Question

How is the main ore of aluminium concentrated?

Answer 1

Conversion of Impure Bauxite to Sodium aluminate

`Al_2O_3.2H_2O + 2NaOH` `2NaAlO_2 + 3H_2O`

Impurities such as `Fe_2O_3` and `S_iO_2` remain unaffected with conc.NaOH.
Conversion of Sodium aluminate to Aluminium hydroxide.

`NaAlO_2 + 2H_2O` `NaOH + Al(OH)_3`

Conversion of `Al(OH)_3` to pure Alumina.

`2Al(OH)_3` `Al_2O_3 + 3H_2O`