Study On The Preparation Of Bismuth Tungstate Visible Light Catalysts And Degradation Of Tetracycline Hydrochloride

In recent years,tetracycline antibiotic wastewater has attracted much attention due to its toxic nature,especially tetracycline hydrochloride（TCH）wastewater.As a common antibiotic,the residue of TCH in the environment may induce the production of anti-pathogens,and it is difficult to remove,seriously threatening human health and development.As a method of removing TCH,photocatalytic technology has the advantages of simple operation,green and non-pollution.Among the photocatalysts,bismuth tungstate（Bi₂WO₆）is a promising visible light type semiconductor catalyst with narrow forbidden band width,better visible light response and other capabilities.Researchers have studied a variety of methods for preparing and modifying Bi₂WO₆,but these methods have disadvantages such as secondary pollution and difficulty in recycling.Therefore,it is of great significance to study the simple and energy-saving modified Bi₂WO₆ catalyst method in practical applications.The research contents of this paper are as follows:（1）Preparation of modified photocatalyst: prepare pure Bi₂WO₆ samples and metal ion La³⁺ modified Bi₂WO₆ were prepared by hydrothermal method to obtain La/Bi₂WO₆;thenγ-Fe₂O₃ or α-Fe₂O₃ is mixed into Bi₂WO₆ or La/Bi₂WO₆ by hydrothermal method or mechanical method,and finally 8 different modified photocatalysts were obtained.（2）Study on the treatment of tetracycline hydrochloride wastewater with different photocatalysts: Under the irradiation of simulated visible light,the doped modified samples were treated with tetracycline hydrochloride wastewater to investigate their photocatalytic performance.The experimental results showed that all the doped modified samples showed higher removal rate of TCH solution than pure Bi₂WO₆;the removal rate of5%γ-Fe₂O₃/La/Bi₂WO₆ for TCH solution is the highest,which is 92.42%.After adding a certain amount of H₂O₂ in the photocatalysis experiment,the removal rate of TCH solution for all doped modified samples was significantly improved,indicating that H₂O₂ can promote the photocatalysis performance.（3）Research on the influencing factors of photocatalyst photocatalysis: 5%γ-Fe₂O₃/La/Bi₂WO₆ sample was used as the research object,and the effects of the photocatalyst dosage,the initial concentration of TCH solution,the initial p H of TCH solution and the H₂O₂ dosage concentration on the removal rate of TCH during the reaction were studied and analyzed.The results showed that when the dosage of the photocatalyst was 60 mg,the initial concentration of the TCH solution was 20mg/L,the p H was 9.0,and the concentration of H₂O₂ was 7mmol/L,the removal rate of the TCH solution reached the highest.（4）Characterization and mechanism study of the photocatalyst: SEM,FTIR,XRD,XPS characterization of the 5% γ-Fe₂O₃/La/Bi₂WO₆ doped samples showed that the Bi₂WO₆ crystal phase and structure of the modified samples were not damaged,the morphology appearing in the shape of nano-sheet,and confirms that the metal La³⁺ and γ-Fe₂O₃ were indeed doped into the samples.The kinetic analysis showed that the photodegradation of TCH solution by pure Bi₂WO₆,La/Bi₂WO₆ and doped modified photocatalyst samples were conformed to the first-order reaction kinetic order.Analysis of the active substances in the photocatalytic process revealed that the main active substances for the removal of TCH solution were h+ and ·O₂^-.According to the characterization and analysis results,the mechanism of photocatalytic degradation of TCH was analyzed.（5）Photocatalytic stability study: The stability and recovery efficiency of5%γ-Fe₂O₃/La/Bi₂WO₆ were studied.The results showed that after four cycles of experiments,with good performance of recovery efficienccy and stable catalytic performance.