species with respect to the rate and extent of Fe(II) prodn. Despite these differences, green rust was the only Fe(II)-bearing solid phase formed under our exptl. conditions, as indicated by X-ray diffraction, Moessbauer spectroscopy, and SEM. The formation of green rust by Shewanella species isolated from a wide range of habitats and possessing varied metabolic capabilities suggests that under favorable conditions biogenic green rusts may be formed by a diverse array of DIRB.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXotV2rtLs%253D&md5=b5fdc2533e0a0b48fd09e760d21ffab0
    25. 25
      Dodge, C. J.; Francis, A. J.; Gillow, J. B.; Halada, G. P.; Eng, C.; Clayton, C. R. Association of uranium with iron oxides typically formed on corroding steel surfaces Environ. Sci. Technol. 2002, 36 (16) 3504– 3511 DOI: 10.1021/es011450+
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      25
      Association of Uranium with Iron Oxides Typically Formed on Corroding Steel Surfaces
      Dodge, C. J.; Francis, A. J.; Gillow, J. B.; Halada, G. P.; Eng, C.; Clayton, C. R.
      Environmental Science and Technology (2002), 36 (16), 3504-3511CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Decontamination of metal surfaces contaminated with low levels of radionuclides is a major concern at Department of Energy facilities. The development of an environmentally friendly and cost-effective decontamination process requires an understanding of their assocn. with the corroding surfaces. We investigated the assocn. of uranium with the amorphous and cryst. forms of iron oxides commonly formed on corroding steel surfaces. Uranium was incorporated with the oxide by addn. during the formation of ferrihydrite, goethite, green rust II, lepidocrocite, maghemite, and magnetite. x-ray diffraction confirmed the mineralogical form of the oxide. EXAFS anal. at the U LIII edge showed that uranium was present in hexavalent form as a uranyl oxyhydroxide species with goethite, maghemite, and magnetite and as a bidentate inner-sphere complex with ferrihydrite and lepidocrocite. Iron was present in the ferric form with ferrihydrite, goethite, lepidocrocite, and maghemite; whereas with magnetite and green rust II, both ferrous and ferric forms were present with characteristic ferrous:total iron ratios of 0.65 and 0.73, resp. In the presence of the uranyl ion, green rust II was converted to magnetite with concomitant redn. of uranium to its tetravalent form. The rate and extent of uranium dissoln. in dil. HCl depended on its assocn. with the oxide: uranium present as oxyhydroxide species underwent rapid dissoln. followed by a slow dissoln. of iron; whereas uranium present as an inner-sphere complex with iron resulted in concomitant dissoln. of the uranium and iron.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xlt1equ7o%253D&md5=62f6b12a6e9e7b3e712cc0e972057171
    26. 26
      Tremaine, P. R.; LeBlanc, J. C. The solubility of magnetite and the hydrolysis and oxidation of Fe2+ in water to 300°C J. Solution Chem. 1980, 9 (6) 415– 442 DOI: 10.1007/BF00645517
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    27. 27
      Musić, S.; Ristić, M. Adsorption of trace elements or radionuclides on hydrous iron oxides J. Radioanal. Nucl. Chem. 1988, 120 (2) 289– 304 DOI: 10.1007/BF02037344
      [Crossref], [CAS], Google Scholar
      27
      Adsorption of trace elements or radionuclides on hydrous iron oxides
      Music, S.; Ristic, M.
      Journal of Radioanalytical and Nuclear Chemistry (1988), 120 (2), 289-304CODEN: JRNCDM; ISSN:0236-5731.
      Factors which influence the adsorption of trace elements or radionuclides on hydrous Fe oxides were investigated. The adsorption of monovalent cations (Cs+, Rb+) on hydrous Fe oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, the adsorption of Ag+, divalent cations (Zn2+, Cd2+, Mn2+, Sr2+) or trivalent cations (Cr3+, La3+, Ce3+, Eu3+, Gd3+, Er3+, Yb3+) strongly depends on the pH. The regularities of the adsorption of these cations on hydrous Fe oxides are discussed. Also, the differences in the adsorption behavior of some divalent and trivalent cations are explained. Freshly pptd. Fe(OH)3 can be used for the decontamination of radionuclides from low-level waste solns. However, the efficacy of decontamination depends on the oxidn. state and the chem. properties of the radionuclides.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXhtl2nur4%253D&md5=ff343da942b2652bb28d7ed0013ee16b
    28. 28
      Latta, D. E.; Mishra, B.; Cook, R. E.; Kemner, K. M.; Boyanov, M. I. Stable U(IV) complexes form at high-affinity mineral surface sites Environ. Sci. Technol. 2014, 48 (3) 1683– 1691 DOI: 10.1021/es4047389
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      28
      Stable U(IV) complexes form at high-affinity mineral surface sites
      Latta, Drew E.; Mishra, Bhoopesh; Cook, Russell E.; Kemner, Kenneth M.; Boyanov, Maxim I.
