Explain electrometallurgy with an example.

Explanation

Electro metallurgy : Metallurgy involving the use of electric arc furnaces, electrolysis and other electrical operations is called electrometallurgy.
`rarr` In the reduction of a molten metal salt , electrolysis is used . These methods are besed on electro Chemical principles.
These are expained by the equation
`DeltaG^(@)=-nFE^(@)`
n= no. of electrons
`E^(@)` =Electrode potential .
Electrolytic Reduction of Alumina : pure Alumina `(Al_(2)O_(3))` is a bad conductor of electricity and it has high melting point `(2050^(@)C)` . So it cannot be electrolysed .Alumina is electrolysed by dissolving in fused cryolite to increase the conductivity and small amount of Fluorspar is added to reduce its melt-ing point .Thus the electroyte is a fused mixture of Alumina, Cryolite and Fluorspar.
Electrolysis is carried out in iron tank lined inside with graphite (carbon)which functions as cathode. A number of carbon rods (or) copper rods suspended in the electrolyte functions as Anode.
An electric current of 100 amperes at 6 to 7 volts is passed through the electrolyte. Heat produced by the current keeps the mass in fused state at 1175 to 1225K. The following reactions take place in the electrolytic cell under these conditions .
`{:(Na_(3)AlF_(6)rarr3NaF+AlF_(3)),("Cryolite"),(4AlF_(3)rarr4Al^(3)+12F^(-)),("At cathode :" 4Al^(3)+12^(-)rarr4AL),("At anode :" 12F^(-)rarr6F_(2)+12e^(-)):}`
`F_(2)` formed at the anode reacts with alumina and forms Aluminium fluoride.
`2Al_(2)O_(3)+6F_(2)rarr4AlF_(3)+3O_(2)`
Aluminium produced at the cathode, sinks to the bottom of the cell .It is removed from time to time through topping hole.