Preparation Of Bismuth Vanadate Composite Photocatalytic Material And Study On The Performance Of Visible Light Degradation Tetracycline Wastewater

A large amount of tetracycline wastewater produced by frequent use of tetracycline（TC）will cause serious harm to the natural environment.However,the traditional physical and chemical methods cannot completely treat TC wastewater,which is easy to cause secondary pollution to the environment.Photocatalytic wastewater degradation has the advantages of low energy consumption,mild reaction conditions and no secondary pollution.Monoclinic BiVO₄ has attracted much attention in the field of photocatalysis due to its advantages of cheap raw materials,simple preparation methods and strong utilization of visible light.At the same time,BiVO₄ also shows some shortcomings such as poor adsorption capacity of pollutants and low separation efficiency of photogenerated charge.Combining with other materials to construct heterojunction structures is an effective way to improve the photocatalytic performance of BiVO₄.In this paper,a series of BiVO₄ composite photocatalytic materials with excellent performance were prepared by combining different materials with BiVO₄ by a simple and practical grinding method for the degradation of high-concentration TC wastewater by visible light emission from LED light source.In this study,the BiVO₄ loaded with Bi nanoparticles was obtained by reducing BiVO₄with NaBH₄,and then NiCo₂O₄ was loaded on the surface of Bi-BiVO₄ by grinding method to prepare the NiCo₂O₄/Bi-BiVO₄ composite photocatalytic material with excellent photocatalytic performance.XRD,SEM,HRTEM and other characteristics confirmed that the material is a ternary composite with core-shell structure.Under the optimal condition,the NiCo₂O₄/Bi-BiVO₄ composite can degrade50 mg/L TC solution under the LED visible light irradiation,and the total removal rate can reach 79.8%after 90 minutes of illumination.A Z-type heterojunction structure was formed between the two semiconductors,which increased the separation efficiency of photogenerated charge.At the same time,the introduction of NiCo₂O₄ and Bi broadened the absorption range of visible light,thus improving the photocatalytic performance of the composite.ESR characterization and active component capture experiments verified that the catalyst could produce h⁺,·O₂^-and·OH active components under the excitation of visible light,among which h⁺and·O₂^-were the main active components.The degradation products were analyzed by LC-MS,and it was found that the products were mainly small molecule products,and a number of possible degradation pathways were speculated through the degradation products.In order to further improve the photocatalytic performance of BiVO₄,ZnSe/BiVO₄composite photocatalytic material was prepared by loading ZnSe nanoparticles with superior photocatalytic performance on the surface of BiVO₄ by grinding method.It was confirmed by XRD,SEM and other characteristics that ZnSe nanoparticles were uniformly loaded on the surface of BiVO₄.The structure is conducive to the formation of heterojunctions.The photoelectric characterization confirmed that the visible light absorption range of the composite was improved compared with BiVO₄.The energy band structure of each component was analyzed,and it was speculated that the composite formed a direct Z-type heterojunction structure.The optimal ratio of ZnSe/BiVO₄composite was used to degrade 50 mg/L TC pollutants,and the TC removal rate reached more than 70%after 30 min of illumination,and more than 80%after 60 min of illumination.The major active components in the reaction were h⁺and·O₂^-,as confirmed by active component capture experiments.Analysis of the degradation products by LC-MS revealed a significant increase in the number and variety of small molecules in the degradation products.