Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China.
Water Res. 2018 Jun 15;137:242-250. doi: 10.1016/j.watres.2018.03.004. Epub 2018 Mar 6.
Degradation of three lipid regulators, i.e., gemfibrozil, bezafibrate and clofibric acid, by a UV/chlorine treatment was systematically investigated. The chlorine oxide radical (ClO) played an important role in the degradation of gemfibrozil and bezafibrate with second-order rate constants of 4.2 (±0.3) × 10 M s and 3.6 (±0.1) × 10 M s, respectively, whereas UV photolysis and the hydroxyl radical (HO) mainly contributed to the degradation of clofibric acid. The first-order rate constants (k') for the degradation of gemfibrozil and bezafibrate increased linearly with increasing chlorine dosage, primarily due to the linear increase in the ClO concentration. The k' values for gemfibrozil, bezafibrate, and clofibric acid degradation decreased with increasing pH from 5.0 to 8.4; however, the contribution of the reactive chlorine species (RCS) increased. Degradation of gemfibrozil and bezafibrate was enhanced in the presence of Br, whereas it was inhibited in the presence of natural organic matter (NOM). The presence of ammonia at a chlorine: ammonia molar ratio of 1:1 resulted in decreases in the k' values for gemfibrozil and bezafibrate of 69.7% and 7%, respectively, but led to an increase in that for clofibric acid of 61.8%. Degradation of gemfibrozil by ClO was initiated by hydroxylation and chlorine substitution on the benzene ring. Then, subsequent hydroxylation, bond cleavage and chlorination reactions led to the formation of more stable products. Three chlorinated intermediates were identified during ClO oxidation process. Formation of the chlorinated disinfection by-products chloral hydrate and 1,1,1-trichloropropanone was enhanced relative to that of other by-products. The acute toxicity of gemfibrozil to Vibrio fischeri increased significantly when subjected to direct UV photolysis, whereas it decreased when oxidized by ClO. This study is the first to report the transformation pathway of a micropollutant by ClO.
系统研究了 UV/氯处理对三种脂调节剂（即吉非贝齐、苯扎贝特和氯贝酸）的降解作用。氯氧化物自由基（ClO）在吉非贝齐和苯扎贝特的降解中起着重要作用，其二级反应速率常数分别为 4.2（±0.3）×10M s和 3.6（±0.1）×10M s，而 UV 光解和羟基自由基（HO）主要贡献了氯贝酸的降解。吉非贝齐和苯扎贝特的降解一级速率常数（k'）随氯剂量的增加呈线性增加，主要是由于 ClO 浓度的线性增加。在 pH 值从 5.0 增加到 8.4 的过程中，吉非贝齐、苯扎贝特和氯贝酸降解的 k'值降低，但活性氯物种（RCS）的贡献增加。Br 的存在促进了吉非贝齐和苯扎贝特的降解，而天然有机物（NOM）的存在则抑制了它们的降解。在氯：氨摩尔比为 1:1 的条件下，氨的存在使吉非贝齐和苯扎贝特的 k'值分别降低了 69.7%和 7%，但使氯贝酸的 k'值增加了 61.8%。ClO 对吉非贝齐的降解是通过苯环上的羟化和氯取代作用引发的。然后，随后的羟化、键断裂和氯化反应导致形成更稳定的产物。在 ClO 氧化过程中鉴定出三种氯化中间产物。氯仿和 1,1,1-三氯丙酮等氯化消毒副产物的形成相对于其他副产物得到增强。与直接 UV 光解相比，吉非贝齐对发光菌 Vibrio fischeri 的急性毒性显著增加，而当被 ClO 氧化时，其毒性降低。本研究首次报道了 ClO 对一种微污染物的转化途径。
