Removal of heavy metals in plating wastewater by electrocoagulation process using cylindrical electrodes

Abstract

This study focuses on removing the metals: chromium, nickel, zinc and copper in high concentrations (particularly with chromium, whose concentration went up to 350 ppm) in plating wastewater by electrocoagulation (EC) method using direct current (DC). The wastewater was contained in a 2 L batch airlift reactor; pure oxygen 99.9 % was blown into the reactor to increase the treatment efficiency. Cylindrical iron electrodes were used in the cell. The results showed that pH, current density, and residence time were three major factors influencing the treatment effectiveness. Over 99.9 % of heavy metals were effectively removed when optimizing the operating conditions with the Response Surface Methodology (RSM) in the current density 8.79 mA/cm2, 30.01 minutes, at pH 4.95. Beside the consideration of the effectiveness of this method in different concentrations of plating wastewater Cyclic Voltammetry (CV) scan, and Tafel line were also used for measuring the existing ability of electrodes in the wastewater to study situations happening while operating the cell in the reality. With high efficiency, simple operation, no cost for chemical, and the power consumption of only 10 kWh/m3, this method can be used in treating plating wastewater in the reality.