Copper catalysts for radical and nonradical persulfate based advanced oxidation processes: Certainties and uncertainties

Ding, Yaobin; Fu, Libin; Peng, Xueqin; Lei, Ming; Wang, Chengjun; Jiang, Jizhou

doi:10.1016/j.cej.2021.131776

Cited by 142 publications

(47 citation statements)

References 169 publications

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“…In Cu-based AOPs, elucidation of the reaction mechanism is mainly, even overly, dependent on results obtained from radical quenching and EPR experiments; however, these results are not always reliable and are often confused with spin trapping artifacts, as already discussed in our recent review . Misassignment of radicals and detection of false positive signals are likely to complicate the explanation of the activation mechanism of oxidants in Cu-based AOPs . In addition, attempts to identify free radicals in such catalytic systems are only made at a certain reaction time and pH value. ,, For instance, both SO 4 •– and • OH were identified as the dominant radicals in the Cu(II)/PMS system at pH 4.0, but no further detail about the conversion and source of the identified signal was provided.…”

Section: Introductionmentioning

confidence: 98%

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EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts

Wang

et al. 2022

Environ. Sci. Technol.

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Electron paramagnetic resonance (EPR) has been extensively used for the identification of free radicals that are generated from advanced oxidation processes (AOPs) so as to establish the reaction mechanism. However, some misinterpretations or controversies on the identity of detected EPR signals remain in the literature. This study, with Cu(II)-based AOPs as examples, comprehensively investigated the origin of 5,5-dimethyl-l-pyrroline N-oxide (DMPO) adducts in Cu(II) alone, Cu(II)/H2O2, Cu(II)/peroxymonosulfate (PMS), and Cu(II)/peroxydisulfate (PDS) systems. In most Cu(II) systems, DMPO-OH signals can be detected even without any peroxygens, indicating the presence of other origins of this adduct in addition to the genuine spin trapping of •OH by DMPO. According to the formed secondary radical adducts (DMPO-OCH3 from a nonradical process or DMPO-CH2OH from a radical oxidation) derived from methanol quenching, we propose that CuO+, instead of free radicals, is involved in the Cu(II)/PMS system, while •OH is indeed generated in the Cu(II)/H2O2 and Cu(II)/PDS systems under neutral conditions. Notably, 17O-incorporation experiments demonstrate that −OH in the detected DMPO-OH adduct originates 100% from water in the Cu(II) alone system but the amount of −OH is over 99.8% from the oxidant while peroxygens are added. In addition, DMPO-O2 – appears only in the Cu(II)/PDS system under highly alkaline conditions and H2O is not involved in superoxide formation.

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Section: Introductionmentioning

confidence: 98%

“…22 Misassignment of radicals and detection of false positive signals are likely to complicate the explanation of the activation mechanism of oxidants in Cu-based AOPs. 23 In addition, attempts to identify free radicals in such catalytic systems are only made at a certain reaction time and pH value. 14,24,25 For instance, both SO 4…”

Section: ■ Introductionmentioning

confidence: 99%

EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts

Wang

et al. 2022

Environ. Sci. Technol.

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“…In the past few years, progress on different PS activation systems has been summarized in various review articles. ,,,− However, many of them mainly introduce the fundamentals of PS and the diverse PS activation methods instead of pointing out an environmentally friendly and promising PS activation technology, which may not be of obvious help to the development of PS-AOPs. Some published review articles mainly focus on a certain type of catalyst (e.g., Fe based, ,, Co based, − Cu based, TiO 2 based, carbon based, ,− bimetal based) used for PS activation, which lacks a comprehensive comparison between different types of catalysts used for PS activation. Recently, some review articles aimed to focus on emerging hot issues, such as single-atom catalytic PS activation − and nonradical oxidation processes. ,− Although they may be indicative for future research, a comprehensive summary and assessment of the mainstream PS-AOPs is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Photocatalytic Activation of Persulfate for the Removal of Organic Contaminants in Water: A Critical Review

Chen

et al. 2022

ACS EST Eng.

129

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Heterogeneous photocatalytic persulfate (PS) activation technologies are being intensively studied for water treatment due to their friendly environmental benefits and photosynergistic effect in comparison with traditional PS activation systems. Previous reviews have summarized diverse PS activation methods and the role of light in the photocatalytic PS activation systems, but it is still urgent to provide a comprehensive review on the deep understanding and rational design of heterogeneous photocatalytic PS-based advanced oxidation processes (AOPs). This review intends to thoroughly address the in-depth fundamentals and mechanisms for the heterogeneous photocatalytic PS-AOPs. Challenges and improvement strategies of the heterogeneous photocatalytic PS-AOPs are also critically discussed. On the basis of a detailed survey of the published studies, heterogeneous photocatalytic PS-AOPs, including Fe-based, TiO2-based, other metal based, bimetallic, and metal-free PS-AOPs, are carefully clarified. Finally, the engineering implications and prospects are enumerated for developing efficient and environmentally friendly heterogeneous photocatalytic PS-AOPs for water treatment. It is expected that this review will motivate researchers to construct novel and promising heterogeneous photocatalytic PS-AOPs for water treatment.

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“…Hence, surface and defect engineering has emerged in recent years as a popular and appealing technique to customize the catalyst and more effectively activate the percursors. [18][19][20][21] There are substantial developments in the rational design of decient transition metal-based materials deployed for advancing AOP strategies. [22][23][24][25][26] Anionic vacancies (e.g., oxygen, sulfur, and nitrogen) introduced to transition metal-based catalysts as point defects always have a pronounced effect on the physical and chemical properties of the catalyst.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reactive oxygen species on transition metal-based catalysts for sustainable environmental applications

et al. 2022

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Copper catalysts for radical and nonradical persulfate based advanced oxidation processes: Certainties and uncertainties

Cited by 142 publications

References 169 publications

EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts

EPR Evidence for Mechanistic Diversity of Cu(II)/Peroxygen Oxidation Systems by Tracing the Origin of DMPO Spin Adducts

Heterogeneous Photocatalytic Activation of Persulfate for the Removal of Organic Contaminants in Water: A Critical Review

Reactive oxygen species on transition metal-based catalysts for sustainable environmental applications

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