title: Visible-light-mediated Sr-Bi2O3 photocatalysis of tetracycline: kinetics, mechanisms and toxicity assessment.
abstract: Photodegradation of tetracycline (TC) was investigated in aqueous solution by visible-light-driven photocatalyst Sr-doped β-Bi2O3 (Sr-Bi2O3) prepared via solvothermal synthesis. The decomposition of TC by Sr-Bi2O3 under visible light (λ>420nm) irradiation followed pseudo-first-order kinetics, and the removal ratio reached 91.2% after 120min of irradiation. Sr-Bi2O3 photocatalysis is able to break the naphthol ring of TC which decomposes to m-cresol via dislodging hydroxyl group step by step by photogenerated electron. This mechanism was verified by electron spin resonance measurement, the addition of radical scavengers and the intermediate product analysis, indicating that the photogenerated electron acts as a reductant and can be the key to the degradation process. In contrast, in TiO2 photocatalysis the naphthol ring is broken via oxidation by hydroxyl radical, while in direct photolysis the ring remains intact. In addition, the toxicity of photodegradation products was analyzed by bioluminescence inhibition. After 120min of irradiation by Sr-Bi2O3, the toxicity decreases by 90.6%, which is more substantial than direct photolysis (70%) and TiO2 photocatalysis (80%), indicating that the Sr-Bi2O3 photocatalysis is more eco-friendly than the other two methods.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China. junfengn@bnu.edu.cn
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
authors.forename: Shiyuan
authors.initials: S
authors.lastname: Ding
authors.forename: Liwen
authors.initials: L
authors.lastname: Zhang
authors.forename: Jinbo
authors.initials: J
authors.lastname: Zhao
authors.forename: Chenghong
authors.initials: C
authors.lastname: Feng
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D002384:Catalysis; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D008027:Light; D010776:Photobacterium / Q000187:drug effects; D010782:Photolysis; D013324:Strontium / Q000737:chemistry*; D013752:Tetracycline / Q000737:chemistry* / Q000633:toxicity*; D014025:Titanium / Q000737:chemistry; D018675:Toxicity Tests
chemical_list: D005609:Free Radicals; C009495:titanium dioxide; C033301:bismuth oxide; D014025:Titanium; D013752:Tetracycline; D001729:Bismuth; D013324:Strontium
keywords: Mechanism; Photodegradation; Tetracycline; Toxicity; Visible light