      Environmental Science & Technology (2014), 48 (3), 1683-1691CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due to its extensive use for energy prodn. Despite advances in modeling the risks of this toxic and radioactive element, lack of information about the mechanisms controlling U transport hinders further improvements, particularly in reducing environments where UIV predominates. Here we establish that mineral surfaces can stabilize the majority of U as adsorbed UIV species following redn. of UVI. Using X-ray absorption spectroscopy and electron imaging anal., we find that at low surface loading, UIV forms inner-sphere complexes with two metal oxides, TiO2 (rutile) and Fe3O4 (magnetite) (at <1.3 U nm-2 and <0.037 U nm-2, resp.). The uraninite (UO2) form of UIV predominates only at higher surface loading. UIV-TiO2 complexes remain stable for at least 12 mo, and UIV-Fe3O4 complexes remain stable for at least 4 mo, under anoxic conditions. Adsorbed UIV results from UVI redn. by FeII or by the reduced electron shuttle AH2QDS, suggesting that both abiotic and biotic redn. pathways can produce stable UIV-mineral complexes in the subsurface. The obsd. control of high-affinity mineral surface sites on UIV speciation helps explain the presence of nonuraninite UIV in sediments and has important implications for U transport modeling.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXltFehtg%253D%253D&md5=89902e5b02f6b1e65a5bc5293deb1f2f
    29. 29
      Scott, T. B.; Allen, G. C.; Heard, P. J.; Randell, M. G. Reduction of U(VI) to U(IV) on the surface of magnetite Geochim. Cosmochim. Acta 2005, 69 (24) 5639– 5646 DOI: 10.1016/j.gca.2005.07.003
      [Crossref], [CAS], Google Scholar
      29
      Reduction of U(VI) to U(IV) on the surface of magnetite
      Scott, T. B.; Allen, G. C.; Heard, P. J.; Randell, M. G.
      Geochimica et Cosmochimica Acta (2005), 69 (24), 5639-5646CODEN: GCACAK; ISSN:0016-7037. (Elsevier)
      To increase the understanding of uranium transport in the environment and in the presence of steel corrosion products, the interaction of U(VI) with natural magnetite has been studied. Sorption studies have been carried out using XPS and secondary ion mass spectrometry (SIMS). The XPS results clearly indicate the redn. of U(VI) to U(IV) on the surface of magnetite facilitated by electron transfer between the Fe and U, leading to a coupled oxidn. of Fe(II) to Fe(III).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXhtlerur%252FJ&md5=d02a97e0191634f5e9485f938c1bc779
    30. 30
      Wang, Z.; Ulrich, K.-U.; Pan, C.; Giammar, D. E. Measurement and Modeling of U(IV) Adsorption to Metal Oxide Minerals Environ. Sci. Technol. Lett. 2015, 2 (8) 227– 232 DOI: 10.1021/acs.estlett.5b00156
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      30
      Measurement and Modeling of U(IV) Adsorption to Metal Oxide Minerals
      Wang, Zimeng; Ulrich, Kai-Uwe; Pan, Chao; Giammar, Daniel E.
      Environmental Science & Technology Letters (2015), 2 (8), 227-232CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)
      Chem. or biol. redn. of U(VI) produces a variety of poorly sol. U(IV) species. In addn. to uraninite (UO2) and biomass-assocd. noncryst. U(IV), recent research has found adsorbed U(IV) species on mineral surfaces. To build on these observations, we evaluated equil. adsorption of U(IV) to magnetite and rutile as a function of pH and total U(IV) loading. Surface complexation models that could simulate the uptake of U(IV) by accounting for UO2 pptn. and adsorption of U(IV) to both the minerals and the reactor surfaces were developed. Application of the models could det. the conditions under which adsorption as opposed to pptn. would dominate U(IV) uptake with solids. The model-predicted U(IV) surface coverages of the minerals were consistent with a recent spectroscopic study. Such models advance our ability to predict the equil. speciation of U(IV) in the subsurface.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFWmtrrF&md5=0150b6d8052c172f00f7f9d7fdbeab54
    31. 31
      Kerisit, S.; Felmy, A. R.; Ilton, E. S. Atomistic simulations of uranium incorporation into iron (hydr)oxides Environ. Sci. Technol. 2011, 45 (7) 2770– 2776 DOI: 10.1021/es1037639
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      31
      Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides
      Kerisit, Sebastien; Felmy, Andrew R.; Ilton, Eugene S.
