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. 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. 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. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. 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. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

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Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Preparation, modification and environmental application of biochar: A review

Advanced oxidation process-mediated removal of pharmaceuticals from water: A review.

Degradation of antibiotics by advanced oxidation processes: An overview.

Reactive species in advanced oxidation processes: Formation, identification and reaction mechanism

Activation of persulfate (PS) and peroxymonosulfate (PMS) and application for the degradation of emerging contaminants

Effect of inorganic anions on the performance of advanced oxidation processes for degradation of organic contaminants

Graphite carbon nitride (g-C3N4) has a stable structure but poor catalytic capability for activating peroxymonosulfate (PMS). In this study, the codoping of g-C3N4 with bimetallic oxides (iron and cobalt) and oxygen was investigated to enhance its catalytic capability. The results showed that iron, cobalt, and oxygen codoped g-C3N4 (Fe-Co-O-g-C3N4) was successfully prepared, which was capable of completely degrading sulfamethoxazole (SMX) (0.04 mM) within 30 min, with a reaction rate of 0.085 min-1, indicating the superior catalytic activity of Fe-Co-O-g-C3N4. The mineralization efficiency of SMX was 22.1%. Sulfate radicals and singlet oxygen were detected during the process of PMS activation. However, the role that singlet oxygen played in degrading SMX was not obvious. Surface-bound reactive species and sulfate radicals were responsible for SMX degradation, in which sulfate radicals contributed to 46.6% of SMX degradation. The superior catalytic activity was due to the synergistic effect of metal oxides and O-g-C3N4, in which O-g-C3N4 could act as a carrier and an activator as well as an electron mediator to promote the conversion of Fe(III) to Fe(II) and Co(III) to Co(II). Four main steps of SMX degradation were proposed, including direct oxidation of SMX, bond fission of N-C, bond fission of N-S, and bond fission of S-C. The effect of the pH, temperature, PMS concentration, chloridion, bicarbonate, and humic acids on SMX degradation was investigated. Cycling experiments demonstrated the good stability of Fe-Co-O-g-C3N4. This study first reported the preparation of bimetallic oxide and oxygen codoped g-C3N4, which was an effective PMS activator for degradation of toxic organic pollutants.

Shizong Wang

Papers

Activation of persulfate (PS) and peroxymonosulfate (PMS) and application for the degradation of emerging contaminants

Reactive species in advanced oxidation processes: Formation, identification and reaction mechanism

Effect of inorganic anions on the performance of advanced oxidation processes for degradation of organic contaminants

Peroxymonosulfate Activation by Fe-Co-O-Codoped Graphite Carbon Nitride for Degradation of Sulfamethoxazole.

Activation of peroxymonosulfate by sludge-derived biochar for the degradation of triclosan in water and wastewater