【作者】 吕金泽；

【导师】 朱利中；

【作者基本信息】 浙江大学 ， 环境科学， 2014， 博士

【摘要】 TiO2光催化是目前最具应用潜力的室内气态有机污染物净化技术之一,但由于室内有机污染物浓度低(ppb级)、催化净化停留时间短(10ms级),导致TiO2吸附-光催化效率较低。同时,光催化剂表面易附着空气中的颗粒物,造成活性位点失活,制约光催化技术的大规模产业化应用。为此,本文研究了TiO2微孔吸附低浓度气态有机污染物的行为及其强化光催化降解的机制,在此基础上,提出优化微孔稳定性和结晶度的新方法。此外,为阻隔空气中的颗粒物,探索了多孔TiO2外层包覆SiO2绝缘纳米薄膜的制备方法,试图为开发经济高效的光催化剂提供技术支持。论文取得以下主要成果：(1)阐明了微孔TiO2吸附及光催化低浓度气态甲苯和环己酮的构效关系。发现随有机污染物浓度降低或停留时间变短,微孔TiO2与P25对污染物去除效率的比值增大；微孔面积和结晶度是决定TiO2对低浓度气态有机污染物吸附-光催化协同效应的关键参数；微孔TiO2表面存在大量TiⅡ和Tim中心,诱导环己酮O=C双键打开,促进环己酮的降解。(2)探明了优化微孔TiO2结构的新方法,显著提升了微孔的稳定性和结晶度。制备的无定形微孔TiO2微孔面积达到493m2/g,是同类材料稳定状态下的2.2倍以上,对低浓度甲苯(0.036mg/m3)的平衡吸附量和吸附速率常数分别是P25的36.8倍和1.53倍；制备了具有锐钛晶型的微孔TiO2,微孔面积达到258m2/g,对低浓度甲苯(0.036mg/m3)的平衡吸附量和吸附速率常数分别是P25材料的10.3倍和1.5倍,去除率和矿化率相比P25提高了11.8%和89%。(3)提出了多孔TiO2外层包覆SiO2纳米薄膜防止颗粒物占据活性位点的方法。材料内部TiO2呈堆积多孔结构,提供反应界面；外部包覆孔径为5-10nm的Si02纳米薄膜,保护TiO2表面,屏蔽TiO2表面电荷,同时不影响TiO2的光催化活性。更多还原

【Abstract】 Adsorption and photodegradation are key steps in indoor air purification. Micropores have been introduced to TiO2nanocatalysts in order to enhance the adsorption of the pollutant on the photocatalyst surface, thereby increasing the utilization of the photo-induced electron-hole pairs. Two different nanocomposites, anatase microporous TiO2and amorphous microporous TiO2, have been synthesized under mild hydrothermal conditions using dodecylamine/dodecyl-2-pyridinyl-methylamine as pore-forming agents and varying temperature of preparation. Samples synthesized at different conditions provided interesting insights into the impact of crystallinity, valence of surface elements, and micropore area on the removal efficiency of gas-phase organic pollutants. Among the two, amorphous microporous TiO2had the largest micropore surface area of493m2·g-1but amorphous phase, while anatase micorporous TiO2had both a relatively large micropore urface area of258m2·g-1and anatase crystal structure. Toluene and cyclohexane were chosen as two models of hydrophilic and hydrophobic air pollutants. Experiments were performed in a single-pass reactor under a variety of experimental conditions, such as varying partial pressures of toluene, contact times, and relative humidities of the mobile gas phase, in order to approximate the realistic conditions. The equilibrium-adsorption-amount of toluene and cyclohexane over amorphous microporous TiO2were36.8and8times higher than those of P25, respectively. Moreover, the amorphous microporous TiO2also showed efficient self-recovery ability. Among the two prototype catalysts, anatase micorporous TiO2showed the highest removal and mineralization efficiency. The adsorption capacity and photocatalytic removal efficiency are controlled by the micropore surface area, concentration of surface TiⅡ andTⅢ, and the crystallinity of the photocatalyst. Besides, to protect the surface active sites of TiO2from being infected by the particles generally existed in atmosphere, porous-SiO2-encapsulated TiO2was developed. The pore size of outside SiO2shell can be well controlled between5-10nm. The inside TiO2nanoparticles aggregated together to form porous profile thereby generating relatively large amount of reactive sites. The results showed that the SiO2shell didn’t reduce the photocatalytic activity of inner TiO2and shield the electric charge on the TiO2surface.更多还原