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In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperature and pressures : Al O (s) 2OH (aq) 2Al O (aq) H O(1) 2 - 32 + ? 22 + - Solid impurities such as Fe2 O3 and SiO2 are removed and then - A 4 l(OH) is reprecipitated : 2Al(OH) Al .O 3H O(s) 2OH (aq) - 232 - 4 ? + . In the industrial world : (A) Carbon dioxide is added to precipitate the alumina (B) Temperature and pressure are dropped and the supersaturated solution seeded (C) Both (A) and (B) are practised (D) The water is evaporated

In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperature and
pressures :
Al O (s) 2OH (aq) 2Al O (aq) H O(1) 2
-
32 + ? 22 + -
Solid impurities such as Fe2
O3
and SiO2
are removed and then - A 4 l(OH) is reprecipitated :
2Al(OH) Al .O 3H O(s) 2OH (aq) -
232
-
4 ? + . In the industrial world :
(A) Carbon dioxide is added to precipitate the alumina
(B) Temperature and pressure are dropped and the supersaturated solution seeded
(C) Both (A) and (B) are practised
(D) The water is evaporated

Grade:

2 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
3 years ago
In original process the alkaline solution was cooled and treated with bubblingCO2​to precipitate alumina.
but the seeding of saturated solution by dropping the temperature and pressure makes the process feasible
Vikas TU
14149 Points
3 years ago
Dear student 
Question is not clear 
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We will happy to  help you 
Good Luck
Cheers

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