Bentonite expands when wet, absorbing as much as several times its dry mass in water. Because of its excellent colloidal properties, it is often used in drilling mud for oil and gas wells and for geotechnical and environmental investigations.
The property of swelling also makes sodium bentonite useful as a sealant. Uses include making slurry walls and forming other impermeable barriers, e.g., to seal off a water well, or to line the base of landfills to prevent migration of leachate.
Envirofert is investigating the potential uses for reprocessed bentonite obtained from the construction industry as a effluent pond liner.