Bentonite

Civil engineering and geotechnical applications
Sealing of ponds and lakes, effluent treatment
Production of drilling muds and seed coatings
​Special Effects

Types of Bentonite

 
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 and Wyoming Bentonite (natural sodium bentonite powders) are used in the manufacture of cosmetics and other specialist applications.

Bentonex White is a high brightness bentonite used primarily in the manufacture of ceramics.

Other bentonites are also available, including "Berkbent 163" and "Berkbent GS".

Technical Background

 
Bentonites are hydrated aluminosilicate minerals, comprised chiefly of montmorillonite. Structurally they consist of alumina sheets sandwiched between tetrahedral SiO4 units. Water is usually present between the triple layers. 
 
A simplified formula for montmorillonite is:
(OH)2Al2Si4O10 or Al2O3.4SiO2.H2O
 
In reality, a proportion of the Al3+ are replaced by Mg2+ and Fe3+ (the plates are therefore positively charged at their edges and negatively charged at their surfaces). Wherever a Mg2+ occurs, the charge imbalance is compensated for by the presence of exchangeable cations – predominantly sodium or calcium, though minor amounts of several other metals will also be present. As a result, bentonites typically exhibit a cation exchange capacity (CEC) of 70 – 100 meq/gram. 
 
When bentonite is mixed with water, the water molecules will enter between the clay plates, forcing them apart. While the plates are dispersed, the bentonite slurry becomes quite fluid. However, on standing the particles become oriented with the negative surfaces of the plates being attracted to the positive edges. Viscosity increases and a gel is formed – a reversible effect known as thixotropy.
 
A typical empirical formula for bentonite is:
(Al, Fe0.67 Mg0.33) Si4O10(OH)2Na,Ca0.33
For further information please contact us.