Bentonite can be defined as a transported stratified clay which has been formed by weathering of volcanic ash approximately 66 million years ago.
It consists of a hydrated aluminium silicate or montmorillonite and is a member of the smectite group of minerals. Bentonite can contain either sodium or calcium as exchangeable cations absorbed on the clay structure which consists of linked three-layer sheets or flakes. Unsatisfied charge within its sheet structure cause a negative surface charge. As a result, bentonite has a strong affinity for cations and water molecules which on absorption are tightly bound within its particles. Whilst absorbing water molecules bentonite swells up to 24 times its dry volume and it is these two factors, its swellability and the fact that the water is tightly bound that makes bentonite so useful in environmental applications.
Sodium Bentonite is eco-friendly and being a clay is harmless to animals and fish.