Surface Hydrophobic Modification Of Normal Silica-Gel And Its Adsorption Properties Study To VOCs

In the past several decades, the harm that the volatile organic compounds (VOCs) have done to environment and human health has increasingly serious, thus the relevant managerial technology and materials has received great attention gradually. VOCs come from various areas,and toluene is considered as one of the major sources of pollution for its wide-spread use.A-type silica gel was hydrophobic modified by grafting method, and its adsorption behavior on toluene was studied in this paper.In this research, A-type silica gel was taken as matrix to prepare phenyltrimethoxysilane (CMTMS) modified silica gel, methyltriethoxysilane(MTES) modified silica gel, triethoxyoctylsilane(OTES) modified silica gel and hexadecyltrimethoxysilane (CTMS) modified silica gel by gas modification. The effect of hydrophobic modification time on saturated adsorption capacity of the modified silica gel was studied, and the results showed that the optimal modification time was 4 hours. The hydrophobic modified silica gel was characterized by FT-IR and BET, and it was found that the grafting of organic groups on the surface would result in blockage of channels.Besides, an analog experimental system of atmospheric adsorption was set up to study the effects of silane modifier on the adsorption behaviors of modified silica gel, which were tested in different concentrations of toluene and toluene-water binary system. The experiments showed that the adsorption of toluene on the hydrophobic modified silica gel was mainly physical adsorption, thus the pore size distribution and specific surface area were the key factors in the determination of adsorption capacity. The hydrophobic modification could enhance the hydrophobicity on modified silica gel surface, and also improve the diffusion velocity of organic gas molecules in the stage of external diffusion, thus increasing its selectivity of organic gases. The silica gel, modified with long-chain silane (CTMS, OTES) at 60℃for 4h, has showed better adsorption selectivity in toluene-water binary system.