1. Mining
Bauxite is an ore rich in aluminum oxide, formed over millions of years by chemical weathering of rocks containing aluminum silicates.
2. Refining
To turn bauxite into alumina, ore is grinded and mixed with lime and caustic soda, the pumped into high-pressure containers for heating. The aluminum oxide is dissolved by the caustic soda, then precipitated out of this solution, washed, and heated to drive off water. The process produces the sugar-like white powder called alumina, or aluminum oxide (AI2O3).
3. Alumina
Alumina chemicals are used to purify water and to make refractory bricks, ceramics, adhesives, catalysts, and fire retardant fillers for fabrics and plastics.
4. Smelting
Alumina becomes aluminum in an electrolytic reduction process known as smelting. The alumina is dissolved in a cryolite bath. When a powerful electric current is passed through the bath, aluminum metal separates from the chemical solution and is siphoned off.