Controlled Hydrolysis of TiO2 from HCl Digestion Liquors of IlmeniteClick to copy article linkArticle link copied!
- Richard G. Haverkamp*Richard G. Haverkamp*E-mail: [email protected]School of Engineering and Advanced Technology, Massey University, Private Bag 11222, Palmerston North 4472, New ZealandMore by Richard G. Haverkamp
- Kia S. WallworkKia S. WallworkNST Central, ANSTO, Lucas Heights, New South Wales 2234, AustraliaMore by Kia S. Wallwork
- Mark R. WaterlandMark R. WaterlandInstitute of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North 4472, New ZealandMore by Mark R. Waterland
- Qinfen Gu
- Justin A. KimptonJustin A. KimptonAustralian Synchrotron, ANSTO, Clayton, Victoria 3168, AustraliaMore by Justin A. Kimpton
Abstract
Traditionally, industrial scale production of the TiO2 pigment is achieved by hydrolysis from H2SO4 solution or by hydrolysis of TiCl4. However, the H2SO4 route produces FeSO4 waste, which is problematic, and the TiCl4 route requires a high grade rutile feedstock or chemically upgraded ilmenite (FeTiO3). Here, we investigate a direct route from ilmenite to TiO2 using aqueous HCl. New Zealand ilmenite digested in 35 wt % HCl to achieve a solution containing typically 1.18 mol kg–1 Fe(aq)2+ and 1.14 mol kg–1 Ti(aq)4+ was hydrolyzed under reflux, after seed preparation in water, or with phosphoric or citric acid. The structure of the seed was determined by Raman spectroscopy and X-ray powder diffraction using pair distribution function analysis, the latter enabling the identification of short-range order in poorly crystalline materials. TiO2 hydrate was precipitated from HCl in either the anatase or the rutile structure. Unlike from H2SO4, the natural structure formed without the use of structure determining agents is rutile. However, seed preparation using 0.4 mol H3PO4 per mole of Ti (resulting in 0.35 wt% H3PO4 in the hydrate) results in anatase hydrate formation. Sodium citrate or citric acid addition also seed anatase hydrate. The mechanism for polymorph control may be kinetic rather than a structural template or surface adsorption. This process has the potential to be used for the commercial scale production of the TiO2 pigment. Anatase hydrate has the advantage that traces of iron may be more readily removed by washing than from rutile precipitate, making the HCl process from ilmenite feasible for pigment grade material.
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Introduction
Experimental Methods
Ilmenite Digestion
Hydrolysis
Structure Determining Agents
Elemental Analysis
Structure Determination
Raman Spectroscopy
X-ray Scattering
Processing of Total Scattering Data
Results
Ilmenite Composition
oxide | concentation wt % as oxide |
---|---|
TiO2 | 47.1 |
FeO | 37.5 |
Fe2O3 | 3.0 |
SiO2 | 5.2 |
Al2O3 | 2.3 |
MnO | 1.7 |
MgO | 0.2 |
CaO | 1.1 |
Na2O | 0.3 |
K2O | 0.3 |
P2O5 | 0.2 |
V2O5 | 0.1 |
Nb2O5 | 0.05 |
Ta2O5 | 0.005 |
Dissolution and Liquor Composition
component | equivalent as an oxide | concentration g kg–1 (as oxide for Fe and Ti) | concentration, mol kg–1 |
---|---|---|---|
FeCl2 | FeO | 85 ± 7 | 1.18 |
”TiOCl2” | TiO2 | 91 ± 3 | 1.14 |
TiCl3 | TiO1.5 | 5 ± 3 | 0.07 |
HCl | HCl | 85 ± 15 | 2.33 |
MClx | MCl2 | 4 ± 2 | 0.04 |
Seeding for Analysis and Hydrolysis
Hydrolysis
label | expt description | additive on the basis of mol P or mol citrate/ mol Ti in seed solution | additive in seed water (P or citrate) mol/kg | drop ratio (by volume) liquor/seed water | % liquor used for seed | liquor Ti (net), g kg–1 TiO2 | liquor Fe, g kg–1 FeO | anatase/rutile in hydrate by Raman, %:% | anatase/rutile in hydrate by XRD, %:% |
---|---|---|---|---|---|---|---|---|---|
HW1 | water seeded hydrate 1 | 0 | 80:20 | 2 | 97 | 98 | rutile (trace anatase) | 2:98 | |
HW2 | water seeded hydrate 2 | 0 | 80:20 | 0:100 | |||||
HW3 | water seeded hydrate 3 | 0 | 80:20 | 2 | 78 | 79 | rutile (trace anatase) | 0:100 | |
HP1 | phosphate seeded hydrate 1 | 0.4 | 5.9 | 80:20 | 2 | 90 | 83 | anatase | 98:2 |
HP2 | phosphate seeded hydrate 2 | 0.4 | 5.9 | 80:20 | 2 | 90 | 83 | rutile and anatase | 29:71 |
HP3 | phosphate seeded hydrate 3 | 0.4 | 9.7 | 80:20 | 2 | 55 | 50 | 100:0 | |
HC1 | trisodium citrate seeded hydrate 1 | 0.4 | 5.7 | 80:20 | 2 | 93 | 81 | 48:52 | |
HC2 | trisodium citrate seeded hydrate 2 | 0.4 | 5.4 | 80:20 | 2 | 98 | 79 | 100:0 | |
HC3 | citric acid seeded hydrate 1 | 0.4 | 80:20 | 2 | 100:0 |
Raman of Hydrolysis Product
Figure 1
Figure 1. Raman spectra of dried titanium seed and hydrate. (a) Degussa P25 reference (calcined) material, black line; phosphate hydrate 1 (HP1), magenta; phosphate hydrate 2 (HP2), red; water hydrate 1 (HW1), blue; water hydrate 2 (HW2), green. (b) Raman spectra of dried TiO2 hydrate “seed”: water seed 1 (SW1), black; water seed 2 (SW2), red; water seed 3 (SW3), green; phosphate seed 1 (SP1), magenta; phosphate seed 2 (SP2), blue.
Raman of Seed
XRD and PDF of Hydrolysis Product
Figure 2
Figure 2. (a) TiO2 hydrate phosphate seeded 1 (anatase; SP1), (b) TiO2 hydrate phosphate seeded 2 (mixed anatase/rutile; SP2), (c) TiO2 hydrate water seeded 1 (rutile; SW1).
Figure 3
Figure 3. Nanocrystalline TiO2 hydrate (phosphate seeded hydrate 1). (a,b) Diffraction data in 2θ for 21 keV X-ray energy with air background and capillary scattering (expanded scale for b). (c) Total scattering function, S(Q). (d) Reduced PDF experimental data showing the interatomic spacings.
Figure 4
Figure 4. Reduced PDF (blue circles) with the fitted structure (red line) and residuals (green line): (a) anatase hydrate 1; (b) rutile hydrate 1.
sample | % anatase from XRD Rietveld | % rutile from XRD Rietveld | cell dimension a and b, Å | cell dimension c, Å | crystallite size, Å |
---|---|---|---|---|---|
anatase hydrate (phosphate seeded 1) PDF | 3.7830 | 9.5055 | 21 | ||
anatase hydrate (phosphate seeded 1) Rietveld | 98 | 2 | 3.7813 | 9.4780 | 22 |
CIF 9008213 anatase (27) | 100 | 3.7842 | 9.5146 | ||
rutile hydrate (water seeded 1) PDF | 4.6051 | 2.9602 | 45 | ||
rutile hydrate (water seeded 1) Rietveld | 2 | 98 | 4.5872 | 2.9443 | 670 |
CIF 9001681 rutile (28) | 100 | 4.5922 | 2.9574 |
Pair Distribution Function and Rietveld Analysis of Seed
Figure 5
Figure 5. X-ray scattering intensity (IQ) for (a) seed SW3 after subtraction of the background for the capillary in air; (b) seed SP2 (seed SP1 looks similar─not shown); (c) seed SP2 G9(r); (d) seed SP2 G(r) scaled × 100 (red solid line) compared with anatase (blue dashed line) and rutile (black dot dash line) from the fitted form for the hydrates.
Elemental Analysis of Hydrolysis Product
Iron Content
oxide | anatase (phosphate seeded), wt % | rutile (no structure determining agent), wt % |
---|---|---|
TiO2 | 94.3 | 95.8 |
P2O5 | 0.82 | 0.49 |
Nb2O5 | 0.13 | 0.13 |
Ta2O5 | 0.009 | 0.009 |
Cl | 4.4 | 3.1 |
FeO | 0.015 (120 ppm Fe) | 0.044 (340 ppm Fe) |
SiO2 | 0.19 | 0.28 |
Al2O3 | 0.07 | 0.03 |
CaO | 0.01 | 0.02 |
K2O | 0.006 | 0.01 |
Calcination of Hydrate to Produce Pigment
Discussion
Ilmenite Source and Suitability
HCl Hydrate Is Rutile
Controlling the Structure of the Hydrate
Variability
How Does the Seeding Work
Figure 6
Figure 6. Block process flow diagram for preparation of TiO2 from ilmenite.
Ilmenite Minor Elements
Why Anatase Hydrate from HCl Might Be Desirable
Conclusions
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.iecr.2c00463.
Figure for hydrolysis experimental arrangement; table of seed preparation for Raman and X-ray analysis of seed; method and figure for UV/vis spectra (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.
Acknowledgments
This research was undertaken on the PD beamline at the Australian Synchrotron, part of ANSTO. The New Zealand Synchrotron Group provided travel and accommodation.
