Removal of arsenate and arsenite from aqueous solution by adsorption on clay minerals

Abstract

Sorption of arsenic species [As(V) and As(III)] on different clay minerals including kaolinite (KGa-1), montmorillonite (SWy-1), and nontronites (NAU-1 and NAU-2) with respect to sorption kinetics, isotherms and pH was investigated. As(V) and As(III) sorption on clay minerals was significantly influenced by pH. Higher sorption of As(V) was observed at low pH that decreased above pH 5.0, while As(III) sorption was maximum around pH 7.0. The sorption kinetics was well described by the pseudo-second-order equation for both As(V) and As(III). Among the tested clay minerals, NAU-2 was most effective for the removal of arsenic with rate constants of 0.084 and 0.056 g mg(-1) min(-1) for As(V) and As(III), respectively. A good correlation was observed between adsorbing capacity (qe) and equilibrium mass concentration (C-e) using the isothermal Freundlich adsorption model for SWy-1, NAU-1, and NAU-2 minerals as indicated by the high values of R-2 coefficient. Our results indicate that clay minerals can serve as effective sorbents for the removal of As from contaminated water streams.