Preparation Of Bismuth Series Oxysalt Based Composite Photocatalytic Material And Study On Its Application In Tetracycline Wastewater Treatment

Antibiotics are widely used in the treatment of various bacterial infectious diseases because of their strong inhibitory and bactericidal effects.In recent years,due to the continuous development of medicine,agriculture,and animal husbandry,the demand for antibiotics has gradually increased from extreme dependence,which has led to the abuse of antibiotics and caused increasingly serious water pollution problems.Tetracycline is a kind of broad-spectrum antibiotic.It has a stable structure and is extremely difficult to degrade under natural conditions.Traditional processing methods are not ideal because of various technical limitations.Against this background,clean and efficient photocatalytic treatment technologies have emerged and attracted much attention.Bismuth series oxysalt based semiconductors stand out from many photocatalytic materials due to their good visible light response and high stability.Aiming at the defects of Bi₂MoO₆,Bi₂WO₆ and BiVO₄ photogenerated electron-hole pairs with low separation efficiency and affecting photocatalytic effect,this article formulated different composite schemes for modification.Bismuth series oxysalt based photocatalysts with different semiconductor composites were constructed to improve their photocatalytic activity.The XRD,SEM,FT-IR,UV-vis,XPS,photocurrent and EIS are used for analysis and evaluation.At the same time,the TC wastewater was degraded under visible light to investigate its visible light catalytic ability;the main active groups involved in the photocatalytic process were explored by free radical capture experiments;the stability of the synthesized samples was studied by cyclic experiments.Finally,the corresponding photocatalytic performance improvement mechanism of composite samples was proposed based on the results of each test.The main contents of this article are as follows:（1）CuBi₂O₄/Bi₂MoO₆ heterojunction was prepared by hydrothermal and solvothermal method.CuBi₂O₄,Bi₂MoO₆ and composite samples were simultaneously exposed to visible light to degrade the TC solution.It was found that the removal efficiency of TC by composite samples was higher than that of CuBi₂O₄ and Bi₂MoO₆.The removal rate of TC by the best compound ratio is 91.4%.Its stability is also confirmed by cyclic experiments.The main active groups involved in the photocatalytic reaction were h⁺and·O₂^-.Based on a variety of test results to analyze the catalytic mechanism,it is proposed that the improvement of CuBi₂O₄/Bi₂MoO₆ catalytic ability is due to the formation of p-n heterojunctions,which effectively improves the photogenerated carriers separation efficiency;（2）The nano-LaCoO₃ was prepared by a citric acid-assisted hydrothermal method,and then the LaCoO₃/Bi₂WO₆ Z-scheme heterojunction was prepared by the hydrothermal.When the composite mass ratio of LaCoO₃ and Bi₂WO₆ reached the optimal ratio（7:3）,the visible light degradation rate of the composite sample for TC at 150min was 85.5%.The SEM results show that the nanosheets in Bi₂WO₆ are tightly bound to the nano-LaCoO₃ and form a heterojunction.The results of UV-vis and electrochemical experiments show that LaCoO₃/Bi₂WO₆ has good visible light response and low impedance,which is conducive to improving the separation of photogenerated electron-hole pairs and photocatalytic performance;（3）Ag-BiVO₄ was prepared by hydrothermal method,and Ag₃PO₄/Ag-BiVO₄ composite photocatalyst was synthesized by in-situ precipitation method.UV-vis showed that the absorption sideband of Ag₃PO₄/Ag-BiVO₄ was red-shifted,which indicated that the response range of the material to visible light was widened.SEM,XRD and photocatalytic experiments show that the introduction of Ag ions does not change the crystal structure of BiVO₄ but effectively improves the morphology and catalytic performance.Compared with pure BiVO4,Ag₃PO₄/Ag-BiVO₄ has successfully improved the photocatalytic effect of TC reaching 81.6%.Capture experiments show that the active groups involved in this reaction are·OH and h⁺.