      Environmental Science & Technology (2011), 45 (7), 2770-2776CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination nos., and lattice distortion for U incorporated in different sites (e.g., unoccupied vs. occupied sites, octahedral vs. tetrahedral) as a function of the oxidn. state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or redn. of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amt. of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidn. states and charge compensation mechanisms. Importantly, U-Fe distances of ∼3.6 Å were assocd. with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available exptl. data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXivFyhsbk%253D&md5=5fa577bda6deb2459d67357af879e308
    32. 32
      Pearce, C. I.; Qafoku, O.; Liu, J.; Arenholz, E.; Heald, S. M.; Kukkadapu, R. K.; Gorski, C. A.; Henderson, C. M. B.; Rosso, K. M. Synthesis and properties of titanomagnetite (Fe 3-xTi xO 4) nanoparticles: A tunable solid-state Fe(II/III) redox system J. Colloid Interface Sci. 2012, 387 (1) 24– 38 DOI: 10.1016/j.jcis.2012.06.092
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    33. 33
      Doornbusch, B.; Bunney, K.; Gan, B. K.; Jones, F.; Gräfe, M. Iron oxide formation from FeCl2 solutions in the presence of uranyl (UO22+) cations and carbonate rich media Geochim. Cosmochim. Acta 2015, 158, 22– 47 DOI: 10.1016/j.gca.2015.02.038
      [Crossref], [CAS], Google Scholar
      33
      Iron oxide formation from FeCl2 solutions in the presence of uranyl (UO2+2) cations and carbonate rich media
      Doornbusch, Brodie; Bunney, Karl; Gan, Bee K.; Jones, Franca; Grafe, Markus
      Geochimica et Cosmochimica Acta (2015), 158 (), 22-47CODEN: GCACAK; ISSN:0016-7037. (Elsevier Ltd.)
      The mineral goethite (α-FeOOH) has previously been investigated as a thermodynamically stable repository for many potentially toxic metals (e.g., Cd, Pb, Cu). The substitution of uranium (U as uranyl, UO2+2) for Fe, however, has been studied sparingly, and conclusive uranium incorporation into the goethite structure has been obscured by formation of polymineralic Fe systems that all appeared involved in U's sequestration. In this study, we investigated the formation of goethite from FeCl2 in the presence of seven nominal uranyl concns. (0.2-4 mol percent, U/(U + Fe) × 100) and characterized the solids using quant. X-ray diffraction (QXRD), X-ray absorption fine structure (XAFS) spectroscopy at the U LIII edge (17,166 eV), diffuse reflectance IR Fourier Transform (DRIFT) spectrometry and congruency of acid dissoln. Our findings show that U does indeed, however sparingly, incorporate into the goethite structure. The unit cell vol., ascertained from Rietveld models of XRD patterns, increased linearly as a function of U content, which could be ascribed to a linear increase of the unit cell length a and c. The highest U-for-Fe substitution was 0.48 mol percent, however, most U-contg. goethite samples showed substitution levels around 0.2 mol percent, which was in good agreement with previous findings. DRIFT spectra showed a shift of the sym. Fe-O and asym. Fe-OH stretch modes (τ-O and τ-OH bands, resp.) to lower frequency, which by Hooks analogy, can only occur if a heavier atom substitutes for Fe, i.e., U. The congruency of acid dissoln. results showed that fractional U release was greater than the corresponding fractional Fe release into soln., suggesting that U was overall more sol. In two of the synthates, however, (initial U mole percent of 2 and 4), the dissoln. was congruent. XAFS data collected on a selected subset of samples showed the disappearance of the uranyl moiety with higher levels of U incorporation and acid extn. In sample S6, non-linear least-square fits of the extended XAFS data demonstrated that the coordination environment around U atoms was sixfold occupied by O/OH atoms and was further coordinated by next nearest Fe neighbors that are 1.063 ± 0.008 times inflated in distance to the normal Fe-Fe distances in goethite without U substitution. Despite low levels of incorporation, U bound by goethite was recalcitrant to desorption/dissoln. in increasingly acidic solns. thus warranting further research into the possibility of using iron oxides as a sink for U.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkvVKrt7w%253D&md5=9a922f272a7bde6a0a28f95c36226270
    34. 34
      Burke, I. T.; Mosselmans, J. F. W.; Shaw, S.; Peacock, C. L.; Benning, L. G.; Coker, V. S. Impact of the Diamond Light Source on Research in Earth and Environmental Sciences: Current Work and Future Perspectives Philos. Trans. R. Soc., A 2015, 373, 20130151 DOI: 10.1098/rsta.2013.0151
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    35. 35
      Dent, A. J.; Cibin, G.; Ramos, S.; Smith, A. D.; Scott, S. M.; Varandas, L.; Pearson, M. R.; Krumpa, N. A.; Jones, C. P.; Robbins, P. E. B18: A core XAS spectroscopy beamline for Diamond J. Phys.: Conf. Ser. 2009, 190 (1) 012039 DOI: 10.1088/1742-6596/190/1/012039
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    36. 36
      Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray absorption spectroscopy using IFEFFIT J. Synchrotron Radiat. 2005, 12, 537– 541 DOI: 10.1107/S0909049505012719
      [Crossref], [PubMed], [CAS], Google Scholar
      36
      ATHENA, ARTEMIS, HEPHAESTUS: data analysis for x-ray absorption spectroscopy using IFEFFIT
      Ravel, B.; Newville, M.
