Process basics

The aluminum is produced extracting it from the aluminum oxide (Al2O3), called also alumina, through an electrolysis process driven by electrical current. The process uses as electrolyte a molten salts called Cryolite (Na3AlF6) capable of dissolve the alumina. Carbon anodes are immersed into the electrolyte (usually referred as the "bath") carrying electrical current which then flows into the molten cryolite containing dissolved alumina. As a result, the chemical bond between aluminum and oxygen in the alumina is broken, the aluminum is deposited in the bottom of the cell, where a molten aluminum deposit is found, while the oxygen reacts with the carbon of the anodes producing carbon dioxide (CO2) bubbles. The alumina reduction process is described by the following reaction:

Aluminum Reduction Reaction

Once passed through the bath, the electrical current flows into the molten aluminum deposit and is then collected by the bottom of the pot, usually called "cathode".

The following is a schematic picture of an aluminum electrolysis cell:

Schematic aluminum reduction cell