Photocatalytic Degradation Of Gaseous Benzene Over ?-Fe₂O₃ Supported Bismuthate

In recent years,with the emissions of VOCs(volatile organic pollutants)in the atmosphere have gradually increased,the atmospheric environment and human health have been seriously threatened.Therefore,the control of VOCs pollution has become an urgent problem.Some traditional techniques for the treatment of VOCs include adsorption,adsorption,combustion,etc.,but these methods can't effectively control the serious pollution caused by VOCs.Therefore,to seek a new type of VOCs governance has become a hot topic of concern to scholars at home and adroad.Being environment-friendly,no secondary pollution,high efficiency and favored,photocatalytic technique has been considered as an acceptable method for degradation of VOCs.A narrow bandgap width,good visible light absorption activity,so the application of a wide range of prospects.In this paper,a series of ?-Fe2O3 loaded bismuth compounds(Bi2WO6,BiVO4,Bi2MoO6)composite catalysts were synthesized by using goethite as precursors.The composite catalysts were characterized by XRD,SEM,BET,DRS and XPS.The mechanism of photocatalytic degradation of gaseous benzene by the composite catalyst was investigated experimentally,and the mineralization rate was calculated by measuring the amount of CO2 produced.Main conclusions were shown as follows:(1)The Bi2WO6/?-Fe2O3 materials with high photocatalytic property were synthesized by hydrothermal-calcination method,the optimum conditions of composite catalyst was Bi2WO6/?-Fe2O3 with molar mass of 0.8:1 calcined at 350 ? and the pH of precursor solution was 3.In the case of 0.7 g dose catalysts,the benzene initial concentration 50 mg/m3 and after 220 min UV irradiation,the degradation rate reached 71.9%and the mineralization was 67.6%,which were significantly higher than that pure Bi2WO6.Photo-generated holes h+ and ·O2-radical played a dominant role in the process of the photocatalytic degradation of benzene.(2)BiVO4/?-Fe2O3 composite catalyst exhibited good photocatalytic activity and were synthesized by using goethite as a precursor through hydrothermal-calcination method.When the mass ratio of ?-FeOOH and BiVO4 was 5:5,the calcinations temperature was 350 ?,the benzene initial concentration 100 mg/m3 and after 365 nm UV irradiation 210 min,the degradation rate and the mineralization of gaseous benzene reached 66.87%and 76.5%in air,respectively.The h+ and reactive oxygen species played an important role in the degradation of benzene.(3)Bi2MoO6/?-Fe2O3 composite photocatalysts were successfully prepared by hydrothermal-calcination method.The results showed that Bi2MoO6/?-Fe2O3 composite photocatalyst has the highest photocatalytic activity when the mass ratio of ?-FeOOH and Bi2MoO6 was 0.2:1 and the calcinations temperature was 300 ? and the degradation rate of gaseous benzene with 100 mg/m3 reached 71.74%after 180 min.The main role of ?-FeOOH was to increase the surface area of the composite catalyst,broaden the visible absorption range and effectively separate the photo-generated hole-electron pairs.In this reaction system,h+,·O2-and ·OH were responsible for the degradation of benzene.