Winning nickel and cobalt with mercaptide extractants and carbon

Abstract

A novel process for extracting, concentrating, and isolating nickel and cobalt from aqueous solution thereof. A cobalt and/or nickel bearing solution is contacted with an extractant comprising a substantially water immiscible organic solvent containing solubilized mercaptide anion to form water insoluble cobalt and nickel mercaptides in the organic phase. The organic phase is then separated from the raffinate and contacted with an alkaline solution and carbon monoxide to produce nickel and cobalt carbonyl compounds. Typically, the nickel carbonyl produced is gaseous Ni(CO).sub.4 which may be easily isolated by known methods from other components in the off-gas stream. Pure nickel metal is then obtained from the nickel tetracarbonyl by known methods. The cobalt carbonyl compound produced is typically water soluble carbonyl cobaltate ion, Co(CO).sub.4.sup.-, which may be oxidized to form water insoluble cobalt carbonyl compounds. The stripped extractant, the cobalt and nickel-free raffinate, and the carbon monoxide from the decomposition of carbonyl may be recycled.