UV/SO32− based advanced reduction processes of aqueous contaminants: Current status and prospects

Abstract

UV/SO32− based Advanced Reduction Processes (ARPs) have attracted increasing attention in recent years due to their high capability for the degradation of some refractory contaminants. In this review, the current status of UV/SO32− ARPs for the pollutant degradation is outlined. A variety of operational conditions influencing the removal efficiency (e.g. pH, sulfite concentration, UV type and intensity, initial concentration of pollutants, dissolved oxygen, coexisting ions and organics) are analyzed and summarized for further research. Based on existing mechanism investigations, radical reactions (eaq−, H and SO3−) usually play a vital role in UV/SO32− ARPs, though direct photolysis and S(IV) are believed to contribute to the reduction processes of some contaminants. It is found that the dominant radicals depend on the operational condition and target pollutants. Furthermore, knowledge gaps and research needs of UV/SO32− ARPs are proposed as a reference for future research. This review can provide an overview for the status and prospective of UV/SO32− ARPs, as well as for the deep understanding of the mechanisms of various contaminants.