剥离膨润土支撑氟改性二氧化钛高效降解甲醛的研究

Study on efficient photocatalytic degradation of formaldehyde over F-doped TiO2 supported by exfoliated bentonite

二氧化钛作为一种最常见的光催化剂,虽然已被广泛研究,但却存在若干缺点而限制了其在实际中的应用.为解决二氧化钛催化剂在反应过程中容易团聚而导致样品不好回收的问题,以及为进一步提高其催化活性,将天然膨润土剥离为片状膨润土,用来支撑经溶胶凝胶法制备的氟掺杂二氧化钛,再以光催化降解甲醛为目标来评价样品的降解活性.结果表明,当氟掺杂量为5%时,样品具有最好的降解效果,氟的掺杂量对样品的活性具有很大影响;氟与二氧化钛有两种结合方式,一种是氟离子物理吸附在二氧化钛表面使得产生大量的羟基自由基,另一种方式是氟可取代氧进入二氧化钛晶格中,进而在样品中形成氧空位与三价钛.羟基自由基和氧空位都有利于光催化反应的发生,因此提高了样品的活性.

As the most common photocatalyst,titanium dioxide(TiO2)has been widely studied.However,there are still some shortcomings that limit its practical application.To resolve the aggression problem and improve the catalytic efficiency of TiO2 sample.In this project,exfoliated bentonite(EB)would be prepared by using natural bentonite and support F-doped TiO2(TF)nanoparticules to prepare the F-doped TiO2/exfoliated bentonite(TF/EB)composite using a facile sol-gel method.In this study,formaldehyde was used as the target pollutant to evaluate the sample′s degradation activity.According to the degradation results,the best performance can be achieved by the sample with F/Ti atom ratio of 5%.Fluorine doping has a great effect on sample activity.F-doping of TiO2 brings the appearance of two types of fluorine species in the solid.The former is the F-ions physically adsorbed on the surface of TiO2 to generate a large number of hydroxyl radicals.The second is F-ions that substitute O2-ions in the TiO2 lattice,then generate oxygen vacancies and Ti3+in the samples.Both hydroxyl radicals and oxygen vacancies are conducive to the occurrence of photocatalytic reactions,thus increasing the activity of the TiO2 sample.