Degradation of chloromethylisothiazolinone antimicrobial by Vacuum-Ultraviolet/Ultraviolet irradiation: Reactive species, degradation pathway and toxicity evaluation. (September 2022)

• Record Type: Journal Article
• Authors: Huang, Nan; Shao, Wan-Ting; Wang, Qi; Wang, Wen-Long; Wu, Qian-Yuan; Hu, Hong-Ying
• Is Part Of: Chemosphere. Volume 302(2022)
• Publication Date: 2022-09
• Subjects: Non-oxidizing antimicrobials -- VUV/UV -- Reactive species -- Degradation pathway -- Toxicity evaluation; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.134821
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Chloromethylisothiazolinone (CMIT) has been extensively used as antimicrobial in cosmetics, detergents, wall paints, and anti-fouling products. To prevent the potential ecological and health risks, the degradation mechanisms and toxicity changes of CMIT by Vacuum-Ultraviolet/Ultraviolet (VUV/UV) irradiation were investigated in this study. VUV/UV irradiation showed better performance on CMIT degradation compared to sole UV photolysis. The removal efficiency of CMIT with photon fluence of 0.6 μEinstein/cm 2 was 8% and 100% by UV or VUV/UV irradiation, respectively. Radical quenching experiments indicated that 254 nm photolysis, 185 nm photolysis, and OH oxidation contributed to CMIT degradation during VUV/UV process, with fluence-based apparent rate constants of 0.16, 0.13, and 4.9 μEinstein −1 cm 2, respectively. The formation of H2 O2 during VUV/UV process increased to 0.7 mg/L at 4.5 min, and the concentration of OH ranged within 1.0–3.8 × 10 −12 M. The degradation of CMIT by VUV/UV irradiation in neutral condition was slightly higher than that in acidic and basic conditions. The removal efficiency of CMIT with reaction time of 2 min decreased from 92.2% to 34.3% when the concentration of HCO3 − /CO3 2− increased to 1 mM. The degradation of CMIT by VUV/UV irradiation in secondary effluents was lower than that in ultrapure water because of the OH scavenging effects, but still 2.9 times higher than that by UV photolysis. Four main degradation mechanisms of CMIT were observed during VUV/UV process, including the oxidation of sulfur, addition of hydroxyl groups on the double-carbon-bond, demethylation on the nitrogen, and substitution of organochlorine atom by hydroxyl group. Based on the quantitative structure activity relationship analysis, most products of CMIT underwent complete detoxification to fish and daphnia. 40% of products still showed acute toxicity to algae, but most of them were less toxic than CMIT. Graphical abstract: Image 1 Highlights: VUV/UV irradiation outperformed UV photolysis for CMIT removal in wastewater effluent. VUV/UV degraded CMIT by 185 nm photolysis, 254 nm photolysis and .OH oxidation The formation of hydrogen peroxide and hydroxyl radicals was quantified. CMIT was degraded by dechlorination, N-demethylation, oxidation of sulfur and alkene. Most products were partially or completely detoxified to fish, daphnia and algae.