Electrochemical reduction of Cr (VI) using a palladium/graphene modified stainless steel electrode

Abstract

In this study, a palladium/graphene modified stainless steel electrode was successfully prepared and applied in an electrochemical reduction device to remove Cr (VI) from the wastewater. Pd was modified onto the electrode mainly via interacting with the carboxyl group of graphene. The Cr (VI) removal efficiency was up to 99.70 ± 0.00% under the optimal condition (Pd content proportion of 3%, electrode potential of −0.9 V, pH = 2 and electrolyte concentration of 6 g/L). It was found that Cr (VI) was removed via the following processes: (1) direct electrochemical reduction by accepting electrons, (2) indirect electrochemical reduction by H2O2 that was generated from H2 in the presence of Pd, (3) adsorption through hydrogen bond, and (4) chemical reduction through alkoxy groups donating electrons. The indirect electrochemical reduction considerably promoted the Cr (VI) removal while a small amount of Cr (VI) was removed via adsorption and chemical reduction. The method could not only be used as a pretreatment technology to solve the problem of excessive Cr (VI) concentration of industrial wastewater, but also could provide reference for the electrochemical reduction of similar metal ions. HIGHLIGHTS Pd/G-SS electrode was prepared for the electrochemical reduction of Cr (VI).; The Cr (VI) removal efficiency was up to 99.70% under the optimal condition.; Cr (VI) was removed via electrochemical reduction, adsorption and chemical reduction.; Cr (VI) removal was enhanced via indirect electrochemical reduction assisted by Pd.;

Keywords

• electrochemical reduction
• fourier transform infrared radiation
• graphene
• hexavalent chromium
• palladium
• stainless steel electrode