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Sodium silicate is a well-known depressant for minerals such as calcite, fluorite, barite, quartz, and other silicates. In flotation operations, sodium silicate keeps these undesirable gangue particles in the water phase while the desirable value particles are carried to the surface by air bubbles. A silicate dosage of 2-11 pounds per ton of ore is required for this application
Silicate is also an important dispersant and grinding aid, especially in sulfide ore flotation. It provides more efficient separation of the value from the gangue, and therefore can lead to higher grades and recoveries. Dosage must be determined experimentally but may be on the order of 0.1-1.0 pounds per ton ore.
For TiO2 pigment applications, adding silicate to an acidic slurry of TiO2 results in the formation of silica gel on the particle surfaces. This precipitated coating protects the TiO2 from UV light that would otherwise discolor it.
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