Treatment of Industrial Electroplating Wastewater by Electrochemical Coagulation Using Carbon and Aluminum Electrodes

Abstract

Electroplating wastewater is considered one of the most hazardous liquid wastes due to the presence of high contraction of toxic metals. Consequently, treatment of such wastewater is essential to protect the environment and waterways. Heavy metal ions are frequently of high toxicity and require treatment to the allowable standards for wastewater discharge. Electrochemical methods are more suitable for heavy metals removal due to their ability to reduce metal concentration to less than the permissible limits as well as allowing recovery of valuable metals. The aim of the present study is treatment of real electroplating wastewater. For this purpose, synthetic as well as real electroplating wastewaters were examined using soluble aluminium electrodes and insoluble carbon electrode along with ferric chloride and / or alum as coagulants. Factors affecting this treatment process were studied extensively, namely: current intensity, material of the electrode, pH and time. The obtained results proved that the best removal was achieved at 30 minutes and a potential difference 15 volt for aluminum electrode and 10 volts for carbon electrode. The later was combined with ferric chloride as coagulant. When the synthetic solution was examined by using aluminum electrode, the removal rate reached 97.2%, 97% and 96% for Zn, Cu, and Ni, respectively. By using carbon electrode in combination with ferric chloride, the respective removal rate reached 97.5%, 97.2% and 97.1%. By using the real electroplating wastewater and aluminum electrode, the removal rate reached 80%, 76.6% and 93.4% for Zn, Cu, and Ni respectively and by using carbon electrode and ferric chloride the achieved removal rate was 81.6%, 77.3% and 94.4% successively. It was concluded that the use of carbon electrode with FeCl3 is more suitable than aluminum electrode due to the dissolution of aluminum ions from electrode into the solution.