Question

Describe the three steps involved in the leaching of bauxite to get pure alumina (equations not expected).

Answer 1

Hall's process for leaching of alumina from bauxite:
(1) Bauxite ore and sodium carbonate are fused toghether to convert aluminium oxide into soluble sodium meta-aluminate. The insoluble residue contains the impurities of silica and iron oxide. The fused mass is treated with water.
(2) The filtrate is warmed and neutralised by passing carbon dioxide through the solution to precipitate aluminium hydroxide.
(3) The precipitate obtained of $Al(OH{)}_3$ in both processes is washed dried and heated (ignited) to get $A{l}_2{O}_3$