FABRICATION OF TERNARY SILICA-CALCIUM-MAGNESIUM AEROGELS: EFFECT OF FEEDING RATE AND MOLAR RATIO ON PROPERTIES

Abstract

The silica-calcium-magnesium ternary aerogels were prepared by a solvent exchange method and a subsequent ambient pressure drying process. The effect of process parameters such as feeding rate (9-70 mL.min-1) and molar ratio (Si/(Ca:Mg) = 1:1 - 3:1) on the material characteristics including density, elemental content, surface area, pore size, pore volume, and morphology of powders were investigated. Aerogels were characterized by Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Barrett–Joiner–Halenda (BJH) and tapping density analysis. It was found that the molar ratio of Si/(Ca:Mg) could remarkably affect the surface area and density of aerogels, while the feeding rate had slight effect. The resultant aerogels exhibited high specific surface areas. The results showed that the aerogel has a Si/(Ca:3Mg) molar composition obtained with 9 mL.min-1 had the highest surface area (524 m2.g?1). The increase of Ca to Mg molar ratio caused a decrease in the surface area and density of samples. The resultant aerogels are promising candidates as adsorbents to remove various contaminants.