Removal of new contaminants from wastewater through advanced oxidation processes - a perspective

Advanced oxidation processes (AOPs) have been widely applied to remove new contaminants in aquatic environments; however, a systematic understanding of the underlying removal mechanisms is still lacking. This perspective provides a brief review of AOPs based on persulfate (PS), peracetic acid (PAA), and periodate (PI), with a particular focus on PS-AOPs and the four principal reaction pathways involved in the degradation of new contaminants: radical oxidation (mainly by sulfate and hydroxyl radicals); nonradical oxidation (e.g., singlet oxygen and high-valent metal-oxo species); electron-transfer process; and polymerization. Through a critical analysis of representative case studies, this paper examines the challenges associated with each reaction pathway and discusses potential solutions. In the future, the complexity of real wastewater matrices demands that further research tackles two fundamental issues: first, how to precisely design highly efficient catalysts to achieve effective removal of new contaminants while remaining cost-effective for practical application; and second, how to effectively identify key mechanisms within intricate reaction systems and establish systematic strategies for targeted regulation. Breakthroughs in these two aspects will collectively advance the transition of AOPs from laboratory research to engineering applications.