A comparative analysis of Cr(VI) reduction with Cu2O, ZnO and Fe2O3 coatings grown by PEO

Coatings on copper, zinc and stainless-steel substrates were fabricated using the plasma electrolytic oxidation (PEO) technique and their photocatalytic activity was evaluated in the reduction of Cr(VI), a highly toxic agent present in wastewater from industrial processes such as electroplating, manufacture of textile dyes, wood curing, and leather tanning. The concentration of hexavalent chromium in drinking water has been regulated to a maximum value established by national and international legislation of 0.05 ppm. The strategy of reduction to less toxic species such as Cr(III), followed by its precipitation in a basic medium, use several methods derived from chemistry, physics and biology for the treatment of water contaminated with this material. In the present work, some coatings of copper, zinc, and iron oxides were obtained over the corresponding metal sheets exposed to PEO, which were tested in a heterogeneous process of advanced oxidation with 1 ppm Cr(VI) solution under ultraviolet radiation. Thus, a reduction rate to Cr(III) close to 100 % in 60 min was obtained.