Solubility of silica gel in water

Abstract

The solubility of silica gel in distilled water and dilute and alkaline solutions has been investigated. The solubility has been studied as a function of the pH of the gel preparation, pH_s, and of the pH of the dissolution media, pH_L. A kinetic model for the dissolution process has been developed that permits the determination of the rate constant as well as the equilibrium value of the solubility of the silica gel. The model explains the dependence of the rate constants on the concentration of catalytically active hydroxyl ions as an adsorption of these ions on the silica gel surface. The solubility of silica gel increases with increasing pH_L. The solubility dependence on pH_S is influenced both by the specific surface area of the gel and gel time. The structure of the gels is determined by the gel time. High solubilities can be achieved by a large specific surface area and a small gel time.