Describe the Electrolysis of Aluminium Oxide

describe the electrolysis of aluminium oxide

Aluminium is one of the most important metals in modern life. It’s used in a huge range of everyday items from frying pans to drink cans and aircraft components. It’s a relatively simple chemical to make but it’s expensive because of the enormous amounts of electricity required.

The main reason for this is because aluminum oxide can’t be extracted using the carbon reduction process, which is usually used to extract other oxides of metals. It is too reactive, so aluminium must be extracted by a different method called electrolysis.

In an electrolysis cell, the bauxite ore is continuously fed into a solution of molten bauxite oxide and the mineral cryolite to lower the melting point of the bauxite ore. Cryolite reduces the amount of energy needed to melt the bauxite ore because it allows the ions in the bauxite ore to move freely at a lower temperature.

Inside the cell, the negative electrode (cathode) is made of graphite – a form of carbon. Graphite is very heavy, so it sinks to the bottom of the cell where the aluminium oxide ions from the bauxite ore react with the graphite to produce liquid aluminium metal.

The positive electrode (anode) is also made of graphite, but it’s much lighter than the aluminium oxide ions from the molten bauxite ore. When the aluminium ions from the molten bauxite oxide at the negative cathode give up their electrons, they’re transformed to molten aluminium, which is then tapped out of the cell and drained away. Oxygen gas bubbles form at the anode as a result of this reaction, which reacts with the carbon at the positive anode to produce carbon dioxide. This gradually burns away, so the anode must be constantly replaced.