Inorganic nanoparticles for reduction of hexavalent chromium: Physicochemical aspects

[Display omitted] •Inorganic nanoparticles are widely used for reduction of Cr(VI) to Cr(III).•Role of nanoparticles in reduction of Cr(VI) depends upon nature of inorganic nanomaterial.•Synthesis, characterization and stabilization of nanoparticles used in Cr(VI) reduction is described.•Reduction of Cr(VI) by different reductants in the presence of inorganic nanocatalysts is discussed.•Mechanism and factors affecting the rate of catalytic reduction of Cr(VI) have been discussed. Hexavalent Chromium [Cr(VI)] is a highly carcinogenic and toxic material. It is one of the major environmental contaminants in aquatic system. Its removal from aqueous medium is a subject of current research. Various technologies like adsorption, membrane filtration, solvent extraction, coagulation, biological treatment, ion exchange and chemical reduction for removal of Cr(VI) from waste water have been developed. But chemical reduction of Cr(VI) to Cr(III) has attracted a lot of interest in the past few years because, the reduction product [Cr(III)] is one of the essential nutrients for organisms. Various nanoparticles based systems have been designed for conversion of Cr(VI) into Cr(III) which have not been critically reviewed in literature. This review present recent research progress of classification, designing and characterization of various inorganic nanoparticles reported as catalysts/reductants for rapid conversion of Cr(VI) into Cr(III) in aqueous medium. Kinetics and mechanism of nanoparticles enhanced/catalyzed reduction of Cr(VI) and factors affecting the reduction process have been discussed critically. Personal future insights have been also predicted for further development in this area.