Question

how is bauxite extracted

Answer 1

bauxite is formed by the decomposition of wide variety of rocks rich in aluminium silicate

Answer 2

Bauxite is a very important aluminium ore therefore, it is very important for us because aluminium is used in various industries. Bauxite is used in cement, chemicals, face makeup, soda cans, dishwashers, siding for houses, and other aluminum products also glass cutting tools.
The extraction of aluminium from bauxite involves three steps:
• The purification of bauxite using Bayer’s process.
• The electrolytic reduction of anhydrous Al2O3 by Hall and Herault’s process.
• The last step is the purification of impure aluminium by Hoope’s process

In Baeyer’s process, impure bauxite is converted into pure alumina. The conversion process involves mainly three reactions:

Concentrated sodium hydroxide solution is heated with amphoteric bauxite at a temperature of 150 to 200° C under pressure to get sodium aluminate.
Sodium aluminate is then diluted with water at a temperature of 50 to 60° C. Thus, sodium aluminate gets hydrolysed to form solid aluminium hydroxide and sodium hydroxide.
Finally, dried aluminium hydroxide precipitate is ignited at a temperature of 1100° C to remove water molecules to get alumina.
Bauxite is also concentrated through Hall’s process, in which sodium aluminate is prepared by adding sodium carbonate to bauxite. When excess carbon dioxide is passed through sodium aluminate in the presence of water, it forms aluminium hydroxide along with sodium carbonate. When dried aluminium hydroxide is ignited, alumina is formed.

Alumina is a very stable oxide and aluminium shows a strong affinity to combine with oxygen. Therefore, reducing it with reducing agents is practically difficult. Hence, it is reduced by electrolytic reduction through Hall-Heroult’s process.