光催化氧化苯甲酸时TiO_2中毒机理及再生方法的研究

Study on deactivated mechanism and regeneration methods of TiO_2 during photocatalytic benzoic acid

以苯甲酸作为模型污染物,采用强制中毒的方法研究了TiO2在悬浮光催化氧化体系中的中毒过程,并通过对中毒TiO2进行IR、SPS及XPS表征,分析了中毒后TiO2的表面性质,揭示了苯甲酸光催化降解过程中TiO2光催化剂的中毒机理.采用高温焙烧、UV光照射及超声波振荡等方法对中毒TiO2进行再生,并考察再生效果.研究表明,实验条件下,催化剂反复使用20次后将完全中毒.引起TiO2中毒的主要原因是苯甲酸及其降解中间产物,如羟基苯甲酸、顺丁烯二酸、反丁烯二酸等吸附、积累在TiO2表面,占据了TiO2的表面活性位置,使其光催化活性下降;TiO2在使用过程中出现的团聚现象也会导致其活性降低.比较了高温焙烧、UV光照及超声波清洗3种方法对中毒催化剂的再生效果的比较研究,结果表明,3种方法均能使中毒后TiO2的催化活性得到一定恢复,其中高温焙烧对中毒TiO2的再生效果较好.

The benzoic acid was used as a model pollutant to investigate the deactivation of titanium dioxide by stimulated continuous photocatalysis reaction. The changes of the structure and chemical states of the catalysis were characterized by IR, SPS and XPS. The deactivation mechanism of TiO2 for photocatalysis degradation of benzoic acid was analyzed. Calcination, ultraviolet irradiation and ultrasonic washing were used to regenerate the deactivated TiO2. The catalysis power of titanium dioxide would nearly dismissed after it was used repeatedly to photocatalysis reaction of benzoic acid under controlled conditions for 20 times. The deactivation of TiO2 was caused by the catalysis site of TiO2 particle surface covered with benzoic acid and some intermediates, such as hydro-benzoic acid, maleic acid, fumaric acid and so on. And strongly accumulation for TiO2 power particles in the solutiion also resulted in the photocatalytie activation lose. The catalysis power of deactivated TiO2 was restored partly by three different regeneration methods mention above. And the best regeneration method was calcination.