Reduction and sorption of chromium by Fe(II)-bearing phyllosilicates; chemical treatments and X-ray absorption spectroscopy (XAS) studies

The reduction of hexavalent chromium species in aqueous solutions by interaction with Fe(II)-bearing solid surfaces was studied using a 0.96 × l0-3 M Cr(VI) solution and iron-rich clays with different Fe(II)/Fe(III) ratios, layer charge, and exchange properties, #ITi.e.#ME, chlorite, corrensite, and...

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Bibliographic Details
Published in:Clays and clay minerals 2000-04, Vol.48 (2), p.272-281
Main Authors: Brigatti, Maria Franca, Lugli, Cristina, Cibin, Giannantonio, Marcelli, Augusto, Giuli, Gabriele, Paris, Eleonora, Mottana, Annibale, Wu, Ziyu
Format: Article
Language:English
Subjects:
absorption
aqueous solutions
chemical composition
chemical fractionation
chlorite
chlorite group
chromium
clay minerals
corrensite
crystal chemistry
crystal structure
Earth sciences
Earth, ocean, space
electrochemical properties
Exact sciences and technology
geochemistry
iron
lattice
lattice parameters
metals
Mineralogy
mixed-layer minerals
montmorillonite
reduction
sheet silicates
Silicates
sorption
X-ray data
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Summary:The reduction of hexavalent chromium species in aqueous solutions by interaction with Fe(II)-bearing solid surfaces was studied using a 0.96 × l0-3 M Cr(VI) solution and iron-rich clays with different Fe(II)/Fe(III) ratios, layer charge, and exchange properties, #ITi.e.#ME, chlorite, corrensite, and montmorillonite. Experimental studies demonstrated that Fe(II)-bearing phyllosilicates reduce aqueous Cr(VI) ions at acidic pH. Chlorite and corrensite, owing to the high Fe(II)/Fe(III) ratio, are electrochemically reactive, as rapid Cr(VI) reduction indicated. In contrast, montmorillonite showed minimum to nil reactivity towards Cr(VI). Furthermore, corrensite, which is high in both Fe(II)/Fe(III) ratio and exchange capacity, adsorbs the greatest amount of chromium. X-ray absorption spectroscopy at Al, Mg, Fe, and Cr K-edges was used to investigate the adsorbed chromium species. The montmorillonite sample, unaffected by treatment with Cr(VI) solution, displays no change at any investigated edge. Edge shape and energy also do not change for the Mg and Al spectra in corrensite, and changes are minor in chlorite. By contrast, the Fe K-edge changes both in chlorite and corrensite, and indicates an increase of Fe(III) in treated samples at the expense of pre-existing Fe(II). Cr K-edge spectra show that chlorite and corrensite sorb Cr(III), which implies its reduction from Cr(VI) in the interacting solution.
ISSN:0009-8604
1552-8367
DOI:10.1346/ccmn.2000.0480214