新型光催化材料的制备与催化性能研究

【作者】 宋海燕；

【导师】 孟广耀；

【作者基本信息】 中国科学技术大学 ， 材料学， 2006， 博士

【摘要】 半导体光催化技术主要用于抗菌、净水、大气净化、防臭以及防污等过程，是目前最经济最简单的污染治理技术。TiO₂半导体具有无毒、催化活性高、稳定性好等优点，是最常用的光催化剂，以TiO₂为基础的光催化技术的研究已经有20多年的历史，但目前还存在一些关键的技术难题，使其广泛的工业应用受到制约。本论文主要从纳米TiO₂的负载、对可见光响应的光催化剂的研制以及新型非TiO₂体系的光催化剂的探索这三个方面展开工作，以期为光催化技术的实用化和产业化奠定基础。 早期光催化技术研究，大都采用纳米TiO₂的悬浮体系降解有机污染物，由于纳米粉体粒径小，回收困难，增加了废水的处理成本，从而影响该技术的实际应用。将TiO₂固定在诸如分子筛、活性炭等惰性载体上，是解决催化剂分离、回收问题的有效方法。但这些多孔载体都是人工合成的产品，制造成本高，工序复杂，使光催化技术的实用化受到限制。我们尝试用廉价的天然非金属矿物粉体作载体，采用溶胶浸渍法制备了一系列天然矿物（硅藻土、沸石、凹凸棒土、高岭土）负载型光催化剂，系统研究了载体对催化剂活性的影响。结果表明，载体对反应底物的吸附性太强或太弱都不利于光催化反应，只有当载体对反应底物具有适中的吸附能力时（如硅藻土），制得的催化剂才是最理想的，此时，载体既可以使有机物富集在TiO₂粒子的周围，又容易使吸附在载体上的有机物在浓度梯度的作用下向TiO₂迁移，促进催化反应的进行。并由此提出了矿物负载光催化剂的催化反应理论模型（吸附—迁移—光降解—脱附模型），为负载型光催化剂的制备过程中载体的选择提供了理论依据。 以上述理论模型为指导，制备TiO₂／硅藻土催化剂，通过对焙烧温度、焙烧时间、负载量、溶液的pH值等不同因素对光催化活性的影响的研究，发现当催化剂的负载量为75-wt％，经600℃焙烧2小时，光催化反应起始溶液的pH=6～8，催化剂的投料量为0.4g／l（TiO₂）时，TiO₂／硅藻土的光催化活性最佳。在该催化剂作用下，紫外光照射3小时后，氯仿的降解率可达67％，反应速率是纯TiO₂粉体的4倍。另外，TiO₂/硅藻土催化剂经多次重复使用后，仍然保持较高的活更多还原

【Abstract】 The water pollution today, caused by hazardous organic chemicals used in industry and agriculture, is a very serious problem. There has been a great effort and there is a number of ways to devote into the treatment of wastewater. Over the past 20 years, the scientific and engineering interest in the semiconductor photocatalysis has grown exponentially because the photocatalytic reactions allow in many cases a complete degradation of organic pollutants in very small and not noxious species, without using chemicals, avoiding sludge production and its disposal. TiO₂ in the crystalline form of anatase has been widely used due to its high photostability, innocuity and low cost. Until now, there are still some serious problems, which hinder the application of TiO₂ in the industry, such as the low quantum production, and the convenience of catalyst immobilization on progressively large particles is bought at the expense of increased average convective-diffusion distance from fluid to catalyst surface.To resolve the problems stated above, this thesis researches on the support, modification of TiO₂ photocatalysts, and its performance under UV and Visible light irradiation. A new series of photocatalysts nano Alkali Titanate were also researched.In chapter 1, TiO₂ photocatalysts have been reviewed, including the principles and mechanisms of photocatalysis, environmental applications, the lattice and electronic structure of TiO₂, its surface modification and immobilization of photocatalysts.In chapter 2, some science aspects in the experimental process of supported catalysts have been represented, such as the classification and the selection of supporter, the connection between the supporter and active component and the preparation method of supported catalysts.In chapter 3, nano TiO₂ particles deposited on crude nonmetallic minerals were prepared by a Sol-dipping process, the photocatalyst for degradation of chloroform was tested, and optimized with respect to TiO₂ loading, catalyst dosage, calcinations temperature and pH value of the initial wastewater. The adsorption properties and更多还原