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

Recently sulfate radical-based advanced oxidation processes (SR-AOPs) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

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.

PAH diagnostic ratios for the identification of pollution emission sources

The invention discloses a method for predicting organic compound and hydroxyl radical reaction rate constant in a water phase based on a quantitative structure-activity relationship. On the base of obtaining a compound molecular structure, a quantitative structure-activity relationship model is built by calculating a molecular structure descriptor through a multi-linear-regression method, and the water phase kOH value of organic compounds can be predicted quickly and efficiently. According to the method, modeling is conducted according to the building and using guide rules of a QSAR model of an economic cooperation and development organization, the model application field is clear, 526 kinds of different organic compounds are included, and particularly compounds containing most compounds of atoms such as nitrogen, phosphorus, and sulphur which are not contained in previous models are covered. The model has good fitting capacity, robustness and predicting capacity, the water phase kOH value of the organic compounds in an application field can be effectively predicted, and an important data support is provided for environmental durability evaluation and ecological risk assessment of organic chemical products.

Method for predicting organic compound and hydroxyl radical reaction rate constant in water phase

Controllable assembly of Fe3O4-Fe3C@MC by in-situ doping of Mn for CO2 selective hydrogenation to light olefins

This invention belongs to the technical field of quantitative structure-activity relationship (QSAR) for chemical persistent assessment, relating to a method for predicting reaction rate constants of organic chemicals with ozone (kO3) at different temperatures. To assess the persistence and fate of organic chemicals in the troposphere, kO3 are needed. This invention developed a QSAR model for the prediction of kO3 at different temperatures, based on quantum chemical descriptors, Dragon descriptors and structural fragments. The developed model was evaluated by internal and external validations, and it's high robustness and good predictability was evidenced. The applicability domain of this model was visualized by Williams plot.

Method for predicting oxidation reaction rate constant between chemicals and ozone based on molecular structure and ambient temperature

Oxytetracycline (OTC) and Zn2+ are both widely used as growth promoters in concentrated animal feeding operations, which are discharged into soil system by manure application. There is special environment significance to study the sorption and interaction of OTC with accompanied metal cations on clays to elucidate their environmental behaviors and to assess ecological risks. Much stronger sorption of OTC was observed on montmorillonite than that on kaolinite, which might be resulted from the larger cation exchange capacity of the former. Different pH-dependent Kd patterns were illustrated on montmorillonite and kaolinite, which might be contributed by the different properties of surface charge. During 4 < pH < 5, OTC sorption was decreased by cation competition of Zn2+, while OTC sorption was promoted by OTC-Zn-clay bridge while 5 < pH < 9, and the most significant effect was shown at pH = 6.5. The sorption of Zn2+ on two clays was decreased by OTC in the pH range studied, which can be explained by cation competition of OTC at lower pH, or by prohibition in the sorption or precipitation resulted from complexation between OTC and Zn2+ at higher pH. CD and UV-Vis spectrometry analysis showed that there was no complexation observed between OTC and Zn2+ at pH = 4. But with increasing of pH value, complexation might happen at the sites of O11, O12 or O12, O1.

Enhanced sorption of OTC on clays via complexation with Zn2

The invention provides a method and a device for combined remediation of petroleum hydrocarbon-contaminated soil by cyclodextrin and sodium persulfate, and belongs to the technical field of soil contamination remediation. According to the method, cyclodextrin is adopted for increasing the effective concentration of petroleum hydrocarbons in aged soil, so that the petroleum hydrocarbons are more liable to be oxidized and degraded by sodium persulfate. Under experimental conditions, the removal rate of petroleum contaminants in the soil can reach 27.5-81.2%. The invention establishes a technology and the device for combined remediation of of the petroleum hydrocarbon-contaminated soil by cyclodextrin and sodium persulfate; by adopting the technology, the degradation rate for the sodium persulfate to remedy the petroleum-contaminated soil is increased, especially that the effect on the aged soil is more significant, and used chemicals are environmentally-friendly and recyclable; therefore, the technology has good environmental and economic benefits.

Xianliang Qiao

Papers

Method for predicting organic compound and hydroxyl radical reaction rate constant in water phase

Controllable assembly of Fe3O4-Fe3C@MC by in-situ doping of Mn for CO2 selective hydrogenation to light olefins

Method for predicting oxidation reaction rate constant between chemicals and ozone based on molecular structure and ambient temperature

Enhanced sorption of OTC on clays via complexation with Zn2

Method and device for combined remediation of petroleum hydrocarbon-contaminated soil by cyclodextrin and sodium persulfate