Organic solvent-saving preparation of water glass based aerogel granules under ambient pressure drying

An organic solvent-saving method of preparing silica aerogel is reported. The silica aerogel was made from water glass (WG) and used as the solvent. Na+ was removed through ion exchange; prior to this ion exchange, concentrated hydrochloric acid (HCl) was added to the WG solution. The sol pH was adjusted to similar to 1 to suppress the condensation to the maximum extent. Ethanol was added to the sol after ion exchange. Surface modification was conducted with the assistance of hexamethyldisiloxane, which was catalyzed by HCl. The entire process can be finished in 6 h. The overall consumption of organic solvent is much lower than that in the previous preparation route. Characterization results indicate that the resulted silica aerogel has a uniform mesoporous structure and low thermal conductivity (0.0237-0.0245 W/m.K at 1 atm).