Preparation Of The Composite Photocatalyst (Polyoxometalate And Bismuth Oxychloride) And Its Mechanism On Phohocatalytic Degradation Of Pollutants

Photocatalytic degradation of organic pollutants is a promising method in water treatment and efficient photocatalyst is the key to the reactions.However,the separation efficiency of photogenerated electrons and holes has an effect on the speed of photocatalytic reaction.Layered BiOCl was a kind of efficient photocatalysts,but the wide spread practical application was hindered by the fast combination speed of photogenerated electron-hole pairs.Heteropoly acids has the ability of storaging and transferring the electrons.Moreover the structural of the polyacids in reduced and oxidized states do not change while gaining or loss electrons,so it is an environmentally friendly functional materials.In this study,we prepared the composite photocatalyst via a hydrothermal method in which BiOCl grown on the surface of the（NH₄）₃PW₁₂O₄₀（NH₄PTA）.What’s more,the composite photocatalyst of BiOCl and polyoxometalate（NH₄PTA and P8W48）that based on graphene（Go）were prepared by photoreduction.The photocatalyst was regulated and controlled by the degradation of dyestuff;structure and crystal form were analysed by various of characterization methods;the extensive application of the composite catalyst was discussed with the degradation of the heavy metal complex（EDTA-Cu）;the mechanism of the degradation of organic pollutants by the catalyst was also discussed.（1）The composite photocatalyst which BiOCl grew on the surface was prepared via a hydrothermal method.The efficient separation of electron-hole pairs has been improved bacause NH₄PTA could accept the photoelectrons from BiOCl,and it has been proved by XPS and electrochemical testing,so it had a better photocatalytic activity.Methyl orange was the simulated pollutants and the mechanism of degradation was shown that when the mole ratio of Bi to W was 1:1,it had the best photo activity（the degradation rate was 100%after the irrigation 25 min）.However,it did not have a good effect on the degradation of EDTA-Cu.The reactive species trapping experiments showed that O₂·^-and·OH were the dominant reactive species for the reactions.（2）The composite photocatalyst rGo-NH₄PTA/BiOCl was prepared via photoreduction.It was shown that the NH₄PTA could act the acceptor of the electrons from BiOCl which improved the separation efficiency of electron-hole pairs and it could been proved by XPS,ESR and electchemical test.The mechanism of degradation pollutants was studied by the simulated pollutants（Rhb）.The experiments showed that when the mass ratio of Go to BiOCl was 10%,it had the best photo activity and the degradation ratio was 93%after 30 min irrigation.However,it did not have a good effect on the degradation of EDTA-Cu.The reactive species trapping experiments showed that O₂·^-played an important role in the reactions of Rhb.（3）The composite photocatalyst rGo-P8W48/BiOCl was prepared by photoreduction and hydrothermal method.It was shown that the P8W48 could also act the acceptor of the electrons from BiOCl which improved the separation efficiency of electron-hole pairs and it could been proved by XPS.The mechanism of degradation pollutants was studied by the simulated pollutants（Rhb）.The experiments showed that when the mass ratio of P8W48to Go was 80,it had the best photo activity and the degradation ratio of Rhb was 96%after 20 min irrigation while the degradation ratio of EDTA-Cu was 100%after 45 min irrigation,and it had a better degradation of EDTA-Cu over the composite photocatalyst before.The reactive species trapping experiments showed that O₂·^-played an important role in the degradation of Rhb while·OH played an important role in the degradation of EDTA-Cu.