title: Kinetic models and pathways of ronidazole degradation by chlorination, UV irradiation and UV/chlorine processes.
abstract: Degradation kinetics and pathways of ronidazole (RNZ) by chlorination (Cl2), UV irradiation and combined UV/chlorine processes were investigated in this paper. The degradation kinetics of RNZ chlorination followed a second-order behavior with the rate constants calculated as (2.13 ± 0.15) × 10(2) M(-2) s(-1), (0.82 ± 0.52) × 10(-2) M(-1) s(-1) and (2.06 ± 0.09) × 10(-1) M(-1) s(-1) for the acid-catalyzed reaction, as well as the reactions of RNZ with HOCl and OCl(-), respectively. Although UV irradiation degraded RNZ more effectively than chlorination did, very low quantum yield of RNZ at 254 nm was obtained as 1.02 × 10(-3) mol E(-1). RNZ could be efficiently degraded and mineralized in the UV/chlorine process due to the generation of hydroxyl radicals. The second-order rate constant between RNZ and hydroxyl radical was determined as (2.92 ± 0.05) × 10(9) M(-1) s(-1). The degradation intermediates of RNZ during the three processes were identified with Ultra Performance Liquid Chromatography - Electrospray Ionization - mass spectrometry and the degradation pathways were then proposed. Moreover, the variation of chloropicrin (TCNM) and chloroform (CF) formation after the three processes were further evaluated. Enhanced formation of CF and TCNM precursors during UV/chlorine process deserves extensive attention in drinking water treatment.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Lang
authors.initials: L
authors.lastname: Qin
authors.affiliation: Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 824, Taiwan, ROC.
authors.forename: Yi-Li
authors.initials: YL
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China. Electronic address: tjwenwu@gmail.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.affiliation: College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, PR China.
authors.forename: Chen-Yan
authors.initials: CY
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Fu-Xiang
authors.initials: FX
authors.lastname: Tian
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Tian-Yang
authors.initials: TY
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Wen-Qian
authors.initials: WQ
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Nai-Yun
authors.initials: NY
authors.lastname: Gao
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry; D054879:Halogenation; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry; D007700:Kinetics; D012385:Ronidazole / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D006843:Hydrocarbons, Chlorinated; D014874:Water Pollutants, Chemical; D002713:Chlorine; D002725:Chloroform; D012385:Ronidazole; C100187:chloropicrin
keywords: Chloropicrin (TCNM); Degradation kinetics; Nitroimidazoles; UV/chlorine; Water treatment