3.6. Types of Bentonite
Commercially, there are two major types of bentonite namely Calcium bentonite and Sodium bentonite.
The type of bentonite is dictated by the type of external cation that is adsorbed onto the surface layer of bentonite particle either by natural means (during the natural process of mineral formation) or by chemical treatment [45].
For most of the applications, Sodium bentonite is preferred over calcium bentonite due to its superior swelling capacity as well as its extremely low hydraulic conductivity to water [46].
The latter advantage makes Sodium bentonite more widely utilized in various hydraulic containment applications whereas the former which is of concern here, renders Sodium bentonite to be a better GIM than Calcium bentonite.
Note that the conclusion drawn regarding Sodium bentonite being a better GIM is only a theoretical assumption.
No research has been done yet to ascertain such assumption although such assumption has been verified in experiments conducted on other applications of bentonite.