Treatment of wastewater from the petrochemical industry by a solar-powered electrocoagulation process: optimization of crucial operating parameters using response surface methodology†

Electrocoagulation (EC) technology is an emerging and clean process in treating oily wastewater due to its high treatment efficiency, reduced sludge generation, and shorter treatment times. The primary objective of the present work is to treat low-concentration petrochemical wastewater by utilizing an aluminum plate as an anode and a stainless-steel mesh (SSM 304) as a cathode in a solar-powered electrocoagulation (SPEC) process. The chemical oxygen demand (COD) removal efficiency was investigated as the primary performance indicator of the SPEC. Response surface methodology (RSM) based on the Box–Behnken design (BBD) model was employed to evaluate treatment efficiency and understand the synergistic effects of major operating parameters. The experimental results demonstrated that under optimal operating conditions (an applied voltage of 35 V, a working time of 30 minutes, an electrode distance of 1.2 cm, and a stirring rate of 249 rpm), the COD removal efficiency reached 52.9%. The generated models had high R² values of 0.9802, indicating the model's effectiveness in predicting the removal rate of COD and optimizing operating conditions. The main properties of the flocs generated were examined using several physicochemical characterization techniques, and the mechanism of oil removal in the SPEC process was investigated in depth. Moreover, using SPEC reduced the cost of the whole process as the electricity fees were eliminated. Overall, the key findings of this study lay the foundation for developing an efficient and cost-effective EC treatment, offering environmental benefits, energy independence, long-term savings, and low maintenance, making it a sustainable industrial process for large-scale applications.