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Removal of arsenate and antimonate by acid-treated Fe-rich clays
- Dousova, Barbora, Lhotka, Miloslav, Filip, Jan, Kolousek, David
- Journal of hazardous materials 2018 v.357 pp. 440-448
- adsorption, arsenates, bentonite, hydrochloric acid, iron, iron oxides, kaolin, leaching, models, oxalic acid, oxides, oxyanions, pH, sorbents
- Iron impurities in clays degrade the quality in many aspects, but available Fe oxides can significantly improve adsorption affinity of clays to anionic particles. Two natural Fe-rich clays (kaolin and bentonite) were treated in 0.5 M HCl (pH = 1.1) and 0.15 M (COOH)2 (pH = 1.2), and then used to adsorb AsV/SbV oxyanions from model solutions. After acid leaching, the equilibrium sorption capacities (qmax) increased from 2.3 × 10-3 to 39.2 × 10-3 mmol g-1 for AsV and from 2.4 × 10-3 to 40.1 × 10-3 mmol g-1 for SbV, more than doubling the adsorption yields (≈95%) of both oxyanions. Leaching in 0.5 M HCl enhanced both AsV and SbV adsorption, whereas leaching in 0.15 M (COOH)2 mainly improved the adsorption of SbV. Bentonite, which contained fewer crystalline forms of Fe, exhibited better sorption properties for both oxyanions. The leaching of Fe followed first-order kinetics, whereas the adsorption of AsV/SbV followed second-order kinetics. Acid leaching of Fe-rich clays can be used for the preparation of highly selective anionactive sorbents.