Improved Method for obtaining a Pure Alumina from a Mineral alumina, Calcined or not, containing impurities

摘要

A cyclic process for obtaining very pure alumina by the hydrochloric acid attack of a silico-aluminous material, the said process comprising, in a first stage, the precipitation of at most 75% of the alumina present in the liquor originating from the attack in the form of hexahydrated aluminum chloride which is subsequently decomposed by heating, then, in a second stage, the treatment of the liquor leaving the first stage with HCl gas in order to precipitate dissolved Al2O3 in the form of hexahydrated aluminum chloride which is recycled into the liquor leaving the attack, while the hydrochloric liquor leaving the second stage and impoverished in Al2O3 but rich in impurities, is treated with a recycled sulphuric liquor in order to precipitate impurities as their corresponding sulphates.