Preparation Of Bismuth Oxybromide Composite Photocatalyst And Its Application In Dye Wastewater

Photocatalytic technology can use solar energy to degrade pollutants.It is one of the most widely used methods to deal with environmental problems,and its core is semiconductor photocatalyst.As a semiconductor photocatalyst,BiOBr has the advantages of unique layer structure,stable chemical properties and good optical properties,but it also has the disadvantages of narrow response range to visible light and high electron-hole recombination probability.Therefore,in this thesis,the modification of BiOBr was studied by means of semiconductor composite.The research contents and results are as follows:1.Bi4Ti3O12/BiOBr composite photocatalyst was prepared by solvothermal method using bismuth nitrate pentahydrate,potassium bromide and butyl titanate as raw materials.The effects of preparation conditions on the degradation ability of the samples were investigated.The effects of initial concentration of pollutants on the degradation rate of the catalysts were discussed.The photocatalytic degradation process of the samples was simulated and analyzed dynamically,and the reaction rate constant was calculated.The composition and morphology of the sample were determined by XRD and SEM.The specific surface area of the sample and the response range to light were determined by BET and UV-Vis DRS.By adding free radical scavenger,the active species which play a major role in photocatalytic degradation were determined,and the mechanism of photocatalytic reaction was preliminarily deduced.The experimental results show that the best performance of the samples is obtained when the synthesis time is 24 h,the synthesis temperature is 180^oC,Bi:Ti:Br=10:7:5,ethylene glycol as solvent,PVP as surfactant and its addition amount is 0.2 g.With LED lamp as light source,the initial concentration of simulated pollutants is 4 mg/L,and the degradation rate can reach 85.1%after 140 min of irradiation.Photocatalyst has good cyclic stability,after three cyclic degradation experiments,the degradation rate of photocatalyst is 65.7%.The microstructure of composite samples is affected by the change of synthesis conditions.Under the optimal conditions,the obtained samples have a large specific surface area and a wide response range to light,h⁺and·O₂^-are the main active species in the degradation of rhodamine B.2.Bi₂O₃/BiOBr composite photocatalyst was prepared by one-step solvothermal method using potassium bromide and bismuth nitrate pentahydrate as raw materials.By means of XRD,SEM,BET and UV-Vis DRS,the composition,morphology,specific surface area and light absorption range of the samples were determined.The influence of synthesis conditions on photocatalytic activity was discussed.The stability of photocatalyst was tested.The active species in the photocatalytic reaction process were explored and the reaction mechanism was deduced.The results showed that when Br:Bi=0.2,synthesis time is 12 h and synthesis temperature is 140 ^oC,the photocatalytic activity of sample is the best.The degradation rate reached 91.4%after140 min of irradiation,and the photocatalytic activity of sample was higher than that of BiOBr.The photocatalyst has good stability after three cycles,the degradation rate of the sample is still 79.3%.In the degradation process,h⁺and·O₂^-play the main active roles.3.Bi/BiOBr photocatalyst was prepared by solvothermal method.The degradation ability of the sample to simulated pollutant Rhodamine B was tested under 7 W LED lamp irradiation.The samples were characterized by XRD,SEM,BET and UV-Vis DRS.The experimental results show that when the synthesis temperature is 180 ^oC,the reaction time is 12 h and anhydrous ethanol as reaction solvent,the sample has high catalytic activity.The degradation rate of the sample is87.8%after 140 min exposure by LED lamp,and it has good cyclic stability.During the degradation of rhodamine B,h⁺and·O₂^-are the main active species.