Adsorption of Btex Vapours Using Modified Silica Aerogels of Different Hydrophobicity

Silica monolith aerogels with different degrees of hydrophobicity by incorporating methyltrimethoxysilane (MTMS) or trimethylethoxysilane (TMES) in standard sol-gel synthesis were prepared. Excellent properties of aerogels, obtained with the sol-gel synthesis, were preserved with supercritical drying with CO2. The degree of hydrophobicity of the aerogels was tested by measuring the contact angle (θ) of a water droplet with the aerogel surface. The organic and inorganic bonds forming the aerogel structure were studied by Fourier transform infrared spectra (FTIR). From the measurements with Differential scanning calorimeter (DSC) thermal stability of the aerogels, in terms of retention of hydrophobicity, was observed. The pore texture and BET surface areas of some samples were determined by nitrogen physisorption. The adsorption capacity measurements of different silica aerogels were done by mini-column method. Continuous adsorption measurements show that silica aerogels are excellent adsorbents of benzene, toluene, ethylbenzene and xylene (BTEX) vapours from waste gas stream. The possibility to tailor hydrophobicity and consequently moisture resistance of silica aerogel adsorbents and their repeated use in many adsorption/desorption cycles make them superior to conventional adsorbents as silica gel and activated carbon.