Treatment of industrial electroplating wastewater for metals removal via electrocoagulation continous flow reactors

Abstract

Abstract A real industrial electroplating rinsing wastewater was collected and subjected to physical and chemical examination. The study showed that it can be categorized as high strength wastewater, at pH- 2, COD 1430 mg/l, and high level of metals above permissible limits, namely: 150, 30, 25, and 2.9 for Ni, Cu, Zn, and Fe mg/l respectively. Therefore, metals must be adequately removed before discharging to avoid any hazardous impact on the environment. Similar synthetic wastewater was prepared to study the effect of chemical coagulation for the precipitation of metals. The optimum removal rate was achieved by using a combination of lime and ferric chloride at 100 and 30 mg/l respectively. The chemically treated electroplating wastewater was subjected to an electrocoagulation study. A comparison between iron and stainless-steel electrodes for the removal of metals was investigated. Furthermore, the effect of different electric voltages, and contact time on metals removal efficiency were also examined. It was found that the optimum removal capacity was achieved when a stainless steel electrode was employed in the presence of ferric chloride as coagulant, at 10 volts, 30 min. contact time, and pH 9 for synthetic solution. In a batch treatment system, the real industrial wastewater was treated at the predetermined optimum operating conditions; the removal of metals was 92.1%, 87.8% and 82.9% for Ni. Zn, and Cu respectively. By employing a continuous flow reactor for the treatment of the same real wastewater and under the same operating conditions, metals removal rate increased to 98.9%, 97.4% and 96.6% for Ni. Zn, and Cu respectively. The level of metals in the final treated wastewater copes with Egyptian Environmental Regulation. The overall results confirmed that the electro-coagulation (EC) technology offers an effective alternative process in combination with the conventional chemical coagulation process for reaching high removal performance of toxic metals from the electroplating wastewater. The advantage of EC technique is achieving high treatment efficiency instead of expensive chemical reagents, high construction cost and/or other conventional processes. In addition, the final treated water can be reused for rinsing process in the electroplating industry and/or discharging without any environmental hazard effect. It is also recommended to employ solar energy instead of electricity to reduce cost of operation.