Question

Aluminium metal is not extracted directly from Bauxite ore. The ore is first purified to give pure alumina from which aluminium is isolated by electro reduction process. Explain.

Answer 1

Bauxite `(Al_(2)O_(3).xH_(2)O)` is associated with the impurities of ferric oxide and silica. In case, Bauxite is used directly for the extraction of aluminium, iron and silica present in it would deposit at the cathode during its electrolyte reduction. As a result, aluminium obtained from cathode gets contaminated with iron and silica. This makes the metal brittle. It is readily attacked by air and water.