title: Oxidation of diclofenac by aqueous chlorine dioxide: identification of major disinfection byproducts and toxicity evaluation.
abstract: Diclofenac (DCF), a synthetic non-steroidal anti-inflammatory drug, is one of the most frequently detected pharmaceuticals in the aquatic environment. In this work, the mechanism and toxicity of DCF degradation by ClO2 under simulated water disinfection conditions were investigated. Experimental results indicate that rapid and significant oxidation of DCF occurred within the first few minutes; however, its mineralization process was longer than its degradation process. UPLC-MS and (1)H NMR spectroscopy were performed to identify major disinfection byproducts that were generated in three tentative degradation routes. The two main routes were based on initial decarboxylation of DCF on the aliphatic chain and hydroxylation of the phenylacetic acid moiety at the C-4 position. Subsequently, the formed aldehyde intermediates were the starting point for further multistep degradation involving decarboxylation, hydroxylation, and oxidation reactions of CN bond cleavage. The third route was based on transient preservation of chlorinated derivatives resulting from electrophilic attack by chlorine on the aromatic ring, which similarly underwent CN bond cleavage. Microtox bioassay was employed to evaluate the cytotoxicity of solutions treated by ClO2. The formation of more toxic mid-byproducts during the ClO2 disinfection process poses a potential risk to consumers.
authors.affiliation: School of Environment, Henan Normal University, Henan Key laboratory for Environmental Pollution Control, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Ministry of Education, Xinxiang 453007, PR China; School of Basic Medicine, Xinxiang Medical University, Xinxiang 453003, PR China.
authors.forename: Yingling
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Environment, Henan Normal University, Henan Key laboratory for Environmental Pollution Control, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Ministry of Education, Xinxiang 453007, PR China.
authors.forename: Haijin
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Environment, Henan Normal University, Henan Key laboratory for Environmental Pollution Control, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Ministry of Education, Xinxiang 453007, PR China; Faculty of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, PR China. Electronic address: liugg@gdut.edu.cn.
authors.forename: Guoguang
authors.initials: G
authors.lastname: Liu
authors.affiliation: School of Environment, Henan Normal University, Henan Key laboratory for Environmental Pollution Control, Key Laboratory for Yellow River and Huaihe River Water Environment and Pollution Control, Ministry of Education, Xinxiang 453007, PR China.
authors.forename: Youhai
authors.initials: Y
authors.lastname: Xie
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D017606:Chlorine Compounds / Q000737:chemistry*; D004008:Diclofenac / Q000737:chemistry*; D004202:Disinfectants / Q000737:chemistry*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D017606:Chlorine Compounds; D004202:Disinfectants; D010087:Oxides; D004008:Diclofenac; C025109:chlorine dioxide
keywords: Byproducts; Chlorine dioxide; Diclofenac; Mechanism; Toxicity; Water treatment