Process development for the separation and recovery of copper from sulphate leach liquors of synthetic Cu–Ni–Co–Fe matte using LIX 84 and LIX 973N

Solvent extraction separation and recovery of copper from liquors from sulphate leaching of synthetic Cu–Ni–Co–Fe matte using oxime based extractants such as LIX 84 and LIX 973N in kerosene was studied. Parameters such as feed pH, extractant concentration, phase ratio, counter current extraction and stripping were optimized. Influence of feed pH on copper extraction indicates that leach liquor acidity was adequate to achieve maximum extraction. Comparison of the extraction behavior of extractants for copper at 40 vol.% concentrations showed 10% more extraction with LIX 973N. Extraction isotherm data with 40 vol.% LIX extractants (barren of copper) at unit phase ratio indicated 3 stages of extraction with LIX 84 and 2 stages of extraction with LIX 973N, are necessary to achieve > 95–99% copper extraction. The co-extraction of Ni, Co and Fe was < 2 mg/L. Stripping of copper from loaded organic phase at unit phase ratio using a synthetic spent electrolyte (SE) solution containing 35 g/L Cu and 180 g/L H2SO4 from Cu-LIX 84 loaded organic (LO) was ∼ 81%, whereas from Cu-LIX 973N LO, it was ∼ 10%. Two stages of stripping of copper from LIX 84-LO at O/A ratio of 1.3 with SE indicated 85% stripping. Recycle of spent organic for further use in copper extraction circuit showed a decrease in efficiency by ∼ 3–4%. Semi-continuous countercurrent extraction (∼ 96%)–stripping (∼ 85%) studies for 4 cycles on lab scale and bench scale mixer settler equipment for 30 h of operation confirmed almost similar extraction–stripping percentages with high purity copper sulphate solution.