Production methods summary

Early Production

The earliest production methods used very reactive metals in a mercury amalgam to displace aluminium from its compounds. Only small quantities could be produced by this method, and so aluminium was an expensive luxury metal.

chemical equations

Two significant developments were:

  • The discovery of the electrolytic method of extraction
  • The development of an efficient process to produce aluminium oxide for electrolysis
For a summary of aluminium production history click here

Bauxite

Bauxite ore is now the principal source of aluminium. The ore usually contains oxides of aluminium, iron, silicon and titanium, and the presence of iron (III) oxide gives it a characteristic red/orange colour. It is found relatively close to the surface, and so is extracted by opencast mining.
The main areas for bauxite mining include Australia, Brazil, Jamaica and Guinea. Bauxite is named after Les Baux de Provence (France), where it was originally discovered, but the French mines were exhausted by the end of the 20th century.

photo: bauxite ore

Aluminium is present as the oxide (Al2O3), which is needed in a pure form for electrolysis. It is extracted from crushed bauxite using the method originally developed by Karl Bayer.
Find out more about this process using this link

Electrolysis

The position of aluminium in the reactivity series indicates that, unlike iron, it could not be extracted by reducing the oxide using carbon or carbon monoxide. Electrolysis of molten aluminium oxide ("alumina") will, however, give aluminium and oxygen.

chemical equation

Aluminium production consumes huge quantities of electrical energy. For this reason plants are sited where hydroelectric power can be utilised, or close to sources of fuel for electricity generation.


Two main technologies have been used, one with a liquid anode ("Soderberg" anode) that solidifies as it comes into contact with the molten electrolyte, and one using solid anodes ("Pre-Baked" anodes). The pre-baked design is by far the most common, is generally better in terms of efficiency and emissions, and the use of Soderbeg technology is in decline.
Click here to find out more about the electrolytic process

photo: aluminium ingot

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