GB740797A - Improved method of recovering metal values from solutions - Google Patents

Abstract

Nickel, cobalt and copper are precipitated from ammoniated solutions in which they are present as soluble compounds by reacting the solutions with a reducing gas such as hydrogen in a reaction vessel under superatmospheric pressure, e.g. above 100 lbs./sq. inch, and superatmospheric temperature, e.g. above 200 DEG F., a nucleating agent being present in the solutions to initiate and accelerate the reducing reaction. A solution being subjected to reduction may contain ammonium sulphate and preferably sufficient ammonia is maintained in the solution during reduction to provide at least 2 mols of ammonia per gram-atom of metal to be reduced. Nuclei produced by such a reduction may be added to a further solution which is then reduced without addition of nucleating agent. Thus successive solutions may be added to the reaction vessel containing reduced metal nuclei until metal begins to plate on the walls of the reaction vessel. The adhering metal is dissolved off and the process repeated. Among the nucleating agents which can be used are those which act as reducing agents such as compounds including a polyvalent metallic ion in its lowest state of oxidation, e.g. a ferrous compound which may be used in an amount greater than 0.1 grams per litre. A mixture of ferrous sulphate and ferrous ammonium sulphate may be used. Other agents which may be used are carbonate, hydroxides, sulphides and finely divided carbon.