Breaking boundaries and collaborative symbiosis: Radical-nonradical-polymerization in persulfate advanced oxidation processes

Persulfate advanced oxidation processes (PS-AOPs) have become a research hotspot in water treatment due to their remarkable efficacy in organic pollutant degradation. Although numerous studies have reported the reaction pathways of PS-AOPs (radical, nonradical, and polymerization), there remains a lack of systematic summarization regarding the dynamic transformation and synergistic effect among these three pathways. Therefore, this review provides a comprehensive bibliometric analysis of PS-AOPs, systematically analyzing the transition and synergistic interactions between radical, nonradical, and polymerization pathways. The advantages and limitations of each pathway are clarified. The mechanisms of intrinsic regulation, interface modification, and energy driven influence on the transition of radical and nonradical are explored. The principle of the synergistic degradation of pollutants by radical and nonradical is revealed. The key factors for radical- and nonradical-induced polymerization are explained. The relationships between polymerization, degradation/mineralization, organic carbon transfer processes (OCTP), direct oxygen transfer processes (DOTP), and pollutant accumulation are clarified. The mechanism of electron transfer-induced polymerization is cleared. Finally, we provide an outlook on the challenges and future development of PS-AOPs, pointing out that “breaking through the limitations of single-pathway and focusing on the synergistic effect of multiple pathways” is the future development direction. • Mechanism of transition and synergy between radical and nonradical is analyzed. • Inducers for the polymerization induced by radical and nonradical are explained. • Emphasize breaking single pathway and constructing multi-pathway collaborative. • Provide an outlook on the challenges and future development of PS-AOPs.