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.