纳米SnO₂/ZnO复合光催化剂的制备表征及其光催化活性研究

【作者】 申利春；

【导师】 周秉明； 曹建新；

【作者基本信息】 贵州大学 ， 化学工程与工艺， 2008， 硕士

【摘要】 近几年，半导体光催化降解技术作为一种新型的环境净化技术已经越来越为人们所重视。ZnO是一种重要的半导体材料，其体相材料的禁带宽度为3．2eV，对应于波长为387nm的紫外光。但是，纯ZnO光催化效率较低，难以工程化应用。半导体复合或掺杂等能提高其光催化效率，因而引起广泛关注。本文采用共沉淀法制备了纳米SnO₂／ZnO复合光催化剂。用热分析仪分析复合光催化剂前驱体的热反应行为，X射线衍射分析煅烧后复合光催化剂的物相组成，并用透射电镜观察其形貌及粒度分布：在高压汞灯照射下，用其降解甲基橙、甲醛等溶液，并对其光催化活性进行分析。实验结果表明：（1）以ZnSO₄·7H₂O和SnCl₄·5H₂O为原料，氨水为沉淀剂，采用共沉淀法制备的纳米SnO₂／ZnO复合光催化剂，其最佳n（Zn）／n（Sn）比为2：1，最佳煅烧温度为600℃保温6h。用纳米SnO₂／ZnO作光催化剂，比同等条件下仅用纳米ZnO对甲基橙的降解率提高显著。复合催化剂添加量为2．5g/L，光照20min后，甲基橙的降解率已达到了100％。光降解甲基橙反应基本符合一级动力学方程，且重复使用性能良好。（2）根据本实验中确定的最佳制备条件得到的前驱体，经不同煅烧温度，不同保温时间制备的复合光催化剂对甲醛、对甲基苯酚和酿酒废水进行光降解。实验结果表明：600℃煅烧6h的复合催化剂效果最好。复合催化剂对甲醛的光催化降解情况类似于甲基橙，反应都符合一级动力学方程，但甲醛较难以降解；对对甲基苯酚的光降解符合零级动力学方程。复合催化剂对酿酒废水中COD的去除，达到了较好的效果。更多还原

【Abstract】 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.更多还原