Alumina is recoverd from aluminum sulfate leach liquors by treatment of the liquor with hcl gas to the point of incipient crystallization of alcl3.6H2o, extraction of the resulting solution with Tertiary amine to remove iron, further treatment with hcl gas to precipitate alcl3.6H2o and roasting of the alcl3.6H2o to al2o3. For example, a sulfate leach liquor was produced by leaching calcined clay with 50 vol pct h2so4. The filtered liquor, which contained 48 g/l al and 1.37 G/l fe, was reacted with a small amount of h2o2 to ensure complete oxidation of the iron. The liquor then was sparged with hcl gas to the point of incipient crystallization. The resulting solution was contacted with 1/3 its volume of a mixture of 15 vol pct alamine 336 (a commercially available long chain Tertiary aliphatic amine), 5 vol pct decyl alcohol, and 80 vol pct kerosene. The iron content of the raffinate was 0.01 G/l. Sparging of the raffinate with hcl gas resulted in crystallization of high purity alcl3.6H2o.
U.S. Pat. 4,107,266, Aug. 15, 1978; Chem. Abstr. Not Found