HYDROMETALLURGICAL SEPARATION OF IRON AND NICKEL

1387269 Leaching Fe and Ni FALCONBRIDGE NICKEL MINES Ltd 8 Sept 1972 [9 Sept 1971] 42021/71 Heading C1A Tron and nickel are leached from particulate sulphidic material (e.g. matte) with hydrochloric acid such that the material, acid and water are fed to an aqueous leaching system at a rate such as to control (1) the acidity of the leach slurry which for a given acid consumption per unit mass of material reduces selectivity as it increases and increases selectivity as it decreases and (2) the acid consumption per unit mass of material which for a given acidity of the leach slurry reduces selectivity as it increases and increases selectivity as it decreases, thereby controlling the selectivity of leaching of iron with respect to nickel, withdrawing the acidic leach slurry from the leaching system and separating it into leached solids and an aqueous acidic leach solution. The leach slurry may be of pH. greater than 1 and the aqueous acidic leach solution may contain at least 100 grams/ litre of iron and may be treated with H 2 S and particulate iron bearing material in which the iron is present as oxide or hydroxide or a combination of both to precipitate Ni, Co and Pb. The iron bearing material may be produced by the hydrolysis of iron chloride or may be a calcine produced by the oxidative roasting of an iron bearing sulphidic material or may be ferrous hydroxide produced by reacting NH 4 OH with iron values already present in the aqueous acidic leach solution. The precipitation may be carried out at a temperature between 50‹ C. and the solution boiling point and the resulting solution may be almost pure ferrous chloride solution which may be used to regenerate hydrochloric acid for the leaching process and iron oxide for the precipitation process. The H 2 S used in the precipitation process may be that produced in the leaching process.