      Journal of Synchrotron Radiation (2005), 12 (4), 537-541CODEN: JSYRES; ISSN:0909-0495. (Blackwell Publishing Ltd.)
      A software package for the anal. of x-ray absorption spectroscopy (XAS) data is presented. This package is based on the IFEFFIT library of numerical and XAS algorithms and is written in the Perl programming language using the Perl/Tk graphics toolkit. The programs described here are: (i) ATHENA, a program for XAS data processing, (ii) ARTEMIS, a program for EXAFS data anal. using theor. stds. from FEFF and (iii) HEPHAESTUS, a collection of beamline utilities based on tables of at. absorption data. These programs enable high-quality data anal. that is accessible to novices while still powerful enough to meet the demands of an expert practitioner. The programs run on all major computer platforms and are freely available under the terms of a free software license.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXltlCntLo%253D&md5=a35c32b41de3dc234b101b63927fca73
    37. 37
      Bannister, M. J.; Taylor, J. C. The crystal structure and anisotropic thermal expansion of β-uranyl dihydroxide, UO 2 (OH) 2 Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1970, 26 (11) 1775– 1781 DOI: 10.1107/S0567740870004879
      [Crossref], [CAS], Google Scholar
      37
      Crystal structure and anisotropic thermal expansion of β-uranyl dihydroxide, UO2(OH)2
      Bannister, M. J.; Taylor, John C.
      Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry (1970), 26 (11), 1775-81CODEN: ACBCAR; ISSN:0567-7408.
      Single-crystal and powder x-ray diffraction techniques were used to det. improved positional, thermal vibration, and lattice parameters for the orthorhombic β-UO2(OH)2. Values obtained for lattice parameters at 21° are: a = 5.6438 ± 0.0001, b = 6.2867 ± 0.0001, c = 9.9372 ± 0.0002 Å. Thermal expansion of this material was studied by elevated temp. x-ray diffraction and hot-stage optical microscopy. Thermal expansion up to 260° was strongly anisotropic, with large contractions in a, large expansions in b, and a smaller cyclic change in c. Expansion at higher temps. was almost isotropic. By using the structural and vibrational data, the anisotropic thermal expansion is interpreted in terms of a thermally induced rotation of the O octahedra surrounding all U atoms.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3MXjsFOnsg%253D%253D&md5=c76a69f4507d0c0ad04bdc93032377ea
    38. 38
      Fleet, M. E. The structure of magnetite Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1981, 37 (4) 917– 920 DOI: 10.1107/S0567740881004597
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    39. 39
      Barrett, S.; Jacobson, A. J.; Tofield, B. C.; Fender, B. E. F. The Preparation and Structure of Barium Uranium Oxide BaUO3+X Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1982, 38, 2775– 2781 DOI: 10.1107/S0567740882009935
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    40. 40
      Simon, L.; François, M.; Refait, P.; Renaudin, G.; Lelaurain, M.; Génin, J. M. R. Structure of the Fe(II-III) layered double hydroxysulphate green rust two from Rietveld analysis Solid State Sci. 2003, 5 (2) 327– 334 DOI: 10.1016/S1293-2558(02)00019-5
      [Crossref], [CAS], Google Scholar
      40
      Structure of the Fe(II-III) layered double hydroxysulphate green rust two from Rietveld analysis
      Simon, Lilian; Francois, Michel; Refait, Philippe; Renaudin, Guillaume; Lelaurain, Michele; Genin, Jean-Marie R.
      Solid State Sciences (2003), 5 (2), 327-334CODEN: SSSCFJ; ISSN:1293-2558. (Editions Scientifiques et Medicales Elsevier)
      Synthetic samples of the Fe(II-III) hydroxysulfate known as green rust two were obtained by aerial oxidn. of Fe(II) hydroxide ppts. and studied using chem. and thermal analyses, transmission Mossbauer spectroscopy and powder x-ray diffraction. The ideal formula is FeII4FeIII2(OH)12SO4·∼8H2O. The structure is trigonal, space group P‾3m1 with a = 0.5524(1) nm, c 1.1011(3) nm and Z = 1/2. It is characterized by the succession of pos. charged hydroxide sheets [FeII4 FeIII2(OH)12]2+ and neg. charged interlayers composed of the sulfate anions and H2O mols., [SO4·∼8H2O]2-. These interlayers are made of two planes of H2O and SO42-, in contrast with those found in the rhombohedral green rust one compds., which are made of a single plane. A superstructure (a = a0√3) is found along the [110] direction of the parent hexagonal unit cell, where a0 is the lattice parameter of Fe(OH)2, and due to an ordering of the sulfate anions in the interlayers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXit1Kgu7c%253D&md5=b5c4fa60921b88b27850206f67d53672
    41. 41
      Gauthier, C.; Solé, V. A.; Signorato, R.; Goulon, J.; Moguiline, E. The ESRF beamline ID26: X-ray absorption on ultra dilute sample J. Synchrotron Radiat. 1999, 6, 164– 166 DOI: 10.1107/S0909049598016835
      [Crossref], [PubMed], [CAS], Google Scholar
      41
      The ESRF beamline ID26: X-ray absorption on ultra dilute sample
      Gauthier, Christophe; Sole, Vicente Armando; Signorato, Riccardo; Goulon, Jose; Moguiline, Eric
      Journal of Synchrotron Radiation (1999), 6 (3), 164-166CODEN: JSYRES; ISSN:0909-0495. (Munksgaard International Publishers Ltd.)
