Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing, 100084, PR China; Beijing Laboratory for Environmental Frontier Technologies, Beijing, 100084, China.
Key Laboratory of Microorganism Application and Risk Control of Shenzhen, Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, PR China.
Chemosphere. 2022 Sep;302:134821. doi: 10.1016/j.chemosphere.2022.134821. Epub 2022 May 4.
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 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 μEinsteincm, respectively. The formation of HO 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 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 HCO/CO 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.
氯甲基异噻唑啉酮 (CMIT) 已被广泛应用于化妆品、洗涤剂、墙壁涂料和防污产品中作为抗菌剂。为了防止潜在的生态和健康风险，本研究考察了真空紫外/紫外（VUV/UV）辐照对 CMIT 的降解机制和毒性变化。与单独的 UV 光解相比，VUV/UV 辐照对 CMIT 的降解效果更好。在光子通量为 0.6 μEinstein/cm 时，UV 或 VUV/UV 辐照对 CMIT 的去除效率分别为 8%和 100%。自由基猝灭实验表明，在 VUV/UV 过程中，254nm 光解、185nm 光解和 •OH 氧化作用均有助于 CMIT 的降解，相应的光解常数分别为 0.16、0.13 和 4.9 μEinsteincm。在 VUV/UV 过程中，HO 的形成量在 4.5 分钟时增加到 0.7mg/L，•OH 的浓度范围在 1.0-3.8×10-5M 之间。在中性条件下，VUV/UV 辐照对 CMIT 的降解略高于酸性和碱性条件。当 HCO/CO 浓度增加到 1mM 时，反应时间为 2 分钟时 CMIT 的去除效率从 92.2%下降到 34.3%。由于 •OH 的清除作用，VUV/UV 辐照在二级出水的降解率低于超纯水，但仍比 UV 光解高 2.9 倍。在 VUV/UV 过程中观察到 CMIT 的四种主要降解机制，包括硫的氧化、双碳键上羟基的加成、氮上的脱甲基化以及有机氯原子被羟基取代。基于定量构效关系分析，CMIT 的大部分产物对鱼类和水蚤进行了完全解毒。40%的产物对藻类仍表现出急性毒性，但大多数产物的毒性比 CMIT 低。
