Investigation of the Effect of Chemical Oxidants on the Electrocoagulation Process for COD Reduction of Caustic Wastewater from the South Pars Gas Complex, Pars Special Economic Energy Zone

Purpose: Caustic wastewater generated from gas refinery washing processes is considered one of the most challenging industrial effluents to treat due to its resistant organic compounds, high chemical oxygen demand (COD), and strong alkalinity. In recent years, the combined application of electrochemical techniques and chemical oxidants has attracted significant attention as an effective approach to enhance the removal efficiency of organic pollutants. Accordingly, this study aims to evaluate the simultaneous performance of selected oxidants including potassium permanganate, polyaluminum chloride (PAC), alum, and hydrogen peroxide in reducing the COD of caustic wastewater. Methods: The electrocoagulation process for treating neutralized caustic wastewater was investigated under optimized pH conditions using a direct current applied between iron anode and cathode electrodes. The samples consisted of ۱۰۰ mL of wastewater neutralized with ۹۸% sulfuric acid. The effects of oxidant type and dosage, reaction time, and applied current intensity on process performance and COD removal efficiency were evaluated. All experiments were conducted in triplicate, and the resulting data were analyzed using Excel and OriginPro software. Results: The results demonstrated that the simultaneous application of chemical oxidants with the electrocoagulation process significantly enhanced the removal efficiency of organic compounds and led to a substantial reduction in COD. Extending the reaction time to ۶۰ minutes produced the greatest improvement in performance, and the concurrent presence of electric current and oxidants indicated a strong synergistic effect between the chemical and electrochemical processes. Conclusion: This study demonstrated that the electrocoagulation process in the presence of chemical oxidants is an effective and efficient approach for reducing the organic and inorganic load of caustic wastewater from gas refineries. A reaction time of ۶۰ minutes and an optimal dosage of ۲ g of each chemical oxidant yielded the highest COD removal efficiency, whereas excessive chemical dosing resulted in a slight decline in performance. The synergistic interaction between chemical and electrochemical processes not only enhanced the removal of organic contaminants but also enabled a notable reduction in heavy metals. Therefore, this combined approach can serve as a practical and viable strategy for managing highly alkaline industrial effluents.

کلیدواژه ها:

Caustic wastewater ، Electrochemistry ، Potassium permanganate ، Polyaluminum chloride (PAC) ، COD reduction