Preparation Of Titanium Dioxide-based Composite Materials And Study Of Their Photocatalytic Propertie

With the rapid development of industry,people pay more attention to the problem of water environment pollution.The chemical industry and tanning industry emit complex and high concentration heavy metal ions,which pollute the ecological environment and affect human health.Traditional methods are difficult to degrade.In recent years,photocatalytic technology,as green chemical technology,has obvious advantages for the removal of heavy metal ions.Titanium dioxide（TiO₂）is a widely used semiconductor photocatalyst,but its photocatalytic efficiency is low due to its structure and other drawbacks.Therefore,it is very important to modify semiconductors to increase their activity.In this paper,two different photocatalytic systems were designed and prepared to utilize element doping and semiconductor coupling,by studying the energy band regulation of semiconductors,the transfer mechanism of interfacial carriers and morphology regulation,to broaden the visible light absorption range and improve the rapid separation of photogenerated carriers.Hexavalent chromium（Cr（VI））was used as the target pollutant to explore the removal efficiency of modified TiO₂ for heavy metal ions.The research work is as follows:（1）Ag modified anatase rutile heterojunction nanocomposites were prepared by ion exchange of Ag⁺and H₂Ti₃O₇ nanowires.XRD and TEM showed that silver doping in anatase lattice induced the transformation from anatase phase to rutile phase,the two phases were in close contact,and the carrier migration was improved.EPR showed that Ti³⁺defect state was produced,which the visible light absorption is enhanced.UV-vis spectrum showed that the strong SPR effect of Ag NPs promoted the generation of hot electrons and further absorbs visible light.Photocatalytic experiments showed that the removal efficiency of Cr（VI）of Ag modified anatase rutile heterojunction nanocomposites is～94%.The cyclic experiments showed that the composites have good stability.Finally,the mechanism of photocatalytic activity of Ag-TiO_2-xheterogeneous junction nanocomposites was proposed.（2）TiO₂ nanowires were coupled with narrow band gap semiconductor Zn In₂S₄by a one-step solvothermal method to form Zn In₂S₄/TiO₂ heterojunction nanocomposites materials,and the optimal molar ratio of TiO₂ to Zn In₂S₄ was explored.XRD,SEM,TEM and other characterization showed that Zn In₂S₄/TiO₂ combined well,and the ultra-thin Zn In₂S₄ nanosheets grew evenly on TiO₂ nanowires.BET showed that the specific surface area was increased and more reaction sites were produced after the coupling Zn In₂S₄ and TiO₂.UV-vis spectrum proved that the composites of Zn In₂S₄/TiO₂ increase the response to visible light and provide suitable band matching.The presence of TiO₂ further improves the carrier migration and prevents its recombination with holes.Under visible light,the removal efficiency of Zn In₂S₄/TiO₂composites for high concentration Cr（VI）reaches～98%.Finally,the photocatalytic mechanism of Zn In₂S₄/TiO₂ composites for Cr（VI）removal was proposed.