Bentonite is rock that consists mainly of montmorillonite, a clay mineral, and contains impurities such as quartz, feldspar, and other minerals.
It is believed that deposits of bentonite were formed by reaction of volcanic ash accumulated following volcanic eruptions several million years or several hundred million years ago under certain temperature or pressure conditions or with hydrothermal solutions.
Bentonite deposits exist in the U.S., Europe, China, Japan, and other areas around the world.
Montmorillonite, which is the main component of bentonite, has the characteristic property of swelling to many times its original volume when it absorbs water. This property is called a swelling property. It becomes viscous when dispersed in water, and has the ability to well adsorb various kinds of cations. Thus, it has various properties. Because of these properties, bentonite is used in a wide range of industrial fields. For example, it is used in the fields of castings, civil engineering and construction, toilet sand for pets, chemical products, and many other products.
Bentonite is listed in the Japanese Pharmacopoeia and the Food Sanitation Act, and is also used in cosmetics, pharmaceuticals, or food additives. This is why bentonite is known as clay with 1,000 uses. Recently, it has been studied as a candidate barrier material used in geological disposal of radioactive waste, widening the range of its use.
