【作者】 屈芳；

【导师】 朱利中； 杨坤；

【作者基本信息】 浙江大学 ， 环境科学， 2010， 博士

【摘要】 空气中挥发性有机化合物(Volatile Organic Compounds, VOCs)的净化处理是环境科学与工程领域的研究热点之一。粘土基类吸附/催化材料对VOCs具有较好的吸附/催化性能,在VOCs污染控制领域有良好的应用前景。本文以有机膨润土(或废弃有机膨润土)为原料合成新型层状多孔粘土异构材料(Porous Clay Heterostructures, PCHs)以及锐钛型粘土基多孔二氧化钛(Ti02)纳米催化材料,研究了它们吸附/催化降解VOCs的性能、机制及构效关系。论文取得了以下有价值的研究结果：(1)建立了典型PCHs吸附VOCs的多元线性数学模型,系统评价了PCHs吸附VOCs的性能与气体分子理化性质(分子截面积、极化率、蒸发焓和临界体积等)之间的构效关系,揭示了PCHs吸附VOCs的特性及作用机制。发现PCHs对丙酮等羰基VOCs的吸附量高于甲苯、乙苯、邻二甲苯、间二甲苯和对二甲苯等芳香烃VOCs。(2)发现空气湿度越高,PCHs和活性炭(AC)对甲苯的平衡吸附量越小,穿透时间越短；与PCHs相比,AC吸附甲苯的性能受水蒸气影响更为明显,甲苯的平衡吸附量下降更大。AC对水蒸气的吸附总量高于PCHs。初步探明了PCHs和AC疏水性能的差异及其水分子循环吸附-脱附机制。(3)开发了锐钛型粘土基多孔Ti02纳米催化材料。该材料比表面积和孔容较大,孔径分布均匀,在紫外200-400 nm范围内有强烈吸收,具有较高的催化活性,对甲苯的光催化降解率与其比表面积呈正相关。加入小分子助表面活性剂(DDA)或对硝基苯酚(PNP)可使催化材料比表面积和孔体积增大、平均孔径减小,并提高其光催化降解甲苯的效率。空气湿度80%时,添加DDA或PNP后制得的光催化材料,其降解甲苯的效率由17.90%分别提高至74.60%和76.50%。更多还原

【Abstract】 With increasing aggravation of indoor air pollution, the removal of volatile organic compounds (VOCs) is a key issue in the field of Environmental Science & Engineering. Clay-based materials have been developed to remove VOCs due to their excellent properties of adsorbents and/or catalysts. In this work, porous clay heterostructures (PCHs) and clay-based anatase titanium dioxide (TiO2) catalyst were synthesized from organic bentonites or disused organic bentonites. The removal performances and the underlying mechanisms of VOCs by adsorption on PCHs or by photocatalystic degradation with clay-based TiO2 were examined and related with the physicochemical properties of VOCs and adsorbents/catalysts. Several conclusions are as follows:1. The multivariate linear model of the adsorption of VOCs on typical PCHs was employed to establish the relationships between the adsorption capacities of VOCs on PCHs and the physicochemical properties of VOCs (e.g., molecular cross-sectional area, polarizability, evaporation enthalpy and the critical volume, etc.). The removal performances and the underlying mechanisms of VOCs by adsorption on PCHs were examined. The adsorption capacity of the carbonyl VOCs (e.g., acetone) on PCHs was higher than that of aromatic VOCs (e.g., toluene, ethylbenzene, O-xylene, m-xylene and p-xylene).2. As the air humidity increased, the equilibrium adsorption capacities of PCHs or AC for toluene decreased and the breakthrough time was shortened. The effect of the water vapor of adsorptive properties of toluene on AC was more obvious than that of PCHs. It showed that the descending tendency of equilibrium adsorption capacities on AC for toluene were more obvious than that of PCHs at relatively higher humidity. The adsorption-desorption isotherms indicated the water vapor adsorption capacities of AC was higher than that of PCHs. The similarities and differences of hydrophobic properties of PCHs and AC were compared. Meanwhile, the adsorption-desorption circulation mechanism of water moleculars was also proved.3. Clay-based anatase titanium dioxide (TiO2) catalyst with large surface area, pore volume and uniform pore size distribution was synthesized, which had strong absorbance in the ultraviolet light wavelength range of about 250-400 nm. The high photocatalytic degradation rate of toluene by clay-based TiO2 depended on the specific surface area of catalysts. The addition of the small co-surfactant (DDA) or p-Nitrophenol (PNP) contributed to the increasing of specific surface area and pore volume, while the decreasing of average diameters. Besides, the degradation efficiency of toluene can also be enhanced by adding DDA or PNP to the surface of catalyst. The degradation rates of toluene by photocatalytic materials increased from 17.90% to 74.60% and 76.50% with the addition of DDA or PNP, respectively, when humidity was 80%.更多还原