      The ESRF beamline ID26 is dedicated to x-ray absorption spectroscopy on Ultra dil. samples. Tech. characteristics are briefly described : optics, monochromator, detectors and sample environment. Recent results are reported to illustrate present performance of the beamline.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXksFCgsb4%253D&md5=4c8619f6e908f4b7633447962ee24990
    42. 42
      Glatzel, P.; Bergmann, U. High resolution 1s core hole X-ray spectroscopy in 3d transition metal complexes - Electronic and structural information Coord. Chem. Rev. 2005, 249 (1–2) 65– 95 DOI: 10.1016/j.ccr.2004.04.011
      [Crossref], [CAS], Google Scholar
      42
      High resolution 1s core hole X-ray spectroscopy in 3d transition metal complexes-electronic and structural information
      Glatzel, Pieter; Bergmann, Uwe
      Coordination Chemistry Reviews (2005), 249 (1-2), 65-95CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. The creation of a 1s core hole in a 3d transition metal ion gives rise to an emission spectrum that can be recorded using a crystal analyzer. K shell x-ray spectroscopy using an analyzer energy bandwidth of ∼1 eV is sensitive to electron-electron interactions and orbital splittings and preserves the advantages of the hard x-ray probe. The authors review recent developments in Kα and Kβ spectroscopy and show how the chem. sensitivity of the fluorescence lines can be exploited for selective x-ray absorption studies. When the photo excitation energy is tuned close to the K edge threshold, the phenomenon known as x-ray resonant Raman or resonant inelastic x-ray scattering (RIXS) occurs. RIXS spectroscopy on 3d transition metals at the 1s resonances with lowest incident energies (K pre-edge) is a very recent technique. The authors discuss basic aspects and demonstrate with several examples its potential as a future routine spectroscopic tool.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFejs7zP&md5=f9d1247588b31237b4a47a9378ae1dd2
    43. 43
      Kvashnina, K. O.; Scheinost, A. C. A Johann-type X-ray emission spectrometer at the Rossendorf beamline J. Synchrotron Radiat. 2016, 23 (3) 836– 841 DOI: 10.1107/S1600577516004483
      [Crossref], [PubMed], [CAS], Google Scholar
      43
      A Johann-type X-ray emission spectrometer at the Rossendorf beamline
      Kvashnina, Kristina O.; Scheinost, Andreas C.
      Journal of Synchrotron Radiation (2016), 23 (3), 836-841CODEN: JSYRES; ISSN:1600-5775. (International Union of Crystallography)
      This paper gives a detailed description, including equations, of the Johann-type X-ray emission spectrometer which has been recently installed and tested at the Rossendorf beamline (ROBL) of the European Synchrotron Radiation Facility. The spectrometer consists of a single spherically bent crystal analyzer and an avalanche photodiode detector positioned on the vertical Rowland cycle of 1 m diam. The hard X-ray emission spectrometer (∼3.5-25 keV) operates at atm. pressure and covers the Bragg angles of 65°-89°. The instrument has been tested at high and intermediate incident energies, i.e. at the Zr K-edge and at the Au L3-edge, in the second exptl. hutch of ROBL. The spectrometer is dedicated for studying actinides in materials and environmental samples by high-energy-resoln. X-ray absorption and X-ray emission spectroscopies.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xntlyjur4%253D&md5=1272cd53368cf43de4696816278ae72b
    44. 44
      Rossberg, A.; Ulrich, K. U.; Weiss, S.; Tsushima, S.; Hiemstra, T.; Scheinost, A. C. SI: Identification of uranyl surface complexes on ferrihydrite: Advanced EXAFS data analysis and CD-music modeling Environ. Sci. Technol. 2009, 43 (5) 1400– 1406 DOI: 10.1021/es801727w
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    45. 45
      Vitova, T.; Kvashnina, K. O.; Nocton, G.; Sukharina, G.; Denecke, M. A.; Butorin, S. M.; Mazzanti, M.; Caciuffo, R.; Soldatov, A.; Behrends, T.; Geckeis, H. High energy resolution x-ray absorption spectroscopy study of uranium in varying valence states Phys. Rev. B: Condens. Matter Mater. Phys. 2010, 82 (23) 235118 DOI: 10.1103/PhysRevB.82.235118
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    46. 46
      Kvashnina, K. O.; Butorin, S. M.; Martin, P.; Glatzel, P. Chemical state of complex uranium oxides Phys. Rev. Lett. 2013, 111, 25 DOI: 10.1103/PhysRevLett.111.253002
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    47. 47
      Soldatov, A. V.; Lamoen, D.; Konstantinović, M. J.; Van den Berghe, S.; Scheinost, A. C.; Verwerft, M. Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis J. Solid State Chem. 2007, 180 (1) 54– 61 DOI: 10.1016/j.jssc.2006.08.038
      [Crossref], [CAS], Google Scholar
      47
      Local structure and oxidation state of uranium in some ternary oxides: X-ray absorption analysis
      Soldatov, A. V.; Lamoen, D.; Konstantinovic, M. J.; Van den Berghe, S.; Scheinost, A. C.; Verwerft, M.
