A study on preparation and properties of fly ash-based SiO2 aerogel material

Using fly ash acid leaching residue as the silicon source, sodium silicate solution was produced by alkali leaching and the wet gel was obtained by the sol-gel method. Hexamethyldisiloxane (HMDSO) was used to modify the surface of the wet gel, thereby reducing the capillary tension during the atmospheric pressure drying process, and finally preparing a silica aerogel material with hydrophobic properties. The effects of different alkali leaching conditions, different sol pH, HMDSO dosage on the aerogel density and the changes of aerogel material properties and composition during the preparation process were investigated, and the reaction mechanism of silica aerogel preparation by atmospheric pressure drying was described. The results showed that the optimum conditions for alkali leaching were 20 wt% NaOH concentration, 2 h reaction time and 100 °C, and the desilication rate was 81.72%; the lowest Silica aerogel density of 108 mg/cm3 at pH 5 to 6; the lowest density of silica aerogel was 110 mg/cm3 at a modifier to wet gel volume ratio of 1:1.4.