Preparation And Characterization Of Composite Bismuth Halide Oxide Photocatalyst Modified By Manganese Zinc Ferrite

Since the beginning of the 21st century,the problem of water environment security has become increasingly prominent,threatening the survival and development of human beings every moment.Using semiconductor photocatalysis technology to deal with water pollution is a method with high efficiency,low consumption and no toxicity.As a typical semiconductor photocatalyst,bismuth chloride oxide（BIOCl）has the advantages of simple preparation process and high photocatalytic efficiency.However,the application of BIOCl is limited by bismuth oxychloride’s inability to respond to visible light,and difficulty in recovery.Therefore,modificating BiOCl and combinating it with magnetic Mn-Zn ferrite（MZF）to form a magnetic composite photocatalyst which can be quickly recovered under the action of external magnetic field is of great significance to the study of BiOCl.The main results are as follows.（1）In order to improve the photocatalytic ability of BiOCl under visible light,a series of BiOCl/BiOBr photocatalysts were prepared by hydrothermal method,and the effect of the ratio of chlorine to bromine on the photocatalytic activity was investigated.The results show that when the molar ratio of chlorine to bromine is 2:8,the modified photocatalyst has the strongest visible light response.The absorption band edge shifts to 426nm,and the band gap narrow to 2.82e V.Under visible light irradiation,the photogenerated carriers can be effectively excited,and superoxide free radicals can be generated to degrade organic matter.The degradation rate of RHB reached 88%under the irradiation of xenon lamp which filtered the ultraviolet light for 100min,and the reaction rate constant was 0.0186min^-1.（2）Mn-Zn ferrite（MZF）was prepared by hydrothermal method in alkaline environment,and BiOCl/BiOBr/MZF composite magnetic photocatalyst was prepared for the first time from this magnetic body.XRD,XPS,SEM and other characterization methods were used to characterize the composite magnetic photocatalyst.The results showed that the doping of MZF did not destroy the original structure of the composite photocatalyst,and effectively increased the specific surface area and enhanced the absorption of visible light.At the same time,the composite magnetic photocatalyst has strong stability and recycling ability.The photocatalytic activity does not greatly decrease after repeated recycling for three times.（3）BiOCl/BiOI semiconductor photocatalyst was prepared by hydrothermal method in organic solvent.These photocatalysts have good microstructure and large specific surface area.Comparing with BiOCl and BiOI,their adsorbability and photocatalytic effect have been greatly improved.The narrow band gap and the expansion of the absorption band edge to visible light region were the keys factors to improve the photocatalytic performance.When the molar ratio of Cl to I is 6:4,the reaction rate constant reaches 0.126min^-1.（4）BiOCl/BiOI/MZF magnetic photocatalyst with originality was synthesized by hydrothermal method.When the mass fraction of MZF is 3%,the performance of photocatalyst is further improved.The introduction of MZF improves the lifetime of the photoelectron-hole pair and widens the wavelength of the absorbed light,so that the photoelectron-hole pair can be generated more effectively under visible light irradiation.At the same time,the saturation magnetization of BiOCl/BiOI/3%MZF reaches2.65emu·g^-1,and the degradation rate of RHB can still reach more than 90%within 40 min after recycling several times.