The production of aluminum from ores depends on the alumina (Al2O3) extracted from the bauxite. Bauxite usually contains 30-60% alumina (commonly called alumina), usually near the Earth's surface. This process can be divided into two parts: (1) extraction of alumina from bauxite, and (2) smelting of aluminum metal from alumina.
Under normal conditions the so-called Bayer process is used to separate the alumina. This includes pulverizing the bauxite into a powder, mixing it with water to make a slurry, heating and adding caustic soda (NaOH). Caustic soda dissolves the alumina, passing the alumina through the filter leaving impurities.
The aluminate solution is then discharged into a dust collector tank, into which aluminum hydroxide particles are added as "seeds." Agitation and cooling cause the aluminum hydroxide to precipitate on the seed material, which is then heated and dried to produce alumina.
Electrolytic cells were used to smelt aluminum from alumina during the discovery by Charles Martin Hall.
Alumina added to the cell was dissolved in the molten cryolite fluorinated bath at 1742 ° F (950 ° C).
Any DC current of 10,000-300,000 A is supplied to the cathode casing through the mixture from the carbon anode in the cell. This current breaks down the alumina into aluminum and oxygen. Oxygen reacts with carbon to produce carbon dioxide, while aluminum is attracted to the carbon cathode cell liner.
Aluminum can then be collected and sent to a furnace into which recyclable aluminum material is fed. About a third of today's aluminum is produced from recycled materials