Detoxification of groundwater contaminated with Cr(VI) using continuous electrochemical cell equipped with copper foam electrode modified with palladium nanoparticles

This study investigated the detoxification of water contaminated with hexavalent chromium through a catalytic electrochemical reduction process using metallic foam cathodes. To select the proper materials to be used in a continuous electrochemical cell, batch experiments were performed on copper and nickel metallic foams, as potential cathodes, in the presence and absence of a coating layer of either palladium or silver nanoparticles, as potential catalysts. Regarding the results, copper foam and copper foam coated with palladium nanoparticles (PdNPs) were chosen. Next, the effects of parameters including pH, flow rate, electrical current intensity, and the initial concentration of hexavalent chromium were studied utilizing the continuous column of copper foam before and after adding PdNPs. The response surface methodology and the Box-Behnken Design approach were applied to optimize the significant parameters. Results indicated that the palladium nanocatalyst has significant effects on reduction efficiency. Through further experiments, we also found that the presence of nitrate and other coexisting ions has negligible impact on reduction efficiency. The optimum charts of chromium reduction were plotted based on the results. A sample optimum point gives a 97.8% reduction efficiency at pH=7, flow rate=50 mL min(-1), initial concentration=0.45 mg L-1, and electric current of 0.3 A.