Combining Electro Fenton With Adsorption Processes for Treatment of Petroleum Refinery Wastewater

This study investigates the elimination of chemical oxygen demand (COD) from an Iraqi petroleum refinery effluent through a combined electro-Fenton and adsorption process (EF+AC). Response surface methodology (RSM) with a Box-Behnken design (BBD) was employed to investigate the effects of FeSO₄ concentration, current density, and electrolysis time on the reduction of COD using the EF technique. According to the results of the analysis of variance (ANOVA) for the EF technique, FeSO₄ concentrations, with a contribution of 40.06%, and current density, with a contribution of 46.35%, exert a considerable influence. The optimum conditions for COD elimination rate (99.06%) and energy consumption (9.805 kWh/kg COD) were achieved using an electrolysis time of 85.12 min, a current density of 25 mA/cm², and a concentration of 1.335 mM FeSO₄. For the EF+AC process, a central composite design (CCD) was used to determine the influence of the packing level of activated carbon (AC) and the time on the reduction of COD at a constant current density of 5 mA/cm² and FeSO₄ concentration of 0.2 mM. The packing level of AC significantly influenced the elimination of COD, with time being the subsequent factor. The results showed that the optimal conditions led to a 98.77% removal of COD, requiring 0.91 kWh/kg COD. This efficiency and energy consumption were attained by using 92% packed AC and allowing the process to run for 85 min. EF+AC was found to have lower energy consumption and a smaller quantity of ferrous sulfate compared to EF. Notably, the current system offers a promising vision by combining the benefits of adsorption and electro-Fenton for wastewater remediation.