Bauxite ore extraction process
  • Name :Bauxite ore extraction process
  • Features:Simple structure, easy maintenance
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Bauxite Ore Processing

Aluminum is found in varying amounts in nature as aluminosilicates (contains aluminum, silicon, and oxygen) in various types of clay. As the minerals are weathered they gradually breakdown into various forms of hydrated aluminum oxide, Al2O3.xH2O, known as bauxite.

The bauxite is purified by the Bayer Process. First the ore is mixed with a hot concentrated solution of sodium hydroxide. The NaOH will dissolve the oxides of aluminum and silicon but not other impurities such as iron oxides, which remains insoluble. The insoluble materials are removed by filtration.

The solution which now contains the oxides of aluminum and silicon are next treated by bubbling carbon dioxide gas through the solution. Carbon dioxide forms a weak acid solution of carbonic acid which neutralizes the sodium hydroxide from the first treatment. This neutralization selectively precipitates the aluminum oxide, but leaves the silicates in solution. Again filtration is used for the separation. After this stage the purified aluminum oxide is heated to evaporate the water.

Aluminum in the metal form is very difficult to obtain by using some of the traditional chemical methods involving carbon or carbon monoxide as reducing agents to reduce the aluminum ions to aluminum metal. One of the earliest and costly methods in 1850 was to reduce aluminum chloride with sodium metal to obtain aluminum metal and sodium chloride. (Sodium metal is not easy to obtain either). As a result some of the earliest aluminum metal was made into jewelry.

Bauxite Mining

Aluminium is the third most abundant element in the Earth’s crust, but does not occur as a metal naturally. The first step in producing aluminium is mining its ore – bauxite.

Bauxite occurs mainly in tropical and sub-tropical areas, like Africa, the West Indies, South America and Australia – there are some small deposits located in Europe.

Australia is the largest producer of bauxite, with five mines supplying around 23 per cent of global production.

Bauxite mining has five steps: Preparation of the mining area; bauxite mining; crushing; ore transport; and rehabilitation.