title: Enhanced debromination of 4-bromophenol by the UV/sulfite process: Efficiency and mechanism.
abstract: Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol (4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH (6.1-10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Bihuang
authors.initials: B
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Xuchun
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Weiming
authors.initials: W
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China. Electronic address: bcpan@nju.edu.cn.
authors.forename: Bingcai
authors.initials: B
authors.lastname: Pan
mesh_terms: D005411:Flame Retardants; D054879:Halogenation; D007700:Kinetics; D008956:Models, Chemical; D010636:Phenols / Q000737:chemistry*; D013447:Sulfites / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D005411:Flame Retardants; D010636:Phenols; D013447:Sulfites; C032037:4-bromophenol
keywords: Brominated aromatics; Debromination; Hydrated electron; Mechanism; UV/sulfite process