References
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- 13Haverkamp, R. G.; Wallwork, K. S. X-ray Pair Distribution Function Analysis of Nanostructured Materials using a Mythen Detector. J. Synchrotron Radiat. 2009, 16 (6), 849– 856, DOI: 10.1107/S0909049509036723Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtlSiu7zE&md5=eddc632c72c87cf59def00844c9cbe0fX-ray pair distribution function analysis of nanostructured materials using a Mythen detectorHaverkamp, Richard G.; Wallwork, Kia S.Journal of Synchrotron Radiation (2009), 16 (6), 849-856CODEN: JSYRES; ISSN:0909-0495. (International Union of Crystallography)Total scattering from nanocryst. materials recorded on the Australian Synchrotron powder diffraction beamline has been analyzed to produce at. pair distribution functions (PDFs) for structural anal. The capability of this beamline, which uses the massively parallel Mythen II detector, has been quantified with respect to PDF structure anal. Data were recorded to a wavevector magnitude, Q, of 20.5 Å-1, with successful PDFs obtained for counting times as short as 10 s for cryst. LaB6 and 180 s for nanocryst. (47 Å) anatase. This paper describes the aspects of a PDF expt. that are crucial to its success, with ref. to the outcomes of anal. of data collected from nanocryst. TiO2 and microcryst. LaB6 and IrO2.
- 14Egami, T.; Billinge, S. J. L. Underneath the Bragg Peaks: Structural Analysis of Complex Materials; Permagon: Oxford, 2003.Google ScholarThere is no corresponding record for this reference.
- 15Schmitt, B.; Brönnimann, C.; Eikenberry, E. F.; Gozzo, F.; Hörmann, C.; Horisberger, R.; Patterson, B. Mythen detector system. Nucl. Instrum. Meth. A 2003, 501, 267– 272, DOI: 10.1016/S0168-9002(02)02045-4Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXivVOksL4%253D&md5=e0d07694f7b58393cf40eb3d3702ad44Mythen detector systemSchmitt, B.; Bronnimann, Ch.; Eikenberry, E. F.; Gozzo, F.; Hormann, C.; Horisberger, R.; Patterson, B.Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2003), 501 (1), 267-272CODEN: NIMAER; ISSN:0168-9002. (Elsevier Science B.V.)Time-resolved expts. in powder diffraction are limited by the long time required to record spectra with current detectors. A major improvement can be made by using a massively parallel x-ray detection system together with a fast read out. The Mythen detector (Microstrip system for time-resolved expts.) was built for the Powder Diffraction Station of the Material Science beamline at the Swiss Light Source to meet these requirements. The specifically developed read out chip (Mythen chip), the detector system and 1st measurements are shown.
- 16Wallwork, K. S.; Kennedy, B. J.; Wang, D. The high resolution powder diffraction beamline for the Australian Synchrotron. In AIP Conf. Proc., Wallwork, K. S., Kennedy, B. J., Wang, D., Eds.; AIP: 2007; Vol. 879, pp 879- 882.Google ScholarThere is no corresponding record for this reference.
- 17Qiu, X.; Thompson, J. W.; Billinge, S. J. L. PDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction data. J. Appl. Crystallogr. 204, 2004 37 (4), 678. DOI: 10.1107/S0021889804011744Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXlvVKmt7w%253D&md5=cdff1721e3b5e02a744b76ba4040d79ePDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction dataQiu, Xiangyun; Thompson, Jeroen W.; Billinge, Simon J. L.Journal of Applied Crystallography (2004), 37 (4), 678CODEN: JACGAR; ISSN:0021-8898. (Blackwell Publishing Ltd.)There is no expanded citation for this reference.
- 18Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, T.; Billinge, S. L. J. PDFfit2 and PDFgui: computer programs for studying nanostructures in crystals. J. Phys-Condens. Mat 2007, 19, 335219, DOI: 10.1088/0953-8984/19/33/335219Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVOqtLfK&md5=3af1c0ad4523068d58f605009d12af9ePDFfit2 and PDFgui: computer programs for studying nanostructure in crystalsFarrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, Th; Billinge, S. J. L.Journal of Physics: Condensed Matter (2007), 19 (33), 335219/1-335219/7CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)PDFfit2 is a program as well as a library for real-space refinement of crystal structures. It is capable of fitting a theor. three-dimensional (3D) structure to at. pair distribution function data and is ideal for nanoscale investigations. The fit system accounts for lattice consts., at. positions and anisotropic at. displacement parameters, correlated at. motion, and exptl. factors that may affect the data. The at. positions and thermal coeffs. can be constrained to follow the symmetry requirements of an arbitrary space group. The PDFfit2 engine is written in C++ and is accessible via Python, allowing it to inter-operate with other Python programs. PDFgui is a graphical interface built on the PDFfit2 engine. PDFgui organizes fits and simplifies many data anal. tasks, such as configuring and plotting multiple fits. PDFfit2 and PDFgui are freely available via the Internet.
- 19Wells, H. C.; Haverkamp, R. G. Characterization of the heavy mineral suite in a holocene beach placer, Barrytown, New Zealand. Minerals 2020, 10 (2), 86, DOI: 10.3390/min10020086Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlSnsL7F&md5=3943fe74adf1fb245ceae9dfce3d9e1fCharacterization of the heavy mineral suite in a Holocene Beach Placer, Barrytown, New ZealandWells, Hannah C.; Haverkamp, Richard G.Minerals (Basel, Switzerland) (2020), 10 (2), 86CODEN: MBSIBI; ISSN:2075-163X. (MDPI AG)The placer deposit at Barrytown, New Zealand, has been worked for gold and is known for high levels of ilmenite that has not been exploited. Other heavy minerals are present but have not been well characterized, which is the purpose of this research. Sand grains were sepd. into the d. fractions and the heavier fractions analyzed by laser ablation ICP-MS for elemental compn. and by SEM (SEM) EDS in whole grains and polished sections. Grain size distributions were detd. from SEM images of polished grain mounts. Elemental assocns. have been identified with different minerals. A wide range of ore minerals, or potential useful industrial minerals, have been shown to be present largely as individual sand grains. These include gold, ilmenite, garnet, zircon, monazite, allanite, uraninite, thorite, cassiterite, wolframite, scheelite, and columbite. The ilmenite contains many inclusions, consisting of silicates and phosphates and 100-400 ppm Nb. Scandium is found to be present in zircon at 100-600 ppm along with 3000 ppm Y. Monazite is depleted in Eu relative to chondrite and contains Ga and Ge at 1000-3000 ppm. Because the sand grains are mostly individual minerals, it is suggested that sepn. may be possible using a combination of d., electrostatic and magnetic methods to obtain almost pure mineral fractions. This knowledge should inform decisions on potential exploitation of the resource.
- 20Duncan, J. F.; Metson, J. B. Acid attack on New-Zealand ilmenite. 2. The structure and composition of the solid. N.Z. J. Sci. 1982, 25 (2), 111– 116Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38Xmt1ShtLY%253D&md5=3a03f416b123821a6ed2fb4e255f2145Acid attack on New Zealand ilmenite. 2. The structure and composition of the solidDuncan, J. F.; Metson, J. B.New Zealand Journal of Science (1982), 25 (2), 111-16CODEN: NZJSAB; ISSN:0028-8365.The structure and compn. of New Zealand ilmenite [12168-52-4] were studied before and after acid leaching. Solns. of 1-10M HCl at temp. of 70° were used to partially dissolve ground and unground samples. Although the material appears quite homogeneous in x-ray, electron microprobe, and optical mineralogical examn., acid leaching causes extensive pore formation parallel to the basal plane. This selective attack can be attributed to parting dislocations and possibly twinning in the basal plane. Moessbauer spectroscopy shows some substitution of Fe2+ in the Ti4+ sites of the mineral, but this does not appear to influence reactivity.
- 21Lafuente, B.; Downs, R. T.; Yang, H.; Stone, N. The power of databases: The RRUFF project. In Highlights in Mineralogical Crystallography; De Gruyter: Berlin, 2016; pp 1– 29.Google ScholarThere is no corresponding record for this reference.
- 22Challagulla, S.; Tarafder, K.; Ganesan, R.; Roy, S. Structure sensitive photocatalytic reduction of nitroarenes over TiO2. Sci. Rep. 2017, 7 (1), 1– 11, DOI: 10.1038/s41598-017-08599-2Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlGgs7bJ&md5=1914b1dcd9407da59b668ca2ef7f79ecStructure sensitive photocatalytic reduction of nitroarenes over TiO2Challagulla, Swapna; Tarafder, Kartick; Ganesan, Ramakrishnan; Roy, SounakScientific Reports (2017), 7 (1), 1-11CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)It is a subject of exploration whether the phase pure anatase or rutile TiO2 or the band alignment due to the heterojunctions in the two polymorphs of TiO2 plays the detg. role in efficacy of a photocatalytic reaction. In this work, the phase pure anatase and rutile TiO2 have been explored for photocatalytic nitroarenes redn. to understand the role of surface structures and band alignment towards the redn. mechanism. The conduction band of synthesized anatase TiO2 has been found to be more populated with electrons of higher energy than that of synthesized rutile. This has given the anatase an edge towards photocatalytic redn. of nitroarenes over rutile TiO2. The other factors like adsorption of the reactants and the proton generation did not play any decisive role in catalytic efficacy.
- 23Swamy, V. Size-dependent modifications of the first-order Raman spectra of nanostructured rutile TiO2. Phys. Rev. B 2008, 77 (19), 1– 4, DOI: 10.1103/PhysRevB.77.195414Google ScholarThere is no corresponding record for this reference.
