Sustainable lithium recovery from spent lithium-ion batteries by coupling chemical leaching with nanofiltration

Global lithium production currently relies on hard rock ores and high-grade brines, although these resources are insufficient to cover the rapidly increasing demand derived from electrification of multiple transportation and industrial sectors and all associated extraction processes generate important enrivonmental impacts. To address this gap and promote a circular economy for this metal, attention is turning to non-conventional sources, including low-grade brines, geothermal fluids, seawater, and industrial or battery recycling. Lithium-ion battery recycling is particularly relevant, as it allows recovery of lithium along with other valuable metals such as cobalt, nickel, and manganese. Conventional processes for lithium recovery, typically yielding lithium carbonate, often require very high temperatures or the use of multiple chemicals. However, this work focuses on the combination of leaching and nanofiltration (NF) techniques as a feasible and more eco-friendly approach to selectively recover lithium from multi-ionic liquors. Different acids and operating conditions were tested for the leaching stage, finding that citric acid exhibited a promising extraction performance while maintaining a suitable pH for subsequent membrane operation. Cross-flow NF was carried out by using a commercial polymeric membrane tested under different transmembrane pressures and pH values. Conditions that ensure a positive zeta potential were found to improve lithium rejection and, consequently, its recovery. Within the lab-scale NF framework, lithium recovery and pH-dependent permeate/retentate compositions are quantified, establishing clear process indicators aligned with the objectives of EU Regulation 2023/1542 and providing a concise data template readily adaptable to Battery Passport reporting.