Is expired colloidal silica available?
In order to recover, the gel must be calcined at high temperature to obtain silica fume and then react with sodium hydroxide solution to filter the silica sol. The sol can also be prepared by dilute solution of water glass, filtering, cation exchange, anion exchange, adjusting pH value and concentrating.
Colloidal silica (colloidal, silka), also known as sol silica (colloidal sol), molecular formula: SiO2 ? nH2O. You say "expired" colloidal silica, may be due to long-term storage or heating, resulting in aqueous colloidal molecules SiO2 - nH2O or in case of dehydration, electrolyte sol, the silica particles gathered each other to form a silicon gel, the molecular formula is n (SiO2), which will be impossible to restore the original shape, can not be reused.
