title: Photosensitized degradation of acetaminophen in natural organic matter solutions: The role of triplet states and oxygen.
abstract: The photolysis of acetaminophen, a widely used pharmaceutical, in simulated natural organic matter solutions was investigated. The triplet states of natural organic matter (3NOM*) were found to play the dominant role in its photodegradation, while the contributions from hydroxyl radicals and singlet oxygen were negligible. Dissolved oxygen (DO) plays a dual role. From anaerobic to microaerobic (0.5 mg/L DO) conditions, the degradation rate of acetaminophen increased by 4-fold. That suggests the involvement of DO in reactions with the degradation intermediates. With increasing oxygen levels to saturated conditions (26 mg/L DO), the degradation rate became slower, mainly due to DO's quenching effect on3NOM*. Superoxide radical (O2-) did not react with acetaminophen directly, but possibly quenched the intermediates to reverse the degradation process. The main photochemical pathways were shown to involve phenoxyl radical and N-radical cations, finally yielding hydroxylated derivatives, dimers and nitrosophenol. A reaction mechanism involving3NOM*, oxygen and O2-is proposed.
authors.affiliation: School of Environmental Science and Engineering, Key Laboratory of Aquatic Product Safety of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Yanyun
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Environmental Science and Engineering, Key Laboratory of Aquatic Product Safety of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Yanheng
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China.
authors.forename: Lushi
authors.initials: L
authors.lastname: Lian
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Yan
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China. Electronic address: wsong@fudan.edu.cn.
authors.forename: Weihua
authors.initials: W
authors.lastname: Song
authors.affiliation: School of Environmental Science and Engineering, Key Laboratory of Aquatic Product Safety of Ministry of Education, Sun Yat-sen University, Guangzhou 510275, China. Electronic address: yangx36@mail.sysu.edu.cn.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
mesh_terms: D000082:Acetaminophen; D010100:Oxygen; D010782:Photolysis; D017319:Photosensitizing Agents; D014874:Water Pollutants, Chemical
chemical_list: D017319:Photosensitizing Agents; D014874:Water Pollutants, Chemical; D000082:Acetaminophen; D010100:Oxygen
keywords: Acetaminophen; Oxygen; Photodegradation; Triplet states organic matter