Performance of water glass-based silica aerogel for adsorption of phenol from aqueous solution

Silica aerogel was synthesized with water glass precursor and ambient pressure drying method. It was modified with activated carbon (AC), and the silica aerogel-AC nanocomposites were synthesized. The properties of samples were characterized by measurement of bulk density and hydrophobicity, scanning electron microscopy analyze, N₂ adsorption–desorption BET surface analyzer, BJH analysis and FTIR spectroscopy. Then the synthesized materials were used as the adsorbent of phenol, and their potential in adsorption from aqueous solution was studied. Mass adsorption and continuous operation with reflux were carried out for evaluation of adsorbents. The effect of addition of AC, the presence of sun light, contact time and initial phenol concentration on the phenol adsorption of silica aerogel were investigated. The presence of sun light played obvious effects on phenol removal. The adsorption process reached equilibrium in 6 h of contact. Increase in the initial phenol concentration could effectively increase the phenol adsorption capacity. The maximum phenol adsorption capacity was obtained as 8.05 (g g⁻¹) for 60 vol% initial phenol concentration in mass adsorption, and 12.87 (mg g⁻¹) for 200 mg l⁻¹ initial phenol concentration in continuous adsorption process at 30 ± 2 °C. The results of mass adsorption method on silica aerogel-AC nanocomposite showed that the addition of AC to silica aerogel had improved the silica aerogel and 0.5 wt% silica aerogel-AC nanocomposite had a higher adsorption capacity compared to pure silica aerogel. It was found that synthesized silica aerogel has an excellent adsorption capacity for concentrated phenol solutions and its performance for adsorption of phenol from dilute solutions is comparable to the literature adsorbents for phenol. The adsorption kinetic and isotherm studies showed that the pseudo-second-order model and Freundlich isotherm were best choices to describe the adsorption behaviors.

In this study, silica aerogel and the silica aerogel-activated carbon nanocomposites were synthesized. Then the synthesized materials were used as the adsorbent of phenol and their potential in adsorption from aqueous solution was studied. It was found that synthesized silica aerogel has an excellent adsorption capacity for concentrated phenol solutions and its performance for adsorption of phenol from dilute solutions is comparable to the literature adsorbents for phenol.