(7−13) In the current literature, “persulfate-AOPs” refer to any physicochemical method that enhances the oxidizing capacity of persulfate regardless of involvement of radicals. (4−6) Unlike H 2O 2, however, persulfate can also oxidize some organics directly, without involving radical species.
–) are produced in situ by cleaving the peroxide bond in the persulfate molecule via energy and electron transfer reactions. –-AOPs), highly reactive, short-lived sulfate radicals (SO 4. In sulfate radical-based AOPs (referred to herein as SO 4 (2,3) Alternative AOPs utilizing peroxymonosulfate (PMS) or peroxydisulfate (PDS) (collectively referred to as persulfate see Figure 1 for their structures) instead of H 2O 2 have emerged based on the same strategy. OH is short-lived, it is generated in situ during ozone- and UV-based processes (1) by activating stable precursors, such as H 2O 2. OH) to abate a wide range of organic pollutants in water with diffusion-limited kinetics. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.Īdvanced oxidation processes (AOPs) employ highly reactive hydroxyl radical ( In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. 
Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways.
Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature.
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