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BENTONITE

Bentonite or Bentonite Clay is also known as Montmorillonite. It is the member of the Smectite clay family. The primary constituent in Bentonite Clay is hydrated Aluminum Silicate. It is impure clay absorbent. Bentonite is most commonly known for its use as a major component of drilling mud, particularly for oil wells, but is also widely used as an additive for viscosity and filtration control.

USES:
a) The greatest application of bentonite is in oil drilling. Bentonite thickens, swells, gels, bonds and lubricates in aqueous systems. Both natural & synthetic Bentonite is used in preparation of drilling mud. It is mainly used as circulation mud in rotary system of drilling for oil. The main purpose of Bentonite is to lubricate & cool the rotary cutting bits, carry away rock cutting fragments & to act as a seal against the escape of gas from the bore hole & to improve & prevent the hole from blowing out. Another function of such Bentonite based fluids is to condition the wall of the drill hole to prevent caving.

b) Bentonite possesses thixotropic properties and deposits a thin water proofing film on the walls of the bore holes & thus renders permeable formations impermeable.

c) Used in: Pharmaceuticals, beverage, food, cosmetics, and personal care products as Suspending agent, gellant and binder.

d) Used as a foundry sand, paints, fuller's earth, drilling mud, bleaching clay, filtering agents, water impedance, inks, additive to ceramic materials, and iron ore pelletizing. In paint industry it is used as a thickener in paints, primers and water based coatings. It is used in manufacture of greases.

COLOR:
Brownish Yellow, White, Grey White

DENSITY:
2.35

FRACTURE:
Earthy – Dull, Clay like fractures.

STREAK:
White

SYNONYM:
Montmorillonite, taylorite, fuller's earth, hectorite, tixoton, volclay, wilkinite.

HARDNESS:
1.5 – 2.0

CHEMICAL DESIGNATION:
Chemical Formula: Al2O34SiO2H2O

Chemical Name: Naturally occurring hydrated aluminum silicate

PROPERTIES OF BENTONITE:
Bentonite thickens, swells, gels, bonds and lubricates in aqueous systems. Bentonites have a very small particle size and extremely high surface area.

  a) SUSPENDING
Effective dispersion and hydration using high shear colloidal mixers achieves bentonite slurry capable of effectively suspending dense particles.
Typical Applications: Drilling Muds, Refractory Paints, Emulsion Paints, Agricultural Sprays, Pumpable Solids and Pharmaceutical Lotions.


  b) PLASTICISING
Bentonite clays with their colloidal like behavior impart improved plasticity to solids/aggregates by providing mobile contact points between larger grains.
Typical Applications: Clay and Cementitious Grouts, Plasters, Pastes and Polishes.


  c) THICKENING
Viscous suspensions can be achieved at addition rates exceeding 3% bentonite in water.
Typical Applications: Adhesives, Paints, support fluids for diaphragm and slurry walls.


  d) BONDING
The coating of sand grains and subsequent mulling with appropriate amounts of water produces a mouldable mass having flow properties.
Typical Applications: In the green sand process for the production of metal castings particularly in iron foundries.


  e) Binding
The use of mixes having high bentonite: water ratios improves pressing and extrusion characteristics.
Typical Applications: Briquetting, crayons, iron ore pelletising, extruded animal feed pellets.


  f) Emulsification
Bentonites have a high surface area often exceeding 100 sq metres per gram. Oils can be added to aqueous clay gels and emulsified by high speed agitation.
Typical Applications: Bitumen, Asphalt, Soaps, Detergents.


  g) Water Treatment
Bentonite concentrations as low as 20 - 80 ppm dispersed in water act as excellent coagulants in waste effluents. Subsequent flocculation and settling is achieved by 1 - 2 ppm dosages of a suitable polymer.
Typical Applications: Sewage treatment, Paper Mill effluent and process water recycling. Clarification of effluents containing oil impurities.


  h) Absorption
When used in powder or granular form bentonites possess good adsorbing and absorbing abilities. Formerly used as the prime means of absorbing oils from wool (fulling process) until the advent of soaps and detergents. Possess good decolorizing ability.
Typical Applications: Oils, Wine and Beer Fining, Desiccation, Pitch Control in paper Manufacture.


  i) Moisture Retention
Bentonites improve the moisture retention of soils and hence are useful in electrical earthing applications.