Kinetics and mechanism of reactive radical mediated fluconazole degradation by the UV/chlorine process: Experimental and theoretical studies
Kinetics and mechanism of reactive radical mediated fluconazole degradation by the UV/chlorine process: Experimental and theoretical studies
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紫外线/氯过程反应自由基介导的氟康唑降解动力学和机制：实验和理论研究
DOI：
10.1016/j.cej.2020.126224
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发表时间：
2020-12-15
影响因子：
15.1
通讯作者：
Ying, Guang-Guo
中科院分区：
文献类型：
--
作者：
Cai, Wen-Wen;Peng, Tao;Ying, Guang-Guo
在UV/Cl工艺中，产生的羟基自由基（HO中心点）和氯衍生自由基（Cl中心点、ClO中心点等）可有效去除新出现的有机污染物。然而，活性自由基与污染物反应的降解机制和途径仍不清楚。本文采用理论计算和实验研究相结合的方法，研究了氟康唑在紫外/氯气工艺中的反应动力学和反应机理。结果表明，紫外线/氯处理能有效降解氟康唑，而紫外线光解和氯处理效果不明显。Cl。是HO。的氢原子转移和自由基加合物的形成机制，分别发挥主要作用，在氟康唑的降解。由于Cl中心点、HO中心点和ClO中心点的自由能垒分别为21.87、35.12和46.05 kcal mol（-1），因此Cl中心点、HO中心点和ClO中心点的单电子转移途径似乎是不可能的。经高分辨质谱鉴定，转化产物经氟康唑脱乙酰化、羟基化、断裂和与三唑环合环等反应形成6个转化产物。水质参数如pH和共存组分（DOM、HCO 3-/CO 32-）可通过影响活性自由基的产生而影响UV/Cl工艺对氟康唑的去除。紫外线/氯处理可以降低氟康唑对水生生物的毒性，仅检测到微量的三氯甲烷。
The emerging organic contaminants can be effectively removed in the UV/chlorine process by produced hydroxyl radical (HO center dot) and chlorine-derived radicals (Cl center dot, ClO center dot, etc.). However, the degradation mechanism and pathways of reactive radical reaction with contaminants are still unclear. Here we investigated the reactive radical mediated reaction kinetics and mechanism of fluconazole in UV/chlorine process using theoretical calculations and experimental studies. The results showed that fluconazole could be degraded effectively by UV/chlorine treatment than by UV photolysis and chlorination alone. The Cl. and HO. were found to play a major role in degradation of fluconazole by hydrogen atom transfer and radical adduct formation mechanisms, respectively. The single-electron transfer pathway of Cl center dot, HO center dot and ClO center dot seems to be impossible due to the high free energy barriers of 21.87 kcal mol(-1), 35.12 kcal mol(-1) and 46.05 kcal mol(-1), respectively. Six transformation products were identified by high resolution mass spectrometry and they were formed via fluconazole defluorination, hydroxylation, cleavage and cyclization with the triazole ring. The water quality parameters such as pH and coexisting components (DOM, HCO3-/CO32-) could influence the removal of fluconazole in UV/ chlorine process by impacting the generation of reactive radicals. The toxicity of fluconazole to aquatic organisms can be decreased by UV/chlorine process, and only trace amounts of chloroform were detected.