The metals like copper, silver, lead etc are usually purified by the process of electrolysis. In electrorefining the pure metal acts as cathode and impure metal acts as the anode, whereas the electrolyte is soluble salt of the same metal.
By the passage of electricity, the pre metal from anode is deposited over cathode. The impurities are settled as anode mud. The electrorefining of copper is shown below.
The chemical equation for this process is given below.
CuSO4 → Cu2+ + SO42-
At cathode the reaction is Cu2+ + 2e– → Cu(s)
At cathode the reaction is Cu → Cu2+ + 2e–