Critical review of organic radical chemistry in peracetic acid-based advanced oxidation processes for water decontamination

Advanced oxidation processes (AOPs) are recognized as state-of-the-art technologies for environmental decontamination, leveraging the generation of highly reactive species (RS). However, current reviews primarily address common inorganic radicals and nonradicals RS, often neglecting the critical role of organic radicals (R-O^•) such as acetyloxyl radical (CH₃C(O)O^•) and acetyl peroxyl radical (CH₃C(O)OO^•). Compared to inorganic radicals (e.g., hydroxyl radical), R-O^• exhibit superior selectivity, longer lifetimes, and the potential to serve as carbon sources for biological treatment or to drive polymerization reactions yielding high value-added products (e.g., polymers), rendering R-O^•-mediated AOPs as promising candidates in water treatment. This critical review examines the fundamental knowledge of R-O^• chemistry in peracetic acid (PAA)-based AOPs and their recent advancements in water decontamination. Firstly, we outline the chemical properties and generation mechanisms of R-O^•. Subsequently, their oxidative behaviors (including kinetics, mechanisms, water matrix effects, byproduct formation, and toxicity) in pollutant degradation are systematically compared from a practical implementation perspective. Furthermore, the identification methods of R-O^• are summarized and key existing controversies are discussed concerning the selection of scavengers/probes and the interpretation of experimental results. Future research should prioritize clearly elucidating R-O^• origins over heterogeneous catalysts, developing highly sensitive in-situ detection techniques and advanced R-O^• regulation strategies, and conducting systematic assessments for engineering applications. This work provides a foundational understanding of the character, reactivity, generation, and identification of R-O^• in PAA-based AOPs, advancing their role in sustainable environmental remediation.