Bauxite is the main ore of aluminium. It is concentrated by leaching
Preparation of bauxite by leaching : Bayer'* Process-
Bauxite ore is treated with caustic soda at 473- 523 K and 35-36 bar pressure. Al2O3dissolves in concentrated solution leaving behind impurities.
The aluminate in solution is neutralised by passing CO2gas and hydrated Al2O3 is precipitated
The sodium silicate *** in the solution and hydrated alumina is filtered dried and heated to get back pure Al2O3.
