Study On The Photocatalytic Degradation Of Toluene By Strontium Hydroxystannate And Its Compound

Volatile organic compounds（VOCs）,as one of the main environmental pollutants,not only directly harm the environment and the human body,but also photochemically react with nitrogen oxides under sunlight to form secondary pollutants,thus causing serious damage to the atmospheric environment.Indirect harm.Photocatalytic technology can generate strong oxidizing active free radicals under mild conditions,thereby degrading organic pollutants such as benzene,toluene,and formaldehyde into other small molecule compounds and CO₂and H₂O.Therefore,photocatalysis technology is regarded as an economical,efficient and environmentally friendly technology that can be used for the degradation of VOCs.Although photocatalysts such as Ti O₂and Zn O have achieved certain results in the treatment of VOCs,most photocatalysts are easily covered by excessive intermediate products and secondary poisonous by-products on their surface active sites during the degradation of organic pollutants,resulting in extremely high catalysts.Easy to deactivate,showing poor photocatalytic stability.The new semiconductor photocatalyst SrSn（OH）₆has a large forbidden band width,has a suitable conduction band and valence band position,and exhibits stronger redox ability.In addition,a large number of hydroxyl groups are evenly distributed on the surface of SrSn（OH）₆.Under ultraviolet light irradiation,hydroxyl groups are easily oxidized by holes to hydroxyl radicals（·OH）,and·OH is the main active group that degrades organic pollutants.Therefore,SrSn（OH）₆has a better performance in photocatalytic oxidation of VOCs.Great potential.However,SrSn（OH）₆has shortcomings such as narrow light absorption range and low photo-generated electron-hole separation efficiency,which leads to its limited photocatalytic efficiency.In order to improve the photocatalytic performance of SrSn（OH）₆,the following modifications were made:（1）Adjusting the microstructure of SrSn（OH）₆;（2）Constructing a ZnSn（OH）₆/SrSn（OH）₆heterojunction.Use XRD,BET,FT-IR,SEM,XPS,TEM,UV-vis DRS,ESR and other characterization methods to analyze the phase structure,microstructure and optical properties of the catalyst,and evaluate its photocatalysis through the degradation of gas phase toluene Performance,using In-situ DRIFTS to dynamically monitor the intermediates and final products in the process of photocatalytic degradation of toluene.The main research work is as follows:（1）Adjust the microstructure of SrSn（OH）₆:Synthesize SrSn（OH）₆（SSH）by a simple hydrothermal method,and change the surface free energy and intermediate products in the reaction system by adjusting the p H value of the reaction precursor solution Different types of SSH have been prepared.According to the characterization results,the photo-generated charge separation efficiency on the rod-shaped SSH-10.5is improved,showing the highest photo-generated electron-hole pair separation efficiency.According to the results of free radical capture experiments,the abundant hydroxyl groups on the surface of SSH-10.5 are efficiently converted into hydroxyl radicals during the photocatalytic process.The photocatalytic performance of SSH was investigated by photocatalytic treatment of gas-phase toluene.The experimental results showed that sample SSH-10.5 had the highest photocatalytic activity,and the degradation efficiency of p-toluene under ultraviolet light irradiation reached 69.56%.Combined with in-situ infrared spectroscopy analysis,·OH and·O₂^-radicals attack the methyl groups on toluene,converting toluene into intermediate products of benzyl alcohol,benzaldehyde and benzoic acid,and finally mineralizing toluene into CO₂.（2）Construction of ZnSn（OH）₆/SrSn（OH）₆heterojunction:A new type of semiconductor photocatalyst ZnSn（OH）₆/SrSn（OH）₆（ZSH/SSH）was successfully prepared by a simple room temperature co-precipitation method.The formation of a heterojunction structure between ZSH and SSH semiconductor materials promotes the effective transfer of photogenerated electrons and holes between the valence band and conduction band of the two,thereby improving the separation efficiency of photogenerated electron-hole pairs.This process allows more active species to participate in the photocatalytic reaction,effectively improving the degradation efficiency of the composite material for pollutants.Taking gas-phase toluene as the target pollutant,the photocatalytic activity of ZSH/SSH was evaluated.The sample ZSH/SSH-10 showed the best photocatalytic activity.Within 30 minutes,the activity of the composite photocatalyst was improved by 14%compared with pure phase SSH.Combined with in-situ infrared spectroscopy,the conversion of toluene onSSH and ZSH/SSH-10 under light conditions and the intermediate and final products were analyzed.