Bentonite has great water binding ability and consequently very law permeability to water. It has been found, that the permeability of the soil is reduced considerably when substituted by sodium bentonite. Hence, this material is often employed in construction engineering ot make a porous medium water-tight. It can be used alone or with some other grouting material.
Use in Drilling Muds
Drilling muds consist of water to which sodium bentonite and pulverized barytes are added. Such muds are prepared mainly for deep drilling, like oil-well drilling. Bentonite imparts two properties : • It gives the fluid a viscosity several times that of water and thixotrophy. • It seals the wall of the holes, thus preventing water loss. The quantity of bentonite used is variable depending upon the depth of the hole to be drilled. Generally one tonne of bentonite is used to prepare about 100 barrels of mud.
Use as Decolourizer
Decolourizing bentonites are those which carry Ca and / or Mg as an exchangeable ion. They are used in the decolourization of animal and vegetable facts (like ground-nut, castor-oil and Vanaspati) and petroleum oil, lubricants, paraffins and other waxes. These are decolourized in two ways: • By the percolation method. • By the contact method.
Use as Foundry Sands
Bentonite is utilized in foundry to bind the sand grains into desired shapes. Bentonite helps in retaining the mechanical shape of the mould by making the particles of sands adhere and also making the surface impermeable. Strength and fusion point are the two important properties desired for selecting bentonite. Generally, the swelling type of bentonite is used though other types of bentonites have also been used.
Use in Cosmetic and Pharmaceutical Preparations
Bentonite gels are used as a carrier for a number of cosmetic preparatios, tooth-pastes, creams for skin and other similar products. For the preparation of cosmetic creams, bentonite is generally used as a paste formed with water and glycerine. Bentonite when intimately mixed with water in the proportion of one to four gives a pasty mass with the consistency of a heavy grease and in this form it is used for the preparation of medicinal ointments. Bentonite in the natural state is non-poisonous and harmless; thus it finds use in tooth-paste and even in the preparation of lipstick. The swelling type of bentonite is finding increasing use in the manufacture of insecticides and paints. The latest use has been its development as a bonding agent in pelletizing iron ore fines in the USA. The taconite agglomeration plant in north-eastern Minnesota consumes a considerable quantity of bentonite.