      Journal of Solid State Chemistry (2007), 180 (1), 54-61CODEN: JSSCBI; ISSN:0022-4596. (Elsevier)
      The authors studied the local at. and electronic structures of two related systematic sets of ternary U oxides, NaUO3-KUO3-RbUO3 and BaUO3-Ba2U2O7-BaUO4, by measuring the x-ray absorption near edge structure (XANES). The results are compared with calcns. based on a self-consistent real space full multiple scattering anal. The authors found a very good agreement between measured and calcd. spectra, which indicates that the U ions are in a pure U5+ oxidn. state in these compds. The low energy shoulder obsd. in the U L3 edge XANES is an intrinsic feature of the U unoccupied 6d electronic states of the U5+ ions within the studied materials. Specific double shoulder features in the higher energy range of the U L3 edge XANES can be interpreted as indicative of the pure cubic perovskite structure.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnt1Cltg%253D%253D&md5=a79106e07d54ccf7b2284648634486fc
    48. 48
      O’Loughlin, E. J.; Kelly, S. D.; Cook, R. E.; Csencsits, R.; Kemner, K. M. Reduction of uranium(VI) by mixed iron(II)/iron(III) hydroxide (green rust): formation of UO2 nanoparticles Environ. Sci. Technol. 2003, 37 (4) 721– 727 DOI: 10.1021/es0208409
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      48
      Reduction of Uranium(VI) by Mixed Iron(II)/Iron(III) Hydroxide (Green Rust): Formation of UO2 Nanoparticles
      O'Loughlin, Edward J.; Kelly, Shelly D.; Cook, Russell E.; Csencsits, Roseann; Kemner, Kenneth M.
      Environmental Science and Technology (2003), 37 (4), 721-727CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Green rusts, which are mixed ferrous/ferric hydroxides, are found in many suboxic environments and are believed to play a central role in the biogeochem. of Fe. Anal. by U LIII-edge x-ray absorption near edge spectroscopy of aq. green rust suspensions spiked with uranyl (UVI) showed that UVI was readily reduced to UIV by green rust. The extended x-ray absorption fine structure (EXAFS) data for U reduced by green rust indicate the formation of a UO2 phase. A theor. model based on the crystal structure of UO2 was generated by using FEFF7 and fitted to the data for the UO2 std. and the U in the green rust samples. The model fits indicate that the no. of nearest-neighbor U atoms decreases from 12 for the UO2 structure to 5.4 for the U-green rust sample. With an assumed 4 near-neighbor U atoms per U atom on the surface of UO2, the best-fit value for the av. no. of U atoms indicates UO2 particles with an av. diam. of 1.7 ± 0.6 nm. The formation of nanometer-scale particles of UO2, suggested by the modeling of the EXAFS data, was confirmed by high-resoln. TEM, which showed discrete particles (∼2-9 nm in diam.) of cryst. UO2. UVI (as sol. uranyl ion) is readily reduced by green rust to UIV as relatively insol. UO2 nanoparticles, suggesting that the presence of green rusts in the subsurface may have significant effects on the mobility of U, particularly under Fe-reducing conditions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXivF2ksQ%253D%253D&md5=3d5b47f2e0ed6891772214c97a2bbca4
    49. 49
      Shuller-Nickles, L.; Bender, W.; Walker, S.; Becker, U. Quantum-Mechanical Methods for Quantifying Incorporation of Contaminants in Proximal Minerals Minerals 2014, 4 (3) 690– 715 DOI: 10.3390/min4030690
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    50. 50
      Marshall, T. A.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Parry, S. A.; Shaw, S. Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions Environ. Sci. Technol. 2014, 48 (20) 11853– 11862 DOI: 10.1021/es503438e
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      50
      Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions
