Electrochemical Fe(III) mediation for reducing hexavalent chromium Cr(VI) on templated copper-nickel foam electrode

Abstract

Hexavalent chromium (Cr(VI)) is highly toxic and migratory, rapidly transported between water bodies. This study synthesized a Cu/Ni electrode which the polyhedral copper crystallites were electroplated on the nickel foam for direct and indirect reduction of Cr(VI). The micromorphology of Cu/Ni in respect to the grain size and crystal facets Cu(200) and Cu(111) was manipulated by the cationic surfactant in specific critical micelle concentrations (CMC). Behaviors of electron transfer between the soluble Cr(VI) and Fe(III) on Cu/Ni as affected by the facet ratio (FCu(200)) were analyzed. Voltammetry showed that the preference of Cu(111) system aided the cathode in the transfer coefficient of Fe(III)/Fe(II) couple. Under electrochemical conditions: current density = 5 mA cm−2, FeCl3 = 3 mM, pH 3.0, Cr(VI) removal and yield of soluble Cr(III) attained 99% and 90%, respectively. Cu(111) exposed on the electrode which catalytically generated the surface-adsorbed Fe2+ was positively correlated to the rate constant of indirectly reducing Cr(VI).