Polarized EXAFS of biotite and chlorite

Manceau, Alain; Bonnin, D.; Kaiser, P.; Frétigny, Christian

doi:10.1007/bf00203202

Cited by 58 publications

(20 citation statements)

References 13 publications

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“…Heteroepitaxy per se can be demonstrated by polarized EX-AFS experiments on single crystal or on highly textured selfsupporting films of fine grained layered minerals (28,91). The angular dependence of the metal sorbate-metal sorbent pair contribution is given by…”

Section: Differentiating Homogeneous From Heterogeneous Precipitationmentioning

confidence: 99%

Evidence for the Formation of Trioctahedral Clay upon Sorption of Co2+ on Quartz

Manceau

Schlegel

Nagy

et al. 1999

Journal of Colloid and Interface Science

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Section: Differentiating Homogeneous From Heterogeneous Precipitationmentioning

confidence: 99%

Evidence for the Formation of Trioctahedral Clay upon Sorption of Co2+ on Quartz

Manceau

Schlegel

Nagy

et al. 1999

Journal of Colloid and Interface Science

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“…P-EXAFS measurements were carried out on self-supporting films (SSF) prepared from the Ͻ0.2 m fraction at incident angles between the electric field vector and the film plane of ␣ ϭ 10°, 35°and 80° (Manceau et al, 1998). Powder EXAFS measurements were performed on pressed pellets from the Ͻ50 m soil fraction at the magic angle (␣ ϭ 35°, Manceau et al, 1988).…”

Section: Exafs Spectroscopymentioning

confidence: 99%

Zinc mobility and speciation in soil covered by contaminated dredged sediment using micrometer-scale and bulk-averaging X-ray fluorescence, absorption and diffraction techniques

Isaure

Manceau

Geoffroy

et al. 2005

Geochimica et Cosmochimica Acta

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The mobility and solid-state speciation of zinc in a pseudogley soil (pH ϭ 8.2-8.3) before and after contamination by land-disposition of a dredged sediment ([Zn] ϭ 6600 mg kg Ϫ1 ) affected by smelter operations were studied in a 50 m 2 pilot-scale test site and the laboratory using state-of-the-art synchrotronbased techniques. Sediment disposition on land caused the migration of micrometer-sized, smelter-related, sphalerite (ZnS) and franklinite (ZnFe 2 O 4 ) grains and dissolved Zn from the sediment downwards to a soil depth of 20 cm over a period of 18 months. Gravitational movement of fine-grained metal contaminants probably occurred continuously, while peaks of Zn leaching were observed in the summer when the oxidative dissolution of ZnS was favored by non-flooding conditions. The Zn concentration in the Ͻ50 m soil fraction increased from ϳ61 ppm to ϳ94 ppm in the first 12 months at 0 -10 cm depth, and to ϳ269 ppm in the first 15 months following the sediment deposition. Higher Zn concentrations and enrichments were observed in the fine (Ͻ2 m) and very fine (Ͻ0.2 m) fractions after 15 months (480 mg kg Ϫ1 and 1000 mg kg Ϫ1 , respectively), compared to 200 mg kg Ϫ1 in the Ͻ2 m fraction of the initial soil. In total, 1.2% of the Zn initially present in the sediment was released to the environment after 15 months, representing an integrated quantity of ϳ4 kg Zn over an area of 50 m 2 . Microfocused X-ray fluorescence (XRF), diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy techniques were used to image chemical associations of Zn with Fe and Mn, and to identify mineral and Zn species in selected points-of-interest in the uncontaminated and contaminated soil. Bulk average powder EXAFS spectroscopy was used to quantify the proportion of each Zn species in the soil. In the uncontaminated soil, Zn is largely speciated as Zn-containing phyllosilicate, and to a minor extent as zincochromite (ZnCr 2 O 4 ), IV Zn-sorbed turbostratic birnessite (␦-MnO 2 ), and Zn-substituted goethite. In the upper 0 -10 cm of the contaminated soil, ϳ60 Ϯ 10% of total Zn is present as ZnS inherited from the overlying sediment. Poorly-crystalline Zn-sorbed Fe (oxyhydr)oxides and zinciferous phyllosilicate amount to ϳ20 -30 Ϯ 10% each and, therefore, make up most of the remaining Zn. Smaller amounts of franklinite (ZnFe 2 O 4 ), Zn-birnessite and Zn-goethite were also detected. Further solubilization of the Zn inventory in the sediment, and also remobilization of Zn from the poorly-crystalline neoformed Fe (oxyhydr)oxide precipitates, are expected over time. This study shows that land deposition of contaminated dredged sediments is a source of Zn for the covered soil and, consequently, presents environmental hazards. Remediation technologies should be devised to either sequester Zn into sparingly soluble crystalline phases, or remove Zn by collecting leachates beneath the sediment.

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“…Different Fe-0 bondlengths in layered silicates, (depending on the oxidation state of the Fe) have been demonstrated previously (54). To investigate this possibility, the filtered data o were fit with 2 Fe-0 subshells, one with the Fe-0 bondlength constrained to equal 2.00 A (to represent the average local environment of Fe(III)) and the other with the Fe-0 bondlength constrained to equal 2.10 Â (to represent the average local environment of Fe(II)).…”

Section: Effect Of Fe Reduction On Clay Structure: Exafsmentioning

confidence: 85%

Degradation of Tetraphenylboron at Hydrated Smectite Surfaces Studied by Time Resolved IR and X-ray Absorption Spectroscopies

Hunter

Gates

Bertsch

et al. 1999

ACS Symposium Series

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The surface catalyzed redox reactivity of an organoboron probe molecule (tetraphenylboron, or TPB) with fully hydrated clay mineral surfaces is described wherein one or both of two degradation pathways can occur. Attenuated total reflectance Fourier transform infrared (ATR-IR) spectroscopy can quantitatively measure, in situ, both acid hydrolytic and oxidative degradation of TPB as controlled by the exchange cation identity and the structural octahedral Fe content of the clay mineral. Oxidation of TPB at smectite surfaces is directly attributable to octahedral Fe(III) in the clay structure.The concomitant reduction of Fe(III) during TPB oxidation can be analytically measured by X-ray absorption near edge structure (XANES) spectroscopy. The resultant distortion of the clay mineral structure during the reduction of structural Fe could be probed directly by extended X-ray absorption fine structure (EXAFS) spectroscopy. The lack of evidence for clay mineral dissolution during the reaction with TPB permits defining the clay as a catalyst. The combination of these three in situ spectroscopic techniques to measure the reaction in real time, provides powerful insight into the reactivity of clay mineral surfaces.

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Polarized EXAFS of biotite and chlorite

Cited by 58 publications

References 13 publications

Evidence for the Formation of Trioctahedral Clay upon Sorption of Co2+ on Quartz

Evidence for the Formation of Trioctahedral Clay upon Sorption of Co2+ on Quartz

Zinc mobility and speciation in soil covered by contaminated dredged sediment using micrometer-scale and bulk-averaging X-ray fluorescence, absorption and diffraction techniques

Degradation of Tetraphenylboron at Hydrated Smectite Surfaces Studied by Time Resolved IR and X-ray Absorption Spectroscopies

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