Decomposition of Molten Aluminium Oxide by Electricity

decomposition of molten aluminium oxide by electricity

The basic industrial process to extract aluminium from its bauxite ore is the electrolysis of a molten solution of aluminium oxide. This solution (aluminium oxide dissolved in a molten solvent called cryolite) is melted at a low temperature to allow the ions in aluminium oxide to move freely towards the electrodes. This means that aluminium can be extracted from the molten Al2O3 without burning out.

Aluminium is a very reactive metal and the extraction of aluminium using electrolysis is expensive due to the high energy used to extract it. Recycling aluminium is an alternative method to the traditional extraction and saves on costs as it uses less energy.

A molten solution of aluminium oxide is placed in an electric cell. The ion’s in the solution move from the anode to the cathode. They gain three electrons to form aluminum atoms and lose two electrons to form oxygen molecule and carbon dioxide.

Reduction – electron gain and Oxidation – electron loss are the two main chemical reactions that occur during electrolysis of aluminium oxide in an electrical cell.

During reduction, the positive aluminium ions gain three electrons at the cathode to form aluminum atoms. The negative oxygen ions lose two electrons at the anode to form neutral oxygen molecules and carbon dioxide.

The aluminum atoms at the cathode sink to the bottom of the cell, but the oxygen ions at the anode flow to the top. This is the end of the reaction, and the aluminum atoms at the cathode are drawn off the cell.