title: Transformation of humic acid and halogenated byproduct formation in UV-chlorine processes.
abstract: The synergistic effect of ultraviolet light (UV) and chlorine on the structural transformation of Humic Acid (HA) and formation of chloro-disinfection byproducts (DBPs) in water were investigated, with chlorination as a reference. The transformation and mineralization of HA were enhanced upon co-exposure to UV and chlorine. Electron spin resonance (ESR) studies revealed that hydroxyl radical (OH) and chlorine radical (Cl) were predominant active species in a pH range from 4 to 7, while Cl dominated at pH 2 and pH higher than 7. The impact of different radicals on the transformation of HA was investigated by UV254, fluorescence and TOC measurements. OH were found to be responsible for the removal of chromophoric groups and mineralization of HA, while Cl mainly reacted with HA and intermediates from HA degradation. Due to the competitive and synergistic reaction of OH and Cl with HA, higher removal of HA and lower formation of chloro-DBPs appeared in UV-chlorine than chlorination, thus the combined UV-chlorine processes should be a promising method for water purification.
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Li
authors.affiliation: College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning Shihua University, Liaoning 113001, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: An
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Hu
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: jhqu@rcees.ac.cn.
authors.forename: Jiuhui
authors.initials: J
authors.lastname: Qu
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D004203:Disinfection; D054879:Halogenation; D006812:Humic Substances; D014466:Ultraviolet Rays; D018508:Water Purification
chemical_list: D006812:Humic Substances; D002713:Chlorine
keywords: Chlorine radical; Disinfection byproducts; Humic acid; Hydroxyl radical; UV-chlorine