Iron Substitution in Soil and Synthetic Anatase

Schwertmann, U.

doi:10.1346/ccmn.1995.0430509

Cited by 26 publications

(19 citation statements)

References 16 publications

(8 reference statements)

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“…Iron was found to replace up to 10 mole % of the titanium in the anatase structure, which resulted in a positive correlation between the extent of iron substitution and the anatase unit cell a parameter. When 10 mole % of the titanium was replaced by iron, the anatase unit cell dimensions increased by 0.7 % (Schwertmann et al, 1995). This is consistent with the shift in anatase peaks observed in these leached residues.…”

Section: Mineralogical Transformations During Leachingsupporting

confidence: 82%

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Leaching of brannerite in the ferric sulphate system. Part 2: Mineralogical transformations during leaching

2016

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractBrannerite, UTi 2 O 6 , is the most common refractory uranium mineral and is the most important uranium ore mineral after uraninite and coffinite. In order to develop an effective treatment method for the hydrometallurgical extraction of uranium from ores containing brannerite, it is necessary to understand the chemistry of the leaching process. Part 1 of this series described the results of a study of the chemical reaction mechanisms of brannerite under conditions similar to those used industrially. In this paper, the mineralogical data obtained from samples collected during the leaching work is used to derive further insight into the transformations that take place during leaching. Detailed characterisation of the brannerite feed specimen and leach residues were carried out using surface imaging and X-ray diffraction techniques. It was shown that the brannerite specimen is heterogeneous, consisting of at least two phases. The brannerite phase was metamict and showed signs of natural alteration to fine-grained (10-20 nm) crystalline anatase. Comparisons between the feed and residues showed that the X-ray amorphous material, in particular lead and silicon enriched areas identified near the anatase were most susceptible to leaching while the crystalline material was relatively resistant to leaching. These results demonstrate that the extent of brannerite alteration and its texture are important considerations to the hydrometallurgical behaviour of a particular ore along with the typical concerns such as grade, liberation size and gangue mineralogy.

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Section: Mineralogical Transformations During Leachingsupporting

confidence: 82%

“…These differences correspond to the dimensions of the unit cell being 0.7% larger than theoretical, consistent with iron substituted anatase (Schwertmann et al, 1995). A C C E P T E D M A N U S C R I P T…”

Section: Accepted Manuscriptsupporting

confidence: 72%

Leaching of brannerite in the ferric sulphate system. Part 2: Mineralogical transformations during leaching

2016

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“…The peak shifts and increased peak width can potentially be explained by variable degrees of crystallinity and by solid solution of Fe 3+ in the anatase structure. Although most natural anatase samples previously analyzed include only 1–3 wt% Fe 2 O 3 [ Liu and Mernagh , 1992], synthetic anatases have been precipitated containing up to Fe/(Ti+Fe) 0.1 mol/mol [ Schwertmann et al , 1995]. Substitution of other metals for titanium in natural rutiles has been documented to shift Raman peak positions [ Smith and Perseil , 1996].…”

Section: Resultsmentioning

confidence: 99%

Silica coatings in the Ka'u Desert, Hawaii, a Mars analog terrain: A micromorphological, spectral, chemical, and isotopic study

Chemtob¹,

Jolliff²,

Rossman³

et al. 2010

J. Geophys. Res.

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[1] High-silica materials have been observed on Mars, both from orbit by the CRISM spectrometer and in situ by the Spirit rover at Gusev Crater. These observations potentially imply a wet, geologically active Martian surface. To understand silica formation on Mars, it is useful to study analogous terrestrial silica deposits. We studied silica coatings that occur on the 1974 Kilauea flow in the Ka'u Desert, Hawaii. These coatings are typically composed of two layers: a ∼10 mm layer of amorphous silica, capped by a ∼1 mm layer of Fe-Ti oxide. The oxide coating is composed of ∼100 nm spherules, suggesting formation by chemical deposition. Raman spectroscopy indicates altered silica glass as the dominant phase in the silica coating and anatase and rutile as dominant phases in the Fe-Ti coating; jarosite also occurs within the coatings. Oxygen isotopic contents of the coatings were determined by secondary ion mass spectrometry (Cameca 7f and NanoSIMS). The measured values, d18 O Fe-Ti = 14.6 ± 2.1‰, and d 18 O silica = 12.1 ± 2.2‰ (relative to SMOW), are enriched in 18 O relative to the basalt substrate. The observations presented are consistent with a residual formation mechanism for the silica coating. Acid-sulfate solutions leached away divalent and trivalent cations, leaving a silicaenriched layer behind. Micrometer-scale dissolution and reprecipitation may have also occurred within the coatings. Chemical similarities between the Hawaiian samples and the high-silica deposits at Gusev suggest that the Martian deposits are the product of extended periods of similar acid-sulfate leaching.

