Properties & Uses of Soluble Silicates

Properties of Soluble Silicates

• Soluble silicates are alkaline and, depending on their molar ratio and concentration, usually have pH values ranging between 10 and 13. Their alkalinity makes them useful in detergents, where they act as buffers. Silicate solutions are very stable and readily form gels, and so they are also widely used in adhesives and binders. Silicate anions have a strong negative charge and will readily adsorb onto exposed mineral and oxide surfaces when in a solution. This property makes soluble silicates very useful in preventing corrosion, particularly in the water industry where they are used to protect pipework.

Detergents

• In terms of metric tons used, the production of detergents, soaps and cleaners is the most widely used application of soluble silicates. In detergents, silicates neutralise acidic soils through their alkalinity, and emulsify oils and fats. When combined with soaps, silicates increase the effectiveness of surfactants by lowering interfacial tension. Silicates stabilize bleach ingredients by complexing with metal ions, which prevents damage to textiles. Silicates in detergents also protect the surfaces of metals and ceramics from corrosion.

Chemical Uses

• Silicates are utilized in industrial inorganic chemistry in a number of ways, typically in the form of crystal sodium silicate. Ion exchange, or the addition of acids to crystal sodium silicate solutions, allows the silicate to be processed into a range of products which are then used as building blocks or auxiliary chemicals in various chemical processes. For example, sodium silicate is used as a stabilizer in pulp and textile bleaching; while precipitated, silica gels are used as fillers in rubber and as a structuring agent in toothpaste.

Adhesives and Binders

• Silicates are one of only a few inorganic materials that are used commercially as adhesives and binders. The readiness of silicate solutions to form gels plus their exceptional bond strength makes silicates very suitable for use in this manner. There are two broad categories of silicate adhesives; one in which silicate is used as the only bonding agent, and the other in which a reaction with other chemicals is used to reinforce the silicate bond.