How is aluminum made from bauxite ore?

The production of aluminum from bauxite ore is a two-step process consisting of refining the ore into alumina and then smelting that alumina to produce metallic aluminum.1

Refining: The Bayer Process

The most widely used method for refining bauxite is the Bayer process, which involves four primary stages:

• Digestion: Bauxite is ground and mixed with a hot, pressurized solution of sodium hydroxide to dissolve the aluminum minerals into sodium aluminate.
• Clarification: Insoluble impurities, known as red mud, are separated from the solution through settling and filtration.
• Precipitation: The solution is cooled and seeded with aluminum hydroxide crystals, which grow and agglomerate.
• Calcination: The crystals are filtered, washed, and heated in kilns at temperatures exceeding 960 °C to drive off water, resulting in pure alumina (aluminum oxide).2

Smelting: The Hall-Héroult Process

Once purified, alumina is converted into aluminum using the Hall-Héroult process. Alumina is dissolved in a molten bath of cryolite and subjected to a strong direct current. This electrolysis causes molten aluminum to deposit at the bottom of the cell, while oxygen from the alumina reacts with carbon anodes to form carbon dioxide.34