Silica gel is a synthetic silica compound that can be extracted from rice husk ash by the sol-gel method.
Silica is removed from residual ash in the form of sodium silicate,
and in a later stage of the process,
treatment with acid converts the silica into gel.
This type of extraction can be done at ambient temperatures,
making it an alternative to the thermal treatment,
which is often used in the production of highly reactivate pozzolanas.
1-5 Previous studies on the preparation and characterization of extracted silica gel from rice husk ash have resulted in a simplified method for obtaining pure silica,
6-9 and this process is called the sol-gel method.