Synthesis Of Bismuth-base Photocatalyst And Investigation On Their Antibiotics Degradation

Bi-based materials as a new kind of semiconductor photocatalyst,such as Bi₂O₃BiOX（X=Cl,Br,I）,Bi₂WO₆,BiTa O₄ etc.,have received the widespread attention due to their layer structure and excellent catalytic performance,especially in the photocatalytic degradation of organic pollutants.However,in the process of photocatalysis,the practical application of the catalyst was limited because of the poor solar spectral responding,weak charge carrier mobility and fast recombination rate of the electron-hole pairs.In recent years,the catalytic performance of photocatalyst has been improved by means of loading precious metals,forming a composite catalyst and controlling the morphology.Therefore,we prepare composite catalyst by coupling layer structure of tungsten acid bismuth or ultrathin g-C₃N₄ with nitrogen doped strontium titanate to promote the separation of electronic-hole pairs,resulting from the improved photocatalytic performance.On the other hand,the composite of photocorrosion semiconductors of the nanosheet bismuth molybdate and silver phosphate of,effectively inhibit the light corrosion phenomenon as well as significantly improve the stability of photocatalyst.The main contents are as follows:1.A series of n–n heterojunctions of Bi₂WO₆/N-Sr TiO₃ were successfully prepared through a two-step hydrothermal method.N-Sr TiO₃ with strong reduction performance,can easily remove the heavy metal ions Cr⁶⁺in the liquid environment.At the same time,Bi₂WO₆ has strong oxidation performance as a result that could show the excellent performance for the degradation of tetracycline hydrochloride.Thus,the mixed contaminants(TC and Cr⁶⁺ions)could be completely removedunder visible light by the assembled Bi₂WO₆/N-Sr TiO₃ material.The matched band structures of Bi₂WO₆ and N-Sr TiO₃ were beneficial for inhibiting the recombination of electron–hole pairs and maintaining the redox capacity through a n–n type heterojunction.Such a bipolar design of photo-oxidative and photo-reductive semiconductor nanomaterials is concluded to be highly effective in remediating complicated toxic residual constituents of both unfixed pharmaceuticals and heavy metals in aquatic environments.2.The novel visible-light-driven Ag₃PO₄/Bi₂Mo O₆ p-n heterojunctions were prepared via a simple deposition precipitation following with a solvothermal method.The thin Bi₂Mo O₆ nanosheets are uniformly attached to the surface of rhombic dodecahedral Ag₃PO₄.The prepared Bi₂Mo O₆/Ag₃PO₄ heterojunctions were used to removal rhodamine B,tetracycline,and aureomycin.The removal mechanism was proposed based on the scavengers trapping test,ESR spectra,XPS spectrum,photocurrent responses,and electrochemical impedance spectroscopy analysis.It proved a fixed content of the metallic Ag is gradually generated from Ag₃PO₄ in the composite under solar light illuminating,which is regarded as charge transmission-bridge to accelerate the charge transfer and consequentially change the charge transfer path.Mediated by metallic Ag in p-n junction,the active species of the present photo-oxidative reaction experienced various period from·OH and h⁺in the initial reaction to the additional·O₂^-in the successive recycle experiment.This study provides a new design strategy to assembling photocorrosion semiconductor materials with high efficiency and durable reusability.3.The ultrathin g-C₃N₄ coupling with Bi₂WO₆ nanosheet composite photocatalyst of 2D-2D structure was prepared by calcining and hydrothermal method.The structure provides a large contact area for the fast separation of the electron-hole pairs in order to form a larger internal electric field.According to the degradation of tetracycline hydrochloride under visible light irradiation,the catalytic activity of the composite photocatalyst were markedly improved,and combined with the capture experiment analysis and electron spin resonance spectra,the photocatalytic mechanism of existence is discussed.By constructing 2D-2D heterogeneous structure with close interfacial contact,it provides a new prospect for the design of high active photocatalyst to control environmental pollution.