CobaltCobalt-nickelNickel separationCobalt-nickel separation isLi-ion batteries an essential process step for many hydrometallurgical flowsheetsFlowsheet. Conventionally, solvent extraction (SXSolvent Extraction (SX)) is used to selectively recover cobaltCobalt from a pregnant leach solution (PLS) containing a mixture of metalsMetals. An alternative to a traditional mixer-settlerMixer-settler (SX)Solvent Extraction (SX) equipment design is supported liquid membraneSupported liquid membranes (SLM) technologyTechnology. SLM utilizes the same basic chemistry principles as SXSolvent Extraction (SX), except extractionExtraction and stripping are carried out simultaneously across a porous membrane, which is laden with the extractant and diluent, the organic phase being supported in the membrane by wetting forces. Previous work demonstrated Co–Ni separation using SLM with 25 cm2 membranes and 300 g of feed and strip phases. The current work increased the scale to 57 m2 hollow fibre membrane modules and feed to 100 kg. The feed phase was a synthetic mixture of 10,000 ppm Co2+ and Ni2+ each as sulphates, with 0.5 M sodium acetate as buffer, while the strip phase was 50 or 100 kg of 10 or 20 wt% H2SO4. The feed pH was controlled via the addition of 2 N NaOH or KOH. The extractant was 10 wt% (approximately 0.3 M) hydrophobic phosphorus acidAcid in a non-aromatic hydrocarbon (D80, Exxon). Complete extractionExtraction of Co2+ was achieved with purities of ~ 99.5–99.8% in a single stage at more than 90% Co2+ recovery. The batch tests were repeated 5 times on a single module and replicated on a 2nd module. Co2+ mass transfer rates decreased during the first two tests, from 3.0 gmol/m2/day to 2.4 gmol/m2/day, and were 2.0 to 2.2 gmol/m2/day in the two subsequent tests.