Antagonistic Separation of Nickel Over Copper from Ammoniacal Binary Solution Using LIX 84-IC Mixture with TBP

In recent times, ammoniacal leaching has received widespread attention in extractive metallurgy, mainly to process the lateritic ores of nickel. Copper has always been found as the companion metal ion in ammoniacal solutions, whose effective separation is highly desirable to achieve product purity. Usually, LIX series extractants are applied to co-extract and their selective stripping is a function of acid concentration, resulting in large hold-up volumes of the solvent. Henceforth, to achieve high selectivity in the extraction step, we studied the antagonistic effect of tributyl phosphate (TBP) mixing with LIX 84-IC, which inhibited nickel extraction with copper from the ammoniacal solution. The determined distribution coefficient values as D_(mix) <  < D_{(LIX 84-IC)} + D_(TBP) and negative ∆D values clearly demonstrate the antagonistic effect caused by the extractant mixture. The highest separation factor, i.e., β_(Cu/Ni) = 1330, was obtained at a molar mixture of LIX 84-IC:TBP = 0.4:0.6 and an organic-to-aqueous (O:A) phase ratio of 1. The extraction thermodynamics indicate an endothermic process (ΔH° = 5.4 kJ/mol) that forms the inner-sphere organometallic complexation. The copper-loaded organic phase was quantitatively stripped by contacting it with a 1.0 mol/L H₂SO₄ solution at an O:A ratio of 1.