Bentonite is a clay consisting of smectite minerals, the most common of which is usually montmorillonite. Bentonite is characterised by exchangeable sodium, calcium or magnesium cations which greatly influence the properties and commercial uses of the clay.
Natural sodium bentonite has dominant sodium cations, a very high swelling capacity, and forms a gel-like mass when added to water.
Calcium bentonite contains mainly calcium cations and has a low swelling capacity.
Sodium-exchanged bentonite is calcium bentonite that has been treated with soda ash to improve swelling capacity.
Acid-activated bentonite is calcium bentonite that has been treated with inorganic acids in order to increase its surface area and porosity, while white bentonite is a high brightness, white, calcium bentonite.
Bentonite is often called the mineral of 1000 uses due to its wide range of applications. The major worldwide applications of bentonite include as an additive in foundry sands and drilling muds, as cat litter, as an additive to stockfeed to aid digestion, as a binder in iron, as pelletization processes and as a clarifying agent in wine making and edible oil refining. Bentonite is also commonly used in the paper industry and as an efficient material to line a seal dams and landfill sites.
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