Question

Briefly explain any three procedures used in the concentration of metal ores.

Answer 1

The processes used in the concentration of metal ores are discussed below:

1. Hydraulic washing:

• This is based on the differences in gravities of the ore and the gangue particles.
• It is therefore a type of gravity separation.
• In this process, an upward stream of running water is used to wash the powdered ore. The lighter gangue particles are washed away and the heavier ores are left behind.

2. Froth flotation:

• This method has been in use for removing gangue from sulfide ores.
• In this process, a suspension of the powdered ore is made with water. To it, collectors and froth stabilizers are added.
• Collectors such as fatty acids enhance the non-wettability of the mineral particles and froth stabilizers such as aerosols stabilize the froth.
• The mineral particles are wet by oils whereas the gangue particles are wet by water. The froth is now skimmed off and dried in order to recover the ore.

3. Magnetic separation:

• This method is based on differences in the magnetic properties of the ore components.
• If either the ore or the gangue (one of these two) is capable of being attracted by a magnetic field, then such separations are carried out (e.g., in the case of iron ores).
• In this method, the ore is finely powdered and placed on a conveyer belt which is moved over a magnetic roller. The particles which are not attracted by the magnetic field fall off the conveyer belt.