US Patent 7837959 Synergistic solvent extraction process

A process for separating one or more metal ions forming a first group of metal ions such as copper, zinc and ferric ions, from one or more other metal ions forming a second group of metal ions such as cobalt and nickel, comprising:contacting an aqueous solution comprising said first and second groups of metal ions with an organic solution comprising a phosphinic acid and a hydroxyoxime to extract one of said groups of metal ions into the organic phase, andseparating the organic and aqueous phases.