Question

Generally which ores are concentrated by froth floatation method? Describe this method.

Answer 1

Sulphide ores (such as galena ($PbS$), zinc blende ($ZnS$) and copper pyrites $\left(CuFe{S}_2\right)$ are concentrated by froth flotation method.
Principle: Metal sulphide particles (of ore) are selectively wetted by oil. Gangue particles are wetted by water.
Finely divided ore is added to water (present in a large tank). Pine oil, eucalyptus oil, xanthates or fatty acids are added. Compressed air is circulated.
Metal sulphide particles (of ore) are selectively wetted by oil. They (and froth) rise to surface. Gangue particles are wetted by water. They settle at the bottom.