Question

The froth flotation process is best suited for the purification of sulphide ores. Give reason.

Answer 1

To purify the sulphide ores we can use froth flotation method

Ores

The metal can be extracted economically and conveniently from the ore.

Gangue

The impurities present in the ore is called as gangue particles.

Sulphide Ores

These are type of ores containing sulphide $\left({\mathrm{S}}^{2-}\right)$ part in it.

Example: galena $\left(\mathrm{PbS}\right)$, cinnabar $\left(\mathrm{HgS}\right)$

In froth flotation method

• To a mixture of impure sulphide ore and water, we have to add pine oil and ethyl xanthate.
• When the air bubbles from the lower portion of the tank, froth formation takes place.
• Since the sulphide ores are lighter and insoluble in water, they will be taken up by the froth to the surface and skimmed off.
• The impurities which are soluble in water (heavy) leave at the bottom.
• In this way we can separate sulphide ores.

The main reason behind choosing froth flotation method to purify sulphide ore is that, sulphide ores can be wetted by the oil (insoluble in water) and impurites are wetted by the water (soluble in water), so that separation of impurities becomes easier.