Synthesis of high specific surface area silica aerogel from rice husk ash via ambient pressure drying

In this study, silica aerogel was synthesized from rice husk ash-derived water glass through ion-exchange, solgel, solvent exchange and ambient pressure drying. The physical and chemical properties of silica aerogel were fully characterized by the Brunauer-Emmett-Teller theory (BET), Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis-differential thermal analysis (TGA-DTA), Fourier transform infrared spectroscopy (FTIR). The effects of processing parameters, especially, the modulus of water glass on the characteristics of the products are deeply investigated. It is found that the modulus of water glass can significantly influence the specific area and pore volume of the aerogel through changing the polymerization degree of Si-O group in the water glass solution. As well as, the pH value of sol-gel process and solvent concentration during modification are of importance for the physical properties of silica aerogel. When water glass modulus was 4.26, the gelation pH was 5.0 and the volumetric ratio of Trimethylchlorosilane (TMCS) to n-hexane was 7/50, silica aerogel was obtained with optimal performances of extremely high specific surface area (945.8m(2)/g), pore volume (0.889 cm(3)/g), low density (0.071 g/cm(3)) uniform pore size distribution, high heat resistance temperature as 400 degrees C. The presented method is promising to synthesize high specific surface area silica aerogel from rice husk ash.