Aluminum compounds are present in all types of clay, but bauxite is the most valuable ore for producing pure aluminium. In addition to 45 to 60 percent aluminium oxide, bauxite contains sand, iron, and other metal impurities. Although some bauxite deposits are composed of hard rock, the vast majority consist of relatively soft soil that is easily excavated from open-pit mines. Australia produces over one-third of the world's bauxite supply. Approximately four pounds of bauxite are required to produce one pound of aluminium metal.
The aluminium compounds in the bauxite are dissolved with caustic soda (sodium hydroxide) in order to separate them from the impurities. Depending on the bauxite ore's composition, relatively small amounts of other chemicals may be used in the extraction process.
Aluminum is produced in two stages: the Bayer process, which refines bauxite ore to produce aluminium oxide, and the Hall-Heroult process, which smelts aluminium oxide to produce pure aluminium.
aluminum-based. Examples are starch, lime, and sodium sulphide.
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In the smelting process, the electrolyte (current-carrying medium) is cryolite, a chemical compound composed of sodium, aluminium, and fluorine. Historically, cryolite was extracted from Greenland, but it is now manufactured synthetically for use in the production of aluminium. Aluminum fluoride is added to lower the electrolyte solution's melting point.
Carbon is the other major component of the smelting process. Electrodes made of carbon conduct the electric current through the electrolyte. Carbon is consumed during the smelting process as it combines with oxygen to form carbon dioxide. In actuality, roughly a half-pound (0.2 kg) of carbon is used to produce every pound (2.2 kg) of aluminium. Some of the carbon used in aluminium smelting is a byproduct of oil refining, while the remainder comes from coal.
Due to the fact that smelting aluminium involves passing an electric current through a molten electrolyte, it requires a substantial amount of electrical energy. The average amount of energy required to produce 2 lb (1 kg) of aluminium is 15 kilowatt-hours (kWh). The cost of electricity accounts for approximately one-third of the total cost of aluminium smelting.
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