How Is Aluminum Extracted From Its Ore?
Aluminum is extracted from bauxite ore by way of the Bayer process. This requires a great deal of electricity; consequently, a large amount of aluminum is processed in Iceland, which gets its electricity through geothermal energy.
To extract aluminum, the bauxite ore is first crushed, then mixed with lime, hot water and soda ash. This mixture is placed into a digester, where it is heated under steam pressure. Caustic soda is added, which dissolves the alumina from the ore. The other impurities are left as solids. After this, a filter separates the solids from the solution.
The solution is allowed to cool in a precipitator. As it does, the alumina precipitates out of the solution and forms crystals. These crystals settle to the bottom of the precipitator. The caustic soda solution that is leftover is returned to the digester to treat more bauxite.
In the meantime, the alumina crystals are sent to a revolving kiln that removes the water. This leaves pure alumina powder behind.
Finally, the aluminum is made by smelting the alumina. This involves dissolving the alumina in a hot cryolite solution in an electrolytic cell or pot. The aluminum forms on the cell's cathode lining. The molten aluminum is then siphoned out of the electrolytic cell and poured into molds.