title: Photodegradation kinetics, products and mechanism of timolol under simulated sunlight.
abstract: The photodegradation of β-blocker timolol in fulvic acid (FA) solution was investigated under simulated sunlight. The triplet excited state of FA ((3)FA(*)) and singlet oxygen ((1)O2) were the main reactive species responsible for the degradation of timolol in the aerated FA solutions. Both dissolved oxygen and iodide ions (I(-)) are the efficient quenchers of (3)FA(*). The photodegradation was drastically accelerated after removing the dissolved oxygen. The presence of I(-) inhibited the photosensitized degradation of timolol in the deoxygenated FA solutions, whereas the role of I(-) in the reaction was concentration-dependent in the aerated solutions. The other halide ions such as chloride (Cl(-)) and bromide (Br(-)) exhibited less effect on the photodegradation of timolol in both aerated and deoxygenated solutions. By LC-DAD/ESI-MS/MS analysis, the photoproducts of timolol in both aerated and deoxygenated FA solutions were identified. Electron transfer interaction occurred between (3)FA(*) and amine moiety of timolol, leading to the cleavage of C-O bond in the side chain and oxidation of the hexatomic ring. These findings suggest the photosensitized degradation was a significant pathway for the elimination of timolol in natural waters.
authors.affiliation: School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. ychen@hust.edu.cn
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Qi
authors.initials: Q
authors.lastname: Liang
authors.forename: Danna
authors.initials: D
authors.lastname: Zhou
authors.forename: Zongping
authors.initials: Z
authors.lastname: Wang
authors.forename: Tao
authors.initials: T
authors.lastname: Tao
authors.forename: Yuegang
authors.initials: Y
authors.lastname: Zuo
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000737:chemistry / Q000528:radiation effects*; D001578:Benzopyrans / Q000737:chemistry; D001965:Bromides / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007454:Iodides / Q000737:chemistry; D007700:Kinetics; D010100:Oxygen / Q000737:chemistry; D010782:Photolysis; D013472:Sunlight; D013999:Timolol / Q000737:chemistry / Q000528:radiation effects*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D000319:Adrenergic beta-Antagonists; D001578:Benzopyrans; D001965:Bromides; D002712:Chlorides; D007454:Iodides; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D013999:Timolol; D010100:Oxygen; C005023:fulvic acid