Question

Describe bayer's process for concentration of bauxite.

Answer 1

The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide).Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the rest being a mixture of silica, various iron oxides, and titanium dioxide.

Answer 2

Answer and Explanation:

Baeyer's process is used to obtain pure alumina.

Bauxite ore usually contains impurities of iron xide $(Fe_2O_3)$, silica $(SiO_2)$ and titanium oxide $(TiO_2)$. The powdered ore is heated with a concentrated solution of $NaOH$ at 473-523 K. The alumina dissolves forming sodium meta aluminate and silica  $SiO_2$ as sodium silicate, leaving behind the impurities.

$Al_2O_3(s)+2NaOH(aq)+3H_2O(l)\rightarrow 2Na[Al(OH)_4](aq)$

$SiO_2(s)+2NaOH(aq)\rightarrow Na_2SiO_3(aq)+H_2O(l)$

The resulting solution is filtered, and cooled and neutralized with carbon dioxide to get aluminium hydroxide as precipitate leaving sodium silicate in the solution.

$2Na[Al(OH)_4](aq)+2CO_2(g)\rightarrow Al_2O_3.xH_2O(s)+2NaHCO_3(aq)$

Hydrated alumina is filtered , washed and heated to get pure alumina.

$Al_2O_3.xH_2O(s)\rightarrow Al_2O_3(s)+xH_2O(g)$