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

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). (C) 2022 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.