Synthesis Of Bi₁₂GeO₂₀-based Composite Photocatalyst And Its Photodegradation Activity Of Tetracycline

Tetracycline（TC）,as a broad-spectrum antibiotic,the use of antibiotics plays an important role in the development of human medicine.Yet,too much antibiotic use can seriously affect or even threaten human health,the environment,and ecological balance.In recent years,environmental and ecological problems ensued while the progress of science,technology and industry is developing rapidly.Among them,water pollution has become one of the major environmental problems that need to be solved urgently today.Among many advanced treatment methods,photocatalytic oxidation technology has been regarded as an environmentally-friendly treatment technology by many scholars for the treatment of water pollution due to its advantages of stable performance,green pollution-free and low cost.Bi₁₂GeO₂₀belongs to Bi₁₂MO₂₀（M=Ge,Si and Ti）structure oxide,and has attracted the attention of many researchers due to its special structure and strong photo-oxidation ability.However,due to the poor visible light absorption capacity of Bi₁₂GeO₂₀,the shortcomings of photo-generated electron-hole recombination have limited its practical application and production.In this paper,firstly,the Ag₂O nanoparticles are supported on the basis of Bi₁₂GeO₂₀,which promotes the separation of photo-generated electrons and holes;Secondly,the introduction of CdS nanoparticles has expanded the visible light absorption range of the photocatalyst;Thirdly,by supporting Bi₂MoO₆ nanosheets,the photocatalyst adsorption performance is improved;Finally,doping semiconductors with non-metal ions and constructing a Z-type heterojunction structure can improve photocatalytic activity.The specific research content is as follows:1.Bi₁₂GeO₂₀0 microspheres were synthesized by hydrothermal method,and Ag₂O nanoparticles were grown on Bi₁₂GeO₂₀0 microspheres by in-situ growth method to prepare Ag₂O/Bi₁₂GeO₂₀0 composite photocatalyst.Characterization analysis was performed through multiple detection techniques,and then the reaction mechanism of degradation of TC under visible light was explored through active radical capture experiments and ESR tests.The consequence reveals that the synthesized Ag₂O/Bi₁₂GeO₂₀0 photocatalyst has a superior photocatalytic degradation capacity.When the Ag₂O loading content is 20.0 wt%,the degradation efficiency can reach65%within 120 minutes.2.Bi₁₂GeO₂₀0 microspheres and CdS nanoparticles were successfully synthesized by hydrothermal method,and then CdS/Bi₁₂GeO₂₀0 binary composite photocatalyst was prepared again by hydrothermal method.The composite photocatalyst was characterized by a series of characterization analytical instruments,and the optimal ratio was determined by regulating the effect of different loadings of CdS nanoparticles on photodegradation of TC.The results show that when the loading of CdS nanoparticles is 30.0 wt%,the photocatalytic effect is optimal,reaching 82%in120 minutes.3.Theγ-Bi₂MoO₆/Bi₁₂GeO₂₀0 binary composite photocatalyst supported onγ-Bi₂MoO₆ nanosheets can be successfully prepared by the hydrothermal method.The test results reveal that introducingγ-Bi₂MoO₆ nanosheets can not only improve the adsorption performance of photocatalyst,but also greatly improve the photocatalyst’s ability to absorb visible light and promote its utilization of light.At the same time,γ-Bi₂MoO₆ and Bi₁₂GeO₂₀,Z-type heterojunction structures,can greatly promote the migration efficiency of photo-generated electrons.The photocatalytic ability of Z-γ-Bi₂MoO₆/Bi₁₂GeO₂₀0 binary composite photocatalyst to degrade TC can reach77%in 120 minutes.4.Using KI as the I source,I-BiOBr nanosheets were successfully prepared by the solution mixing method at room temperature.Bi₁₂GeO₂₀0 was successfully prepared by a hydrothermal method,and then I-BiOBr/Bi₁₂GeO₂₀0 binary composite photocatalyst was successfully prepared by a water bath method.The experimental results indicate that the photocatalytic ability of I^-doped BiOBr to degrade tetracycline is much greater than that of pure phase BiOBr,indicating that the doping of non-metal ions has an important effect on the characteristics of semiconductors.In the meantime,the binary composite photocatalyst has a good ability to remove TC organic pollutants under visible light,reaching 80%in 120 minutes,further proving that the loading of I-BiOBr nanosheets can improve the photocatalytic activity to some extent.In addition,the construction of Z-type heterojunctions not only promotes the separation of photogenerated electrons and holes,but also maintains the redox capacity of the photogenerated electrons and holes.