A comparison of the effectiveness of electrocoagulation to coagulation processes using ferric chloride for the removal of cadmium from aqueous solution

Cadmium removal from industrial wastewater due to its stability and accumulation properties is essential before discharge to the environment or a sewage collection network. The aim of this study was the comparison of the effectiveness of the removal of cadmium from industrial wastewater by electrocoagulation process, to a coagulation process. The effect of variables such as pH, concentration of ferric chloride coagulant and sedimentation time in a coagulation process and variables such as pH, retention time, voltage and distance of the electrodes in the electrocoagulation process by iron electrodes in the removal of cadmium were examined. All experiments were repeated three times. Optimal conditions were tested on real samples. The efficiency of each process was analyzed by using analysis of variance and regression. A cadmium removal efficiency 31.3% was obtained in the coagulation process in optimal conditions of pH 7, coagulant concentration 9 g/L and sedimentation time of 50 min. Alternatively, the cadmium removal efficiency of 99.12% was obtained in the electrocoagulation process in optimal conditions of pH 9, voltage difference 36 V and electrode distance 1.5 cm. In the real sample and optimal conditions, the cadmium removal for coagulation and electrocoagulation obtained was 21.72% and 88.2%, respectively. There was a significant difference between the two tested processes. By increasing pH, voltage and retention time, the electrocoagulation process had more efficiency in cadmium removal. Also, in the coagulation process increasing the coagulant concentration and the retention time in neutral pH showed less efficiency than the electrocoagulation process.