Bentonite is the general description of clay consisting essentially of montmorillonite. Bentonite is typically formed by the alteration of volcanic ash. This ash was deposited under marine conditions while some deposits were formed in alkaline lake conditions and formed Bentonite as we know it today. In 1898 the name bentonite was suggested for clay in the Benton Shale in Wyoming. The Benton Shale was named after Fort Benton in Montana.
In the structure of Bentonite some of the aluminum atoms are replaced by iron or magnesium atoms. This results in a negative charge at the surface of the plates which attracts cations which are too big to be incorporated in the structure. These cations are usually Calcium, Sodium, Magnesium or Potassium which are known as being exchangeable. The total of the cations are is reported as CEC, Cation Exchange Capacity). The most important varieties are calcium and sodium bentonite which are commercially utilized for many applications.
Bentonite has excellent water binding capacity and show good colloidal properties. Bentonite has many unique properties as water absorption, binding capacity and sealing which makes bentonite a valuable product for the following products and applications;
- in drilling fluids for vertical-, horizontal directional drilling and (micro-) tunnelling
- in support fluids in diaphragm walls and vertical cut-off walls
- as a sealer in non-permeable liners for landfill sites
- as a binder in the production of iron-ore pellet
- as a retention-aid in the paper manufacture
- in wine production for the clarification
- in fertilisers
- in waste water treatment.