Preparation, Characterization, and Application of Silica Aerogel for Adsorption of Phenol: An In-Depth Isotherm Study

This study evaluated silica aerogel as an adsorbent for phenol removal from aqueous solutions. Silica aerogel was prepared through the sol-gel process and characterized by different analyses. Then, it was used for phenol removal under various conditions of operational parameters. Also, twelve isotherm parameters were employed to describe the behavior of phenol-silica aerogel adsorption system. The chemical structural analysis confirmed -OH functional groups in amorphous SiO₂ and proved the adsorption of phenol onto the surface of silica aerogel. The findings of the adsorptive behavior of silica aerogel toward phenol showed increasing pH, up to 8.5, and contact time, and adsorbent dose increased the phenol removal. The removal efficiency reached over 90% when phenol concentration was below 50 mg L^-1. The reaction kinetics followed the pseudo-first order model. The isotherm study showed that equilibrium adsorption data were well-described by Freundlich and Halsey equations, among two-parameter isotherms, and Hill, Sips, and Koble-Corrigan, among three-parameter isotherms. Jovanovic and BET were the worst isotherm models for prediction of experimental equilibrium data. The maximum adsorption capacity of 75.23 mg.g^-1 was calculated in phenol-silica aerogel adsorption system. The study showed silica aerogel as an efficient adsorbent to remove phenol from phenol-containing solutions.