- 24Schmutz, C.; Barboux, P.; Ribot, F.; Taulelle, F.; Verdaguer, M.; Fernandezlorenzo, C. EXAFS, Raman and P-31 NMR-study of amorphous titanium phosphates. J. Non-Cryst. Solids 1994, 170 (3), 250– 262, DOI: 10.1016/0022-3093(94)90054-XGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXkvFynsLg%253D&md5=3505a16c22edbfef52abc17c927c76c0EXAFS, Raman and 31P NMR study of amorphous titanium phosphatesSchmutz, C.; Barboux, P.; Ribot, F.; Taulelle, F.; Verdaguer, M.; Fernandez-Lorenzo, C.Journal of Non-Crystalline Solids (1994), 170 (3), 250-62CODEN: JNCSBJ; ISSN:0022-3093.The reaction of H3PO4 with Ti alkoxides for a PO4/Ti ratio ranging from 0.5 to 2 was studied. For these compns., amorphous ppts. are obtained. Their microstructure was studied by Raman, NMR and x-ray absorption spectroscopies. The phosphatation of Ti alkoxide increases the Ti coordination no. to 6 and the symmetry becomes purely octahedral for a P/Ti ratio of 2. For the compn. range 0 < PO4/Ti ≤ 2, phosphate anions are homogeneously dispersed in the ppt. and bound to Ti, the coordination of which is completed by oxo-, hydroxo- and remaining alkoxy- groups. Short Ti-O distances are obsd. in the materials having the lowest P/Ti ratios.
- 25Nguyen-Phan, T. D.; Liu, Z.; Luo, S.; Gamalski, A. D.; Vovchok, D.; Xu, W.; Stach, E. A.; Polyansky, D. E.; Fujita, E.; Rodriguez, J. A. Unraveling the Hydrogenation of TiO2 and Graphene Oxide/TiO2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function Analysis. J. Phys. Chem. C 2016, 120 (6), 3472– 3482, DOI: 10.1021/acs.jpcc.5b09504Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Khu7Y%253D&md5=1b03b558e63c0dfc9755d84b187db652Unraveling the Hydrogenation of TiO2 and Graphene Oxide/TiO2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function AnalysisNguyen-Phan, Thuy-Duong; Liu, Zongyuan; Luo, Si; Gamalski, Andrew D.; Vovchok, Dimitry; Xu, Wenqian; Stach, Eric A.; Polyansky, Dmitry E.; Fujita, Etsuko; Rodriguez, Jose A.; Senanayake, Sanjaya D.Journal of Physical Chemistry C (2016), 120 (6), 3472-3482CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The functionalization of graphene oxide (GO) and graphene by TiO2 and other metal oxides has attracted considerable attention due to numerous promising applications in catalysis, energy conversion, and storage. Hydrogenation of this class of materials has been proposed as a promising way to tune catalytic properties by altering the structural and chem. transformations that occur upon H incorporation. Herein, we investigate the structural changes that occur during the hydrogenation process using in situ powder X-ray diffraction and pair distribution function anal. of GO-TiO2 and TiO2 under H2 redn. Sequential Rietveld refinement was employed to gain insight into the evolution of crystal growth of TiO2 nanoparticles in the presence of two-dimensional (2D) GO nanosheets. GO sheets not only significantly retarded the nucleation and growth of rutile impurities, stabilizing the anatase structure, but was also partially reduced to hydrogenated graphene by the introduction of at. hydrogen into the honeycomb lattice. We discuss the hydrogenation processes and the resulting composite structure that occurs during the incorporation of at. H and the dynamic structural transformations that leads to a highly active photocatalyst.
- 26Fernandez-Garcia, M.; Belver, C.; Hanson, J. C.; Wang, X.; Rodriguez, J. A. Anatase-TiO2 nanomaterials: Analysis of key parameters controlling crystallization. J. Am. Chem. Soc. 2007, 129 (44), 13604– 13612, DOI: 10.1021/ja074064mGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtFert7zI&md5=5565061b607982e9bbfa4559d8565dafAnatase-TiO2 Nanomaterials: Analysis of Key Parameters Controlling CrystallizationFernandez-Garcia, Marcos; Belver, Carolina; Hanson, Jonathan C.; Wang, Xianqin; Rodriguez, Jose A.Journal of the American Chemical Society (2007), 129 (44), 13604-13612CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Nanoparticulated TiO2 materials with anatase structure were synthesized by using a microemulsion method. The structural characteristics of the amorphous solid precursors and their evolution during thermal treatments were studied by X-ray absorption structure (X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS)), X-ray diffraction-pair distribution function (XRD-PDF), and IR spectroscopy. Concerning the precursor materials, XANES and EXAFS showed a local order closely related to that of the anatase structure but contg. defective, undercoordinated Ti5c4+ species in addn. to normal Ti6c4+ species. The PDF technique detects differences among samples in the local order (<1 nm) and showed that primary particle size varies throughout the amorphous precursor series. The phys. interpretation of results concerning the amorphous materials and their evolution under thermal treatment gives conclusive evidence that local, intraparticle ordering variations det. the temp. for the onset of the nucleation process and drive the solid behavior through the whole crystn. process. The significance of this result in the context of current crystn. theories of oxide-based nanocryst. solids is discussed.
- 27Horn, M.; Schwerdtfeger, C. F.; Meagher, E. P. Refinement of the structure of anatase at several temperatures. Z. Kristallogr. NCS 1972, 136 (3–4), 273– 281, DOI: 10.1524/zkri.1972.136.3-4.273Google ScholarThere is no corresponding record for this reference.
- 28Swope, R. J.; Smyth, J. R.; Larson, A. C. H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutile. Am. Mineral. 1995, 80 (5–6), 448– 453, DOI: 10.2138/am-1995-5-604Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXms1Wlu7s%253D&md5=9f4a2bf80ffe32e3a1be63e801a49586H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutileSwope, R. Jeffrey; Smyth, Joseph R.; Larson, Allen C.American Mineralogist (1995), 80 (5-6), 448-53CODEN: AMMIAY; ISSN:0003-004X. (Mineralogical Society of America)The crystal structure of natural hydrous rutile from a mantle eclogite nodule has been refined from single-crystal neutron diffraction data collected at 24 K. Chem., the rutile contained 95.52 TiO2, 0.74 Fe2O3, 0.68 Al2O3, 1.16 Cr2O3, 1.86 Nb2O5, and 0.04 wt% MnO, with approx. 1300 ppm OH-, as estd. by IR spectroscopy. The position of the H atom was located by examg. the neg. residuals in the difference Fourier maps. The refined position is near the shared edge of the cation octahedron at x/a = 0.42(1), y/b = 0.50(1), and z/c = 0 with a site occupancy of 2.7%, which is consistent with the H concn. estd. by IR spectroscopy. The O-H bond distance is 1.05 Å and the OH vector is in the (001) plane, which is consistent with the strong ω-polarization of the OH absorption obsd. in the IR spectra. Single-crystal X-ray data were collected from a synthetic anhyd. rutile crystal and a hydrous rutile crystal from the same mantle nodule as the sample used in the neutron study. The detailed X-ray structures of both rutiles were compared and no significant differences were found; the a/c ratios and the O position were identical within error. Therefore, we conclude that the addn. of H into rutile for the purpose of charge-balancing excess 3+ cations does not significantly change the structure.
- 29Hanaor, D. A. H.; Sorrell, C. C. Review of the anatase to rutile phase transformation. J. Mater. Sci. 2011, 46 (4), 855– 874, DOI: 10.1007/s10853-010-5113-0Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFaqtrfJ&md5=2cd2e668dd749e5f0a2f47d0f8802320Review of the anatase to rutile phase transformationHanaor, Dorian A. H.; Sorrell, Charles C.Journal of Materials Science (2011), 46 (4), 855-874CODEN: JMTSAS; ISSN:0022-2461. (Springer)A review. Titanium dioxide, TiO2, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examd., followed by a discussion of the thermodn. of the phase transformation and the factors affecting its observation. A comprehensive anal. of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius vs. the valence characterized by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which exptl. data are unavailable, on the phase transformation are deduced and presented on the basis of this anal.
- 30Caffyn, P. H. Ilmenite Reserves at Barrytown, New Zealand; Ministry of Economic Development: Wellington, New Zealand, 1976.Google ScholarThere is no corresponding record for this reference.
- 31Ohtsuka, Y.; Fujiki, Y.; Suzuki, Y. Impurity effects on anatase-rutile transformation. J. Mineral. Petrol. Sci. 1982, 77, 117– 124, DOI: 10.2465/ganko1941.77.117Google ScholarThere is no corresponding record for this reference.
- 32Karvinen, S. The effects of trace elements on the crystal properties of TiO2. Solid State Sci. 2003, 5 (5), 811– 819, DOI: 10.1016/S1293-2558(03)00082-7Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvV2gtb4%253D&md5=300a73ee32f138a85a2010be3849bbd3The effects of trace elements on the crystal properties of TiO2Karvinen, SailaSolid State Sciences (2003), 5 (5), 811-819CODEN: SSSCFJ; ISSN:1293-2558. (Editions Scientifiques et Medicales Elsevier)The effects of trace element doping of TiO2 on the crystal growth and anatase-to-rutile phase transformation were examd. The copptn. process, from sulfate soln., of doped (Cr, Fe, V, Nb, Si, P) TiO2 was also studied. The heating temps. were 473, 673, 873, 993, 1133 K and a higher temp. needed to achieve a rutile content of 98-99%. Traces of reduced titanium were found in freshly calcined anatase by X-ray diffraction. Pure anatase structure was found in 85% of the samples heated at <1000K. Anatase-to-rutile transformation was accelerated by the mmol% content of Nb, Cr, Si, and Fe in TiO2. Interaction of copptd. or impregnated cations was found crit. in the phase transformation process. Nb retarded the crystal growth during calcination. Sulfate ions minimized the sp. surface area of TiO2 heated at low temps. These results of doped TiO2 serve to promote the development of new high-technol. TiO2 products for photocatalytic purposes.
