Electro refining of Copper

• Electrolyte - Aqueous copper sulphate solution (acidified)
• Cathode - Pure copper metal (thin rod)
• Anode - Impure copper metal (thick block)
• Dissociation of copper sulphate -

 Cathode pure thin sheet of copper lined with graphite so that the deposited copper can be
removed easily.
Anode blister copper (got above)

Electrode reaction
Copper sulphate dissociates
CuSO₄ ------------Cu₂+ + SO4_2-

H2O -------- H+ +OH

At the cathode the copper ion changes to copper atom by gaining two electrons which
get deposited in the pure copper rod.
Cu2+ +2e- ------- Cu
The sulphate ion and hydroxide ion move towards anode but none of them is discharged.
The copper anode itself loses electrons and gives copper ion in the solution.

At the anode Cu - 2e------- Cu2+
The impure block of copper thus will be used The impurities settles at the bottom of the
electrolytic cell. This is known as anode mud or slime.
The impurities iron, zinc etc ionize and dissolves in the copper sulphate solution. They are above copper in the activity series. So they can displace copper from copper sulphate solution.
The weight of cathode will increase. The copper obtained is 100%pure.e