▎ 摘　　要

Green rust, a double layered (Fe-II, Fe-III) hydroxide, can impact the mobility and toxicity of highly reactive contaminants such as chromate through reduction of Cr-VI to Cr-III. The reduction of Cr-VI by sulfate and chloride green rusts (GRs) was comparatively studied for a range of initial Cr-VI concentrations and pH values. At an equal molar ratio of Cr-VI to Fe-II in GR, sulfate green rust (GRSO(4)) removed higher amounts of Cr-VI from solution than chloride green rust (GRC1). The rate of the reactions with respect to initial concentration of Cr-VI is well described by pseudo-second order model. The GRCI reacted with chromate much faster than GRSO(4). The obtained pseudo-second order rate coefficients for the GRC1 and GRSO(4) ranged from 99.53 to 14.24 and 35.45 to 4.53 mmol/s; respectively. Graphene-based green rust nanocomposites were prepared using partially reduced graphene (PRG) and examined for removal of Cr-VI. The efficiency of Cr-VI removal by GRSO(4)/PRG and GRCl/PRG nanocomposites was dependent on the mass ratio of PRG to total Fe precipitated as GR (PRG:Fe-(s)) and the highest removal was observed at PRG:Fe-(s) mass ratios of 1:2. In comparison with bare GRs, the GR/PRG nanocomposites removed higher amounts of Cr-VI from solution. However, the reduction rates of Cr-VI by GR/PRG nanocomposites were similar to 2 to 3-fold lower than those observed by bare GRs in both sulfate and chloride systems. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.