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

Sulfate radical-based advanced oxidation processes (SR-AOPs) employing heterogeneous catalysts to generate sulfate radical (SO4 −) from peroxymonosulfate (PMS) and persulfate (PS) have been extensively employed for organic contaminant removal in water. This article aims to provide a state–of–the–art review on the recent development in heterogeneous catalysts including single metal, mixed metal, and nonmetal carbon catalysts for organic contaminants removal, with particular focus on PMS activation. The hybrid heterogeneous catalyst/PMS systems integrated with other advanced oxidation technologies is also discussed. Several strategies for the identification of principal reactive radicals in SO4 −–oxidation systems are evaluated, namely (i) use of chemical probe or spin trapping agent coupled with analytical tools, and (ii) competitive kinetic approach using selective radical scavengers. The main challenges and mitigation strategies pertinent to the SR-AOPs are identified, which include (i) possible formation of oxyanions and disinfection byproducts, and (ii) dealing with sulfate produced and residual PMS. Potential future applications and research direction of SR-AOPs are proposed. These include (i) novel reactor design for heterogeneous catalytic system based on batch or continuous flow (e.g. completely mixed or plug flow) reactor configuration with catalyst recovery, and (ii) catalytic ceramic membrane incorporating SR-AOPs.

Generation of sulfate radical through heterogeneous catalysis for organic contaminants removal: Current development, challenges and prospects

Application of peroxymonosulfate and its activation methods for degradation of environmental organic pollutants: Review

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.

The reactions between peroxymonosulfate (PMS) and quinones were investigated for the first time in this work, where benzoquinone (BQ) was selected as a model quinone. It was demonstrated that BQ could efficiently activate PMS for the degradation of sulfamethoxazole (SMX; a frequently detected antibiotic in the environments), and the degradation rate increased with solution pH from 7 to 10. Interestingly, quenching studies suggested that neither hydroxyl radical (•OH) nor sulfate radical (SO4•–) was produced therein. Instead, the generation of singlet oxygen (1O2) was proved by using two chemical probes (i.e., 2,2,6,6-tetramethyl-4-piperidinol and 9,10-diphenylanthracene) with the appearance of 1O2 indicative products detected by electron paramagnetic resonance spectrometry and liquid chromatography mass spectrometry, respectively. A catalytic mechanism was proposed involving the formation of a dioxirane intermediate between PMS and BQ and the subsequent decomposition of this intermediate into 1O2. Accordi...

Activation of Peroxymonosulfate by Benzoquinone: A Novel Nonradical Oxidation Process

Iodinated aromatic products of high toxicity can be generated during permanganate (Mn(VII)) oxidation of phenolic compounds in the presence of iodide (I−), mainly due to the interactions between phenols and hypoiodous acid (HOI) formed in situ from Mn(VII) oxidation of I−. In this work, the feasibility of peroxymonosulfate (PMS) addition to control the formation of iodinated aromatic products during Mn(VII) oxidation of a representative phenolic compound methylparaben (MeP, a widely used preservative) in the presence of I− under various conditions was investigated. The HOI-enhanced transformation of MeP by Mn(VII) was generally inhibited by the addition of PMS, and stronger inhibitive effect at higher PMS concentration or higher pH was obtained resulting mainly from the competitive oxidation of HOI to iodate (IO3−) by PMS vs. MeP. Formation of iodinated aromatic products from MeP treated by Mn(VII) in the presence of I− (i.e., mono- and di- iodinated MeP) at pH 5, 7, and 9 in synthetic water as well as authentic water was also decreased by the addition of PMS, especially at higher PMS concentration, and IO3− formation was promoted in parallel under the same conditions. A similar inhibitory effect of PMS on the formation of iodinated aromatic products from MeP by manganese dioxide (MnO2) in the presence of I− was also observed. These results suggest that PMS may be a promising oxidant for controlling iodinated aromatic products during manganese oxidation processes.

