title: A novel photocatalytic material for removing microcystin-LR under visible light irradiation: degradation characteristics and mechanisms.
abstract: OBJECTIVE
  Microcystin-LR (MC-LR), a common toxic species in contaminated aquatic systems, persists for long periods because of its cyclic structure. Ag3PO4 is an environment-friendly photocatalyst with relatively good degradation capacity for hazardous organic pollutants. This study aimed to investigate the degradation capacity of Ag3PO4 for MC-LR under visible light.
  
  
  METHODS
  An Ag3PO4 photocatalyst was synthesized by the ion-exchange method and characterized by X-ray diffraction, field-emission scanning electron microscope, and UV-Vis spectrophotometer. MC-LR was quantified in each sample through high-performance liquid chromatograph. The degradation efficiency of MC-LR was affected by initial pH, initial Ag3PO4 concentration, initial MC-LR concentration, and recycle experiments. The degradation intermediates of MC-LR were examined by liquid chromatography-mass spectrometry (LC/MS).
  
  
  RESULTS
  The degradation process can be well fitted with the pseudo-first-order kinetic model. The maximum MC-LR degradation rate of 99.98% can be obtained within 5 h under the following optimum conditions: pH of 5.01, Ag3PO4 concentration of 26.67 g/L, and MC-LR concentration of 9.06 mg/L. Nine intermediates were detected and analyzed by LC/MS. Three main degradation pathways were proposed based on the molecular weight of the intermediates and the reaction mechanism: (1) hydroxylation on the aromatic ring of Adda, (2) hydroxylation on the diene bonds of Adda, and (3) internal interactions on the cyclic structure of MC-LR.
  
  
  CONCLUSIONS
  Ag3PO4 is a highly efficient catalyst for MC-LR degradation in aqueous solutions.
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sui
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai, China.
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Wang
authors.affiliation: South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.
authors.forename: Honghui
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai, China.
authors.forename: Guotao
authors.initials: G
authors.lastname: Peng
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai, China.
authors.forename: Shoubing
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Environmental Science & Engineering, Fudan University, Shanghai, China.
authors.forename: Zhengqiu
authors.initials: Z
authors.lastname: Fan
mesh_terms: D002384:Catalysis; D006900:Hydroxylation; D008027:Light; D008387:Marine Toxins; D013058:Mass Spectrometry; D052998:Microcystins; D010710:Phosphates / Q000737:chemistry; D010777:Photochemistry; D018030:Silver Compounds / Q000737:chemistry; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D010710:Phosphates; D018030:Silver Compounds; D014874:Water Pollutants, Chemical; C057862:cyanoginosin LR; C039072:silver phosphate
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