Metals acquired during the reduction process would not be very pure and are therefore, purified or refined through some process, based on the nature of those metals. This purification of reduced metals is called the refining of metals.
Three common methods used for refining are:
1. Distillation: Metals that are volatile in nature like mercury, zinc, etc., are distilled to the vapour state and condensed later to get pure metals.
2. Oxidation: Metals containing impurities like sulphur, carbon and phosphorus are subjected to oxidation whereby, these impurities are converted to their respective oxides and removed from the molten metal. For example, pig iron is refined to steel by oxidation.
3. Electrolytic refining method: This method is widely used for refining metals like copper, silver, gold, aluminium, etc., by involving the electrolysis phenomenon. Here, the pure metal is taken as the cathode and the impure metal, as the anode. The acidified salt solution of the metal is taken as the electrolyte. When electricity is passed, cations from the anode go into the electrolyte and get deposited as metal at the cathode. The impurities are dissolved or get precipitated as anode mud.