Extraction of Silica From Micro-silica and Preparation of Silica Aerogels

The choice of silica-based precursors has an important impact on silica (SiO₂) aerogel materials. The main objective of this study is to explore a new route for the preparation of SiO₂ aerogels using micro-silica. Firstly, the difference in silica extraction rate between micro-silica and quartz and analytically pure SiO₂ under different conditions, and analyzed the reasons for the difference from the aspect of raw materials. Secondly, the SiO₂ was extracted by a low-temperature alkaline melting method using micro-silica as the silicon source, avoiding the disadvantages of the fire method and the wet method, and the SiO₂ aerogel was synthesized by drying under atmospheric pressure. The result shows the extraction rate of micro-silica was up to 94.2% comparing with the quartz and analytically pure SiO₂. It found that a high extraction rate and modulus of silica resources could be obtained at a mass ratio of NaOH to micro-silica of 1.4, a calcination temperature of 450 °C, and a calcination time of 60 min. The prepared SiO₂ aerogel had a typical nanoporous structure, with a density of 0.1421 g/cm³, a specific surface area of 236 m²/g, a porosity of 93.54%, and a thermally stable temperature of 400 °C, under 800 °C, the aerogel skeleton structure remains unchanged. This study gives a new way for exploring the high-value utilization of industrial solid waste.