Preparation Of Tungsten Oxide Heterojunction Materials And Their Photocatalytic Degradation Of Pollutants

The rapid development of the pharmaceutical industry has led to the increasing use of antibiotics by humans and animals,and the widespread use of antibiotics has saved many lives by avoiding bacterial infections in humans and animals.However,for the ecological environment,the pollution problem caused by the discharge of antibiotics should also be taken seriously.In recent decades,experts have tried to find safe and effective methods to degrade antibiotics in the aqueous environment.Among them,photocatalytic technology has attracted much attention because of its green and environmentally friendly properties.Tungsten oxide（WO₃）,a new type of semiconductor catalyst,has been widely used in recent years for studies such as the degradation of pollutants.It has the advantages of non-toxicity,low cost,excellent hole mobility,tunable bandgap,and high stability under extreme conditions.Therefore,WO₃is chosen as a catalyst in this paper,but it still has some problems,such as a wide band gap and response only to the UV region.In order to solve these problems,WO₃ is chosen to be compounded with other materials in this paper.Among them,the tungstate compound has the advantages of a narrow band gap and strong visible light absorption properties,and there are fewer reports on the compounding of WO₃ with the tungstate compound,so the compounding with the tungstate compound is chosen.However,due to its low degradation effect,WO₃ is later chosen to be compounded with nickel ferrate（Ni Fe₂O₄）because Ni Fe₂O₄has the advantages of environmental friendliness,low price,easy availability,stronger visible light absorption ability,narrower band gap,etc.,and there are very few reports on the compounding of both.In this paper,WO₃ nanomaterials are synthesized by hydrothermal and high-temperature calcination methods,and then WO₃ is compounded with Ni WO₄（nickel tungstate）,Fe WO₄（iron tungstate）and Ni Fe₂O₄ to prepare three composite systems with different loading ratios of WO₃/Ni WO₄,WO₃/Fe WO₄,and WO₃/Ni Fe₂O₄,respectively.They are characterized by X-ray diffraction spectroscopy（XRD）,UV-vis diffuse reflectance spectroscopy（UV-vis DRS）,X-ray photoelectron spectroscopy（XPS）,transmission electron microscopy（TEM）,and photoluminescence spectroscopy（PL）,indicating that WO₃ and the three composite systems are successfully prepared.After that,the photocatalytic performance of WO₃ and the three composite systems are tested under light with tetracycline hydrochloride as the target pollutant,and their degradation effects are referenced to the changes in their absorbance.To investigate the catalytic principle in depth,methanol（MT）,triethanolamine（TEOA）,isopropanol（IPA）,sodium sulfate（Na₂SO₄）,and ascorbic acid（VC）are used as sacrificial agents for vacancies（h⁺）,hydroxyl radicals（·OH）,electrons（e^-）and superoxide radicals（·O₂^-）,respectively.The experiments on the capture of reactive groups are carried out.The results show that WO₃ forms heterojunctions with Ni WO₄,Fe WO₄,and Ni Fe₂O₄,and all four reactive groups·O₂^-,h⁺,e^-,and·OH play a role.In addition,the three composite systems degrade tetracycline hydrochloride more effectively than the pure phase WO₃,and the WO₃/Ni Fe₂O₄ composite system degrades more effectively than the other two composite systems.This indicates that the composite systems have better performance in the degradation of organic pollutants.