Fabrication Of Novel Bismuth Bromide Based Photocatalysts And Its Application On Sulifisoxazole Degradaotin In Water Environment

In recent years,with the development of science and technology,people pay more attention to the water environment.In addition to traditional pollutants,some new types of pollutants such as pharmaceutical and personal care products（PPCPs）including antibiotics have gradually attracted much attention.The abuse of antibiotics may lead to the generation of resistance genes and instability of ecosystem.Compared with other water treatment technologies,photocatalysis has some advantages such as no secondary pollution,good stability and portablility,nonselective degradation and high degradation efficiency.Among various kinds of photocatalysts,the bismuth bromide oxide-based composites are widely used in photocatalytic degradation as they have proper band gap,simple preparation method and good stability especially can be excitable by visible light.However,the research on the degradation of antibiotics by bismuth bromide composite photocatalyst was not enough.The further study should be done to impove the light utilization and the fast recombination of photogenerated carriers.In this study,BiOBr was modified by preparing BiOBr/CeO₂ heterojunction.Then the Ag/BiOBr/CeO₂ composite photocatalyst was prepared by in-situ photodeposition method on the basis of the BiOBr/CeO₂heterojunction for the purpose of increasing the photocatalytic efficiency.The photocatalytic efficiency of the composite was investigated by degrading sulfamethoxazole and carbamazepine.Various characterization were used to investigate the physical and chemical characters of the as-prepared materials and the reason of enhanced catalytic performance was explored.The main contents are as follows:（1）BiOBr/CeO₂ composite was prepared by high-temperature calcination and co-precipitation method and was used to degrade sulfamethoxazole.The catalysts were characterized by XRD,SEM,XPS,FTIR,UV-Vis,BET and EIS.Among different CeO₂ content,the BiOBr/CeO₂ composites with 15%CeO₂ content（BC-15）had the highest removal rate for degrading sulfamethoxazole.When the dosage is 0.5g/L,the degradation rate could reach 98.1%within 180min irradiation.The degradation rate constants were 3.2 times and 29.3 times larger than that of BiOBr and CeO₂,which proved that the BiOBr/CeO₂ composite effectively improved the photocatalytic efficiency.After the recycle experiments,BC-15 still showed a high photocatalytic efficiency,which suggested the good stability and reusability.The free radical trapping experiments indicated that h⁺and·O₂^-played the main roles in the degradation system.The photocatalytic degradition mechanism could be speculated that the formation of BiOBr/CeO₂heterojunction promoted the transfer of photogenerated carriers and reducing the recombination of electrons and holes.Therefore,the photocatalytic efficiency of the composite was significantly enhanced.（2）For the purpose of increasing the photocatalytic efficiency,Ag/BiOBr/CeO₂ composite photocatalyst was prepared by in-situ photodeposition method on the basis of the BiOBr/CeO₂heterojunction.It was used to degrade sulfamethoxazole and carbamazepine.The catalysts were characterized by XRD,SEM,TEM,HRTEM,XPS,UV-Vis,BET,transient photocurrent responses and EIS.Among different Ag content,the Ag/BiOBr/CeO₂ composites with 10%Ag content（ABC-10）had the highest removal rate for both degrading sulfamethoxazole and carbamazepine.When the dosage is 1.0g/L,the sulfamethoxazole was totally degraded within 20min irradiation.The degradation rate constants were 22.07 times and 40.47 times larger than that of BC-15 and BiOBr.After the recycle experiments,ABC-10 still showed a high photocatalytic efficiency,which suggested the good stability and reusability.The free radical trapping experiments indicated that h⁺and·O₂^-played the main roles in the degradation system.In consideration of the results of UV-vis,photocurrent response and EIS characterization,the improvement of the photocatalytic efficiency of Ag/BiOBr/CeO₂ composite could be attributed to the surface plasmon resonance effect of Ag.Proper dosage of Ag doping can enhance the absorption in the visible region and effectively increase the photogenerated electron-hole pairs separation efficiency,which could significantly enhance the photocatalytic efficiency of the photocatalysts.