Hydrophobic modification of TEOS on silica gel surface and its adsorption characteristics of VOCs

Volatile organic compounds (VOCs) have become one of the main atmospheric pollutants. Most of VOCs contain a large amount of water vapor, and the relative humidity (RH) is >60%. Therefore, it is crucial to developing hydrophobic adsorbents. In this contribution, tetraethyl orthosilicate (TEOS) was used as a hydrophobic agent to modify the surface of hydrophilic silica gel and prepare the hydrophobic silica gel through hydroxyl grafting reaction. The structure and stability of the adsorbent after grafting reaction was characterized by BET, FT-IR, XRD and TG-DTG. The performances of adsorption on various VOCs were investigated. The results shown that TEOS was successfully grafted on the surface of silica gel and hydrophobic silica gel was prepared. In addition, the mechanical strength has been increased to 66.85%, and stability of silica gel have been improved, the adsorbent after calcination in air at 550℃ is still hydrophobic and its adsorption capacity is twice than before. Last but the most important, higher adsorption capacity of VOCs as well as excellent thermal regeneration of this hydrophobic silica gel could be received under the conditions of high humidity and high concentration VOCs. The adsorption capacity of the hydrophobic silica gel at high concentration was 10 times than that at the low concentration and not affected by water vapor; the adsorption/desorption of the silica gel for 10 cycles was almost unchanged and the desorption rate of 90% was reached in 15-30min under certain conditions. © 2020, Editorial Board of China Environmental Science. All right reserved.