Preparation of hydrophobic granular silica aerogels and adsorption of phenol from water

Granular silica aerogels with different degrees of hydrophobicity were prepared via sol–gel synthesis followed by drying at ambient pressure. The effects of preparation conditions, including pH and modification time, on aerogel characterization were investigated. The aerogels were characterized using nitrogen adsorption at 77 K. We found that the aerogel was a nano-structured material with high specific surface area and high porosity. The aerogels were used for phenol adsorption from water. The effects of hydrophobicity degree, phenol concentration, and contact time were studied. Batch kinetic and isotherm studies were carried out to evaluate the effects of contact time and phenol concentration. The Freundlich model and the pseudo-second-order fitted the experimental data. The results also indicated that the phenol adsorption process involved both boundary layer diffusion and intraparticle diffusion. When the equilibrium concentration of phenol was 290 mg L−1, the adsorption of phenol on the aerogel was 142 mg g−1.