Nano Of Sno <sub> 2 </ Sub> / Zno Composite Photocatalyst Preparation And Characterization Of Its Photocatalytic Activity Study

Currently, the photocatalytic technology is paid greater attention as a new environment-purifying technique among various techniques for purifying environment. ZnO is a kind of important semiconductor material, its bulk material's energy gap is 3.2eV, corresponding to the ultraviolet light of the wavelength 387nm, which gained people comprehensive research in recent years. But photocatalytic efficiency of pure ZnO is lower, so it is hard to apply in the engineering. And its photocatalytic efficiency is improved by compounding semiconductors or adulterating, which was researched widely.The SnO₂/ZnO nanocomposites were prepared by coprecipitation method. The phase was analyzed by XRD, the particle figure and the size distribution were analyzed by TEM, and the photocatalytic activity was analyzed through degradating the solution of methyl orange which was irradiated by the high-voltage mercury lamp. The results showed:(1) The SnO₂/ZnO nanocomposites were prepared by coprecipitation method. SnCl₄·5H₂O and ZnSO₄·7H₂O were the starting materials and NH₃·H₂O was used as the precipitant. The best molar ratio of Zn and Sn was 2:1, the best calcination temperature was 600℃for 6h. The photocatalytic activity of SnO₂/ZnO nanocomposites was obviously improved than the pure ZnO in the same conditions. The degradation rate of methyl orange was close to 100% after irradiated 20min and the addition of catalyst was 2.5g/L. The reaction of nanocomposites photodegradating methyl orange was in accord with first order kinetic model. And we found the photocatalytic activity had no change by using it for many times.(2) The composite photocatalyst was prepared with different calcination temperature and different holding time by precursor which was prepared according to the best preparation condition in this experiment, which was used to degradate formaldehyde,p-cresol and brewery wasterwater. Results showed that the photocatalytic effect of composite photocatalyst which was prepared by 600℃for 6h was best. The reaction of composite photocatalyst degradating formaldehyde was similar to degradating methyl orange. They were in accord with first order kinetic model. But formaldehyde was hard to be degradatied. The reaction of degradating p-cresol was in accord with zero order kinetic model. The removal efficiency of COD in brewery wasterwater was good.