Performance Evolution of Silica Aerogel Synthesized from Sodium Silicate in the Adsorption of Phenol from Aqueous Solutions

Phenol is a toxic and persistent substance in the environment. The aim of this study was to evaluate the performance of silica aerogel synthesized using sodium silicate in the adsorption of phenol from aqueous solutions.
Material and Silica aerogel was prepared by Sol-Gel process. The influence of effective variables such contact time, initial pH of the solution, adsorbent dose, and initial phenol concentration on the adsorption efficiency was investigated. The characterization of prepared silica aerogel and confirmation of phenol adsorption was determined through SEM, XRD analysis and NMR, FTIR spectra respectively. The adsorption data was evaluated via Langmuir and Freundlich isotherms and pseudo-first and pseudo-second-order kinetics.
This research found that the phenol adsorption efficiency increased by increasing pH from 3 to 11, so that after 60 min, the absorption efficiency at the 100 mg/L initial phenol concentration and 0.5 g adsorbent obtained 84 and 96.4 % at pH 3 and 11, respectively. The SEM image and XRD patternof synthesized silica aerogel confirmed the creation of porous and amorphous structure. After the phenol absorption, the NMR and FTIR spectra of silica aerogel, confirmed the creation of new bands because of phenol molecule at the adsorbent structure. The absorption of phenol was compatible with Freundlich isotherm and pseudo-second-order kinetic. The maximum absorption capacity (qm) obtained was 47.39 mg/g.
Silica aerogel as an adsorbent, due to special characteristics in the structure and usage, can be a promising treatment process for adsorption of toxic and persistent substances.