      Marshall, Timothy A.; Morris, Katherine; Law, Gareth T. W.; Mosselmans, J. Frederick W.; Bots, Pieter; Parry, Stephen A.; Shaw, Samuel
      Environmental Science & Technology (2014), 48 (20), 11853-11862CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Technetium incorporation into magnetite and its behavior during subsequent oxidn. has been investigated at high pH to det. the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) contg. cement leachates (pH 10.5-13.1), and crystn. of magnetite was induced via addn. of Fe(II)aq. A combination of X-ray diffraction (XRD), chem. extn., and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidn. of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Anal. of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidn. in air, the incorporated Tc(IV) was recalcitrant to oxidative dissoln. with less than 40% remobilization to soln. despite significant oxidn. of the magnetite to maghemite/goethite: All solid assocd. Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissoln. Immobilization of Tc(VII) by redn. and incorporation into magnetite at high pH and with significant stability upon reoxidn. has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geol. disposal of radioactive wastes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFKrsb7O&md5=c7f4658634192fd58ef1a0f805afdb14
    51. 51
      McBriarty, M. E.; Soltis, J. A.; Kerisit, S.; Qafoku, O.; Bowden, M. E.; Bylaska, E. J.; De Yoreo, J. J.; Ilton, E. S. Trace Uranium Partitioning in a Multiphase Nano-FeOOH System Environ. Sci. Technol. 2017, 51 (9) 4970– 4977 DOI: 10.1021/acs.est.7b00432
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      51
      Trace Uranium Partitioning in a Multiphase Nano-FeOOH System
      McBriarty, Martin E.; Soltis, Jennifer A.; Kerisit, Sebastien; Qafoku, Odeta; Bowden, Mark E.; Bylaska, Eric J.; De Yoreo, James J.; Ilton, Eugene S.
      Environmental Science & Technology (2017), 51 (9), 4970-4977CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      The characterization of trace elements in minerals using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities and contaminants interact with the host phase and the environment. However, limitations to EXAFS interpretation complicate the anal. of trace concns. of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio mol. dynamics (AIMD)-informed EXAFS anal. was employed to investigate the immobilization of trace uranium assocd. with nanophase iron (oxyhydr)oxides, a model system for the geochem. sequestration of radiotoxic actinides. The reductive transformation of ferrihydrite [Fe(OH)3] to nanoparticulate iron oxyhydroxide minerals in the presence of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (α-FeOOH) over lepidocrocite (γ-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is supported by atomically resolved transmission electron microscopy. We demonstrate how AIMD-informed EXAFS anal. lifts the strict statistical limitations and uncertainty of traditional shell-by-shell EXAFS fitting, enabling the detailed characterization of the local bonding environment, charge compensation mechanisms, and oxidn. states of polyvalent impurities in complex multiphase mineral systems.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXmtVCmt7s%253D&md5=2a59124a8b68edb010d6049c4c224923
    52. 52
      Latta, D. E.; Boyanov, M. I.; Kemner, K. M.; O’Loughlin, E. J.; Scherer, M. Reaction of Uranium(VI) with Green Rusts: Effect of Interlayer Anion Curr. Inorg. Chem. 2015, 5, 156– 168 DOI: 10.2174/1877944105666150420235350
      [Crossref], [CAS], Google Scholar
      52
      Reaction of Uranium(VI) with Green Rusts: Effect of Interlayer Anion
      Latta, Drew E.; Boyanov, Maxim I.; Kemner, Kenneth M.; O'Loughlin, Edward J.; Scherer, Michelle
      Current Inorganic Chemistry (2015), 5 (3), 156-168CODEN: CICUBF; ISSN:1877-9441. (Bentham Science Publishers Ltd.)
