As(V) removal from aqueous media using α-MnO2 nanorods-impregnated laterite composite adsorbents

Abstract We present a novel way of enhancing the utility of low cost readily available laterite by impregnating it with the α-MnO 2 nanorods, thus making a composite material suitable for the removal of As(V) from aqueous media. The composites were synthesized by two methods: (i) ball-milling of a physical blend of laterite with pre-synthesized MnO 2 ; and (ii) in situ formation of MnO 2 in the presence of laterite. The BET surface area of composites prepared by both methods was markedly higher compared to un-modified laterite, and the presence of MnO 2 in the composite was also confirmed by XRD analysis and TEM microscopy. The adsorption capacity for As(V) was found to be highly pH dependent and the adsorption kinetics followed a pseudo second-order kinetic model. The Langmuir adsorption isotherm was found to be the best model to describe the adsorption equilibrium of As(V) onto un-modified laterite as well both ball-milled and in situ formed composite. The adsorption capacities at room temperature and pH 7.0 were found to be 1.50 mg g −1 , 8.93 mg g −1 and 9.70 mg g −1 , for un-modified laterite, ball-milled and in situ formed composite, respectively.