Explain froth floatation process.[OR]
How will you concentration sulphide ores? [OR]
Explain the concentration of copper pyrites and galena ores.

Explanation

Froth flotation:This method is commonly used to concentrate sulphide ores such as galena(PbS),Zinc blende (ZnS) etc.In this method ,the method ,the metalic ore particles which are preferentially wetted by oil be separated from gangue.In this method,the crushed ore is suspended in water and mixed with frothing agent such as pine oil,eucalyptus oil etc.A small quantity of sodium ethyl xanthate which acts as a collector is also added.A froth is generated by blowing air through this mixture.The collector molecules attach to the ore particle and make them water repellent.As a result,ore particles wetted by the oil,rise to the surface along with the forth .The forth is skimmed off and dried to recover the concentrared ore.The gangue particles that are preferentially wetted by water settle at the bottom.
When a sulphide ore of a metal of intrest contains other metal sulphides as inpurities,Depressing agents such as sodium cyanide ,sodium etc are used to selectively prevent other metal sulphides from coming to the forth.For example,when impurities such as ZNS is present in galena (PbS),sodium cyanide (NaCN) is added to depresses the flotation property of ZnS by forming a layer of zinc complex `Na_(2)[Zn(CN)_(4)]` on the surface of zinc sulphide