Question

Describe zone refining method used to obtain metals of high degree purity.

Answer 1

When a metal with a high degree of purity is required, this method is used. For example, this process refines silicon, gallium, and germanium, which are utilised as semiconductors. The method is based on the observation that an impurity’s solubility depends on the metal to be purified is liquid or solid.

The impure metal is cast into a thin rod using this technique. This pole has a round heater attached to it. Slowly, the heater is moved along the rod. The rod melts at the heated zone, and while the heater continues, the impurities move to the nearby molten zone, causing the remaining pure metal to recrystallise. As a result, as the heater travels along the rod, the pollutants continue to flow from one zone to the next before eventually gathering at the other end of the rod. After a number of repetitions, the end that contains the contaminants is finally chopped off. The metal that makes up the remaining rod is extremely pure.