Preparation Of BiVO₄ Nanosheet Composite And Its Photocatalytic Activity For Degradation Of Tetracycline

In recent years,excessive dependence on antibiotics has led to a sharp increase in their production and use.Among them,most of the antibiotics ingested into the body are excreted into the environment and water bodies in the form of original drugs,and the extremely low concentration of antibiotics can threaten the virtuous cycle of the ecological environment and destroy the integrity of the food chain.Therefore,how to remove antibiotic residues in water bodies in a green,economical and efficient manner is an important issue for researchers.Semiconductor photocatalytic technology with high reactivity,no secondary pollution and only the use of solar energy in nature is considered to be one of the most promising water treatment methods today.Among many photocatalytic materials,BiVO₄ is favored by researchers because of its wide range of raw materials,suitable band structure,built-in electric field,certain visible light response,anti-light and chemical corrosion.However,BiVO₄ still has shortcomings such as narrow photoresponse range,low utilization rate of light energy,easy recombination of photogenerated carriers,low yield of hydroxyl radicals and poor adsorption capacity of pollutants,which limits its application in photocatalysis.Therefore,it is necessary to carry out further modification work on BiVO₄ to enhance its photocatalytic performance.In this paper,we synthesized m-BiVO₄ nanosheets with high activity（010）crystalsurfaceusinghydrothermalmethodassistedbysodium dodecylbenzenesulfonate（SDBS）.A Novel Ternary Cu₂O/BiVO₄/RGO composite photocatalyst was designed by co-modification of m-BiVO₄ with reduced graphene oxide（RGO）and strongly adsorbable Cu₂O concave cubes.Secondly,self-induced Fenton-like photocatalyst Fe（III）-BiVO₄ was constructed by anchoring Fe（III）species on the surface of m-BiVO₄ nanosheets.Finally,noble metal Ag was deposited on the surface of m-BiVO₄ nanosheets to prepare Ag-BiVO₄ composite photocatalyst with Schottky barrier and SPR.The main contents are as follows:1.A novel ternary Cu₂O/BiVO₄/RGO photocatalyst is successfully constructed by hydrothermal and evaporation-induced method,and the degradation efficiency of TC reached 81.2%in 60 min.Meanwhile,the visible light absorption range of composite photocatalyst is effectively broadened by the formation of heterojunction with narrow band gap semiconductor Cu₂O.And the separation efficiency of the photogenerated electron-hole pairs is significantly enhanced by the synergistic effect of Cu₂O and RGO.More importantly,the adsorption of TC by ternary Cu₂O/BiVO₄/RGO possesses high adsorption capacity,which is 23.73 times higher than that of pure BiVO₄.In addition,radical trapping experiment and electron spin-resonance（ESR）spectroscopy clearly reveal that?O₂^-is the main active species in the degradation process.2.A novel self-induced Fenton-like photocatalyst（Fe（Ⅲ）grafted BiVO₄）has been successfully synthesized via a simple wet-impregnation method.When the mass ratio of Fe（Ⅲ）reaches 7%,the as-prepared Fe（Ⅲ）-BVO photocatalyst exhibits the highest photodegradation performance for various organic pollutants including tetracycline（TC）,ciprofloxacin（CIP）,gatifloxacin（GAT）,levofloxacin（LVX）and2,4-dichlorophenol（2,4-DCP）under visible light irradiation,whose degradation rate reach up to about 1.35,4.34,1.40,1.11 and 1.10 times than that of pure BVO,respectively.Results reveal that the grafting of Fe（Ⅲ）enhances the specific surface area of sample and possess more reaction sites.Meanwhile,the Fe（Ⅲ）species serve as trapping centers for photogenerated electrons to improve the separation ability of charges,and the self-induced surface Fenton reaction of the self-redox cycles of iron ions significantly promote the generation of hydroxyl radicals.Additionally,the possible reaction mechanism and intermediate products are clearly revealed by radical trapping experiment,ESR,detection experiment of hydroxyl radicals and mass spectrometry.This strategy provides a promising insight to construct high-performance photocatalyst for solving environmental pollution problem.3.Ag-BVO composite photocatalytic material is synthesized by photodeposition and characterized by XRD,SEM,XPS,UV-vis DRS and electrochemistry.The results show that noble metal Ag distributes uniformly on the surface of BiVO₄ nanosheets with very small particle size,and the best photocatalytic effect can be achieved with very small Ag loading（0.1%）.Meanwhile,the surface plasmon resonance（SPR）of precious metal Ag effectively broadens the visible light response range of the catalyst,and forms Schottky barrier at the interface between Ag and BiVO₄ as the electron capture center to enhance the separation efficiency of photogenerated carriers,thereby enhancing the photocatalytic degradation performance of the whole system.In addition,radical trapping experiment and ESR spectroscopy show that?O₂^-is the main active species in the degradation process.