Treatment of Wastewater Containing Nickel by Electrocoagulation Process Using Photovoltaic Energy

To avoid deficiencies of traditional electrocoagulation process, electrocoagulation process powered by renewable photovoltaic energy has been directly used to remove nickel from wastewater. Results show that under the solar irradiation intensity (SII) of 750 ± 30 W/m2, aluminum electrode has higher nickel removal efficiency (NRE) than graphite and titanium, and its NRE is nearly 100% in 40 min. An optimum distance of 20 mm is determined for the electrode gap. NRE in 40 min nearly decreases from 99.6% to 78.8% when initial Ni2+ concentration increases from 100 to 300 mg/L. Under the SII of 610 ± 40 W/m2, solution containing SO42− of 3.4 mmol/L gets the highest NRE, while wastewater containing Cl− of 6.8 mmol/L has the lowest. Furthermore, effluent, including SO42− of 1.7 and Cl− of 3.4 mmol/L, shows a higher NRE too. NRE in 40 min increases when output power of the photovoltaic panel changes from 30 to 90 W, but doesn't show an obviously increasing tendency when the power improves further to 120 W. NRE for a fine day is the highest and is 100% in 40 min. However, its energy utilization efficiency is the lowest, but the saving cost is the most. In addition, MAl, Ct, and Ca sharply increase with the SII enhancing. Therefore, for some enterprises or regions with serious environmental burden and insufficient economic input, this process will provide an effective alternative approach to remove heavy metals from wastewater in a renewable and low-cost way.