- 33Grzmil, B.; Rabe, M.; Kic, B.; Lubkowski, K. Influence of phosphate, potassium, lithium, and aluminium on the anatase - Rutile phase transformation. Ind. Eng. Chem. Res. 2007, 46 (4), 1018– 1024, DOI: 10.1021/ie060188gGoogle Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjtVehuw%253D%253D&md5=cc7aacfe369bd2f57d7200e79c9c8cc8Influence of Phosphate, Potassium, Lithium, and Aluminium on the Anatase-Rutile Phase TransformationGrzmil, Barbara; Rabe, Magdalena; Kic, Bogumil; Lubkowski, KrzysztofIndustrial & Engineering Chemistry Research (2007), 46 (4), 1018-1024CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Calcination process was investigated on the lab. scale with the use of hydrated titanium dioxide contg. rutile nuclei from the industrial installation (sulfate process). The influence of temp. (750-900°) on the anatase-rutile phase transformation and on the crystallites growth variation was detd. Phosphate, potassium, lithium, and aluminum were introduced into calcination suspension. It was found that whereas an introduction of lithium, in phosphate presence, either increased or stabilized the anatase-rutile transformation degree, the introduction of potassium significantly decreased it. The intensity of these changes depended on both the temp. of the process and on phosphate content. The introduction of aluminum, in const. phosphate presence, had an intermediate influence on the rutilization of anatase between that of either potassium and phosphate on the one hand and lithium and phosphate on the other. Similarly to potassium, aluminum intensified the influence of phosphate but to a smaller degree and only at lower temps. The introduction of lithium, regardless of whether or not phosphate and potassium were present, increased rutilization degree. This dependence was more clearly seen at lower temps. of the process. Aluminum, either in const. phosphate and potassium or phosphate and lithium presence, increased the anatase-rutile transformation. The degree of these changes depended on both the presence of modifying agents in their mixt. and on the temp. of the process. It was found that the introduction to hydrated titanium dioxide of additives causing an increase in the surface area of TiO2, as a result of limitations of crystallite growth in the calcination process, results in elevation of temp. of the anatase-rutile phase transformation (phosphates, potassium) whereas the introduction of additives that decrease the surface area (crystallite growth) enhances the degree of transformation of anatase to rutile (lithium).
- 34Roy, B.; Fuierer, P. A. Influence of sodium chloride and dibasic sodium phosphate salt matrices on the anatase-rutile phase transformation and particle size of titanium dioxide powder. J. Am. Ceram, Soc. 2010, 93 (2), 436– 444, DOI: 10.1111/j.1551-2916.2009.03415.xGoogle Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhvFOhtrc%253D&md5=499ff023ec33946dee84ff41e5ee08ffInfluence of sodium chloride and dibasic sodium phosphate salt matrices on the anatase-rutile phase transformation and particle size of titanium dioxide powderRoy, Banasri; Fuierer, Paul AntonJournal of the American Ceramic Society (2010), 93 (2), 436-444CODEN: JACTAW; ISSN:0002-7820. (Wiley-Blackwell)The effects of sodium chloride (NaCl) and dibasic sodium phosphate (Na2HPO4·2H2O, DSP) on the phase transformation and particle size of titania powder were examd. The salt matrix was shown to suppress both the amorphous to anatase transition and the anatase to rutile transition. DSP was particularly effective. Irresp. of the additives, transformation vs. time curves of the anatase to rutile conversion were obsd. to be sigmoidal, and were interpreted in terms of a first order, nucleation-growth controlled phenomenon. Anal. of these curves using appropriate rate laws yielded activation energies for nucleation of ∼4.3 eV for NaCl salt matrix and ∼8.6 eV for DSP salt matrix, compared with ∼3.2 eV for a sample with no salt. Activation energies for the growth or propagation stage were ∼5 and ∼8.9 eV for NaCl and DSP powders, resp., compared with ∼3.8 eV for no salt. In the solid state, salt matrixes suppressed the particle growth as well. These behaviors, in general are thought to be governed by the presence of salt impurities, esp. anions chemisorbed at the surface.
- 35Gesenhues, U. Calcination of metatitanic acid to titanium dioxide white pigments. Chem. Eng. Technol. 2001, 24 (7), 685– 694, DOI: 10.1002/1521-4125(200107)24:7<685::AID-CEAT685>3.0.CO;2-1Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXlvFCktb4%253D&md5=d020838139d28c835d91b98817ac106dCalcination of metatitanic acid to titanium dioxide white pigmentsGesenhues, UlrichChemical Engineering & Technology (2001), 24 (7), 685-694CODEN: CETEER; ISSN:0930-7516. (Wiley-VCH Verlag GmbH)A review, with refs. In the sulfate process for the prodn. of TiO2 white pigments, gel-like metatitanic acid is calcined in a rotary kiln to microcrystals of the rutile polymorph. This process is monitored by the addn. of alkali ions, Al3-, phosphate and rutile nuclei. During the last decade, a scientific understanding has developed how these additives influence the solid-state reactions of the material in the kiln, i.e., crystal growth, transformation of anatase to rutile, incorporation of dopants and aggregation of crystals. This review describes mechanisms and kinetics of the reactions, using modern concepts of solid state and surface chem. and physics. It also describes the effects of the reactions on the quality of the calciner product for upgrading, e.g., the grindability to pigment particles, their light-scattering properties and photocatalytic activity.
- 36Li, Y.; Yang, Y.; Guo, M.; Zhang, M. Influence of acid type and concentration on the synthesis of nanostructured titanium dioxide photocatalysts from titanium-bearing electric arc furnace molten slag. RSC Adv. 2015, 5 (18), 13478– 13487, DOI: 10.1039/C4RA13942AGoogle Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXos1Whtg%253D%253D&md5=8d65cf02b3bfe64611428a844fc3031cInfluence of acid type and concentration on the synthesis of nanostructured titanium dioxide photocatalysts from titanium-bearing electric arc furnace molten slagLi, Yang; Yang, Yang; Guo, Min; Zhang, MeiRSC Advances (2015), 5 (18), 13478-13487CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)In this paper, nanostructured titanium dioxide (TiO2) photocatalysts with different crystal structures and morphologies were successfully synthesized from titanium-bearing elec. arc furnace molten slag (Ti-bearing EAF slag). The effects of different kinds of acid and acid concns. during the acidolysis process on the crystal structures and morphologies of TiO2 were systematically studied. The TiO2 crystal phase transformation mechanism and morphol. evolution in different acid systems and concns. were discussed in detail. In addn., the photocatalytic properties of TiO2 obtained in different acid systems were investigated. It is shown that rutile and anatase type TiO2 were obtained in hydrochloric acid and sulfuric acid, resp., while two types coexisted in nitric acid. With increasing sulfuric acid concn., anatase would be apt to change to rutile. The growth mechanism of TiO2 from Ti-bearing EAF slag was also discussed. The TiO2 synthesized from sulfuric acid showed better photocatalytic activity than that from hydrochloric or nitric acid, and its photodegrdn. efficiency can reach 90.52% in 90 min for rhodamine B solns.
- 37Arbiol, J.; Cerda, J.; Dezanneau, G.; Cirera, A.; Peiro, F.; Cornet, A.; Morante, J. R. Effects of Nb doping on the TiO2 anatase-to-rutile phase transition. J. Appl. Phys. 2002, 92 (2), 853– 861, DOI: 10.1063/1.1487915Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XkvFyjsro%253D&md5=374ceeacd074f18e37cfff48a4422d46Effects of Nb doping on the TiO2 anatase-to-rutile phase transitionArbiol, J.; Cerda, J.; Dezanneau, G.; Cirera, A.; Peiro, F.; Cornet, A.; Morante, J. R.Journal of Applied Physics (2002), 92 (2), 853-861CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The authors study the influence of Nb doping on the TiO2 anatase-to-rutile phase transition, using combined TEM, Raman spectroscopy, x-ray diffraction and selected area electron diffraction anal. This approach enabled anatase-to-rutile phase transition hindering to be clearly obsd. for low Nb-doped TiO2 samples. Also, there was clear grain growth inhibition in the samples contg. Nb. The use of high resoln. TEM with the authors' samples provides an innovative perspective compared with previous research on this issue. The authors' anal. shows that Nb is segregated from the anatase structure before and during the phase transformation, giving NbO nanoclusters on the surface of the TiO2 rutile nanoparticles.
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This article is cited by 5 publications.
- Richard G. Haverkamp, Peter Kappen, Katie H. Sizeland, Kia S. Wallwork. Niobium K-Edge X-ray Absorption Spectroscopy of Doped TiO2 Produced from Ilmenite Digested in Hydrochloric Acid. ACS Omega 2022, 7
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- Pujita Ningthoukhongjam, Ranjith G. Nair. Role of titania photoanode phase on the performance of the Dye Sensitized Solar Cell. 2023, 1-5. https://doi.org/10.1109/SILCON59133.2023.10404856
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Abstract
Figure 1
Figure 1. Raman spectra of dried titanium seed and hydrate. (a) Degussa P25 reference (calcined) material, black line; phosphate hydrate 1 (HP1), magenta; phosphate hydrate 2 (HP2), red; water hydrate 1 (HW1), blue; water hydrate 2 (HW2), green. (b) Raman spectra of dried TiO2 hydrate “seed”: water seed 1 (SW1), black; water seed 2 (SW2), red; water seed 3 (SW3), green; phosphate seed 1 (SP1), magenta; phosphate seed 2 (SP2), blue.
Figure 2
Figure 2. (a) TiO2 hydrate phosphate seeded 1 (anatase; SP1), (b) TiO2 hydrate phosphate seeded 2 (mixed anatase/rutile; SP2), (c) TiO2 hydrate water seeded 1 (rutile; SW1).
Figure 3
Figure 3. Nanocrystalline TiO2 hydrate (phosphate seeded hydrate 1). (a,b) Diffraction data in 2θ for 21 keV X-ray energy with air background and capillary scattering (expanded scale for b). (c) Total scattering function, S(Q). (d) Reduced PDF experimental data showing the interatomic spacings.
Figure 4
Figure 4. Reduced PDF (blue circles) with the fitted structure (red line) and residuals (green line): (a) anatase hydrate 1; (b) rutile hydrate 1.
Figure 5
Figure 5. X-ray scattering intensity (IQ) for (a) seed SW3 after subtraction of the background for the capillary in air; (b) seed SP2 (seed SP1 looks similar─not shown); (c) seed SP2 G9(r); (d) seed SP2 G(r) scaled × 100 (red solid line) compared with anatase (blue dashed line) and rutile (black dot dash line) from the fitted form for the hydrates.
