title: Degradation kinetics and chloropicrin formation during aqueous chlorination of dinoseb.
abstract: The kinetics of chlorination of dinoseb and the corresponding formation of disinfection by-products (DBPs) were studied between pH 4 and 9 at room temperature (25±1°C). The reactivity shows a minimum at pH 9, a maximum at pH 4 and a medium at neutral conditions. pH profile of the apparent second-order rate constant of the reaction of dinoseb with chlorine was modeled considering the elementary reactions of HOCl with dinoseb species and an acid-catalyzed reaction. The predominant reactions at near neutral pH were the reactions of HOCl with the two species of dinoseb. The rate constants of 2.0 (±0.8)×10(4)M(-2)s(-1), 3.3 (±0.6) and 0.5 (±0.1)M(-1)s(-1) were determined for the acid-catalyzed reaction, HOCl reacted with dinoseb and dinoseb(-), respectively. The main degradation by-products of the dinoseb formed during chlorination have been separated and identified by GC-MS with liquid-liquid extraction sample pretreatment. Six volatile and semi-volatile DBPs were identified in the chlorination products, including chloroform (CF), monochloroacetone, chloropicrin (TCNM), 1,1-dichloro-2-methy-butane, 1,2-dichloro-2-methy-butane, 1-chloro-3-methy-pentanone. A proposed degradation pathway of dinoseb during chlorination was then given. TCNM and CF formation potential during chlorination of dinoseb reached as high as 0.077 and 0.097μMμM(-1) dinoseb under the traditional condition (pH=7 and Cl2/C=2). Their yields varied with Cl2/C, pH and time. The maximum yields of TCNM appeared at molar ratio as Cl2/C=1 and pH 3, while the maximum of CF appeared at molar ratio as Cl2/C=4 and pH 7. [TCNM]/[CF] decreased with reaction time and increased solution pH.
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.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Chen-Yan
authors.initials: CY
authors.lastname: Hu
authors.forename: Mian
authors.initials: M
authors.lastname: Li
authors.forename: Sheng-Ji
authors.initials: SJ
authors.lastname: Xia
authors.forename: Fu-Xiang
authors.initials: FX
authors.lastname: Tian
authors.forename: Nai-Yun
authors.initials: NY
authors.lastname: Gao
mesh_terms: D019297:2,4-Dinitrophenol / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010575:Pesticides / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D006843:Hydrocarbons, Chlorinated; D010575:Pesticides; D014874:Water Pollutants, Chemical; C100187:chloropicrin; D019297:2,4-Dinitrophenol; C018527:dinoseb
keywords: Chlorination; Chloropicrin; Dinoseb; Disinfection by-product formation; Kinetics