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

We present a novel way of enhancing the utility of low cost readily available laterite by impregnating it with the α-MnO2 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 MnO2; and (ii) in situ formation of MnO2 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 MnO2 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.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Enhance utility of laterite adsorbent by incorporating nano α-MnO2 properties. ► Ball-milling and in situ approaches were used to obtain hybrid composites. ► Hybrid composites are potential candidates for As(V) adsorption. ► Such composites accelerate solid/liquid separation after As(V) treatment.