Nanoscale zerovalent iron decorated on graphene nanosheets for Cr(VI) removal from aqueous solution: Surface corrosion retard induced the enhanced performance

Chemical reduction technology based on nanoscale zerovalent iron (NZVI) is an effective method for in-situ remediation of Cr(VI)-polluted water. However, it is difficult to overcome the associated surface passivation during the reaction process, thus losing the reduction reactivity. In this study, a novel system based on the NZVI/graphene nanosheets (NZVI/GNS) is constructed for the effective removal of Cr(VI) in water. Immobilization of NZVI onto graphene improves the stability of the NZVI, while graphene coupling facilitates the electron transfer in the NZVI and retards the surface passivation of the NZVI, thus enhancing the performance of the NZVI toward Cr(VI) removal. The NZVI/GNS exhibits significantly higher activity toward Cr(VI) removal than that of bare NZVI. The Cr(VI) removal efficiency is closely correlated to the graphene amounts in the NZVI/GNS. Based on X-ray photoelectron spectroscopy (XPS) and steady-state polarization measurements, the mechanism of Cr(VI) reduction reaction with the NZVI/GNS has been unraveled as well.