Bentonite is an industrial mineral, essentially impure clay mineral called montmorillonite and it is an absorbent aluminium phyllosilicate. The absorbent clay was named bentonite by Wilbur C. Knight in 1898 in Wyoming. For several tens of million of years, temperature and pressure were applied to the volcanic ash and lava deposited on the bottoms of seas and lakes and this formed bentonite by changing the molecular-level structure of the minerals. Finally, a mineral aggregate called Bentonite was created. We can say that it is a very rare condition, and it may be regarded as a gift from the God.
Its components depend on the deposit. The main component of bentonite is a mineral called montmorillonit, a magnesium-aluminum silicate. Other components are many minerals such as, quartz, mica, feldspar, and zeolite.
Bentonite has superior thermal stability and is not deteriorated at room temperature. (The molecular structure of bentonite is stable up to 400℃ .) Bentonite does not rot because it is completely inorganic. It conforms to the environmental quality standards for soil and the standards required. It is assured that bentonite is harmless to humans and the environment. Bentonite is also expected to become a key material for improving the properties nanocomposite resins.
Bentonite is extracted from the earth using open-pit mining and underground mining. It is mined by surface “open pit” methods. Various types of heavy equipment including excavators and rubber-tired scrapers are used to remove the soft rock overlying the bentonite. If the layer is deep under the ground, it is extracted by building an underground road.
For industrial purposes, two main classes of bentonite exist: the Sodium Bentonite and Calcium Bentonite. These two Bentonites have different characteristics and are therefore used for different purposes.
Sodium Bentonite: Especially superior swelling, thickening and suspension stability, gelling and thermal durability. The structure of Bentonite is much like a sandwiched deck of cards. When placed in water, these cards or clay platelets shift apart. It attracts water to its negative face and magnetically holds the water in place. Hence, sodium Bentonite can swell up to many times its original size and absorb up to 10 times its own weight in water.
Calcium Bentonite: Especially superior caking property but with less swelling
Major deposits are in USA, Argentina, Brazil, Cyprus, Germany, Greece, India, Italy, Mexico, and Turkey. Bentonite deposits in Turkey can be found in Edirne-Enez, Çankırı, Tokat-Reşadiye, Ankara-Kalecik ve Giresun-Tirebolu
Bentonite uses and applications
FOUNDRY: Used as a bonding material in the preparation of moulding sand for the production of cast iron, steel, and non-ferrous casting. The unique properties of bentonite are a good flowability, compactability, and thermal stability. bentonite insures the durability of the mold during these high temperatures. Once the process is finished, the bentonite mold can then be taken away from the casting face and reused.
CAT LITTER: it is used for cat litter, due to its advantage of absorbing refuse by forming clumps, swelling and odor controlling characteristic. Bentonite forms clumps when wet, the clumps can easily be removed and disposed of. The remainder of the unused material stays intact and can continue to be used and it will last longer with less frequency of changing. Hence, cat litter has become very popular as an economical alternative to conventional non-clumping type cat litters.
FEED GRADE BENTONITE: it promotes integrity of the cubes and pellets tougher making them more durable and, when eaten, slows the digestive movement allowing ruminants to absorb and better utilize the feed nutrients. Due to its high adsorption power, it is particularly effective against micotoxins. Under European regulations, it is classified as a food additive, with E number E558.
OIL AND GAS DRILLING: Bentonite muds are thus employed for oil and water well drilling, tunnel, and microtunnel drilling. Drilling mud, or drilling gel, is a major part in the well drilling process. When the bentonite is mixed with water, forms a fluid (or slurry) that is pumped through the drill stem, and out through the drill bit. The bentonite extracts the drill cuttings from around the bit, which are then floated to the surface. The drilling mud, or gel, also serves to cool and lubricate the drill bit as well as seal the drill hole against seepage and to prevent wall cave-ins. Its functions are mainly to stabilise the borehole, seal the borehole walls, and remove drill cuttings.
Pharmaceuticals, Cosmetics and Medicine
Binding agents for Iron Ore palletizing plant
Paint, Printing Inks and Surface Coatings
Soil improvement & Soil Remediation
Rubber and Plastic Production
Wine and Juice Clarification
Adsorption of impurities in white water system in paper manufacturing plants and Paper Recycling
Adhesives and Laminates
Plasticizing of ceramic compounds , improvement of strength/ fluxing agent.
Diaphram wall – retaining walls for large construction projects
Reservoir and Pond lining & sealing
Plasticizing agent in cement and plasters
Agriculture and Animal Feeds
An anti-settling agent in ceramic enamels.
Construction and Civil Engineering
Construction, to waterproof below-grade walls and foundations and form impermeable barriers.
Iron Ore Pelletizing
Paints, Dyes and Polishes
As inner lining in furnaces of refractories, to prevent erosion of molten metals form destroying these.
Sulfur refining and decolorizing
In BES ( Bentonite Enhanced Soil ) mixes to impart the necessary impermeability to the lining of landfill sites
Superfine Bentonite is used by pencil industry to bind the graphite compound into pencil lead.