Preparation Of Functionalized Mesoporous Silica And Study On Its Adsorption/Desorption Performance For P-xylene

The adsorption capacity of organic matter on ordered mesoporous silica（SiO₂）material is impaired under high humidity for the rich hydroxyl on silica surface.Hydrophobic modification of ordered mesoporous SiO₂ materials can be achieved by organic functionalization method,but some problems still exist such as loss of pore size and specific surface.In order to realize the hydrophobic modification of ordered mesoporous silica surface and avoid the problem of specific surface area decreasing,vinyltriethoxysilane（VTES）was selected as the modifier in this study to obtain a mesoporous SiO₂ adsorption material with water-resistant property.The main contents include:Dissipative particle dynamics（DPD）has been applied to simulate the modified synthesis process of mesoporous SiO₂.The results show that when a certain proportion of VTES is added to the mesoscopic system,the mesoscopic structure of mesoporous SiO₂ would change from two-dimensional structure to three-dimensional structure.Meanwhile the water resistance of the material surface is increased.The adsorption performance of mesoporous SiO₂ modified by VTES has been examined by Density functional（DFT）simulation.The results show that the adsorption performance of organic matter on mesoporous SiO₂ modified by VTES is enhanced compared with the unmodified mesoporous SiO₂.The above results indicate that VTES is a theoretically feasible modifier for mesoporous SiO₂ functionalization.Vinyl functionalized ordered mesoporous SiO₂ material was prepared by co-condensation method,and the structure and properties of the synthesized materials were characterized.It has been confirmed that the vinyl groups are successfully introduced into the pore-wall surface of the materials,and the introduction of vinyl could improve the water resistance and adsorption capacity of organic matter.In addition,when the molar ratio of VTES/（VTES+TEOS）increases to 15%,the pore structure of ordered mesoporous silica changes from two-dimensional hexahedral structure（P6m）to three-dimensional cubic structure（Ia3d）,which can increase the specific surface area of the material by 4%～10%.To explore the adsorption behavior,the dynamic absorption and desorption experiment of p-xylene on ordered mesoporous materials has been conducted.The experimental results show that after modification,these silica materials show enhanced humidity resistance with the Q_wet/Q_dry increasing from 56.2%to 85.2%(Q_dry and Q_wetrepresent the adsorption capacity under dry and wet condition,respectively).The desorption experiments show that the functionalized ordered mesoporous materials still have a high-level desorption rate under wet condition with the desorption rate of p-xylene up to 88.1%.The adsorption/desorption recycling tests prove that the v-SiO₂possesses prominent stability with over 91%adsorption capacity being kept after six cycles.The new mesoporous silica material synthesized in this study has extensive application prospect and provides a theoretical and practical guidance for the development of similar materials.