Bentonite are special and noble mineral clays only a few volcanic ashes turns into industrial usable bentonite, The applications are many and for the most different segments, Bentonite is a very much requested for its property to from a stable and chemically active colloidal gel, permitting one of the most diversified types of applications.
BENTONITE – CHEMICAL POINT OF VIEW
Bentonites are hexagonal philosylicates of hydrated Aluminum and magnesium having negative charge (on the surface) and positive charges (laterally). They are finally divided lamellar particles (less than 2 microns) and they are active, and in each blade – orlamelle – area of 25A,and thickness of 9.6 A) there are hydrated interchangeable cat ions (natural or industrially processed).
When a trivalent cat ion (Al) is substituted by divalent cat ion (mg ) , this result in a excess of electrons which migrate to the surface searching for the balancing cat ions. These interchangeable cat ions, which are present in the formation environment, can be ca+, mg+, Na+ etc.
Predominate cat ion gives it name is the clay mineral, which is ca+ = calcium bentonite Na+: sodium bentonite etc.
There is always co-existence of other cat ions and it is technically possible to change the presence of these native cat ions for others of specific interest, there by adding corresponding characteristics to the predominate cat ions. These cat ions may be inorganic, organic, organometalic, polymers etc.
This is the solvation of the cat ions provoking the inter-leave distancing of the lamellas. The phenomenon is equal times the original bentonite volumes. Example of Application: hydraulic expansion (civil construction)
This is the cellular dispersion by the moving away and inter – leave repulsion produced by the salvation of the cat ions, reaching up to 0.2 A of Diameter.
The viscosity is caused by the inter- leave attraction forces – inherent to the edge (+) and (-) plane joining of the lamellas.
The suspensions are the non- Newtonian, resistance to the braking and reconstructing of the gel; Joining edge (+) and (-) of the lamellas.
Colloidal plastic film over surface (cohesion).
Physical attraction of the material to be absorb by superficial action on the exposed surface of bentonite.
Attraction and retention of the material to be adsorbed by chemisorptions in the active centers of the bentonite (Point of electronic substitution, Al+3,Mg+2)
Originally our bentonite is having sodium and calcium cat ions and it require alkali activation to convert in to sodium bentonite. The sodium activation process is consist of exchanging (by means of diffusion) the native calcic cat ion for a sodium cat ion. This process is preformed under appropriate conditions of humidity, concentration and mixing time. The sodium is highly hygroscopic becomes responsible for Solvation - Dispersion – inter particle interaction (tri – name) which provides the product 7 characteristics required for sodium bentonite.