Influence of the composition of Cu–Co–Fe alloys on their dissolution in ammoniacal solutions

The dissolution of a range of Cu–Co–Fe alloys in ammoniacal solutions was examined. High-copper alloy dissolution was possible in ammonia–ammonium sulphate solution with the addition of copper(II) ions. Such a process was spontaneous, selective and efficient with almost all copper dissolved. No iron was found in the solution and the residual slimes contained iron and cobalt. Low-copper alloys were unaffected by the copper(II) ions but dissolved during electrolysis in ammonia–ammonium chloride solution with an anodic current efficiency of 97%. Under these conditions, almost all iron and copper transferred into the slimes and the cobalt was plated onto the cathode.