Synthesis Of Bismuth Tantalate-based Photocatalyst And Investigation On Their Photodegradation Performance Of Tetracycline

Over the past decades,with the population continuous increasing and the heavy use of antibiotics,more and more antibiotic residues have been discharged into the aquatic environment on which we depend,which has caused an ecological environment.Tetracycline（TC）,as an economical,convenient and easy-to-use antibiotic,has been widely used in human beings and animal husbandry to prevent and treat various diseases.Therefore,it is increasingly important to research and explore a green and sustainable method for degradating TC wastewater.Photocatalytic degradation has the characteristics of green,low cost and high removal rate,which has been widely used in the treatment of TC wastewater.In actual life and production,there are various concentrations of TC wastewater.At the same time,bismuth tantalate（Bi₃TaO₇）has a relatively positive valence band potential（usually+3.25 eV）,so its oxidation performance is strong.With its excellent oxidation performance,it can achieve efficient degradation of organic pollutants in water environment.Therefore,this paper uses other photocatalysts to composite with Bi₃TaO₇,and the band gap is regulated by forming different heterojunctions,so as to achieve the degradation of a wide range of tetracycline concentrations under simulated sunlight and visible light by various composite photocatalysts.The main research contents of this article are as follows:（1）Bi₃TaO₇ and ferric oxide（Fe₂O₃）were prepared with hydrothermal method under different conditions,and various proportions of Fe₂O₃-Bi₃TaO₇ composites were also synthesized with it.XRD,HRTEM,XPS,FT-IR and other characterization methods were used to analyze the structure and elemental composition of the samples,and the interaction between the surface-specific functional groups and tetracycline.At the same time,the morphology,element distribution and element content of the catalysts were analyzed using SEM,TEM and EDX.It was shown that the Fe₂O₃-Bi₃TaO₇ composites were a two-dimensional catalytic material formed by stacking multiple nanosheets on top of each other.With Fe₂O₃ introduced,the band gap of the composite has been decreased significantly（Eg=2.15 eV）,the absorption and utilization of visible light has been greatly enhanced,and the effective degradation of tetracycline under full light has been achieved,and the removal rate of TC at 20 mg/L is 95%.Simultaneously,the PL,EIS and photocurrent results indicate that the separation efficiency of the photo-generated electrons and holes over the Fe₂O₃-Bi₃TaO₇ composites is significantly improved.Therefore,Fe₂O₃-Bi₃TaO₇ can be used as a promising two-dimensional photocatalytic material to remove TC in the environment.（2）The new N-SrTiO₃/Bi₃TaO₇ composite was prepared by hydrothermal method.The catalyst has increasingly broadened the absorption capacity of the solar spectrum,improved the separation efficiency of photo-generated carriers,and achieved to degrade high concentration tetracycline solution（TC=50 mg/L）under simulated sunlight irradiation.The degradation of TC over N-SrTiO₃/Bi₃TaO₇composites with different mass ratios has been investigated.When the mass ratio is15%,the degradation rate is 90.2%,and the photodegradation rate constant is 0.68 h^-1,which is 2.4 times that of pure phase N-SrTiO₃ and Bi₃TaO₇.It was found that the heterojunction formed in the composite can effectively inhibite the recombination of photogenerated electrons and holes,which can be proved by photocurrent and impedance.Finally,a possible catalytic reaction mechanism for the degradation of high concentration of TC has been proposed utilizing trapping experiment and ESR.The research in this chapter provides new ideas for the degradation of high-concentration TC,as well as the preparation of more green,novel and efficient photocatalysts.（3）The microsphere-shaped Bi₂MoO₆ was prepared by a simple hydrothermal method,and the splintery Bi₃TaO₇ was successfully dispersed on the surface of Bi₂MoO₆ by hydrothermal method.The prepared composite photocatalyst was used to remove low concentration of TC in water environment under visible light irradiation.The effects of temperature,pH,catalyst concentration,and TC concentration have been discussed.It is shown that when the TC concentration was 3mg/L and 5 mg/L,they were completely degraded after illumination of 1 h and 2 h,respectively.Based on photoelectrochemical measurement and radical trapping experiment,the photocatalytic reaction mechanism was proposed.The new type of composite material has a good effect on the removal of low-concentration TC.At the same time,this green,simple,and efficient method will have wider practical applications in the photocatalytic degradation of low-concentration antibiotics.