Bleaching earth consists primarily of hydrous aluminium silicates (clay minerals) of varying composition. Common components are montmorillonite, kaolinite and attapulgite. Small amounts of other minerals may be present in bleaching earth deposits, including calcite, dolomite, and quartz. In some localities bleaching earth refers to calcium bentonite, which is altered volcanic ash composed mostly of montmorillonite. Bentonite as a Bleaching Earth is a particular kind of clay derived from volcanic ash and consists mainly of montmorillonite with minor amount of illite, kaolinite, cristobalite and other minerals. Bentonite has strong colloidal properties and, when in contact with water, increases its volume several fold by swelling, forming a tixotropic, gelatinous substance. Main uses of Bentonite as a bleaching earth take advantages of these colloidal properties. Application of bleaching earth for the purification of vegetable oils has led to several problems such as oil retention, filtration and environmental effect. If the amount of bleaching earth used is higher than the required value, oil losses will be greater due to the oil retention properties of bleaching earth. The types of clays and their particle sizes influence the filtration efficiency. Clays made up of very fine particles are more compact and needs a longer filtration time to separate the clays from the oils. In addition, the excessive use of activated bleaching earth can cause environmental problems and increase the land-fill disposal costs. Due to these problems, numerous researches attempting to improve the effectiveness of bleaching earth have been carried out in the recent years. Thus, due to demand it is a good project for entrepreneurs to invest. Few Indian Major Players are as under • 20 Microns Nano Minerals Ltd. • Ashapura Claytech Ltd. • Ashapura Minechem Ltd. • Ashapura Volclay Ltd. • Ashok Alco-Chem Ltd. • Refnol Resins & Chemicals Ltd. • Soubhik Exports Ltd.
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