Figure 6
Figure 6. Block process flow diagram for preparation of TiO2 from ilmenite.
References
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- 3Saeed, M. A.; Yoo, K.; Kang, H. C.; Shim, J. W.; Lee, J. J. Recent developments in dye-sensitized photovoltaic cells under ambient illumination. Dyes Pigm. 2021, 194, 109626, DOI: 10.1016/j.dyepig.2021.1096263https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhs1ejtrfN&md5=2ea8de48b7795a17f1f53d0943be1e66Recent developments in dye-sensitized photovoltaic cells under ambient illuminationSaeed, Muhammad Ahsan; Yoo, Kicheon; Kang, Hyeong Cheol; Shim, Jae Won; Lee, Jae-JoonDyes and Pigments (2021), 194 (), 109626CODEN: DYPIDX; ISSN:0143-7208. (Elsevier Ltd.)A review. Dye-sensitized photovoltaic cells (DSPVs) have great potential in indoor photovoltaic applications for light energy recycling because of their exceptional light-harvesting capability under ambient illumination conditions. The feasibility of DSPVs for use in ambient energy harvesting is verified by their record-high power-conversion efficiency (PCE) of over 30% under indoor illumination conditions, colorful esthetics, cost-effectiveness, stable device performance, and PCE retention of up to 99%. This review provides an insightful overview of the application of DSPVs under the illumination of diffuse and low-intensity light. The key foci of this study are the synergistic impacts of various factors, including the design of dyes, compn. of electrolytes, long-term stability, effect of TiO2 mesoporous films, and blocking layers on the indoor performance of DSPVs. Addnl., the review touches upon the com. aspects of DSPVs that operate under low light intensities, and it provides a crit. perspective.
- 4Nabi, I.; Bacha, A. U. R.; Ahmad, F.; Zhang, L. Application of titanium dioxide for the photocatalytic degradation of macro- and micro-plastics: A review. J. Environ. Chem.Eng. 2021, 9, 105964, DOI: 10.1016/j.jece.2021.1059644https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhsFOgurfO&md5=44bcddf120f5012cf42e068cea526be9Application of titanium dioxide for the photocatalytic degradation of macro- and micro-plastics: A reviewNabi, Iqra; Bacha, Aziz-Ur-Rahim; Ahmad, Farhad; Zhang, LiwuJournal of Environmental Chemical Engineering (2021), 9 (5), 105964CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)A review. The advancement in industries and modern technol. has been escorted by an expansion in the utilization of chems. to obtain plastic-based products. Increased plastic prodn. and disposal have greatly affected the environment and living organisms globally. Macro and micro-plastics have a persistent nature, and their natural degrdn. takes years. Transport, impact, behavior, and degrdn. have attracted growing research attention. However, a review study on titanium dioxide (TiO2) based photocatalytic degrdn. of macro and micro-plastics has not been summarized. Herein, a brief overview of the TiO2 application for macro and micro-plastics degrdn. has been summarized. Different prepn. methods for TiO2 synthesis and its modification for plastics decompn. have been presented. The degrdn. efficiency and applied system limitations with future research directions are proposed. Nevertheless, the existing knowledge about the TiO2 application for macro and micro-plastics is still limited. This work provides a good ref. for plastic pollution control.
- 5Das, A.; Adak, M. K.; Mahata, N.; Biswas, B. Wastewater treatment with the advent of TiO2 endowed photocatalysts and their reaction kinetics with scavenger effect. J. Mol. Liq. 2021, 338, 116479, DOI: 10.1016/j.molliq.2021.1164795https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhtlensL7O&md5=3cbb646334b136aa2988e039f6b55952Wastewater treatment with the advent of TiO2 endowed photocatalysts and their reaction kinetics with scavenger effectDas, Ajit; Adak, Mrinal K.; Mahata, Nagendranath; Biswas, BhaskarJournal of Molecular Liquids (2021), 338 (), 116479CODEN: JMLIDT; ISSN:0167-7322. (Elsevier B.V.)A review. In the view of long-term water sustainability and worldwide problems of environmental pollution, new and novel scientific studies on modern technologies and advance scientific processes, deep understanding of the mechanistic aspects of the processes and the circumstances affecting it, exhaustive research on the photocatalyst based wastewater treatment hold a great promise. Over the last decade, photon-mediated titanium dioxide, photo-Fenton processes, and their modifications have been widely investigated as an efficient, robust, and attractive photocatalytic system for wastewater treatment, however, the correlation between TiO2 based composites, treatment processes and photocatalytic performances remains still under debate. This review provides an overview of the development of TiO2 based photocatalytic systems and new functionalized photocatalysts, their kinetic studies, and role of scavengers related to the advance and modified processes in wastewater treatment. Furthermore, the treatment of real wastewater in industrial sector and the futuristic cost-effective alternative with high catalytic capacity have also been delineated.
- 6Lavacchi, A.; Bellini, M.; Berretti, E.; Chen, Y.; Marchionni, A.; Miller, H. A.; Vizza, F. Titanium dioxide nanomaterials in electrocatalysis for energy. Curr. Opin. Electrochem. 2021, 28, 100720, DOI: 10.1016/j.coelec.2021.1007206https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXotVWitbs%253D&md5=c7a3c3e510a692da6868452039629d7eTitanium dioxide nanomaterials in electrocatalysis for energyLavacchi, Alessandro; Bellini, Marco; Berretti, Enrico; Chen, Yanxin; Marchionni, Andrea; Miller, Hamish Andrew; Vizza, FrancescoCurrent Opinion in Electrochemistry (2021), 28 (), 100720CODEN: COEUCY; ISSN:2451-9111. (Elsevier B.V.)Over the last two decades, researchers have found many strategies to obtain high surface area nanostructured titanium dioxide. These nanostructures have recently found application as supports for the fabrication of electrodes for electrochem. energy conversion and storage devices. The properties that make titanium dioxide appealing for these applications are as follows: (i) stability in a variety of conditions relevant to electrocatalysis, (ii) electronic cond., (iii) synergistic effects with metal catalysts. The work splits TiO2 nanomaterials into the following two classes: (i) powders and (ii) embedded nanoarchitectures (e.g. titania nanotubes on titanium support). We give an overview of the latest applications, with a special emphasis on fuel cells, electrolysis, and carbon dioxide electroredn. We conclude with a list of the research needs that, in the opinion of the authors, will support the exploration and consolidation of the use of titania in electrocatalysis for energy.
- 7Peng, P. P.; Wu, Y. R.; Li, X. Z.; Zhang, J. H.; Li, Y. W.; Cui, P.; Yi, T. F. Toward superior lithium/sodium storage performance: design and construction of novel TiO2-based anode materials. Rare Met. 2021, 40 (11), 3049– 3075, DOI: 10.1007/s12598-021-01742-z7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhtlSjtbvJ&md5=97683d04a8342aa244f610b5b9ef8a52Toward superior lithium/sodium storage performance: design and construction of novel TiO2-based anode materialsPeng, Pan-Pan; Wu, Yu-Rong; Li, Xue-Zhong; Zhang, Jun-Hong; Li, Yan-Wei; Cui, Ping; Yi, Ting-FengRare Metals (Beijing, China) (2021), 40 (11), 3049-3075CODEN: RARME8; ISSN:1001-0521. (Journal Publishing Center of University of Science and Technology Beijing)A review. TiO2-based materials have been considered as one of most promising alternatives for high-performance Li(Na)-ion batteries because of the low cost, simple compn., easy synthesis, good environmental protection, excellent safety and relatively high specific capacity. Nonetheless, the inferior electronic cond. and poor ion diffusion coeffs. are the biggest bottlenecks that restrict the popular application. Much effort has been focused on resolving these problems toward large-scale applications, and numerous significant advances have been accomplished. In the present work, a comprehensive overview of structure characteristics, electrochem. reaction mechanism and modification strategies of TiO2-based materials was presented. The recent advances of various efficient ways for improving cond., Li(Na) storage capacity, rate capability and cycle stability are systematically summarized, including surface engineering, constructing composite and element doping, etc. Constructing TiO2-based materials with novel porous heterogeneous core-shell structures have been regarded as one of the most effective ways to resolve these challenges. Finally, the future research directions and development prospects of TiO2-based anode materials used in the manuf. of high-performance Li(Na)-ion batteries are prospected. This review can provide important comprehension for the construction and optimization of high-performance of TiO2-based anode materials.
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- 10Haverkamp, R. G.; Kruger, D.; Rajashekar, R. The digestion of New Zealand ilmenite by hydrochloric acid. Hydrometallurgy 2016, 163, 198– 203, DOI: 10.1016/j.hydromet.2016.04.01510https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XnvVarurc%253D&md5=87a7de060a35d961b15defbe3fbb1740The digestion of New Zealand ilmenite by hydrochloric acidHaverkamp, Richard G.; Kruger, Desiderius; Rajashekar, RanjeethHydrometallurgy (2016), 163 (), 198-203CODEN: HYDRDA; ISSN:0304-386X. (Elsevier B.V.)A review. Ilmenite (FeTiO3) is an important source of titanium, for which the main application is TiO2 pigment. One route to the prodn. of TiO2 from ilmenite may be the digestion of both the Fe and Ti components in hydrochloric acid and the subsequent direct hydrolysis of the Ti. The process requires that the Ti be solubilized. A kinetic study is performed of the leaching of New Zealand (Barrytown) placer ilmenite (ground to a 10μm median particle diam.) by hydrochloric acid in a stirred reactor. Around 90% extn. of both Fe and Ti is achieved with a 32% wt./wt. HCl concn., with a 2:1 wt./wt. ratio of HCl to FeTiO3 over the temp. range 60 to 90°C. The shrinking sphere model is a good representation of the kinetics if particle size distribution is accounted for. The reaction rate is estd. to be 4th order in HCl concn. The temp. rise due to an exothermic reaction is calcd. to be c. 41°C. Undesirable, in situ hydrolysis of Ti during digestion can be limited by control of temp., reaction time and acid concn. The data and models presented may facilitate the preliminary design of an industrial process to digest ilmenite to dissolve and retain Ti in soln.
