Recovery of nickel from the pregnant leach solution of spent NMC batteries using Versatic acid 10 and mixer-settler operations

Nickel (Ni), one of the most expensive strategic metals, is frequently utilized in Li-ion batteries and other metal alloy applications due to its unique features that include corrosion resistance, high strength, storage capacity, and energy density. In this study, selective recovery of Ni from hydrometallurgical battery recycling solution of real industrial spent nickel‑manganese‑cobalt oxide (NMC) batteries was investigated. Versatic Acid 10 diluted in Isopar L was used as an organic extractant for the selective extraction of Ni 2+ ions, followed by crystallization of nickel sulfate hexahydrate (NiSO 4 .6H 2 O). The kinetics of solvent extraction was studied in batch scale over a time range of 1 to 15 min at pH 6.8 ± 0.1. Results showed that the equilibrium needed for effective extraction and volumetric mass transfer coefficient could be rapidly achieved (within 3 min, 0.9 M Versatic Acid 10). The counter-current solvent extraction process was scaled up in a mixer-settler system for a pilot run using the optimized parameters established by the batch-scale experiments. Almost 100% Ni extraction was achieved through a two-stage counter-current process using 0.9 M Versatic Acid 10, with an organic-to-aqueous phase ratio (θ) of 1. The Ni loaded organic phase was subsequently stripped in two stages using 0.2 M sulfuric acid (H₂SO₄) at θ = 1. NiSO 4 .6H 2 O salt with 99.26 ± 0.01% purity was recovered from the stripped raffinate solution obtained after the mixer-settler operation via evaporative crystallization at 35 °C and a vacuum pressure of 0.1 MPa. Purity, morphology and phases of the recovered crystallized powder were analyzed with inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques respectively. Recovered crystallized nickel sulfate was determined to have sufficient purity for use as precursor cathode active materials (pCAM) in nickel-based lithium-ion battery manufacture. • Selective Ni extraction from industrial PLS of NMC batteries using Versatic Acid 10. • The kinetics behavior during extraction of Ni ions was systematically investigated. • Pilot-scale Ni extraction tested using a mixer-settler with optimized conditions. • 99.6% Ni extraction was achieved through a two-stage counter-current process. • 99.26% pure NiSO 4 .6H 2 O salt recovered using evaporative crystallization.