Updated By SaraNextGen

On March 11, 2024, 11:35 AM

Question 6.1:

Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method?

Answer:

If the ore or the gangue can be attracted by the magnetic field, then the ore can be concentrated by the process of magnetic separation. Among the ores mentioned in table 6.1, the ores of iron such as haematite (Fe₂O₃), magnetite (Fe₃O₄), siderite (FeCO₃), and iron pyrites (FeS₂) can be separated by the process of magnetic separation.

Question 6.2:

What is the significance of leaching in the extraction of aluminium?

Answer:

In the extraction of aluminium, the significance of leaching is to concentrate pure CHAPTER - alumina (Al₂O₃) from bauxite ore.

Bauxite usually contains silica, iron oxide, and titanium oxide as impurities. In the process of leaching, alumina is concentrated by digesting the powdered ore with a concentrated solution of NaOH at 473-523 K and 35-36 bar. Under these conditions, alumina (Al₂O₃) dissolves as sodium meta-aluminate and silica (SiO₂) dissolves as sodium silicate leaving the impurities behind.

The impurities are then filtered and the solution is neutralized by passing CO₂ gas. In this process, hydrated Al₂O₃ gets precipitated and sodium silicate remains in the solution. Precipitation is induced by seeding the solution with freshly prepared samples of hydrated Al₂O₃.

Hydrated alumina thus obtained is filtered, dried, and heated to give back pure alumina (Al₂O₃).