Study Of Preparation Of BiOBr Composites And Their Photocatalytic Activity For Organic Pollutants

With the development of social economy,water pollution has become increasingly serious.The health and living environment of human beings are seriously affected by organic pollutants,which are toxic,harmful and difficult to degrade.As a green and efficient technology for removing organic pollutants in water,photocatalysis has the advantages of mild reaction conditions,easy operation,reusability and no secondary pollution.As a photocatalyst with great application potential,Biobrium bromide?BiOBr?not only in response to the sunlight,but also has good stability.However,the application of BiOBr is severely limited by the following two aspects.On the one hand,the unmodified BiOBr can only respond to a part of visible light.On the other hand,the recombination rate of photogenerated electrons and holes is high,which leads to a decrease in photocatalytic activity.BiOBr composites were prepared by solvothermal method in order to improve the photocatalytic activity.The phase composition,morphology and optical properties of the prepared BiOBr composites were characterized by a series of techniques.The degradation and mechanism of BiOBr composites towards organic pollutants in water were also investigated.The main conclusions were following:?1?BiOBr/PVP/Zn²⁺composites were synthesized by solvothermal method,and photocatalyzed degradation of rhodamine B under visible light??=420 nm?.The results showed that the photocatalytic activity of BiOBr/PVP/Zn²⁺composites was significantly higher than that of unmodified BiOBr.BiOBr/PVP/Zn²⁺composites(the molar ratio of Zn²⁺/BiOBr=4%)exhibited the highest photocatalytic activity towards rhodamine B,which also had good stability.According to a series of characterization techniques,the improvement of adsorption capacity was mainly attributed to increasing of the specific surface area by the adding of PVP,and the improvement of photocatalytic performance may be mainly ascribed to lower recombination rate of photogenerated electron-hole pairs?e^-/h⁺?by the doping of Zn²⁺.?2?BiOBr/Bi₂WO₆ composites were prepared by solvothermal method,and photocatalyzed degradation of tetracycline hydrochloride under visible light??=420nm?.The results showed that the photocatalytic activity of BiOBr/Bi2WO6composites was significantly higher than that of pure BiOBr and pure Bi₂WO₆.When the molar ratio of Bi₂WO₆/BiOBr was 30%,BiOBr/Bi₂WO₆ composites exhibited the highest photocatalytic activity towards tetracycline hydrochloride,which also had good stability.In addition,the photocatalytic activity of the BiOBr/Bi2WO6composites were enhanced after the addition of H₂O₂ in the photocatalytic process.Accoding to a series of characterization techniques,BiOBr/Bi2WO6 composites reduced the recombination rate of photogenerated electron-hole pairs?e^-/h⁺?.Moreover,the combination of H₂O₂ and e^-not only reduced the recombination rate of photogenerated electrons and holes,but also formed?OH.Both could improve the photocatalytic activity of the BiOBr/Bi2WO6 composites.?3?BiOBr/MIL-100?Fe?composites were prepared by solvothermal method,and photocatalyzed degradation of levofloxacin under visible light??=420 nm?.The results showed that the photocatalytic activity of BiOBr/MIL-100?Fe?composites were significantly higher than that of pure BiOBr and pure MIL-100?Fe?.When the BiOBr/MIL-100?Fe?molar ratio was 60%,BiOBr/MIL-100?Fe?composites exhibited the highest photocatalytic activity towards levofloxacin,which also had good stability.Accoding to a series of characterization techniques,the recombination rate of photogenerated electron-hole pairs was reduced by the BiOBr/MIL-100?Fe?composites.Moreover,the photocatalytic performance of the BiOBr/MIL-100?Fe?composites were further improved by the assistance of H₂O₂,which may be ascribed to the effective separation of photogenerated electrons and holes.Besides,?OH generated by the combination of H₂O₂ and e^-facilitated the improvement of photocatalytic efficiency.In addition,Fe³⁺may react with H₂O₂ to form?OH,which improved the photocatalytic activity of the BiOBr/MIL-100?Fe?composites.