Hexavalent chromium removal by monopolar electrodes based electrocoagulation system: optimization through Box–Behnken design

The aim of the present study was to investigate the performance of the graphite and aluminum electrode in monopolar arrangement to assess chromium removal efficiency. The aluminum anode has been used for generation of metal coagulants species, while the cathode material was replaced with monopolar graphite cathode to accomplish a major challenge, i.e., reduce energy consumption and cost of treatment. Moreover, the process has been optimized through the Box–Behnken design application under response surface methodology by selecting process variables such as current density, pH, process time and a distance between electrodes. The optimized process variables found to be responsible for maximum removal are current density of 2.38 mA/cm², pH of 7.29, process time 23 min, and electrode distance 3.5 cm. It has been found that the power consumed under the optimized condition was low for graphite cathode monopolar arrangement (0.194 kWh/m³) in comparison to aluminum cathode (0.425 kWh/m³) for approximate removal of the hexavalent chromium under similar optimized process variables as applied voltage reduced in the case of graphite cathode due to structural properties and hydrogen adsorption capacity of graphite cathode.