Preparation And Characteristics Of Titanium Dioxide Photocatalyst Supported By Artificial Zeolite

Nano titanium dioxide?TiO₂?is considered as the most promising photocatalytic material due to its excellent properties such as chemical stability,non-toxicity,corrosion resistance,low cost and eco-friendliness.It has been used for wastewater degradation of toxic substances and dyes.However,the bandgap of anatase TiO₂ is about 3.2 eV and can only be excited by UV light,and its photoluminescence yield is also very low.In addition,the rapid aggregation of TiO₂ in solution leads to the reduction of the effective surface area and the further reduction of its catalytic efficiency,which is not conducive to the recovery after the completion of the photocatalytic reaction and is likely to cause secondary pollution.Therefore,it is necessary to improve the photocatalytic activity of TiO₂ under visible light irradiation by modifying the TiO₂ to reduce the band gap of TiO₂ and reduce the electron-hole recombination rate.On the basis of this,zeolite,as the load,can effectively fixed TiO₂ and increase the effective surface area of photocatalyst,but also to achieve the catalyst recycling.In this paper,the material of Ag-TiO₂ supported by artificial zeolite?Ag-TiO₂/Z?was synthesized by the sol-gel method.The prepared samples were characterized by XRD,SEM,EDS,XPS,UV-vis DRS and N₂ adsorption-desorption isotherms.The photocatalytic performance and stability of the samples were tested.The effects of silver doping amount,MB initial concentration,catalyst dosage,illumination time and loaded times on the photocatalytic properties of the samples were studied.Based on the theory of photocatalysis,a novel photocatalytic mechanism model was proposed.The results show:The TiO₂ in the material has an anatase phase.The dopant Ag was in the form of Ag⁰and Ag₂O nanocrystalline,the existence of Ag₂O can introduce impurity level and reduce the band gap of TiO₂,which can lead to the absorption spectrum of the sample shift into the region of visible light,with 2.75eV band gap energy.The combination of TiO₂ and zeolite enables the photocatalyst to be supported on a porous structure so as to reduce the agglomeration effect of titanium dioxide and effectively increase the specific surface area of the catalyst,which is more conducive to the adsorption and degradation of pollutants.Among the samples with different silver doping content,3at%Ag-TiO₂/Z showed the best photocatalytic activity,and the degradation rate was 93.08%within 90 minutes.The degradation rate of 3at%Ag-TiO₂/Z after 5 times of degradation remains at about 89%,indicating that the composite has good stability.After the sample was loaded several times,it was found that with the increase of the number of loads,the degradation rate of the sample first increased and then decreased.Among them,the 3 at%Ag-TiO₂/Z₃ sample after three loads had the highest degradation rate of 96.10%.According to the experimental results,a photocatalytic model based on Schottky contact was proposed.It is believed that the remarkable photocatalytic effect is the result of the interaction between silver and titanium dioxide or between silver and silver oxide,and the combination of titanium dioxide and silver oxide semiconductors.