- 11Olanipekun, E. A kinetic study of the leaching of a Nigerian ilmenite ore by hydrochloric acid. Hydrometallurgy 1999, 53, 1– 10, DOI: 10.1016/S0304-386X(99)00028-611https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXksV2rtrg%253D&md5=8bc04ba89b8ef107d4dc49e08b5d5acfA kinetic study of the leaching of a Nigerian ilmenite ore by hydrochloric acidOlanipekun, EdwardHydrometallurgy (1999), 53 (1), 1-10CODEN: HYDRDA; ISSN:0304-386X. (Elsevier Science B.V.)A kinetic study of the leaching of powd. ilmenite ore by hydrochloric acid has been investigated. The effects of (a) stirring speed ranging from 100 to 500 min-1, (b) particle size ranging from 20 to 74 μm, (c) acid concn. ranging from 7.2 to 9.6 M and (d) temp. ranging from 70 to 90°C on titanium and iron dissoln. are reported. The dissoln. rates are significantly influenced by the temp. and concn. of the acid solns. The exptl. data for the dissoln. rates of titanium and iron have been analyzed with the shrinking-core model for reaction control. The obsd. effects of the relevant operating variables on the dissoln. rates are consistent with a kinetic model for diffusion control. The apparent activation energy for the dissoln. of titanium and iron has been evaluated using the Arrhenius expression.
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- 13Haverkamp, R. G.; Wallwork, K. S. X-ray Pair Distribution Function Analysis of Nanostructured Materials using a Mythen Detector. J. Synchrotron Radiat. 2009, 16 (6), 849– 856, DOI: 10.1107/S090904950903672313https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtlSiu7zE&md5=eddc632c72c87cf59def00844c9cbe0fX-ray pair distribution function analysis of nanostructured materials using a Mythen detectorHaverkamp, Richard G.; Wallwork, Kia S.Journal of Synchrotron Radiation (2009), 16 (6), 849-856CODEN: JSYRES; ISSN:0909-0495. (International Union of Crystallography)Total scattering from nanocryst. materials recorded on the Australian Synchrotron powder diffraction beamline has been analyzed to produce at. pair distribution functions (PDFs) for structural anal. The capability of this beamline, which uses the massively parallel Mythen II detector, has been quantified with respect to PDF structure anal. Data were recorded to a wavevector magnitude, Q, of 20.5 Å-1, with successful PDFs obtained for counting times as short as 10 s for cryst. LaB6 and 180 s for nanocryst. (47 Å) anatase. This paper describes the aspects of a PDF expt. that are crucial to its success, with ref. to the outcomes of anal. of data collected from nanocryst. TiO2 and microcryst. LaB6 and IrO2.
- 14Egami, T.; Billinge, S. J. L. Underneath the Bragg Peaks: Structural Analysis of Complex Materials; Permagon: Oxford, 2003.There is no corresponding record for this reference.
- 15Schmitt, B.; Brönnimann, C.; Eikenberry, E. F.; Gozzo, F.; Hörmann, C.; Horisberger, R.; Patterson, B. Mythen detector system. Nucl. Instrum. Meth. A 2003, 501, 267– 272, DOI: 10.1016/S0168-9002(02)02045-415https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXivVOksL4%253D&md5=e0d07694f7b58393cf40eb3d3702ad44Mythen detector systemSchmitt, B.; Bronnimann, Ch.; Eikenberry, E. F.; Gozzo, F.; Hormann, C.; Horisberger, R.; Patterson, B.Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2003), 501 (1), 267-272CODEN: NIMAER; ISSN:0168-9002. (Elsevier Science B.V.)Time-resolved expts. in powder diffraction are limited by the long time required to record spectra with current detectors. A major improvement can be made by using a massively parallel x-ray detection system together with a fast read out. The Mythen detector (Microstrip system for time-resolved expts.) was built for the Powder Diffraction Station of the Material Science beamline at the Swiss Light Source to meet these requirements. The specifically developed read out chip (Mythen chip), the detector system and 1st measurements are shown.
- 16Wallwork, K. S.; Kennedy, B. J.; Wang, D. The high resolution powder diffraction beamline for the Australian Synchrotron. In AIP Conf. Proc., Wallwork, K. S., Kennedy, B. J., Wang, D., Eds.; AIP: 2007; Vol. 879, pp 879- 882.There is no corresponding record for this reference.
- 17Qiu, X.; Thompson, J. W.; Billinge, S. J. L. PDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction data. J. Appl. Crystallogr. 204, 2004 37 (4), 678. DOI: 10.1107/S002188980401174417https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXlvVKmt7w%253D&md5=cdff1721e3b5e02a744b76ba4040d79ePDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction dataQiu, Xiangyun; Thompson, Jeroen W.; Billinge, Simon J. L.Journal of Applied Crystallography (2004), 37 (4), 678CODEN: JACGAR; ISSN:0021-8898. (Blackwell Publishing Ltd.)There is no expanded citation for this reference.
- 18Farrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, T.; Billinge, S. L. J. PDFfit2 and PDFgui: computer programs for studying nanostructures in crystals. J. Phys-Condens. Mat 2007, 19, 335219, DOI: 10.1088/0953-8984/19/33/33521918https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVOqtLfK&md5=3af1c0ad4523068d58f605009d12af9ePDFfit2 and PDFgui: computer programs for studying nanostructure in crystalsFarrow, C. L.; Juhas, P.; Liu, J. W.; Bryndin, D.; Bozin, E. S.; Bloch, J.; Proffen, Th; Billinge, S. J. L.Journal of Physics: Condensed Matter (2007), 19 (33), 335219/1-335219/7CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)PDFfit2 is a program as well as a library for real-space refinement of crystal structures. It is capable of fitting a theor. three-dimensional (3D) structure to at. pair distribution function data and is ideal for nanoscale investigations. The fit system accounts for lattice consts., at. positions and anisotropic at. displacement parameters, correlated at. motion, and exptl. factors that may affect the data. The at. positions and thermal coeffs. can be constrained to follow the symmetry requirements of an arbitrary space group. The PDFfit2 engine is written in C++ and is accessible via Python, allowing it to inter-operate with other Python programs. PDFgui is a graphical interface built on the PDFfit2 engine. PDFgui organizes fits and simplifies many data anal. tasks, such as configuring and plotting multiple fits. PDFfit2 and PDFgui are freely available via the Internet.
- 19Wells, H. C.; Haverkamp, R. G. Characterization of the heavy mineral suite in a holocene beach placer, Barrytown, New Zealand. Minerals 2020, 10 (2), 86, DOI: 10.3390/min1002008619https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlSnsL7F&md5=3943fe74adf1fb245ceae9dfce3d9e1fCharacterization of the heavy mineral suite in a Holocene Beach Placer, Barrytown, New ZealandWells, Hannah C.; Haverkamp, Richard G.Minerals (Basel, Switzerland) (2020), 10 (2), 86CODEN: MBSIBI; ISSN:2075-163X. (MDPI AG)The placer deposit at Barrytown, New Zealand, has been worked for gold and is known for high levels of ilmenite that has not been exploited. Other heavy minerals are present but have not been well characterized, which is the purpose of this research. Sand grains were sepd. into the d. fractions and the heavier fractions analyzed by laser ablation ICP-MS for elemental compn. and by SEM (SEM) EDS in whole grains and polished sections. Grain size distributions were detd. from SEM images of polished grain mounts. Elemental assocns. have been identified with different minerals. A wide range of ore minerals, or potential useful industrial minerals, have been shown to be present largely as individual sand grains. These include gold, ilmenite, garnet, zircon, monazite, allanite, uraninite, thorite, cassiterite, wolframite, scheelite, and columbite. The ilmenite contains many inclusions, consisting of silicates and phosphates and 100-400 ppm Nb. Scandium is found to be present in zircon at 100-600 ppm along with 3000 ppm Y. Monazite is depleted in Eu relative to chondrite and contains Ga and Ge at 1000-3000 ppm. Because the sand grains are mostly individual minerals, it is suggested that sepn. may be possible using a combination of d., electrostatic and magnetic methods to obtain almost pure mineral fractions. This knowledge should inform decisions on potential exploitation of the resource.
- 20Duncan, J. F.; Metson, J. B. Acid attack on New-Zealand ilmenite. 2. The structure and composition of the solid. N.Z. J. Sci. 1982, 25 (2), 111– 11620https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38Xmt1ShtLY%253D&md5=3a03f416b123821a6ed2fb4e255f2145Acid attack on New Zealand ilmenite. 2. The structure and composition of the solidDuncan, J. F.; Metson, J. B.New Zealand Journal of Science (1982), 25 (2), 111-16CODEN: NZJSAB; ISSN:0028-8365.The structure and compn. of New Zealand ilmenite [12168-52-4] were studied before and after acid leaching. Solns. of 1-10M HCl at temp. of 70° were used to partially dissolve ground and unground samples. Although the material appears quite homogeneous in x-ray, electron microprobe, and optical mineralogical examn., acid leaching causes extensive pore formation parallel to the basal plane. This selective attack can be attributed to parting dislocations and possibly twinning in the basal plane. Moessbauer spectroscopy shows some substitution of Fe2+ in the Ti4+ sites of the mineral, but this does not appear to influence reactivity.
- 21Lafuente, B.; Downs, R. T.; Yang, H.; Stone, N. The power of databases: The RRUFF project. In Highlights in Mineralogical Crystallography; De Gruyter: Berlin, 2016; pp 1– 29.There is no corresponding record for this reference.
