How is Alumina Produced?

Production processes

The goal of refining is to isolate and retain only the aluminium hydroxy-oxides (Al2O3.H2O or Al2O3.3H2O) from bauxite and let the impurities (principally iron oxides and silica minerals) pass from the process. The outputs of the refining process are alumina tri-hydrate and a ‘red mud’ waste stream containing the impurities. The alumina tri-hydrate is then calcined at ~1000°C to drive off the water, leaving alumina at typically >99.5% purity.