There are many commercial uses of electrolysis. Some of them are mentioned here.
1. In the extraction of metals
The electrolysis of the molten chlorides or oxides of reactive metals like sodium, calcium, magnesium and aluminum, gives the metal. For example, sodium metal is obtained by the electrolysis of molten sodium chloride. Similarly, aluminium is obtained by the electrolysis of molten aluminium oxide (A12O3). In each case, metal is deposited at the cathode.
2. Refining of metals
Metals like zinc, copper and aluminium are refined by the electrolysis of aqueous solution of a salt of the metal concerned. For example, impure copper is refined as follows:
A block of impure copper is made the anode, while a strip of pure copper is made the cathode. Copper sulphate solution is used as the electrolytic solution.
Copper sulphate solution contains Cu2+ and SO42- ions. On passing an electric current Cu2+ ions present in the solution move to the cathode. These ions take up electrons from the cathode and get deposited at the cathode as neutral copper atoms.
Cu2+ + 2e → Cu (at cathode)
Copper atoms at the anode lose two electrons each and go into solution as Cu2+ ions.
Cu → Cu2+ + 2e (at anode)
Thus, pure copper is transferred from anode to cathode.
One of the important uses of electrolysis is in electroplating. The process of depositing a thin layer of a superior metal over the surface of an inferior metal with the help of electric current is known as electroplating.