Chapter : 1. Metals & Non Metals
Enrichment or dressing of an ore
Enrichment or dressing of an ore : An ore mined from the earth's crust contains a number of impurities (gangue), which must be removed. The ore, free from gangue, then becomes suitable for subsequent treatment. Enrichment or dressing of an ore is carried out by the following methods.
(i) Levigation : The powdered ore is washed in a jet of water. The lighter, rocky and earthy impurities are washed away by water, while heavier ore particles are left behind to settle down at the bottom. This process is also called hydraulic washing.
(ii) Froth floatation : Sulphide ores of copper, lead and zinc are generally concentrated by this method.
The finely powdered ore is mixed with water and a small amount of oil in a tank. Air is blown into the mixture. A froth or scum is produced at the surface. The ore particles are carried by the froth to the surface. The earthy impurities sink to the bottom. The froth along with the ore is removed. An acid is added to break up the froth. The concentrated ore is filtered and dried.
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