Question

The following question refer to the extraction of aluminium and iron from their ores:
Iron and aluminum ores both, contain impurities. Explain briefly how these impurities are removed in each case.

Answer 1

Aluminium	Iron
1. Aluminium ore contains impurities of FeO and SiO2	1. Iron ore contains impurities of silica and sand. These are removed by magnetic separation .
2. Bauxite containing FeO is calcinated at high temperature	2. FeO is oxidized to Fe2O3
3. Calcinated ore is then treated with NaOH when Al2O3 is converted into soluble NaAIO2 (sodium meta - aluminate)	3 . The insoluble Fe2O3 and silica can thus be filtered off.
4. The filtrate is hydrolysed to get Aluminum hydroxide which on ignition gives pure alumina ( Al2O3).