title: New insights into the primary phototransformation of acetaminophen by UV/H2O2: photo-Fries rearrangement versus hydroxyl radical induced hydroxylation.
abstract: The phototransformation of acetaminophen (APAP) by UV/H2O2 in deionized water and sewage treatment plant (STP) effluents was studied systematically by a combination of analysis of the reaction intermediates and kinetic study. 1-(2-amino-5-hydroxyphenyl)ethanone (P1) and the reported N-(3,4-dihydroxyphenyl)acetamide (P2) were identified as the main transformation intermediates during the transformation of APAP by UV/H2O2. There was no influence of OH on the formation kinetics of P1, while its decay was promoted. The formation and decay kinetics of P2 were accelerated by increases in the concentration of OH. The second-order rate constants for the reaction of OH with APAP, P1, and P2 were 3.9 × 10(9), 8.1 × 10(9), and 4.7 × 10(9) M(-1) s(-1), respectively. The kinetic study indicated that the main transformation of APAP also included transformation to 1,4-hydroquinone, although the accumulated concentration of 1,4-hydroquinone was quite low. The presence of anions (Cl(-), HCO3(-)/CO3(2-) NO2(-)/NO3(-)), humic acid, commercial drug components or adjuvants, and dissolved organic matters in STP effluents not only changed the transformation kinetics of APAP, but also altered the distribution of the intermediates. The kinetics and pathway of APAP transformation in STP effluent were markedly different from those in deionized water.
authors.affiliation: School of Resources and Environmental Science, Wuhan University, Wuhan, 430079, PR China.
authors.forename: Shixiang
authors.initials: S
authors.lastname: Feng
authors.affiliation: School of Resources and Environmental Science, Wuhan University, Wuhan, 430079, PR China. Electronic address: xuzhangwhu@gmail.com.
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: School of Chemical and Environmental Engineering, Jianghan University, Wuhan, 430056, PR China. Electronic address: yxliujd@163.com.
authors.forename: Yanxiang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D006900:Hydroxylation; D007700:Kinetics; D010782:Photolysis; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D000082:Acetaminophen; D006861:Hydrogen Peroxide
keywords: Acetaminophen; Hydroxylation; Kinetics; Mechanism; Photo-Fries; UV/H(2)O(2)