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“…gration of Ti, it remains unclear if the Ti-bearing phases observed in this study are authigenic or allogenic constituents. Figure 4 shows a best-fit line through the observed a unit-cell lengths as a function of Fe substitution for four samples of natural anatase from Schwertmann et al (1995) to estimate Fe content for the anatase samples studied here. The resulting values of 0.020-0.045 tool mol ~ in the anatase is relatively small and Fe content appears lower than the soil-derived Fe-bearing anatase (Schwertmann et al, 1995).…”

Section: Discussionmentioning

confidence: 99%

“…Figure 4 shows a best-fit line through the observed a unit-cell lengths as a function of Fe substitution for four samples of natural anatase from Schwertmann et al (1995) to estimate Fe content for the anatase samples studied here. The resulting values of 0.020-0.045 tool mol ~ in the anatase is relatively small and Fe content appears lower than the soil-derived Fe-bearing anatase (Schwertmann et al, 1995). With the small size of the anatase (--0.1 Ixm), grains may be transported long distances and deposited without evidence of physical abrasion.…”

Section: Discussionmentioning

confidence: 99%

Ti-Bearing Phases in the Huber Formation, an East Georgia Kaolin Deposit

Schroeder

Shiflet

2000

Clays and clay miner.

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Abstract--Six kaolin samples from the Lower Tertiary Huber Formation near Wrens, Georgia were analyzed using transmission electron microscopy (TEM), electron diffraction (ED), powder X-ray diffraction (XRD), chemical analysis, and magnetic susceptibility to characterize the Ti-bearing phases. Selected samples were treated with 5 M NaOH to remove kaolinite and concentrate the Ti-bearing phases for additional analysis. TiO 2 content in the bulk fraction ranges from 1.2 to 5.4 wt. %. There are at least three Ti-bearing phases, including anatase, ruffle, and a poorly defined nanocrystalline form. Anatase is most abundant and is commonly found with {010} faces in association with kaolinite edge and basal faces. The nanocrystalline form occurs at 0-1 wt. %, and ruffle occurs in trace amounts. Bulk XRD analysis correlates well with the bulk TiO2 chemical measurements. Average anatase unit-cell parameters are a = 0.37908 -+ 0.0002 nm and c = 0.951 +_ 0.001 nm. These parameters indicate an approximate chemical formula of Fe3+0.05Ti4+0.95Oi.95(OH)0.05.The distribution of TiO2 content as a function of depth may be useful to obtain original grain-slze variations associated with relative sea-level changes responsible for the deposition of the Huber Formation. Evidence for original depositional sediment properties can be seen in the occurrence of pseudomorphic replacement of micas and fecal pellets by kaolinite. Additional evidence for post-depositional changes includes the sub-micrometer euhedral character and low Fe content of the anatase (relative to soil-derived anatase). These observations for the Hnber Formation are consistent with a previously published theory for kaolin genesis that includes biomineralization of originally coarser-grained aluminosilieates into a kaolinite-rich ore body.

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Iron Substitution in Soil and Synthetic Anatase

Cited by 26 publications

References 16 publications

Leaching of brannerite in the ferric sulphate system. Part 2: Mineralogical transformations during leaching

Leaching of brannerite in the ferric sulphate system. Part 2: Mineralogical transformations during leaching

Silica coatings in the Ka'u Desert, Hawaii, a Mars analog terrain: A micromorphological, spectral, chemical, and isotopic study

Ti-Bearing Phases in the Huber Formation, an East Georgia Kaolin Deposit

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