title: Photocatalytic degradation kinetics and mechanism of pentachlorophenol based on superoxide radicals.
abstract: The micron grade multi-metal oxide bismuth silicate (Bi12SiO20, BSO) was prepared by the chemical solution decomposition technique. Photocatalytic degradation of pentachlorophenol (PCP) was investigated in the presence of BSO under xenon lamp irradiation. The reaction kinetics followed pseudo first-order and the degradation ratio achieved 99.1% after 120 min at an initial PCP concentration of 2.0 mg/L. The pH decreased from 6.2 to 4.6 and the dechlorination ratio was 68.4% after 120 min at an initial PCP concentration of 8.0 mg/L. The results of electron spin resonance showed that superoxide radical (O2*-) was largely responsible for the photocatalytic degradation of PCP. Interestingly, this result was different from that of previous photocatalytic reactions where valence band holes or hydroxyl radicals played the role of major oxidants. Some aromatic compounds and aliphatic carboxylic acids were determined by GC/MS as the reaction intermediates, which indicated that O2*- can attack the bond between the carbon and chlorine atoms to form less chlorinated aromatic compounds. The aromatic compounds were further oxidized by O2*- to generate aliphatic carboxylic acids which can be finally mineralized to CO2 and H2O.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China. liyang_bnu@yahoo.cn
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
authors.forename: Lifeng
authors.initials: L
authors.lastname: Yin
authors.forename: Wenlong
authors.initials: W
authors.lastname: Wang
authors.forename: Yueping
authors.initials: Y
authors.lastname: Bao
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Yanpei
authors.initials: Y
authors.lastname: Duan
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D010416:Pentachlorophenol / Q000737:chemistry*; D010782:Photolysis; D017640:Silicates / Q000138:chemical synthesis*; D013481:Superoxides / Q000737:chemistry*
chemical_list: D004785:Environmental Pollutants; D017640:Silicates; D013481:Superoxides; D010416:Pentachlorophenol; D001729:Bismuth