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

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

Grade:upto college level

1 Answers

Raheema Javed
156 Points
9 years ago



In the extraction of aluminium, the significance of leaching is to concentrate pure 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 pure alumina (Al2O3).


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