In mineral processing applications, sodium silicate affects the surface chemistries of particles in ways that enhance the separation of the value (for example, copper or gold) from the undesirable gangue (for example, clay slimes). Sodium silicate is used in the ore flotation method of mineral processing. In a flotation cell, gas bubbles up from the bottom of the cell through a slurry of raw feed (that is, ground ore). The value particles are attracted to and attach to the bubbles. They are carried to the surface where they are skimmed off the top. The gangue particles stay in the water, however, and sink to the bottom, where they are removed.

The surfaces of the gangue particles must be hydrophilic (literally, water loving), so that they stay in the water and sink. The surfaces of the value particles must be hydrophobic (literally, water fearing), so that they prefer to attach to the gas bubbles and rise to the top. Various chemicals are added to influence the surface chemistries appropriately. In some cases, sodium silicate is used as a depressant for such gangue materials as quartz and silicate minerals. Sodium silicate is also used for some salt-type minerals, including calcite, fluorite, and barite. The silicate helps to keep the gangue from floating to the top with the value.

Sodium silicate is also an important dispersant in flotation operations. For example, silicate helps to disperse clay particles (just as in detergent applications) that might be stuck to the gangue or the value, interfering with other chemicals that help the gangue to sink and the value to rise. The dispersant function of sodium silicate also improves the efficiency of the pre-flotation grinding step. In these ways, silicate increases process efficiency and raises both the recovery rate and the grade of the value.

Details about the effects of sodium silicate addition on the processing of various minerals and ores are available through PQ's Technical Service Group. We can provide guidance and support for lab and plant trials.

Applications
Depressant    Pigments (TiO2)
Dispersant    Wastewater Treatment
Grinding Aid

Recommended Products
Liquid Sodium Silicate

Recommended Literature
The Reemergence of Sodium Silicate as a Dispersant in Sulfide Mineral Flotation, Article
Dispersion Characteristics of Sodium Silicate, Bulletin 17-67
Interactions of Aqueous Metal Silicates with Mine Water, Article

Please contact Technical Service if you would like assistance in selecting the appropriate product for these applications or others.