Photocatalytic Degradation Of Gaseous Benzene Over Pyrite Supported Bismuth Compounds

Bismuth-based semiconductor materials have been extensively studied as new visible light photocatalysts because of their narrow band gap and good visible light absorption activity.A series of pyrite supported bismuth compound composite catalysts(Bi₂WO_6/FeS₂,BiVO₄/FeS₂,FeS₂/Bi₂MoO₆)were synthesisd via hydrothermal-calcinations method using pyrite as precursor.Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,scanning electron mi-croscopy（SEM）,UV-Vis reflection spectrometer（DRS）,and N₂adsorption-desorption measurement（BET）were employed to characterize the composition,optical absorption region,surface morphology and structure of the composite catalysts.The catalytic performance and degradation mechanism of the composite catalyst were discussed experimentally.At the same time,the mineralization rate was calculated by measuring the amount of CO₂ produced.The conclusions were shown as follows:（1）Bi₂WO₆/FeS₂ composite catalysts were prepared by hydrothermal-calcinations method with pyrite as precursor.When the molar ratio of pyrite to bismuth tungstate was 1:1,the pH of precursor solution was 3 and the calcinations temperature was350℃,the composite catalysts had high photocatalytic activity.After 140 min under365 nm UV light irradiation,the degradation rate and mineralization rate of benzene with initial concentration of 100 mg/m³ could reach 66%and 61.8%,respectively.It was found that Bi₂WO₆/FeS₂ composite catalysts had larger specific surface area and wider optical absorption range than pure Bi₂WO₆ catalysts by characterization of different catalysts.The mechanism of photocatalytic degradation of benzene with Bi₂WO₆/FeS₂ composite catalyst was investigated.It was found that the photogenerated electron holes（h⁺）produced by Bi₂WO₆ and superoxide free radical(·O^2-)played a dominant role in the process of photocatalytic degradation of benzene.（2）BiVO₄/FeS₂ composite catalyst synthesized via hydrothermal-calcinations method with pyrite as precursor had good photocatalytic activity.When the molar ratio of pyrite to BiVO₄ was 0.6:1,calcinations temperature was 350℃ and the pH of precursor solution was 5,the composite catalyst exhibited the highest activity.After140 min under 365 nm UV light irradiation,the degradation rate and mineralization rate of 100 mg/m³ initial concentration benzene were 63.1%and 58.1%,respectively.The mechanism of photocatalytic degradation of gaseous benzene over BiVO₄/FeS₂composite catalyst was studied.It was found that photogenerated electron（h⁺）produced by BiVO₄/FeS₂ composite catalyst and hydroxyl radical（·OH）were the main active species in the process of photocatalytic degradation of gaseous benzene.（3）FeS₂/Bi₂MoO₆ composite catalyst prepared by hydrothermal-calcinations method with pyrite as precursor has high photocatalytic activity.When the mass ratio of pyrite to FeS₂/Bi₂MoO₆ is 0.05:1 and the calcinations temperature is 350 ℃,the composite catalyst has the highest activity.When irradiated by 365 nm ultraviolet light for 140minutes,the degradation rate and mineralization rate of 100 mg/m³ benzene were66.9%and 63.5%,respectively.The mechanism of photocatalytic degradation of gaseous benzene over FeS₂/Bi₂MoO₆ composite catalysts was studied.It was found that the photogenerated electron holes（h⁺）produced by FeS₂/Bi₂MoO₆ composite and superoxide free radical(·O^2-)and hydroxyl radical（·OH）played a dominant role in the process of photocatalytic degradation of benzene.