- 22Challagulla, S.; Tarafder, K.; Ganesan, R.; Roy, S. Structure sensitive photocatalytic reduction of nitroarenes over TiO2. Sci. Rep. 2017, 7 (1), 1– 11, DOI: 10.1038/s41598-017-08599-222https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtlGgs7bJ&md5=1914b1dcd9407da59b668ca2ef7f79ecStructure sensitive photocatalytic reduction of nitroarenes over TiO2Challagulla, Swapna; Tarafder, Kartick; Ganesan, Ramakrishnan; Roy, SounakScientific Reports (2017), 7 (1), 1-11CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)It is a subject of exploration whether the phase pure anatase or rutile TiO2 or the band alignment due to the heterojunctions in the two polymorphs of TiO2 plays the detg. role in efficacy of a photocatalytic reaction. In this work, the phase pure anatase and rutile TiO2 have been explored for photocatalytic nitroarenes redn. to understand the role of surface structures and band alignment towards the redn. mechanism. The conduction band of synthesized anatase TiO2 has been found to be more populated with electrons of higher energy than that of synthesized rutile. This has given the anatase an edge towards photocatalytic redn. of nitroarenes over rutile TiO2. The other factors like adsorption of the reactants and the proton generation did not play any decisive role in catalytic efficacy.
- 23Swamy, V. Size-dependent modifications of the first-order Raman spectra of nanostructured rutile TiO2. Phys. Rev. B 2008, 77 (19), 1– 4, DOI: 10.1103/PhysRevB.77.195414There is no corresponding record for this reference.
- 24Schmutz, C.; Barboux, P.; Ribot, F.; Taulelle, F.; Verdaguer, M.; Fernandezlorenzo, C. EXAFS, Raman and P-31 NMR-study of amorphous titanium phosphates. J. Non-Cryst. Solids 1994, 170 (3), 250– 262, DOI: 10.1016/0022-3093(94)90054-X24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXkvFynsLg%253D&md5=3505a16c22edbfef52abc17c927c76c0EXAFS, Raman and 31P NMR study of amorphous titanium phosphatesSchmutz, C.; Barboux, P.; Ribot, F.; Taulelle, F.; Verdaguer, M.; Fernandez-Lorenzo, C.Journal of Non-Crystalline Solids (1994), 170 (3), 250-62CODEN: JNCSBJ; ISSN:0022-3093.The reaction of H3PO4 with Ti alkoxides for a PO4/Ti ratio ranging from 0.5 to 2 was studied. For these compns., amorphous ppts. are obtained. Their microstructure was studied by Raman, NMR and x-ray absorption spectroscopies. The phosphatation of Ti alkoxide increases the Ti coordination no. to 6 and the symmetry becomes purely octahedral for a P/Ti ratio of 2. For the compn. range 0 < PO4/Ti ≤ 2, phosphate anions are homogeneously dispersed in the ppt. and bound to Ti, the coordination of which is completed by oxo-, hydroxo- and remaining alkoxy- groups. Short Ti-O distances are obsd. in the materials having the lowest P/Ti ratios.
- 25Nguyen-Phan, T. D.; Liu, Z.; Luo, S.; Gamalski, A. D.; Vovchok, D.; Xu, W.; Stach, E. A.; Polyansky, D. E.; Fujita, E.; Rodriguez, J. A. Unraveling the Hydrogenation of TiO2 and Graphene Oxide/TiO2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function Analysis. J. Phys. Chem. C 2016, 120 (6), 3472– 3482, DOI: 10.1021/acs.jpcc.5b0950425https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1Khu7Y%253D&md5=1b03b558e63c0dfc9755d84b187db652Unraveling the Hydrogenation of TiO2 and Graphene Oxide/TiO2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function AnalysisNguyen-Phan, Thuy-Duong; Liu, Zongyuan; Luo, Si; Gamalski, Andrew D.; Vovchok, Dimitry; Xu, Wenqian; Stach, Eric A.; Polyansky, Dmitry E.; Fujita, Etsuko; Rodriguez, Jose A.; Senanayake, Sanjaya D.Journal of Physical Chemistry C (2016), 120 (6), 3472-3482CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The functionalization of graphene oxide (GO) and graphene by TiO2 and other metal oxides has attracted considerable attention due to numerous promising applications in catalysis, energy conversion, and storage. Hydrogenation of this class of materials has been proposed as a promising way to tune catalytic properties by altering the structural and chem. transformations that occur upon H incorporation. Herein, we investigate the structural changes that occur during the hydrogenation process using in situ powder X-ray diffraction and pair distribution function anal. of GO-TiO2 and TiO2 under H2 redn. Sequential Rietveld refinement was employed to gain insight into the evolution of crystal growth of TiO2 nanoparticles in the presence of two-dimensional (2D) GO nanosheets. GO sheets not only significantly retarded the nucleation and growth of rutile impurities, stabilizing the anatase structure, but was also partially reduced to hydrogenated graphene by the introduction of at. hydrogen into the honeycomb lattice. We discuss the hydrogenation processes and the resulting composite structure that occurs during the incorporation of at. H and the dynamic structural transformations that leads to a highly active photocatalyst.
- 26Fernandez-Garcia, M.; Belver, C.; Hanson, J. C.; Wang, X.; Rodriguez, J. A. Anatase-TiO2 nanomaterials: Analysis of key parameters controlling crystallization. J. Am. Chem. Soc. 2007, 129 (44), 13604– 13612, DOI: 10.1021/ja074064m26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtFert7zI&md5=5565061b607982e9bbfa4559d8565dafAnatase-TiO2 Nanomaterials: Analysis of Key Parameters Controlling CrystallizationFernandez-Garcia, Marcos; Belver, Carolina; Hanson, Jonathan C.; Wang, Xianqin; Rodriguez, Jose A.Journal of the American Chemical Society (2007), 129 (44), 13604-13612CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Nanoparticulated TiO2 materials with anatase structure were synthesized by using a microemulsion method. The structural characteristics of the amorphous solid precursors and their evolution during thermal treatments were studied by X-ray absorption structure (X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS)), X-ray diffraction-pair distribution function (XRD-PDF), and IR spectroscopy. Concerning the precursor materials, XANES and EXAFS showed a local order closely related to that of the anatase structure but contg. defective, undercoordinated Ti5c4+ species in addn. to normal Ti6c4+ species. The PDF technique detects differences among samples in the local order (<1 nm) and showed that primary particle size varies throughout the amorphous precursor series. The phys. interpretation of results concerning the amorphous materials and their evolution under thermal treatment gives conclusive evidence that local, intraparticle ordering variations det. the temp. for the onset of the nucleation process and drive the solid behavior through the whole crystn. process. The significance of this result in the context of current crystn. theories of oxide-based nanocryst. solids is discussed.
- 27Horn, M.; Schwerdtfeger, C. F.; Meagher, E. P. Refinement of the structure of anatase at several temperatures. Z. Kristallogr. NCS 1972, 136 (3–4), 273– 281, DOI: 10.1524/zkri.1972.136.3-4.273There is no corresponding record for this reference.
- 28Swope, R. J.; Smyth, J. R.; Larson, A. C. H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutile. Am. Mineral. 1995, 80 (5–6), 448– 453, DOI: 10.2138/am-1995-5-60428https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXms1Wlu7s%253D&md5=9f4a2bf80ffe32e3a1be63e801a49586H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutileSwope, R. Jeffrey; Smyth, Joseph R.; Larson, Allen C.American Mineralogist (1995), 80 (5-6), 448-53CODEN: AMMIAY; ISSN:0003-004X. (Mineralogical Society of America)The crystal structure of natural hydrous rutile from a mantle eclogite nodule has been refined from single-crystal neutron diffraction data collected at 24 K. Chem., the rutile contained 95.52 TiO2, 0.74 Fe2O3, 0.68 Al2O3, 1.16 Cr2O3, 1.86 Nb2O5, and 0.04 wt% MnO, with approx. 1300 ppm OH-, as estd. by IR spectroscopy. The position of the H atom was located by examg. the neg. residuals in the difference Fourier maps. The refined position is near the shared edge of the cation octahedron at x/a = 0.42(1), y/b = 0.50(1), and z/c = 0 with a site occupancy of 2.7%, which is consistent with the H concn. estd. by IR spectroscopy. The O-H bond distance is 1.05 Å and the OH vector is in the (001) plane, which is consistent with the strong ω-polarization of the OH absorption obsd. in the IR spectra. Single-crystal X-ray data were collected from a synthetic anhyd. rutile crystal and a hydrous rutile crystal from the same mantle nodule as the sample used in the neutron study. The detailed X-ray structures of both rutiles were compared and no significant differences were found; the a/c ratios and the O position were identical within error. Therefore, we conclude that the addn. of H into rutile for the purpose of charge-balancing excess 3+ cations does not significantly change the structure.
- 29Hanaor, D. A. H.; Sorrell, C. C. Review of the anatase to rutile phase transformation. J. Mater. Sci. 2011, 46 (4), 855– 874, DOI: 10.1007/s10853-010-5113-029https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFaqtrfJ&md5=2cd2e668dd749e5f0a2f47d0f8802320Review of the anatase to rutile phase transformationHanaor, Dorian A. H.; Sorrell, Charles C.Journal of Materials Science (2011), 46 (4), 855-874CODEN: JMTSAS; ISSN:0022-2461. (Springer)A review. Titanium dioxide, TiO2, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examd., followed by a discussion of the thermodn. of the phase transformation and the factors affecting its observation. A comprehensive anal. of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius vs. the valence characterized by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which exptl. data are unavailable, on the phase transformation are deduced and presented on the basis of this anal.
- 30Caffyn, P. H. Ilmenite Reserves at Barrytown, New Zealand; Ministry of Economic Development: Wellington, New Zealand, 1976.There is no corresponding record for this reference.
- 31Ohtsuka, Y.; Fujiki, Y.; Suzuki, Y. Impurity effects on anatase-rutile transformation. J. Mineral. Petrol. Sci. 1982, 77, 117– 124, DOI: 10.2465/ganko1941.77.117There is no corresponding record for this reference.
