Study on synergistic effect of ozone and monochloramine on the degradation of chloromethylisothiazolinone biocide
| Autor: | Qian-Yuan Wu, Bei Ye, Nan Huang, Min-Yong Lee, Zi-Bin Xu, Hong-Ying Hu, Zi-Fan Liang, Wen-Long Wang |
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| Rok vydání: | 2020 |
| Předmět: |
Reaction mechanism
Environmental Engineering Ozone 010504 meteorology & atmospheric sciences Radical chemistry.chemical_element 010501 environmental sciences 01 natural sciences Water Purification Hydroxylation chemistry.chemical_compound Chlorine Environmental Chemistry Waste Management and Disposal 0105 earth and related environmental sciences Chloramine Singlet oxygen Hydroxyl Radical Chloramines Pollution chemistry Hydroxyl radical Oxidation-Reduction Water Pollutants Chemical Nuclear chemistry Disinfectants |
| Zdroj: | The Science of the total environment. 754 |
| ISSN: | 1879-1026 |
| Popis: | In this study, it was found that monochloramine induced the formation of reactive species during ozonation of chloromethylisothiazolinone (CMIT). CMIT was found recalcitrant to chloramine. However, chloramine promoted the degradation of CMIT by ozonation significantly. Hydroxyl radicals contributed most to CMIT degradation (87%) during ozone/chloramine synergistic oxidation process (SOP). The hydroxyl radical exposure during ozone/chloramine SOP was around 7.9 times higher than that of ozonation process. The hydroxyl radical yield of ozone/chloramine SOP was estimated to be 32%. The reaction mechanisms between ozone and chloramine were postulated to include the oxygen transfer reaction to form singlet oxygen, and the formation of hydroxyl radical by the insertion pathway or electron transfer pathway. Chloramine dosage and pH are essential influencing factors. The degradation of CMIT increased from 41% to 74% with increasing chloramine dosage (0–20 μM), and then decreased to 65% when chloramine dosage continually increased to 40 μM. Ozone/chloramine SOP showed better performance at acidic or neutral conditions than basic condition. Based on the intermediates identified, the degradation pathway of CMIT during ozone/chloramine SOP included the oxidation of sulfur atom and the substitution of chlorine group by hydroxyl group. The oxidation of sulfur atom induced lower toxicities of transformation products. The toxicities of hydroxylation products were lower to fish and algae, but higher to daphnia. Based on the GC-ECD results, only trichloromethane (1.94 μg/L) was detected after ozone/chloramine SOP, accounting for 0.17% (μM/μM) of the CMIT removal. |
| Databáze: | OpenAIRE |
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