Applications of bentonite: where bentonite is used

Bentonite is a natural clay based on smectite minerals, most often montmorillonite. Because it can swell, bind particles, retain water and adsorb impurities, bentonite is used in construction, drilling, foundry production, metallurgy, winemaking, agriculture, cosmetics and absorbent products.

The wide range of bentonite applications is not explained by one universal property, but by a combination of plasticity, swelling, thixotropy, binding ability and the large surface area of clay particles.

What is bentonite?

Bentonite is a natural clay material. Its properties depend on mineral composition and the dominant exchangeable cations. In practice, sodium bentonite and calcium bentonite are most often distinguished.

Sodium bentonite usually swells more strongly in water and forms viscous suspensions well. For this reason, it is widely used in drilling fluids, waterproofing and low-permeability barriers. Calcium bentonite swells less, but can be useful as an adsorbent, binder or raw material for specific industrial products.

Main properties of bentonite

When in contact with water, bentonite can increase in volume, form a gel-like mass and reduce the permeability of a layer. In suspensions it helps keep solid particles suspended, and in dry mixtures it can work as a binder.

Important properties of bentonite include:

• swelling when wetted;
• ability to form viscous suspensions;
• adsorption of proteins, oils, impurities and ions;
• binding of sand and mineral particles;
• low permeability of a compacted layer;
• chemical inertness in many construction and process tasks.

These properties determine where bentonite is used and which grade is needed for a particular industry.

Where and how bentonite is used

Bentonite is used in many industries because the same mineral can work as a swelling waterproofing material, sorbent, binder, thickener or processing additive. Main application areas include:

1. In construction, bentonite is used for foundation waterproofing, seepage barriers, geosynthetic clay liners, slurry wall works, tunnels and underground structures in difficult water-bearing soils.
2. In the textile industry, bentonite can be used as a more affordable substitute for starch-based sizing compositions when preparing cotton fabrics and yarns for weaving.
3. In cosmetics, purified bentonite is used in masks, creams, lotions, eye shadows, pastes and other products where sorption, thickening and formulation stability are important.
4. In household chemicals, bentonite is used in detergents, cleaning products, pastes, suspensions and some protective coatings.
5. In agriculture, bentonite is used to improve certain soil properties, as a carrier for fertilizers and crop protection products, and as a component of some feed additives and granulated products.
6. In the food industry, suitable purified bentonite is used to clarify wine materials, juices and some beverages, as well as in selected processes where haze must be reduced or some impurities must be bound.
7. In oil refining and oil purification, bentonite materials can help remove part of sulfur-containing, nitrogen-containing and other impurities.
8. In mechanical engineering, foundry work and metallurgy, bentonite is used in molding sands, as a sand binder and as an additive in iron ore pelletizing.
9. In medicine and pharmaceuticals, only specially purified materials based on bentonite and approved for that purpose may be used. Construction or technical bentonite is not suitable for such applications.

Related article: bentonite specific weight and density.

Construction and waterproofing

In construction, bentonite is used for waterproofing and seepage control. It is included in geosynthetic clay liners, clay barriers, waterproofing layers and materials for tunnels, underground structures, excavations, foundations and landfill liners.

When wetted, bentonite swells and fills voids, so a compacted layer becomes less permeable to water. This property is useful where moisture filtration through soil must be reduced or a structure must be protected from contact with water.

Drilling, foundry work and metallurgy

One of the best-known uses of bentonite is drilling fluids. In drilling, it helps stabilize borehole walls, carry cuttings, keep solids suspended, reduce filtration and improve the performance of the mud.

In foundry production, bentonite is used as a binder for molding sands. It helps a sand mold keep its strength and shape before metal is poured. In metallurgy, bentonite is used as a binder in iron ore pelletizing and pellet production.

Food industry, agriculture and everyday uses

In the food industry, purified bentonite is used as a fining agent, for example in wine and some beverage processing. It can bind part of the protein compounds and reduce the risk of haze in the finished product.

In agriculture, bentonite may be used as a carrier for fertilizers and crop protection products, as a component of feed additives, as a pellet binder and as a material for improving some soil properties. In household and pet products, bentonite is known as an absorbent in cat litter because it takes up moisture and helps retain odors.

Bentonite is also found in cosmetics, detergents, pastes, suspensions, adsorbents, fillers, paints and materials for oil purification. Each application uses its own grade and purification level, so construction bentonite should not automatically be considered suitable for food, cosmetic or medical use.

What to consider when choosing bentonite

Different applications require different bentonite grades. Drilling requires viscosity, mud yield and filtration performance. Waterproofing requires swelling and low permeability. Foundry work requires binding strength. Winemaking and food applications require purity and compliance with food-additive requirements.

Therefore, when choosing bentonite, it is important to look not only at price, but also at material type, moisture, particle size, swelling capacity, filtration value, impurity content and supplier documents. This is especially important if the material will be used outside construction, in food, cosmetic or other regulated industries.