Zone Refining

Zone refining is an industrial technique used to obtain ultra-pure metal solids. A hot loop starts by heating one portion of a metal rod, this portion is known as the molten zone. As the loop travel along the metal rod, the molten zone migrates with it and takes impurities with it. The impurities in the metal therefore all collect at the end of the metal rod, while the pure metal recrystallizes just behind the molten zone.

Figure 1: Mechanism of purifying copper metal using zone refining