Silica aerogels modified with mercapto functional groups used for Cu(II) and Hg(II) removal from aqueous solutions

Abstract

A new adsorbent, silica aerogel modified with mercapto (-HS) functional group, was synthesized by standard sol–gel synthesis. Excellent properties of aerogels, obtained with the sol–gel synthesis, were preserved with supercritical drying with CO2. The adsorbent was characterized by Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC) and thermal gravimetry (TG) measurements, nitrogen physisorption and scanning electron microscope (SEM). The ability of modified silica aerogel with mercapto group to remove Cu(II) and Hg(II) from aqueous solutions was assessed using batch adsorption technique under equilibrium conditions. Adsorbent exhibits very high adsorption potential for both heavy metal ions and more than 99.0% removal was achieved in the pH range 4–6. The equilibrium data were fitted well by the Freundlich and Langmuir isotherm model (R2>0.9).