Aluminum is obtained from pure alumina by means of Hall’s process. In this process, alumina (Al2O3) is dissolved in fused cryolite (Na3AlF6) to get the molten electrolyte.
The electrolysis is carried out in a steel tank, internally lined with a layer of “graphite to act as cathode. The anode made up of carbon rods is suspended from above in the molten electrolyte. A low voltage must be used to avoid thedecomposition of the cryolite. The temperature is maintained at 950-1900°C by the passage of electric current.
The aluminum metal obtained is 99% pure. The trace impurities present are iron, silicon and Al2O3 which can be removed during the refining of Aluminium.