Removal of antimonate ions and simultaneous formation of a brandholzite-like compound from magnesium-aluminum oxide

Magnesium-aluminum oxide (Mg-Al oxide), obtained by thermal decomposition of a Mg-Al layered double hydroxide (Mg-Al LDH), was found to remove Sb(OH)(6)(-) (Sb(V)) in solution because of rehydration, and to combine with Sb(V) to form a brandholzite-like structure. Although the Sb concentration decreased with increasing amounts of Mg-Al oxide, differences in the Mg/Al molar ratio had little effect on this relationship. The removal of Sb(V) in solution by Mg-Al oxide was partially prevented by coexistent anions with high charge densities (SO(4)(2-) and CO(3)(2-)). In this case, Mg-Al oxide likely rehydrates and competitively combines with Sb(V) in solution to construct a brandholzite-like structure or with anions to reconstruct the LDH structure. However, in the case of coexistent anions with low charge densities (Cl(-) and OH(-)), Mg-Al oxide likely rehydrates and preferentially combines with Sb(V) in solution to construct the brandholzite-like structure. A high concentration of Cl(-) and SO(4)(2-) had little effect on the decrease in sb concentration, whereas a high concentration of CO(3)(2-) had a large effect. (C) 2011 Elsevier B.V. All rights reserved.