Treatment of petroleum refinery wastewater by a combination of anodic oxidation with photocatalyst process: Recent advances, affecting factors and future perspectives

Abstract

The progress in human activities, industrialization, and urbanization has led to the generation of enormous quantities of polluted wastewaters, especially those produced by petroleum refineries. Generally, physicochemical and biological treatment methods are employed to treat petroleum refinery wastewaters. However, they suffer from low efficiency in removing pollutants due to the nature of these wastewaters. Among all wastewater treatment methods, electrochemical oxidation, photocatalytic oxidation, and their hybrid processes are regarded as feasible and promising options for establishing an effective effluent treatment approach in such cases. It was found that these methods depend on the generation of hydroxyl radicals, extremely reactive oxidizing agents that effectively degrade pollutants present in the petroleum refinery wastewaters. This review presents contemporary views on the state of the art for electrooxidation, photocatalytic degradation, and their hybrid processes. The comparison of these methods with conventional treatment methods indicates that both processes provided a high rate of treatment efficiency with lower energy consumption. Additionally, the mechanisms and operating variables of both anodic oxidation and photocatalytic processes were explained and evaluated. Furthermore, the use of the combined process for treatment of petroleum refinery wastewater was also outlined, focusing on its beneficial characteristics. Based on the results of most previously conducted laboratory studies, hybrid processes were found to be more effective in removing COD from petroleum refinery wastewater compared to individual processes.