Sodium Silicate → Orthosilicic acid

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Reaction Steps

Colloidal silica particles commonly used as polishing particles are made by a wet chemical method, which includes the steps of: preparing a dilute solution of a water glass (e.g., sodium water glass and potassium water glass, which are primarily composed of sodium silicate and potassium silicate, respectively) solution; passing the water glass solution through a cationic exchange resin to remove metallic ions, such as Na+ and K+, from the water glass solution to form an aqueous active silicic acid solution; adding a basic agent to the silicic acid solution for alkalization at appropriate temperature and pH value to conduct polycondensation of active silicic acid to form particles of colloidal silica; and ultra-filtering the particles of colloidal silica to obtain a silica sol. In consideration of safety, operating convenience, and production costs, the alkalization is usually conducted using sodium hydroxide or sodium water glass.

Provenance & Evidence