Electrolysis of copper is carried out on a massive scale in industry as it is the only best method to remove the impurities from the metal extract of copper, although even with electrolytic refining it is not possible to produce a 100% pure copper.
During the electrolysis of copper, the blister copper, that is virtually pure copper having an excess of 99% of copper, are made the anodes and immersed in an electrolytic solution containing copper sulfate and sulfuric acid. Pure copper cathodes are arranged between the blister copper anodes and a current of over 200 A passed through the electrolytic solution.
Blister copper, is the copper so obtained from the bessemerisation process where air had been blown through the molten matte of copper sulfide, converting it into molten copper and the oxidized sulfur part of the ore converted into sulfur dioxide escapes out of the molten metal producing blisters on its surface. The virtually pure copper then having an excess of 99% copper, is made the anode and immersed in an electrolyte containing copper sulfate and sulfuric acid. Pure copper cathode is arranged between the blister copper anode and a current of over 200 A passed through the electrolytic solution. On passage of electricity under these conditions, the copper atoms dissolve from the impure anode to form copper ions. These then migrate towards the cathodes where they get deposited back as pure copper atoms.
At the anode:
Cu(s) → Cu2+(aq) + 2e-
At the cathode:
Cu2+(aq) + 2e- → Cu(s)
We have performed a simple form of this electrolysis in the school laboratories.
Generally, gold, silver, platinum, tin, etc... are the usual impurities that settle as anode mud and do not get deposited on the cathode.
Some of the soluble impurities containing metals such as iron and nickel, remain dissolved in the electrolyte, which can get deposited on the cathode if the electrolyte is not replaced continually.