Synthesis And Photocatalytic Antibacterial Performance Of γ-Fe₂O₃/Ag/TiO₂

In this paper,a magnetic Ti02 photocatalyst doped with metal of sliver was prepared by two-step process,and the catalysis performance was characterized by X-ray Powder Diffraction(XRD),Scanning Electron Microscope(SEM),X-ray Photoelectron Spectroscopy(XPS),and Magnetic Property Measurement System(MPMS).The photocatalytic antibacterial performance and influence factors of y-Fe2O3/Ag/TiO2 were investigated,And the bactericidal mechanism of y-Fe2O3/Ag/Ti02 was also analyzed simultaneously.The main results were as follows:(1)The photocatalyst y-Fe2O3/Ag/Ti02 with highly visible-light response was successfully synthesized by two-step process,using Fe(NO3)3·9H2O as Fe source,tetrabutyl orthotitanate as Ti source and AgNO3 as Ag source.The E.coli was used as the target bacteria to evaluate the photocatalytic antibacterial performance of y-Fe2O3/Ag/TiO2 under visible light by the plate count method.The influence of n(Ti)/n(Ag),calcination temperatures,calcination time on the preparation of y-Fe2O3/Ag/Ti02 catalyst was investigated using the log reduction of E.coli as the evaluation index.And the optimal preparation parameters,such as n(Ti):n(Ag)=1:0.05,the calcination temperature 350℃,the calcination time 3h,were determined.(2)The crystal structure,morphological,element composition and hysteresis loop of y-Fe2O3/Ag/Ti02 were analyzed by XRD,SEM,XPS,MPMS.The results indicated that y-Fe2O3/Ag/Ti02 showed good crystal structure,high crystallinity.The silver loaded on the surface of the catalyst was metallic silver and Ti02 was a pure anatase phase.According to the characterization of y-Fe2O3/Ag/TiO2 by UV-vis,the results demonstrated that y-Fe2O3/Ag/TiO2 had a good response capacity to visible light.(3)The magnetic substance in the composite catalyst was y-Fe2O3.The magnetization saturation value of y-Fe2O3/Ag/TiO2 catalyst is about 10.7 emu·g-1 which is lower than that of pure y-Fe2O3(31.41emu·g-1).The results showed the catalyst still had excellent magnetic,and y-Fe2O3/Ag/TiO2 catalyst could be readily separated from water solution after the disinfection process by applying an external magnetic field.(4)The antibacterial performance of y-Fe2O3/Ag/TiO2 under different conditions was discussed,such as the catalyst dosages,the irradiation time and the humic acid concentration.The results demonstrated that the catalyst showed high antibacterial performance for E.coli,which the log reduction reached 6.09 after 30min under visible light irradiation as the dosage of catalyst 1.00g·L-1,and the initial bacterium suspension concentration of E.coli 107CFU·ml-1.·The addition of humic acid had certain influence on antibacterial performance of y-Fe2O3/Ag/TiO2,however,there was little influence on antibacterial ability under different concentrations of humic acid,and log reduction remained at 4.18-4.66 log.After 30min of visible light irradiation in presence of y-Fe2O3/Ag/TiO2,the surface of the bacterial cell was significantly damaged,and some wrinkles and depressions along with other phenomenan on the surface of bacteria appeared,and finally the cells corrupted and disappeared completely.The results revealed that the catalyst had strong antibacterial properties.(5)Under the condition of darkness,the visible light and sunlight,corresponding log reduction of E.xoli was 4.57,5.36 and 6.28,respectively.The results indicated the application of y-Fe2O3/Ag/TiO2 was not restricted by the light source,and the sterilization effect of the catalyst was particularly obvious under the sunlight condition.The results showed that the y-Fe2O3/Ag/TiO2 catalyst can be applied to drinking water disinfection.The good antibacterial performance of the catalyst is due to the metallic silver on the surface of the catalyst under dark condition,and the dual effect of metallic silver and reactive groups under visible light.