Environmental Purification with Use of Titanium Dioxide-Loaded Adsorbent Photocatalysts

利用二氧化钛作为光催化剂来修复被污染的水和空气，对多种有机污染物进行了广泛的光催化降解研究。在实际应用中预期的光降解率通常很低，因为在大多数情况下目标物质的浓度很低。如果使用吸附剂作为二氧化钛的载体，则污染物必须集中在光催化剂周围。我们研究了吸附剂负载二氧化钛对有机基质光分解反应的影响，得到了如下结果。(1)负载二氧化钛的吸附剂光催化剂膜对气态丙醛的吸附性能在不同的吸附剂中存在差异。光催化剂对丙醛的光分解速率有促进作用，但不同吸附剂对丙醛的光分解速率的影响程度有较大差异，由此得出吸附底物在光催化剂上的吸附性能和扩散性能是决定丙醛光分解速率的关键因素。(2)使用活性炭作为二氧化钛的载体，可以提高丙酰胺的光分解速度，降低溶液中间体的浓度。活性炭载体的使用具有实际意义，因为吸附的底物被分解成二氧化碳而不将中间产物释放到溶液中。(3)不同粒径（30 ~ 500微米）负载二氧化钛的活性炭对溶解于水中的4-氯甲苯的光分解研究表明，随着活性炭粒径的减小，光分解速率增大，说明活性炭内部吸附的底物向负载二氧化钛的扩散控制了光分解速率。

Photocatalytic degradation of numerous organic pollutants has been extensively studied using titanium dioxide as a photocatalyst to remediate the contaminated water and air. The photodegradation rates to be expected in practical applications are usually very low, because in most cases the concentration of target substances is low. If the adsorbent is used as the support for titanium dioxide, the pollutants must be concentrated around the photocatalyst. We have investigated the effect of the use of the adsorbents for titanium dioxide loading on the photodecomposition reaction of organic substrate and obtained the results described below.(1) The titanium dioxide-loaded adsorbent photocatalysts film had the different adsorbability of the gaseous propionaldehyde among the kind of adsorbent used. While the photodecomposition rate of propionaldehyde was enhanced by being adsorbed on the photocatalyst, the degree was greatly different among the kind of adsorbents used, and the conclusion was derived that both adsorbability and diffusibility of adsorbed substrates on photocatalysts playd crucial roles in determination of the photodecomposition rate. (2) The use of activated carbon as a support for titanium dioxide was found to enhance the rate of photodecomposition of propyzamide and to reduce the concentration of solution-phase intermediates. The use of activated carbon support has practical significance in the sense that adsorbed substrate is decomposed to carbon dioxide without releasing the intermediate to solution. (3) With studies on photodecomposition of 4-chlorotoluene dissolved in water on titanium dioxide-loaded activated carbon of various sizes (30-500 micrometer), the photodecomposition rate increased with decrease of the size of activated carbon, indicating that the diffusion of adsorbed substrate inside the activated carbon to the loaded titanium dioxide control the photodecomposition rate.