Solvent Extraction of Nickel and Cobalt from Ammonia-Ammonium Carbonate Solution by Using LIX 84-ICNS

In the present paper, separation of nickel and cobalt in ammonia-ammonium carbonate solution that simulates pregnant leach solution of Caron Process by solvent extraction using LIX 84-ICNS was studied. LIX 84-ICNS is a novel extractant which is still being studied, especially for nickel and cobalt separation in ammonia-ammonium carbonate solution. A series of solvent extraction tests were performed at various equilibrium pH, temperature, extractant concentration, and volume ratio of organic to aqueous solution (O/A ratio). The investigation results show that the highest nickel and cobalt extraction percentages of 99.8% and 90.3% were obtained from the extraction test at equilibrium pH of 8.75, temperature of 55°C, extractant concentration of 40% (v/v) and O/A ratio of 1/1, respectively. Oxidation of cobalt in aqueous solution prior to extraction is needed to minimize co-extraction of cobalt. Co-extracted cobalt can be decreased from 90.3% to 30.3% by mixing 1% (v/v) H₂O2₂ in aqueous solution prior to the extraction stage. It was found that nickel and cobalt extractions by LIX 84-ICNS are endothermic processes with enthalpy changes of +171.03 and +7.64 kJ/mole, respectively. Based on constructed McCabe-Thiele Diagram, nickel extraction level of more than 99.9% can be obtained in 2 stages at O/A ratio of 0.5. The highest stripping percentages of nickel and cobalt of 98.82% and 3.16% respectively were obtained at 200 g/l H₂SO₄ stripping agent.