Question

Explain the principle of the method of electrolytic refining of metals. Give one example.

Hint: Metals tend to lose an electron to form a cation. Different types of metals are extracted from their ore based on their properties. For example, based on the charge present on the pure and impure metals, we can use electrolytic refining to separate them.

-The electrolytic refining is the process of metallurgy in which the pure metal is refined from impure metals by using the electricity.
-The process works on the principle that when the electricity is passed through the solution of the same metal's salt then the cation moves towards the cathode which is made up of pure metal.
- Whereas the anion moves towards anode which is made up of impure metal.
- The solution of the electrolyte consisting of a salt of the same metal which is used for the refining.
- For example, Copper can be extracted using this method.
- The electrodes are prepared firstly i.e. anode is made of impure copper and cathode is made up of pure copper and then dipped into the electrolytic solution.
- The solution is made of copper sulphate which is also acidic.
- When the electricity is passed the pure copper dissolves from the anode in the solution, it moves towards the cathode.
The reaction is:
At anode: $\text{C}{{\text{u}}_{\left( \text{s} \right)}}\ \to \text{ Cu}_{\left( \text{aq} \right)}^{2+}\ \text{+ 2}{{\text{e}}^{-}}$
At cathode: $\text{Cu}_{\left( \text{aq} \right)}^{2+}\ \text{+ 2}{{\text{e}}^{-}}\ \to \text{C}{{\text{u}}_{\left( \text{s} \right)}}$
- So, the pure copper deposits on the cathode whereas the impurities settle down under the anode and are known as anode mud.

Note: The impurities such as iron, zinc, nickel and cobalt are more electropositive and are soluble in the solution whereas the impurities like selenium, silver, gold, antimony and platinum are less electropositive so they do not dissolve in the solution and forms the anode mud or anode sludge.