Bentonites belong to a smectite group of clays. Structurally they are hydrated aluminosilicate minerals consisting mostly of montmorillonite, with some feldspar, mica and quatrz. They consist of alumina sheets sandwiched between tetrahedral SiO4 units and water molecules.
Here is the simplified formula for montmorillonite:
(OH)2Al2Si4O10 or Al2O3.4SiO2.H2O
A number of the Al3+ are replaced by Mg2+ and Fe3+ making the plates positively charged at the edges and negatively charged at the surfaces. Where Mg2+ is encountered, the charge imbalance is compensated for by the presence of exchangeable cations – predominantly sodium or calcium and a small proportion of other metals. As a result, bentonite clays typically exhibit a cation exchange capacity (CEC) of 70 – 100 meq/gram.
When bentonite is hydrated, the water molecules will enter between the clay plates which forces them to come apart, turning clay into a slurry. Eventually the particles become oriented with the negative surfaces of the plates being attracted to the positive edges. Viscosity increases and a gel is formed.
- Civil engineering and geotechnical applications
- Sealing of ponds and lakes
- Production of drilling muds
- Wine purification
- Cheese making
Agriculture & veterinary use:
- Additive to feed
- Sorbent (animal and poultry farming) – absorbs urine, feces, neutralises bacteria
- Wound healing (large animals)
- Cat litter
Natural health & beauty
- Face mask
- Body wrap
- Soap making
- Other cosmetic products
- Bath (detox)
Medical & pharmaceutical uses
- Production of medical & pharmaceutical preparations (pharmaceutical grade bentonite is normally used for this purpose)
Types of Bentonite
- Calcium bentonite
- Sodium bentonite
Bentonite clay can also be called montmorillonite, fuller’s earth, smectite etc. There are a lot of brand name around – like ‘Living clay’, ‘Terramin’, ‘Aztec clay’, etc. These all are bentonite clay minerals which come from various parts of the world and belonging to the same smectite group. Generally, the higher the level of montmorillonite, the higher the cation exchange rate.
Bentonites we stock
Several different types of bentonite are stocked and all can be supplied in 25Kg sacks; most are also available in 1 tonne IBCs. Bentonite powders can also be supplied in bulk (tanker deliveries).
- Bentonex CB (calcium bentonite powder, also known as Fullers Earth) is used in pelletising applications, fertilisers, seed coatings and effluent treatment.
- Bentonex SB (sodium bentonite powder) is ideal for the production of slurries and grouts for civil engineering and geotechnical applications. It is popular for the lining of lakes and ponds and is also used in effluent treatment.
- Bentonex SB Granular (sodium bentonite granules) offers slow hydration, allowing use in deep water applications. It is ideal for a range of civil engineering and geotechnical applications such as filling cable trenches and the plugging of boreholes and landfill gas wells. This product is also used to improve electrical conduction around earthing rods.
- Bentonex CES Pellets (sodium bentonite pellets) provide delayed swelling for the sealing of bore holes and other deep water applications.
- Bentonex WS (natural sodium bentonite powder) is used in specialist applications.
- Bentonex White is a high brightness bentonite used in the manufacture of ceramics and other applications.