title: Chlorination of chlortoluron: kinetics, pathways and chloroform formation.
abstract: Chlortoluron chlorination is studied in the pH range of 3-10 at 25 ± 1°C. The chlorination kinetics can be well described by a second-order kinetics model, first-order in chlorine and first-order in chlortoluron. The apparent rate constants were determined and found to be minimum at pH 6, maximum at pH 3 and medium at alkaline conditions. The rate constant of each predominant elementary reactions (i.e., the acid-catalyzed reaction of chlortoluron with HOCl, the reaction of chlortoluron with HOCl and the reaction of chlortoluron with OCl(-)) was calculated as 3.12 (± 0.10)×10(7)M(-2)h(-1), 3.11 (±0.39)×10(2)M(-1)h(-1) and 3.06 (±0.47)×10(3)M(-1)h(-1), respectively. The main chlortoluron chlorination by-products were identified by gas chromatography-mass spectrometry (GC-MS) with purge-and-trap pretreatment, ultra-performance liquid chromatography-electrospray ionization-MS and GC-electron capture detector. Six volatile disinfection by-products were identified including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone, dichloronitromethane and trichloronitromethane. Degradation pathways of chlortoluron chlorination were then proposed. High concentrations of CF were generated during chlortoluron chlorination, with maximum CF yield at circumneutral pH range in solution.
authors: State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Aquatic Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors: Bin
authors: B
authors: Xu
authors: Fu-Xiang
authors: FX
authors: Tian
authors: Chen-Yan
authors: CY
authors: Hu
authors: Yi-Li
authors: YL
authors: Lin
authors: Sheng-Ji
authors: SJ
authors: Xia
authors: Rong
authors: R
authors: Rong
authors: Da-Peng
authors: DP
authors: Li
mesh_terms: D002725:Chloroform / Q000032:analysis / Q000138:chemical synthesis*; D054879:Halogenation; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010671:Phenylurea Compounds / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification
chemical_list: D006540:Herbicides; D010671:Phenylurea Compounds; D014874:Water Pollutants, Chemical; D002725:Chloroform; C007033:chlortoluron