Froth floation process is used to separate gangue from sulphide ores.In this process,a suspension of the powdered ore is made with water and collectors like pine oil,fatty acids and froth stabilisers are added.The function of stabiliser is to stabilise the froth.Cresols,aniline are the examples of stabiliser.The collectors added enhance non-wettability of the mineral particles.In this way mineral particles become wet by oils while the gangue-particles by the water.A rotating paddle agitates the mixture and draws air in it.As a result of this froth is formed which carries the mineral particles.Being light froth is skimmed off and then dried for recovery of ore particles.
Sometimes,two sulphide ores can be separated by use of depressants.For example ore containing ZnS and PbS can be separated by use of NaCN as depressant,which prevents ZnS from coming to the froth but allows PbS to come with the froth.
