GB746780A - Improvements in or relating to hydrometallurgy of nickel and cobalt - Google Patents

Abstract

Substantially cobalt-free nickel-bearing solutions are recovered from liquor containing both metals in the form of sulphates or carbonates by adjusting the metal content of the liquor to up to 100 grams/litre of dissolved cobalt plus nickel for carbonate solutions and up to 135 grams/litre for sulphate solutions, 1-4 mols of amonium carbonate per mol of dissolved cobalt plus nickel salts and sufficient available ammonia to retain cobalt and nickel in solution under atmospheric conditions, heating the solution under pressure to above 140 DEG C. till precipitation substantially ceases and separating the precipitate containing cobalt carbonate from the solution. Where the nickel : cobalt ratio in the liquor is less than 1 the treatment may take place in two stages, a substantially nickel-free cobalt precipitate being obtained in the first stage, the precipitation in the second stage being continued till the solution is substantially cobalt free. Heating preferably takes place in an atmosphere of hydrogen. In carbonate solutions the mol ratio of free ammonia : dissolved nickel and cobalt may be 1.5-2.0 but is preferably higher and up to 4.0, a good range being 2.5-3.5. To ensure selective precipitation the solution should contain a proportion of ammonium carbonate which varies with the ratio of nickel : cobalt, the mol ratio of ammonium carbonate : nickel + cobalt being, for example 1 : 1 when the nickel:cobalt ratio is 1.5 or lower and 3:1 or 4:1 when the nickel:cobalt ratio is higher. The proportions given above are varied slightly in sulphate solution. The cobalt carbonate precipitate and the residual solution may be separately treated to recover the metals in metallic form. (See Group II.)ALSO:Cobalt carbonate precipitated from a nickel-and cobalt-containing solution (see Group III) is treated to recover cobalt as metal by slurrying the carbonate in water to form a 25-40 per cent slurry and subjected to an elevated temperature of 100 DEG F. to 500 DEG F. or above, preferably 200-450 DEG F., and to a partial pressure of at least 100 lbs./sq. in. gauge of a non-sulphidising reducing gas such as hydrogen. The resulting slurry of cobalt metal is cooled and the metal powder dried. The solution resulting from cobalt carbonate precipitation may be treated to recover nickel and any residual cobalt as metals by adjusting the ammonia and carbonate contents and treating the liquor at different but increasing elevated temperatures with a reducing gas to recover a low cobalt-content nickel powder and finally a low nickel-content cobalt powder.