Bentonite is a clay mineral composed mainly of montmorillonite. It is formed from volcanic ash that has been weathered over time and has a layered structure with a high cation exchange capacity.
It has a strong affinity for cations and water molecules which on absorption are tightly bound within its particles. Whilst absorbing water molecules bentonite swells up to 24 times its dry volume and it is these two factors, its swellability and the fact that the water is tightly bound that makes bentonite so useful in environmental applications.
Sodium Bentonite is eco-friendly and being a natural clay is harmless to animals and fish.
It is our recommendation to seal new earth dams and earth dams which are empty with Sodium Bentonite.
Sodium Bentonite clay has been successfully used as a sealant for earth dams where the soil is of a permeable nature and where less than optimum compaction can be achieved.
It is extremely important that the Bentonite clay is incorporated and compacted correctly as less than satisfactory results may be obtained if attention is not given to applying the process correctly.
Sodium Bentonite can be thought of as a concentrated clay such that relatively small amounts blended with sandy soils drastically reduces permeability.
Sodium Bentonite is most effective, when used as a mixed blanket, in the construction stage of a dam or when an existing dam has been completely drained, as only under these conditions can the necessary compaction be achieved.
Bentonite clay is perfectly safe, environment-friendly and can be used in most earth dams, irrigation dams and channels, wildlife and domestic farm animal watering holes, without negatively impacting the environment.
Our expertise includes the construction and sealing of clear and polluted water storage dams, evaporation ponds, leach pads, wetlands, decorative ponds, and streams.
The key to designing Bentonite liners and vertical cut-off barriers lies in understanding clay chemistry.
Bentonite is a clay mineral made of hydrous aluminosilicate sheets or plates. Unsatisfied charges within its crystal structure resulting from the substitution of aluminium by magnesium atoms cause a net negative surface charge. To counteract this charge imbalance, Bentonite has a strong affinity for cations and water molecules.
This attraction results in the formation of several diffuse layers of cations and water molecules that surround the clay crystal. These layers increase the effective size of the clay structure, giving Bentonite it’s well-known swelling properties when hydrated with water.
Bentonite properties are greatly influenced by the types of cations absorbed on the clay structure. These alter the water absorption, depending on their size and valence.
Sodium Bentonite have relatively more diffuse layers and therefore absorb much more water than Calcium Bentonite which have larger divalent calcium ions which are held more strongly to the clay and the net negative surface charges on each clay particle are lower, Calcium Bentonites, therefore, have smaller diffuse layers, absorb less water and do not swell as much as Sodium Bentonite.
Bentonite behavior in liners and cut-off trenches depends on the size of diffuse layers. Clay plate faces have a negative charge and the edges a positive charge. This results in a repulsion between the crystal faces and an attraction between the edges and the faces.
For Sodium Bentonite, the diffuse layer is large and its particles well dispersed, with little face to face contacts. However, when monovalent sodium ions are exchanged with multivalent ions from contaminated groundwater or waste leachate, the diffuse layer is reduced and repulsion between crystal faces lowered. High salt concentration in contaminants also alters the diffuse layer by changing the electrical potential between clay particles and the absorbed pore water.
At smaller interparticle spacings, attractive forces, are greater than repulsive forces and the clay particles flocculate giving an increase in permeability.
Highly concentrated organic compounds, high salt solutions, and low pH levels can cause a sudden and dramatic failure in bentonite liners.
Simply!! Sodium Bentonite powder coats all the particles and with the addition of water swells and fills the voids with a dense clay barrier.
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