      Green rusts are widely recognized as an important metastable intermediate phase in Fe biogeochem. cycling and Fe metal corrosion and are strong reductants capable of reducing a widerange of contaminants. Here we investigate the effect of interlayer anion on the reaction of green rusts with hexavalent uranium (U(VI)). We react three synthetic green rusts, including carbonate, sulfate, and chloride green rust, as well as pyroaurite, a redox-inactive Mg(II)-Fe(III) structural analog of carbonate green rust with U(VI). The majority of U(VI) (> 80%) was removed from soln. in about an hour at pH 8.0 in 0.1 M N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS) buffer. Similar kinetics of U(VI) uptake on green rusts and pyroaurite suggest that the obsd. uptake kinetics reflect an adsorption step rather than redn. of U(VI) by structural Fe(II) in the green rusts. X-ray absorption spectroscopy (XAS) of the green rust solids indicates significant redn. of U(VI) to U(IV) for all three green rusts, with complete redn. obsd. for sulfate and chloride green rust and varied extents of redn. (34 to 100%) obsd. for carbonate green rust depending on the soln. conditions. No redn. of U(VI) was obsd. in the presence of pyroaurite, consistent with the absence of Fe(II) in the pyroaurite structure. The decreased extent of U(VI) redn. obsd. with carbonate green rust in TAPS buffer may be due to modification of the redox reactivity of U(VI) or green rust due to interaction with the TAPS buffer mols. XAS results indicate that U(VI) was reduced to U(IV) and was present as a monomeric-type U(IV) species in the presence of TAPS buffer. In deionized water, however, carbonate green rust reduced U(VI) to nanoparticulate UO2. Green rusts may be an important phase in the fate and transport of U(VI) in the contaminated subsurface, or under conditions where it forms on corroding U-bearing waste containers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1OmsLrP&md5=ef893a596df35f65bc17b403078649c4
    53. 53
      Neidig, M. L.; Clark, D. L.; Martin, R. L. Covalency in f-element complexes Coord. Chem. Rev. 2013, 257 (2) 394– 406 DOI: 10.1016/j.ccr.2012.04.029
      [Crossref], [CAS], Google Scholar
      53
      Covalency in f-element complexes
      Neidig, Michael L.; Clark, David L.; Martin, Richard L.
      Coordination Chemistry Reviews (2013), 257 (2), 394-406CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. The presence of covalency in complexes of the 4f and 5f elements has been a source of intense research and controversy. In addn. to academic interest in this debate, there is an industrial motivation for better understanding of bonding in f-element complexes due to the need to sep. trivalent trans-plutonium elements from trivalent lanthanide fission products in advanced nuclear fuel cycles. This review discusses the key evidence for covalency in f-element bonds derived from structural, spectroscopic and theor. studies of some selected classes of mols., including octahedral hexahalides, linear actinyl and organometallic sandwich complexes. This evidence is supplemented by a discussion of covalency, including the possibility of both overlap and near-degeneracy driven covalency and the need to quantify their relative contributions in actinide metal-ligand bonds.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVekurrE&md5=e0a768f5c3c99b19283f5dc76d74c41c
    54. 54
      Hubbard, C. G.; West, L. J.; Rodriguez-Blanco, J. D.; Shaw, S. Laboratory study of spectral induced polarization responses of magnetite — Fe2+ redox reactions in porous media Geophysics 2014, 79 (1) D21– D30 DOI: 10.1190/geo2013-0079.1
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    55. 55
      Finch, R. J.; Ewing, R. C. The corrosion of uraninite under oxidizing conditions J. Nucl. Mater. 1992, 190 (C) 133– 156 DOI: 10.1016/0022-3115(92)90083-W
      [Crossref], [CAS], Google Scholar
      55
      The corrosion of uraninite under oxidizing conditions
      Finch, Robert J.; Ewing, Rodney C.
      Journal of Nuclear Materials (1992), 190 (), 133-56CODEN: JNUMAM; ISSN:0022-3115.
      Uraninite contains "impurities" such as Pb, Ca, Si, U6+, Th, Zr, and lanthanides. These affect the thermodn. properties of uraninite, the rate of uraninite alteration, and the compn. of the corrosion products. Uraninite can contain a significant amt. of radiogenic Pb, and the Pb-uranyl oxide hydrates (Pb-UOH) are the most common corrosion products formed by the oxidative alteration of Pb-bearing uraninites. Incongruent alteration of the Pb-UOHs in natural waters produces increasingly Pb-enriched uranyl phases, effectively reducing the amt. of U lost from the corrosion rind. This is not true of other uranyl oxide hydrates, such as schoepite, UO3·2H2O, or becquerelite, CaU6O19·11H2O, which can dissolve completely under similar geochem. conditions. The most common end product of Pb-UOH alteration is curite. Curite may provide surface nucleation sites for certain uranyl phosphates, thereby enhancing their formation. Uranyl phosphates are generally less sol. than other uranyl phases. In the absence of Pb, schoepite and becquerelite are the common initial corrosion products. The reaction path for the alteration of Pb-free uraninite results in the formation of uranyl silicates, which are generally more sol. than the uranyl phosphates. Thus, the long-term oxidn. behavior for ancient, Pb-bearing uraninite is different from young, Pb-free uraninite. Because the presence of Pb effectively reduces the mobility of uranium in oxidizing waters, the concn. of uranium in groundwaters assocd. with oxidized uranium ore deposits will depend in part on the age of the primary uraninite.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38XmtlOhtLs%253D&md5=b6a3c857c5246e7038d7b52696244f6a

  • 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/acs.estlett.7b00348.

    • Additional figures and tables showing XRD patterns, TEM images and EDS analyses, HERFD-XANES data and fitting results, EXAFS fitting parameters, dissolution data, and a description of the EXAFS fitting process (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 [ 2MB]

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