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Nanoscale zero-valent iron (nZVI) assembled on graphene oxide (GO) (rGO-nZVI) composites were synthesized by reduction of GO and ferrous ions with potassium borohydride,for use in Cr(Ⅵ) removal from aqueous solution.The results showed that the two-dimensional structure of GO could provide a skeleton support for Fe0,thus overcoming the bottleneck of aggregation for nZVI.Also,rGO-nZVI would form a ferric-carbon micro-electrolysis system in Cr(Ⅵ)-contaminated aquifers,enhancing and accelerating electron transfer,exhibiting high rate and capacity for Cr(Ⅵ) removal.The optimum dosage of the applied rGO-nZVI was linearly correlated with the initial CR(Ⅵ) concentration.Characterization of rGO-nZVI before and after reaction with Cr(Ⅵ) revealed the process of Cr(Ⅵ) removal:rGO-nZVI firstly transferred electrons from Fe° cores via their Fe(Ⅱ)/Fe(Ⅲ) shells to the GO sheet;there,negatively charged Cr(Ⅵ) received electrons and changed into positively charged Cr(Ⅲ),which was adsorbed by the negatively charged GO sheet,avoiding the capping and passivating of nZVI.rGO-nZVI formed a good electrically conductive network,and thus had long-term electron releasing properties,which was important for groundwater remediation.