title: Evidence of superoxide radical contribution to demineralization of sulfamethoxazole by visible-light-driven Bi2O3/Bi2O2CO3/Sr6Bi2O9 photocatalyst.
abstract: Photocatalytic degradation of sulfamethoxazole (SMX) was investigated using Bi2O3/Bi2O2CO3/Sr6Bi2O9 (BSO) photocatalyst under visible light (>420 nm) irradiation. The photochemical degradation of SMX followed pseudo-first-order kinetics. The reaction kinetics was determined as a function of initial SMX concentrations (5-20 mg L(-1)), initial pH (3-11) and BSO concentrations (6-600 mg L(-1)). Approximately, 90% of SMX (10 mg L(-1)) degradation and 36% of TOC reduction were achieved at pH 7.0 after 120 min irradiation. The main mineralization products, including NH4(+), NO3(-), SO4(2-) and CO2, as well as intermediates 3-amino-5-methylisoxazole (AMI), p-benzoquinone (BZQ), and sulfanilic acid (SNA) were detected in aqueous solution. The formation of O2(*-) radical was evidenced by using electron spin resonance and a chemiluminescent probe, luminal. A possible degradation mechanism involving excitation of BSO, followed by charge injection into the BSO conduction band and formation of reactive superoxide radical (O2(*-)) was proposed for the mineralization of SMX. During the reaction, the O2(*-) radical attacks the sulfone moiety and causes the cleavage of the SN bond, which leads to the formation of two sub-structure analogs, AMI and SNA.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Shiyuan
authors.initials: S
authors.lastname: Ding
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
authors.forename: Yueping
authors.initials: Y
authors.lastname: Bao
authors.forename: Lijuan
authors.initials: L
authors.lastname: Hu
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry; D001729:Bismuth / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D008027:Light; D055668:Photochemical Processes; D013420:Sulfamethoxazole / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D013481:Superoxides; D013420:Sulfamethoxazole; D001729:Bismuth
keywords: Demineralization; Photodegradation; Sulfamethoxazole; Superoxide radical; Visible light irradiation