Efficient and selective removal of Se and As mixed contaminants from aqueous media by montmorillonite-nanoscale zero valent iron nanocomposite.

Nanoscale zero-valent iron (NZVI) and NZVI supported onto montmorillonite (NZVI-Mt) were synthetized and used in this study to remove Se and As from water in mono- and binary-adsorbate systems. The adsorption kinetics and isotherm data for Se and As were adequately described by the pseudo-second-order (PSO) (r>0.94) and Freundlich (r>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L As and Se concentration, the maximum adsorption capacity (q) and partition coefficient (PC) for As on NZVI-Mt in monocomponent system were 54.75 mg g and 0.065 mg g·μM, which dropped respectively to 49.91 mg g and 0.055 mg g·μM under competitive system. For Se adsorption on NZVI-Mt in monocomponent system, q and PC were 28.63 mg g and 0.024 mg g·μM, respectively. Values of q and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for As. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt.