Recovery of metals from spent lithium-ion battery leach solutions with a mixed solvent extractant system

Abstract

A mixed extractant system has been developed for the separation and purification of cobalt and lithium from spent lithium-ion battery leach solutions. The addition of Acorga M5640 to the Ionquest 801 organic solution generated a significant pH isotherm shift for copper with a ΔpH 50 value of 3.45. As a result, the separation of iron(III), copper and aluminium from cobalt, nickel and lithium could easily be realised with the mixed extractant system. The McCabe–Thiele diagrams at an A/O ratio of 2:1 and pH 4.0 showed that three theoretical stages are needed for the extraction of iron, copper and aluminium. The extraction kinetics of iron(III) and copper was rapid, but the extraction kinetics of aluminium was slow. With the increase of temperature from room temperature to 40 °C, the aluminium extraction kinetics increased substantially. It is therefore recommended that the metal extraction should be carried out at 40 °C. The stripping kinetics of aluminium and copper was rapid, but iron cannot be stripped effectively. Thus an organic bleed may be required to remove the iron with higher acid concentration in the strip solution. It is proposed that in the mixed organic system, Ionquest 801 played a role of extractant and Acorga M5640 a synergist for copper extraction. A process flowsheet is proposed for recovering cobalt and lithium from spent lithium-ion battery leach solutions using the mixed Ionquest 801 and Acorga M5640 system in the first solvent extraction circuit, and Cyanex 272 in the second solvent extraction circuit. The advantage of this process is that pure cobalt and lithium products could be obtained.