What Is Bentonite Clay Used For?

Bentonite is a type of clay composed primarily of montmorillonite or other smectite minerals. Derived from volcanic ash, bentonite's two major commercial varieties are sodium bentonite and calcium bentonite. Sodium bentonite is readily absorbent and swells in the presence of water. Calcium bentonite's structure, on the other hand, does not permit it to expand when liquid is added. Both types of bentonite are effective binding agents.

History

• Early use of bentonite included applying it to the skin or consuming it for medicinal purposes. Bentonite received its name from the Benton Shale, a Wyoming geological formation where Wilbur Knight found deposits of the clay in the late 1800s. As new uses for bentonite developed, bentonite mining increased to meet commercial, industrial and medicinal demand. Many countries mine and produce bentonite, including Greece, France, Africa and Australia. The principle producer of the clay in the United States is Wyoming, where sodium bentonite predominates.

Drilling Fluid

• Because of its ability to expand, sodium bentonite plays a major role in the oil and gas drilling industry. Drillers pump a slurry of bentonite, water and other additives down through the drill string. The fluid rises back up along the outside of the drill string, carrying the drill cuttings (soil and crushed rock) out with it. The binding of bentonite to the cuttings aids in the removal of this debris. The swelling nature of sodium bentonite proves useful in the sealing of drill holes to avoid drill hole ruptures and seepage.

Iron Ore Pelletizer

• Most iron ore produced in the United States is processed into iron ore pellets. After being crushed into powder, the ores go through several mechanical processes to eliminate various minerals and other waste materials, leaving a concentration of iron mineral dust. Adding sodium bentonite to the iron mineral dust along with water allows the bentonite to bind with the iron mineral dust to form solid iron pellets. After tumbling and firing, the pellets are ready for use in steel production.

Foundry Uses

• Foundries use bentonite as a bonding material in the sand casting process. Bentonite bonds sand particles together to form thermally stable molds for molten iron, steel, copper, aluminum and brass. Sodium bentonite is the preferred binding agent for use in bonding of metals and foundry sands, although calcium bentonite enhances foundry sand's flowability and figures in the manufacture of nonferrous moldings. Foundries also employ sodium bentonite to clean impurities from melted metals before pouring them.

Medicine

• Bentonite serves as both a filler and an active ingredient in medicines and personal care products. It is an important component of creams, lotions, compresses and topical anti-irritants. Bentonite's properties as a binding agent make it a potent antidote for heavy metal poisoning. Alternative health practitioners use the clay as a digestion aid to improve elimination, to alleviate irritable bowel syndrome and Crohn's symptoms, for detoxification and to treat acne. According to researchers Steven M. Lipson and G. Stotzky, bentonite has the ability to absorb pathogenic viruses and other toxins from within the body (Canadian Journal of Microbiology Vol. 31, 1985, pp. 50--53).

Clarifying Agent

• Bentonite's binding and absorbing properties render it an excellent clarifying agent for liquids including wine, water, juice, cooking oil, beer and honey. When added to these liquids, bentonite absorbs and coagulates with impurities such as proteins, solids and tannins so they can be easily filtered and removed.

Other Uses

• Among its many other applications, bentonite is a common sealant for ponds, lagoons, ditches and dams, as well as a landfill liner material that keeps toxins and waste from leaching into the soil. It is used in the treatment of wastewater, as an animal feed supplement, as an absorbent in pet litter, and as an ingredient in cosmetics, detergents, cleansers, crayons and paper.