Electrochemical Reduction of Cr (VI) Using a Graphene-Modified Stainless Steel Electrode

Abstract

Electrochemical reduction using a metal-based electrode is a novel method for treatment of Cr (VI)-containing wastewater. However, the removal efficiency with a metal-based electrode is limited by the low conductivity and specific surface area. In this study, a stainless steel (SS) electrode modified with graphene was fabricated and used to reduce Cr (VI) in an electrochemical system. Under the optimal conditions (i.e., the graphene loading of 1.50 mg·cm−2, −0.7 V, pH 1.5 and the electrolyte concentration (Na2SO4) of 10 g·l−1), this composite electrode removed 99.7 ± 0.00% of Cr (VI) with an initial concentration of 10 mg·l−1 in 80 min Cr (VI) was removed by the following pathways: (1) under the additive electric field, Cr (VI) was mainly reduced into Cr (III) directly by accepting electrons, (2) Cr (VI) was reduced to Cr (III) by −OH of graphene, (3) −COOH on the surface of graphene underwent bonding with H+ thereby producing hydrogen bonding to adsorb Cr (VI). Meanwhile, COO− was produced via losing H+ to adsorb Cr (III).