Pilot-Scale Lanthanide Precipitation from Sulfate-Based Spent Ni-MH Battery Leachates: Thermodynamic-Based Choice of Operating Conditions

Access to critical metals required for high-performance technologies, particularly, the light rare earth elements (REEs = La, Ce, Nd, Pr), has become a major challenge import-dependent economies such as European Union. In this regard, recycling of spent nickel metal hydride (Ni-MH) batteries by hydrometallurgical processes can serve an attractive secondary source REEs. processes, precipitation REEs from pregnant leach solutions (PLS) in sulfate media using Na2SO4 is often reported. However, little consideration given whether and how sodium ions influence efficiency selectivity. This work focuses on better understanding process coupling pilot-scale (2 L) experiments industrially sourced PLS containing 50 g/L Ni 17 REEs, with thermodynamic modeling, assess temperature (25 °C < T 60 °C) Na/REEs molar ratio (0.8:1 3.2:1). Equilibria calculations were performed OLI Systems Inc. software whose database covers compound properties accurate description aqueous electrolytes. Highly selective was obtained at 4:1. A lanthanide-alkali solid solution identified multianalytical characterization.