Australia is one of the world's largest producers of aluminium. Aluminium is produced from Bauxite which is an ore comprised of several aluminium oxides. This is formed in nature by extensive chemical weathering of other rocks and contains the compound Al2O3. Chemical weathering is more intense in warm, humid regions fro this reason bauxite deposits are found within tropical rainforests in broad shallow layers under the soil. Because the ore is spread in layers under the soil, it is mined in open pits which is a highly destructive method of mining and destroys the habitats of inhabitants.
The extraction methods used are determined by the reactivity of the minerals in the ore and the strength of the bonds within them. Which means aluminium is extremely difficult to extract from Al2O3 because of the strong ionic bonds that are present within the compound.
During the preparation of a site for open-cast mining, the surface soil is removed to get access to the bauxite.
In order to avoid soil erosion and to ensure that vegetation is returned to the land, many companies have water drainage practices during mining operations, separate removal of top soil (50 per cent reuse it directly after the mining operation) and over 60 per cent have their own nursery plant facilities. The underlying bauxite is mined by front Enders, power shovels, or hydraulic excavators. Sometimes the bauxite is crushed and washed to remove the clay and sand and then dried in rotary kilns. The ores are then loaded into trucks then ships or to refineries.
Most alumina is extracted from bauxite using the Bayer refining process discovered by Carl Bayer in 1888.
1: Digestion- The finely grounded bauxite is fed into a digester. It is mixed under pressure with a solution of caustic soda. Some of...