Question

Baeyer’s process is used to concentrate bauxite ore to alumina.

Give balanced chemical equation for the reaction taking place for its conversion from bauxite ore to alumina.

Answer 1

Conversion of impure bauxite to sodium aluminate:

\[\ce{\underset{Amphoteric oxide}{\underset{[Impure bauxite]}{Al2O3*2H2O}} + \underset{Blue}{\underset{[Conc. soln]}{2NaOH}} ->[150-200^\circ C]{2NaAlO2} + \underset{Water}{3H2O}}\]

Conversion of sodium aluminate to aluminium hydroxide:

\[\ce{\underset{[Sodium aluminate]}{NaAlO2} + 2H2O ->[50-60^\circ] \underset{[Sodium hydroxide]}{NaOH} + \underset{[Aluminium hydroxide]}{Al(OH)3}}\]

Conversion of Al(OH)₃ - to pure alumina - heat on Al(OH)₃:

\[\ce{\underset{[Aluminium hydroxide]}{2Al(OH)3} ->[1100^\circ C] \underset{[Pure alumina]}{Al2O3} + 3H2O}\]

Precipitated Al(OH)₃ is ignited to give pure alumina [Al₂O₃].