bentonit

Bentonite is a naturally occurring clay primarily composed of the mineral montmorillonite, a member of the smectite family. It forms from the alteration of volcanic ash and volcanic rocks. Bentonite has a large surface area and a net negative charge, which enables it to adsorb water and ions. When it comes into contact with water, it can swell significantly and exhibit high plasticity, a property exploited in various industrial processes.

Geology and deposits: The largest commercial deposits are associated with volcanic ash beds and are found worldwide. The most famous source is the Fort Benton formation in Wyoming, United States, which gave the mineral its name. Other important sources include regions in Spain, France, Greece, Turkey, India, China, and Australia. Bentonite is mined, processed, and milled to produce a range of particle sizes for different applications.

Forms and processing: Bentonite is typically mined, dried, and ground into a fine powder. Two main cation forms are important for industrial uses: sodium bentonite and calcium bentonite. Sodium bentonite swells dramatically in water and is commonly used in drilling muds and sealing applications, while calcium bentonite swells less and is frequently used as filler, sealant, or cosmetic clay. Ion-exchange processes can convert calcium bentonite to sodium bentonite to tailor properties for specific uses.

Uses: It is employed as a rheology modifier and stabilizer in drilling fluids, as a binder and sealant in earthworks, and as a foundry sand binder. Other applications include absorbents, cosmetics and pharmaceuticals, cat litter, and soil conditioning in agriculture to improve water retention and nutrient retention. Bentonite can also be used to bind toxins in some filtration and remediation contexts.

Safety and regulation: Bentonite handling requires dust control; inhalation of dust should be avoided, and ingestion should be limited. Specific safety guidelines depend on the product grade and application.