title: Oxidative degradation of N-Nitrosopyrrolidine by the ozone/UV process: Kinetics and pathways.
abstract: N-Nitrosopyrrolidine (NPYR) is an emerging contaminant in drinking water and wastewater. The degradation kinetics and mechanisms of NPYR degradation by the O3/UV process were investigated and compared with those of UV direct photolysis and ozonation. A synergistic effect of ozone and UV was observed in the degradation of NPYR due to the accelerated production of OH• by ozone photolysis. This effect was more pronounced at higher ozone dosages. The second-order rate constants of NPYR reacting with OH• and ozone was determined to be 1.38 (± 0.05) × 10(9) M(-1) s(-1) and 0.31 (± 0.02) M(-1) s(-1), respectively. The quantum yield by direct UV photolysis was 0.3 (± 0.01). An empirical model using Rct (the ratio of the exposure of OH• to that of ozone) was established for NPYR degradation in treated drinking water and showed that the contributions of direct UV photolysis and OH• oxidation on NPYR degradation were both significant. As the reaction proceeded, the contribution by OH• became less important due to the exhausting of ozone. Nitrate was the major product in the O3/UV process by two possible pathways. One is through the cleavage of nitroso group to form NO• followed by hydrolysis, and the other is the oxidation of the intermediates of amines by ozonation.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China. Electronic address: fangjy3@mail.sysu.edu.cn.
authors.forename: Jingyun
authors.initials: J
authors.lastname: Fang
authors.affiliation: Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, Taiwan. Electronic address: chfan@ntu.edu.tw.
authors.forename: Chihhao
authors.initials: C
authors.lastname: Fan
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Hong Kong Branch of Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Hong Kong.
authors.forename: Chii
authors.initials: C
authors.lastname: Shang
mesh_terms: D007700:Kinetics; D009242:N-Nitrosopyrrolidine / Q000737:chemistry*; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D010782:Photolysis; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
chemical_list: D014874:Water Pollutants, Chemical; D010126:Ozone; D009242:N-Nitrosopyrrolidine
keywords: Advanced oxidation process (AOP); Hydroxyl radicals; Nitrosamines; Ozone; Ultraviolet; Water treatment