Solvent extraction of nickel and cobalt with synergistic systems consisting of carboxylic acid and aliphatic hydroxyoxime

Metal extraction pH isotherms and extraction and stripping kinetics have been determined with Versatic 10 acid and LIX® 63 and modifier TBP in an attempt to develop synergistic SX systems for the separation, purification and recovery of nickel and cobalt from leach solutions.The combination of LIX® 63 with Versatic 10 acid resulted in significant synergistic shifts for nickel, cobalt, copper, zinc, and manganese and antagonistic shifts for calcium and magnesium. With the 0.5 M Versatic 10 acid/0.35 M LIX® 63 system, the ΔpH50 values of nickel, cobalt, copper, zinc and manganese compared to Versatic 10 acid alone were found to be 2.79, 3.50, > 2.0, 1.99 and 1.17 pH units, respectively. The ΔpH50(Mn–Ni) and ΔpH50(Mn–Co) values were found to be 1.96 pH and 2.53 pH units, respectively, indicating easy separation of nickel and cobalt from manganese, calcium and magnesium. The extraction and stripping kinetics of cobalt, copper, zinc, and manganese were fast and the extraction and stripping kinetics of nickel were slow with the Versatic 10 acid/LIX® 63 synergistic system. The nickel stripping kinetics increased with the addition of TBP. Within 2 min, the stripping efficiency of nickel increased from 18% with no TBP to 91% with 0.5 M TBP addition. The addition of TBP to the Versatic 10 acid/LIX® 63 system also improved the nickel extraction kinetics.It is proposed that in the Versatic 10 acid/LIX® 63 synergistic system, LIX® 63 plays the role of an extractant and Versatic 10 acid a synergist for nickel while LIX® 63 plays the role of a synergist and Versatic 10 acid an extractant for cobalt.