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| - ATR-IR Spectroscopic Study of Antimonate Adsorption to Iron Oxide
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| - Antimonate ions adsorb to iron oxides in mining contexts, but the nature of the adsorbed antimonate species hasnot frequently been investigated. In this study, ATR-IR spectroscopy was used to reveal that the adsorption of Sb(OH)6-ion from aqueous solutions onto an amorphous iron oxide particle film is accompanied by changes in the Sb(OH)6-spectrum and the loss of OH stretching absorptions from iron oxide surface hydroxyl groups. These spectral changesupon adsorption imply an inner-sphere surface interaction with the formation of Sb−O−Fe bonds as well as someouter-sphere adsorption. The corresponding results from solutions of antimonate in D2O confirm that chemisorptionoccurs. The dependence of antimonate adsorption on pH in the range from 8 to 3 follows that expected for anionson iron oxide considering its pH-dependent surface charge, with the greatest amount of adsorbed antimonate at pH3. The study of adsorption/desorption kinetics showed a more rapid desorption of adsorbed antimonate under alkalineconditions. This trend is expected from the pH dependence of the antimonate charge and iron oxide surface charge,but it might be partly due to the fact that high pH favors hydrolysis of antimonate oligomers formed on the iron oxidesurface from adsorption under acidic conditions.
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