Method of obtaining pure alumina by acid attack on aluminous minerals containing other elements

Abstract

A method of obtaining alumina of high purity from aluminous mineral containing impurities in which the mineral is attacked with a sulphuric acid liquor followed by separation of a liquid phase from the resulting solid residue comprising (1) mixing the liquid phase with a liquor containing HCl and H.sub.2 SO.sub.4 at elevated temperature, (2) cooling the mixture with the precipitation of hydrated aluminum chlorosulphate having the formula AlSO.sub.4 Cl.6- 7H.sub. 2 O, (3) separating the precipitate from the remaining liquor which contains the major part of the impurities in solution, (4) suspending the separated precipitate in a hydrochloric acid liquor, (5) chlorinating the suspension by introduction of gaseous HCl with precipitation of AlCl.sub.3.6H.sub. 2 O, (6) separating the precipitated AlCl.sub.3.6H.sub. 2 O, and (7) pyrolizing the separated precipitate to produce alumina of high purity and gaseous HCl.

Dependencies are inferred from the claim text.