- 32Karvinen, S. The effects of trace elements on the crystal properties of TiO2. Solid State Sci. 2003, 5 (5), 811– 819, DOI: 10.1016/S1293-2558(03)00082-732https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvV2gtb4%253D&md5=300a73ee32f138a85a2010be3849bbd3The effects of trace elements on the crystal properties of TiO2Karvinen, SailaSolid State Sciences (2003), 5 (5), 811-819CODEN: SSSCFJ; ISSN:1293-2558. (Editions Scientifiques et Medicales Elsevier)The effects of trace element doping of TiO2 on the crystal growth and anatase-to-rutile phase transformation were examd. The copptn. process, from sulfate soln., of doped (Cr, Fe, V, Nb, Si, P) TiO2 was also studied. The heating temps. were 473, 673, 873, 993, 1133 K and a higher temp. needed to achieve a rutile content of 98-99%. Traces of reduced titanium were found in freshly calcined anatase by X-ray diffraction. Pure anatase structure was found in 85% of the samples heated at <1000K. Anatase-to-rutile transformation was accelerated by the mmol% content of Nb, Cr, Si, and Fe in TiO2. Interaction of copptd. or impregnated cations was found crit. in the phase transformation process. Nb retarded the crystal growth during calcination. Sulfate ions minimized the sp. surface area of TiO2 heated at low temps. These results of doped TiO2 serve to promote the development of new high-technol. TiO2 products for photocatalytic purposes.
- 33Grzmil, B.; Rabe, M.; Kic, B.; Lubkowski, K. Influence of phosphate, potassium, lithium, and aluminium on the anatase - Rutile phase transformation. Ind. Eng. Chem. Res. 2007, 46 (4), 1018– 1024, DOI: 10.1021/ie060188g33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXjtVehuw%253D%253D&md5=cc7aacfe369bd2f57d7200e79c9c8cc8Influence of Phosphate, Potassium, Lithium, and Aluminium on the Anatase-Rutile Phase TransformationGrzmil, Barbara; Rabe, Magdalena; Kic, Bogumil; Lubkowski, KrzysztofIndustrial & Engineering Chemistry Research (2007), 46 (4), 1018-1024CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Calcination process was investigated on the lab. scale with the use of hydrated titanium dioxide contg. rutile nuclei from the industrial installation (sulfate process). The influence of temp. (750-900°) on the anatase-rutile phase transformation and on the crystallites growth variation was detd. Phosphate, potassium, lithium, and aluminum were introduced into calcination suspension. It was found that whereas an introduction of lithium, in phosphate presence, either increased or stabilized the anatase-rutile transformation degree, the introduction of potassium significantly decreased it. The intensity of these changes depended on both the temp. of the process and on phosphate content. The introduction of aluminum, in const. phosphate presence, had an intermediate influence on the rutilization of anatase between that of either potassium and phosphate on the one hand and lithium and phosphate on the other. Similarly to potassium, aluminum intensified the influence of phosphate but to a smaller degree and only at lower temps. The introduction of lithium, regardless of whether or not phosphate and potassium were present, increased rutilization degree. This dependence was more clearly seen at lower temps. of the process. Aluminum, either in const. phosphate and potassium or phosphate and lithium presence, increased the anatase-rutile transformation. The degree of these changes depended on both the presence of modifying agents in their mixt. and on the temp. of the process. It was found that the introduction to hydrated titanium dioxide of additives causing an increase in the surface area of TiO2, as a result of limitations of crystallite growth in the calcination process, results in elevation of temp. of the anatase-rutile phase transformation (phosphates, potassium) whereas the introduction of additives that decrease the surface area (crystallite growth) enhances the degree of transformation of anatase to rutile (lithium).
- 34Roy, B.; Fuierer, P. A. Influence of sodium chloride and dibasic sodium phosphate salt matrices on the anatase-rutile phase transformation and particle size of titanium dioxide powder. J. Am. Ceram, Soc. 2010, 93 (2), 436– 444, DOI: 10.1111/j.1551-2916.2009.03415.x34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhvFOhtrc%253D&md5=499ff023ec33946dee84ff41e5ee08ffInfluence of sodium chloride and dibasic sodium phosphate salt matrices on the anatase-rutile phase transformation and particle size of titanium dioxide powderRoy, Banasri; Fuierer, Paul AntonJournal of the American Ceramic Society (2010), 93 (2), 436-444CODEN: JACTAW; ISSN:0002-7820. (Wiley-Blackwell)The effects of sodium chloride (NaCl) and dibasic sodium phosphate (Na2HPO4·2H2O, DSP) on the phase transformation and particle size of titania powder were examd. The salt matrix was shown to suppress both the amorphous to anatase transition and the anatase to rutile transition. DSP was particularly effective. Irresp. of the additives, transformation vs. time curves of the anatase to rutile conversion were obsd. to be sigmoidal, and were interpreted in terms of a first order, nucleation-growth controlled phenomenon. Anal. of these curves using appropriate rate laws yielded activation energies for nucleation of ∼4.3 eV for NaCl salt matrix and ∼8.6 eV for DSP salt matrix, compared with ∼3.2 eV for a sample with no salt. Activation energies for the growth or propagation stage were ∼5 and ∼8.9 eV for NaCl and DSP powders, resp., compared with ∼3.8 eV for no salt. In the solid state, salt matrixes suppressed the particle growth as well. These behaviors, in general are thought to be governed by the presence of salt impurities, esp. anions chemisorbed at the surface.
- 35Gesenhues, U. Calcination of metatitanic acid to titanium dioxide white pigments. Chem. Eng. Technol. 2001, 24 (7), 685– 694, DOI: 10.1002/1521-4125(200107)24:7<685::AID-CEAT685>3.0.CO;2-135https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXlvFCktb4%253D&md5=d020838139d28c835d91b98817ac106dCalcination of metatitanic acid to titanium dioxide white pigmentsGesenhues, UlrichChemical Engineering & Technology (2001), 24 (7), 685-694CODEN: CETEER; ISSN:0930-7516. (Wiley-VCH Verlag GmbH)A review, with refs. In the sulfate process for the prodn. of TiO2 white pigments, gel-like metatitanic acid is calcined in a rotary kiln to microcrystals of the rutile polymorph. This process is monitored by the addn. of alkali ions, Al3-, phosphate and rutile nuclei. During the last decade, a scientific understanding has developed how these additives influence the solid-state reactions of the material in the kiln, i.e., crystal growth, transformation of anatase to rutile, incorporation of dopants and aggregation of crystals. This review describes mechanisms and kinetics of the reactions, using modern concepts of solid state and surface chem. and physics. It also describes the effects of the reactions on the quality of the calciner product for upgrading, e.g., the grindability to pigment particles, their light-scattering properties and photocatalytic activity.
- 36Li, Y.; Yang, Y.; Guo, M.; Zhang, M. Influence of acid type and concentration on the synthesis of nanostructured titanium dioxide photocatalysts from titanium-bearing electric arc furnace molten slag. RSC Adv. 2015, 5 (18), 13478– 13487, DOI: 10.1039/C4RA13942A36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXos1Whtg%253D%253D&md5=8d65cf02b3bfe64611428a844fc3031cInfluence of acid type and concentration on the synthesis of nanostructured titanium dioxide photocatalysts from titanium-bearing electric arc furnace molten slagLi, Yang; Yang, Yang; Guo, Min; Zhang, MeiRSC Advances (2015), 5 (18), 13478-13487CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)In this paper, nanostructured titanium dioxide (TiO2) photocatalysts with different crystal structures and morphologies were successfully synthesized from titanium-bearing elec. arc furnace molten slag (Ti-bearing EAF slag). The effects of different kinds of acid and acid concns. during the acidolysis process on the crystal structures and morphologies of TiO2 were systematically studied. The TiO2 crystal phase transformation mechanism and morphol. evolution in different acid systems and concns. were discussed in detail. In addn., the photocatalytic properties of TiO2 obtained in different acid systems were investigated. It is shown that rutile and anatase type TiO2 were obtained in hydrochloric acid and sulfuric acid, resp., while two types coexisted in nitric acid. With increasing sulfuric acid concn., anatase would be apt to change to rutile. The growth mechanism of TiO2 from Ti-bearing EAF slag was also discussed. The TiO2 synthesized from sulfuric acid showed better photocatalytic activity than that from hydrochloric or nitric acid, and its photodegrdn. efficiency can reach 90.52% in 90 min for rhodamine B solns.
- 37Arbiol, J.; Cerda, J.; Dezanneau, G.; Cirera, A.; Peiro, F.; Cornet, A.; Morante, J. R. Effects of Nb doping on the TiO2 anatase-to-rutile phase transition. J. Appl. Phys. 2002, 92 (2), 853– 861, DOI: 10.1063/1.148791537https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XkvFyjsro%253D&md5=374ceeacd074f18e37cfff48a4422d46Effects of Nb doping on the TiO2 anatase-to-rutile phase transitionArbiol, J.; Cerda, J.; Dezanneau, G.; Cirera, A.; Peiro, F.; Cornet, A.; Morante, J. R.Journal of Applied Physics (2002), 92 (2), 853-861CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The authors study the influence of Nb doping on the TiO2 anatase-to-rutile phase transition, using combined TEM, Raman spectroscopy, x-ray diffraction and selected area electron diffraction anal. This approach enabled anatase-to-rutile phase transition hindering to be clearly obsd. for low Nb-doped TiO2 samples. Also, there was clear grain growth inhibition in the samples contg. Nb. The use of high resoln. TEM with the authors' samples provides an innovative perspective compared with previous research on this issue. The authors' anal. shows that Nb is segregated from the anatase structure before and during the phase transformation, giving NbO nanoclusters on the surface of the TiO2 rutile nanoparticles.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.iecr.2c00463.
Figure for hydrolysis experimental arrangement; table of seed preparation for Raman and X-ray analysis of seed; method and figure for UV/vis spectra (PDF)
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