A novel strategy using peroxymonosulfate to control the formation of iodinated aromatic products in treatment of phenolic compounds by permanganate

The invention provides a method for cracking sludge by virtue of singlet oxygen and relates to a sludge cracking method. The method comprises the steps of adding a catalyst pyroracemic acid and antioxidants peroxides (peroxymonosulfate and percarbonate) into to-be-cracked sludge, stirring to react, pumping supernate of the cracked sludge back into an aeration tank, and carrying out treatments including dehydration and the like on the residual sludge. According to the method, a bisepoxy intermediate is generated by catalyzing peroxides by virtue of pyroracemic acid and further reacts with peroxides to generate singlet oxygen and pyroracemic acid, peroxides are continuously catalyzed by generated pyroracemic acid, and generated pyroracemic acid plays a role of circular catalysis during reaction, generated high-activity singlet oxygen is capable of damaging the structure of sludge floc and releasing bound water, improving the dehydration performance of sludge and damaging the cell structures of microorganisms. The method has the characteristics that the sludge treatment effect is good, toxic and harmful products are not generated, a required carbon source is provided for sewage treatment, and the catalyst pyroracemic acid and the antioxidants peroxides are environmentally friendly and safe and have no toxic and side effects.

Method for cracking sludge by virtue of singlet oxygen

The invention provides a method for utilizing singlet oxygen for removing algae and relates to an algae removal method. According to the algae removal method, a catalyst pyruvic acid and an oxidizing agent peroxide such as monosulfate and percarbonate are added into water containing algae, and stirred, and react to complete algae removal. Pyruvic acid catalyzes the peroxide to generate a double-resin intermediate, the double-resin intermediate reacts with the peroxide to generate singlet oxygen and pyruvic acid, generated pyruvic acid continues to catalyze the peroxide, and has a circular catalytic effect in the reaction process, and the generated high-activity singlet oxygen acts on the algae fast, kills algae cells, enables the algae to be inactivated, and achieves the purpose of algae removal. The algae removal method has the advantages that algae removal efficiency is high, generation of poisonous and harmful products is avoided, the catalyst pyruvic acid and the oxidizing agent peroxide are environmentally friendly, safe and free of toxic and side effects, can be applied on a large scale and are more suitable for emergency treatment of algae outbreak, and the reaction is affected little by the water body condition.

Method for utilizing singlet oxygen for removing algae

The invention discloses a method for in-situ preparation of ferrate by means of singlet oxygen and relates to compound preparation methods. The method comprises the steps of mixing strong base with the catalyst pyruvic acid, adding the oxidizing agent peroxide (peroxymonosulfate or percarbonate), conducting even stirring, adding ferric salt quickly, and conducting stirring to obtain an atropurpureus ferrate solution. The peroxide is catalyzed by pyruvic acid to generate a dual-epoxy midbody, the dual-epoxy midbody reacts with the peroxide to generate singlet oxygen and pyruvic acid, the generated pyruvic acid is still used for catalyzing the peroxide and plays a role of cyclic catalysis in reaction, ferric salt is oxidized into ferrate by means of the generated high-activity singlet oxygen, and pyruvic acid also has a complexing action, so that the stability of the ferrate solution is improved and preparation is achieved. The catalyst pyruvic acid and the oxidizing agent peroxide are environmentally friendly, safe and free of side effect, preparation is easy and safe, the yield of the ferrate solution is high, the stability of the ferrate solution is high, and the ferrate solution is suitable for being prepared when needed.

Method for in-situ preparation of ferrate by means of singlet oxygen

The invention discloses a water treatment method for controlling lead ion dissolution with monopersulfate in a chloramine sterilization process, relates to water treatment methods, and aims to solve the problem of lead ion dissolution in the chloramine sterilization process. The water treatment method disclosed by the invention comprises the following steps: adding chloramines into water to be treated for sterilization treatment, adding a monopersulfate solution, keeping stirring, and oxidizing a reduction product generated from self decomposition of the chloramines into nitrate by virtue of the oxidation of the monopersulfate, thereby inhibiting dissolution reduction of lead dioxide in a tube wall corrosion substance by the reduction product, that is, completing in-situ control on lead ion dissolution. By adopting the water treatment method, the reduction product generated from self decomposition of the chloramines can be quickly oxidized into nitrate by using the monopersulfate, and thus effective control on the lead ions in the chloramine sterilization process can be achieved; in addition, the chloramines are not consumed by the monopersulfate, and the monopersulfate can exist together with the chloramines; meanwhile, the monopersulfate is included into a drinking water sanitizer product catalog of China officially and can be used in water purification plants and tube nets; and the water treatment method is simple and convenient to operate and low in treatment cost.

Yuan Gao

Papers

A novel strategy using peroxymonosulfate to control the formation of iodinated aromatic products in treatment of phenolic compounds by permanganate

Method for cracking sludge by virtue of singlet oxygen

Method for utilizing singlet oxygen for removing algae

Method for in-situ preparation of ferrate by means of singlet oxygen

Water treatment method for controlling lead ion dissolution with monopersulfate in chloramine sterilization process