Q.6.1. Which of the ores mentioned in Table 6.1 page 6/2 can be concentrated by magnetic separation method ?
Ans. Ores which are magnetic in nature can be separated from the non-magnetic gangue particles by magnetic separation. For example, ores of iron such as haematite (haematite (Fe2O3), magnetite ( FeCO3) and iron pyrites(FeS3) being magnetic can be separated from non-magnetic silica and other impurities by magnetic separation method.
Q.6.2. What is the significance of leaching in the extraction of aluminum?
Ans. Bauxite is the principal ore of aluminum. It usually contains silica (SiO3), iron oxide (〖Fe〗_2 O_3) and titanium oxide (TiO2) as impurities. These impurities can be removed by the process of leaching. During leaching, the powdered bauxite ore is heated with a concentrated (45%) solution of NaOH at 473-523 K and 35-36 bar pressure when alumina dissolves as sodium meta-aluminate and silica (SiO2) as sodium silicate leaving Fe2O3, TiO2 and other impurities behind.
The impurities are filtered off and the solution of sodium meta-aluminate is neutralized by passing Co2 when hydrated alumina separates out while sodium silicate remains in the solution.
The impurities are filtered off and the solution of sodium meta-aluminate is neutralized by passing Co2 when hydrated alumina separates out while sodium silicate remains in the solution.
Q.6.4. Is it true that under certain certain conditions, Mg can reduce SiO2 and Si can reduce MgO ? What are the conditions ?
