Removal of nickel, copper, zinc and chromium from synthetic and industrial wastewater by electrocoagulation

In this work, the performance of electrocoagulation with aluminum electrodes for simultaneous removal of nickel, copper, zinc and chromium from synthetic aqueous aliquot solutions and actual electroplating wastewater was studied. Parameters affecting the electrocoagulation process, such as initial pH, current density, initial metal ion concentration, COD and contact time were investigated. Best removal capacity for all studied metals was achieved in the pH range 4–8. Mixed solutions containing the same concentrations of all metals i.e. 75, 150 and 300 mg/L were tested. Nickel, copper and zinc showed similar removal rates. They were completely removed in 20, 40 and 50 minutes respectively, while for the corresponding complete removal of chromium 40, 60 and 80 minutes were needed. Increased current density accelerated the electrocoagulation process, however, on cost of higher energy consumption. Results revealed that best removal was achieved at a current density of 40 mA/cm²• The electrocoagulation process was successfully applied to the treatment of an electroplating wastewater sample, where the concentrations of nickel, copper, zinc, chromium and COD were effectively reduced under the admissible limits in 60 minutes. Consequently, the electrocoagulation process is a reliable, safe and cost-effective method for removing heavy metals and COD from water and wastewater.