Recovery of cobalt and nickel from iron-rich mattes and alloys by leaching

摘要

A process for selectively extracting a value metal from a ferrous solid, the value metal being selected from the group consisting of cobalt, nickel and copper, and the ferrous solid being selected from mattes and alloys containing iron and the value metal in metallic form. In a first leach step, an aqueous solution is provided in contact with an oxygen-containing atmosphere, the first aqueous solution having a pH of less than about 2.0 and containing sufficient sulfate ion to form a soluble sulfate with the value metal contained in the ferrous solid. The ferrous solid is added to the first aqueous solution over a period of at least one hour to increase the pH to the range of about 4 to 6, while maintaining the temperature of the first aqueous solution at less than about 100 DEG C during addition of at least the last fifty percent of the solid. At the end of the first leach, a solid/liquid separation is performed to separate a first liquid fraction containing soluble sulfates of the value metal from a solid iron-containing residue. The solid residue is preferably treated in a second leach step to recover copper and unleached cobalt. The second leach step comprises treating the solid residue with an acidic aqueous solution at elevated pressure and a temperature of about 120 to 220 DEG C, to thereby oxidize copper sulfides present in the residue and cause copper to enter the liquid phase as soluble copper salts.