It has recently become obvious that regeneration is the best way of dealing with used oil. It allows to return the waste into the production processes and reuse the oil. Regeneration also reduces environmental loads.
It has been calculated that if collection and regeneration of waste oil is done properly, the cost of the product of such regeneration is 40-70% less than the cost of new oil.
Water causes a lot of harm to oil. Water can be solved or emulsified in oil. The reaction of water with oil forms acids, bases and other contaminants which degrade the quality of the product.
Modern regeneration techniques widely use adsorption, that is, special adsorbent substances which can capture tar and other contaminants, such as acids and oxides, formed in the process of oil aging.
Bleaching earth has surface area of 100-300 m2/g. The efficiency of this material in oil regeneration is due to the structure of its crystals and the nature of the material. This substance is relatively inexpensive, which is another advantage.
Bleaching clay treatment may also be used in combination with other methods. Such comprehensive approach improves regeneration efficiency.
In practice, the bleaching clay most often used with oil is bentonite.
Bentonite is a material which is a finely dispersed highly plastic mineral, with binding, thixotropic and adsorptive properties. Usually the material is thick, viscous and greasy and comes in various colors, from white to black.
The main structural mineral of bentonite, defining its adsorptive properties, is montmorillonite.
Bentonites have a well developed surface, and perform physical and molecular adsorption apart from ion exchange.
This mineral is highly selective in regard to organic ions and molecules, even higher than for inorganic ions.