Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway
Recently, ClO<sub>2</sub>-based oxidation has attracted increasing attention to micropollutant abatement, due to high oxidation potential, low disinfection byproduct (DBPs) formation, and easy technical implementation. However, the kinetics, reactive sites, activation methods, and degrad...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-06-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/14/13/2028 |
| _version_ | 1797441625487572992 |
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| author | Xiaohong Ma Huan Chen Ruihuan Chen Xiaojun Hu |
| author_facet | Xiaohong Ma Huan Chen Ruihuan Chen Xiaojun Hu |
| author_sort | Xiaohong Ma |
| collection | DOAJ |
| description | Recently, ClO<sub>2</sub>-based oxidation has attracted increasing attention to micropollutant abatement, due to high oxidation potential, low disinfection byproduct (DBPs) formation, and easy technical implementation. However, the kinetics, reactive sites, activation methods, and degradation pathways involved are not fully understood. Therefore, we reviewed current literature on ClO<sub>2</sub>-based oxidation in micropollutant abatement. In direct ClO<sub>2</sub> oxidation, the reactions of micropollutants with ClO<sub>2</sub> followed second-order reaction kinetics (k<sub>app</sub> = 10<sup>−3</sup>–10<sup>6</sup> M<sup>−1</sup> s<sup>−1</sup> at neutral pH). The k<sub>app</sub> depends significantly on the molecular structures of the micropollutant and solution pH. The reactive sites of micropollutants start with certain functional groups with the highest electron densities including piperazine, sulfonyl amido, amino, aniline, pyrazolone, phenol groups, urea group, etc. The one-electron transfer was the dominant micropollutant degradation pathway, followed by indirect oxidation by superoxide anion radical (O<sub>2</sub><sup>•−</sup>) or hydroxyl radical (<sup>•</sup>OH). In UV-activated ClO<sub>2</sub> oxidation, the reactions of micropollutants followed the pseudo-first-order reaction kinetics with the rates of 1.3 × 10<sup>−4</sup>–12.9 s<sup>−1</sup> at pH 7.0. Their degradation pathways include direct ClO<sub>2</sub> oxidation, direct UV photolysis, ozonation, <sup>•</sup>OH-involved reaction, and reactive chlorine species (RCS)-involved reaction. Finally, we identified the research gaps and provided recommendations for further research. Therefore, this review gives a critical evaluation of ClO<sub>2</sub>-based oxidation in micropollutant abatement, and provides recommendations for further research. |
| first_indexed | 2024-03-09T12:25:48Z |
| format | Article |
| id | doaj.art-7802aba7fe8941eca27625b50ddf5db7 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-09T12:25:48Z |
| publishDate | 2022-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-7802aba7fe8941eca27625b50ddf5db72023-11-30T22:35:10ZengMDPI AGWater2073-44412022-06-011413202810.3390/w14132028Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation PathwayXiaohong Ma0Huan Chen1Ruihuan Chen2Xiaojun Hu3School of Geography and Environment Science, Northwest Normal University, Lanzhou 730070, ChinaDepartment of Environmental Engineering and Earth Science, Clemson University, Clemson, SC 29634, USACollege of Life and Environmental Science, Wenzhou University, Wenzhou 325035, ChinaSchool of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, ChinaRecently, ClO<sub>2</sub>-based oxidation has attracted increasing attention to micropollutant abatement, due to high oxidation potential, low disinfection byproduct (DBPs) formation, and easy technical implementation. However, the kinetics, reactive sites, activation methods, and degradation pathways involved are not fully understood. Therefore, we reviewed current literature on ClO<sub>2</sub>-based oxidation in micropollutant abatement. In direct ClO<sub>2</sub> oxidation, the reactions of micropollutants with ClO<sub>2</sub> followed second-order reaction kinetics (k<sub>app</sub> = 10<sup>−3</sup>–10<sup>6</sup> M<sup>−1</sup> s<sup>−1</sup> at neutral pH). The k<sub>app</sub> depends significantly on the molecular structures of the micropollutant and solution pH. The reactive sites of micropollutants start with certain functional groups with the highest electron densities including piperazine, sulfonyl amido, amino, aniline, pyrazolone, phenol groups, urea group, etc. The one-electron transfer was the dominant micropollutant degradation pathway, followed by indirect oxidation by superoxide anion radical (O<sub>2</sub><sup>•−</sup>) or hydroxyl radical (<sup>•</sup>OH). In UV-activated ClO<sub>2</sub> oxidation, the reactions of micropollutants followed the pseudo-first-order reaction kinetics with the rates of 1.3 × 10<sup>−4</sup>–12.9 s<sup>−1</sup> at pH 7.0. Their degradation pathways include direct ClO<sub>2</sub> oxidation, direct UV photolysis, ozonation, <sup>•</sup>OH-involved reaction, and reactive chlorine species (RCS)-involved reaction. Finally, we identified the research gaps and provided recommendations for further research. Therefore, this review gives a critical evaluation of ClO<sub>2</sub>-based oxidation in micropollutant abatement, and provides recommendations for further research.https://www.mdpi.com/2073-4441/14/13/2028Chlorine Dioxide (ClO<sub>2</sub>)micropollutantkineticsdegradation pathwayreactive sites |
| spellingShingle | Xiaohong Ma Huan Chen Ruihuan Chen Xiaojun Hu Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway Water Chlorine Dioxide (ClO<sub>2</sub>) micropollutant kinetics degradation pathway reactive sites |
| title | Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway |
| title_full | Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway |
| title_fullStr | Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway |
| title_full_unstemmed | Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway |
| title_short | Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway |
| title_sort | direct and activated chlorine dioxide oxidation for micropollutant abatement a review on kinetics reactive sites and degradation pathway |
| topic | Chlorine Dioxide (ClO<sub>2</sub>) micropollutant kinetics degradation pathway reactive sites |
| url | https://www.mdpi.com/2073-4441/14/13/2028 |
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