In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperature and pressures: Al2 O3 (s)+2OH- (aq) →2Al2 O-2(aq)+H2O (l) Solid impurities such as Fe2O3 and SiO2 are removed and then Al(OH)-4 is reprecipitated: 2Al(OH)4- → Al2 O3. 3H2O (s)+2OH- (aq). In the industrial world :

Question

In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperature and pressures: Al2 O3 (s)+2OH- (aq) →2Al2 O-2(aq)+H2O (l) Solid impurities such as Fe2O3 and SiO2 are removed and then Al(OH)-4 is reprecipitated: 2Al(OH)4- → Al2 O3. 3H2O (s)+2OH- (aq). 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

Tardigrade Admin · Accepted Answer

Industrially, in the extraction of alumina, temperature and pressure are dropped and the super saturated solution seeded. Sometimes CO 2 is also used to precipitate alumina.

Carbon dioxide is added to precipitate the alumina

Temperature and pressure are dropped and the supersaturated solution seeded

Both (A) and (B) are practised

The water is evaporated

Industrially, in the extraction of alumina, temperature and pressure are dropped and the super saturated solution seeded. Sometimes CO2​ is also used to precipitate alumina.

Industrially, in the extraction of alumina, temperature and pressure are dropped and the super saturated solution seeded. Sometimes $C O_{2}$ is also used to precipitate alumina.