short note on hydraulic washing, froth-floatation process and magnetic separation method.

Hydraulic washing:

It is based on gravity differences between the ore and the gangue particles. In one such process, the lighter gangue particles are washed away by a stream of water, leaving behind the heavier ore.

Froth-Floatation method:

This method is applied to remove gangue from sulphide ores. In this process, mineral and gangue particles are separated by first wetting the mineral particles with oil, and gangue particles with water, and then the mineral particles are carried out by forming froth. Sometimes, depressants are used for separating two sulphide ores by selectively preventing one ore from forming froth. For example, NaCN is used as a depressant for separating two sulphide ores, ZnS and PbS.

Magnetic separation

the process in which valuable minerals which are attracted by magnetic field are recovered from a mixture using a magnetic force.

This technique is used in metallurgy to remove unwanted particles like sand, clay rocks, etc. known as gangue particles from the ore. This method is applicable to those ores which in pure forms are attracted by magnetic field but the impure forms (sand, clay, rocks etc.) of the ore do not. In this process, the ground ore is carried on a travelling band which passes over a magnetic roller. The ore leaves the band and falls from it, the particles are attracted by the magnetic field and form a separated pile.

It is used to remove unwanted gangue particles from magnetite (Fe₃O₄), chromite (FeCr₂O₄).

This method is also used to remove tungsten ore particles from cassiterite (SnO₂).