title: Faster photodegradation rate and higher dioxin yield of triclosan induced by cationic surfactant CTAB.
abstract: Triclosan has received extensive attention as it has been frequently detected in the aquatic environment. Photolysis was found to be a major pathway governing the fate of triclosan in the aquatic environment. However, the effects of surfactants that usually coexist with triclosan, on the photodegradation of triclosan, are largely unknown. In this study, the effects of selected surfactants on the photodegradation of triclosan were investigated experimentally. The results show that anionic sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and neutral polyoxyethylene (20) sorbitan monooleate inhibit the photolysis of triclosan, whereas cationic cetyltrimethylammonium bromide (CTAB) significantly accelerates the photodegradation rate of triclosan. The interactions between the hydrophilic group of CTAB and anionic triclosan lead to the apparent decrease of pKa of triclosan from 8.4 to 6.1, which increase the fraction of anionic triclosan from 4% to 89% in neutral solution. A red shift in the UV-VIS absorption spectrum is exhibited, thus leading to the increased photodegradation rate of triclosan. The accelerations caused by CTAB were observed under xenon lamp and Hg lamp irradiances, as well as under natural sunlight. Effect of CTAB demonstrated pH dependence with significantly enhancement under pH 5∼9 and inhibition at pH=3. The presence of CTAB also increased the yield of 2,8-dichlorodibenzo-p-dioxin from the photolysis of triclosan about 7 times at pH=7.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China. Electronic address: xlqiao@dlut.edu.cn.
authors.forename: Xianliang
authors.initials: X
authors.lastname: Qiao
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Xianhai
authors.initials: X
authors.lastname: Yang
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Weifeng
authors.initials: W
authors.lastname: Xue
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000528:radiation effects*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D004147:Dioxins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010782:Photolysis; D013472:Sunlight; D013501:Surface-Active Agents / Q000737:chemistry*; D014260:Triclosan / Q000737:chemistry / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D000900:Anti-Bacterial Agents; D002593:Cetrimonium Compounds; D004147:Dioxins; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D014260:Triclosan; C068993:2,8-dichlorodibenzo-4-dioxin; D000077286:Cetrimonium
keywords: Anionic speciation, Dioxin yield; CTAB; Surfactants; Triclosan; pKa