The vanadate adsorption on a mesoporous boehmite and its cleaner production application of chromate

Abstract

A mesoporous boehmite (γ-AlOOH) synthesis and vanadate (V(V)) ion adsorption and desorption on the mesoporous γ-AlOOH were investigated. The synthesis and adsorption studies showed that the mesoporous γ-AlOOH with a BET surface of 442 m² g⁻¹ and a pore size of 2.75 nm possessed a maximum V(V) ion adsorption capacity of 3.28 mmol g⁻¹. The adsorption mechanism results showed that the mesoporous γ-AlOOH liberated surface hydroxyls to form coordinatively unsaturated Al^VI centres to adsorb V(V) ions which connected oxygen of the coordinatively unsaturated Al^VI centres with mono-oxo, VO terminal double bonds. The desorption studies showed that the V(V) ions could be desorbed by NH₃·H₂O easily. In the cleaner production application of chromate, the mesoporous γ-AlOOH was synthesized in the Na₂CrO₄–NaAlO₂–NaVO₃–H₂O solutions of the chromate production and then in situ adsorbed the V(V) ions. The results showed that the V(V) ions were removed effectively, so that the highly carcinogenic CaCrO₄ containing Ca(VO₃)₂ residue which was obtained by the typical process of chromate production was eliminated. Therefore, green separation of V(V) ions to reduce waste pollution ensuring economy and feasibility could be expected.