Abstract
The rapid growth of lithium-ion battery (LIB) manufacturing and deployment has intensified the need for recycling processes capable of recovering high-purity critical metals while minimizing environmental impacts. Hydrometallurgical processing of NMC black mass offers a pathway to produce battery-grade Ni, Co, Mn, and Li; however, leaching of the cathode material generates high concentrations of fluoride ions. Elevated fluoride levels reduce extraction efficiency in downstream separation steps and present environmental and regulatory risks if not properly managed. Effective fluoride removal is therefore essential for industrial-scale, closed-loop recycling of NMC-based LIBs. This work evaluates activated alumina as a viable, selective, and operationally simple fluoride removal strategy for NMC black mass leachates. While precipitation can remove up to 98% of fluoride, it also results in undesirable losses of critical metals. Activated alumina offers an adsorption-based alternative that mitigates metal co-loss while meeting industrial process requirements. Under optimized conditions, activated alumina achieved 90% fluoride removal with <5% loss of Ni, Co, Mn, and Li. These conditions are compatible with existing hydrometallurgical circuits and avoid the formation of large sludge volumes characteristic of precipitation-based approaches. By providing a selective, regenerable method for fluoride removal, this work supports the development of cleaner hydrometallurgical processes and strengthens critical-materials recovery from end-of-life LIBs. The results offer actionable guidance for industrial implementation, improving downstream metal extraction performance, reducing environmental liability, and enhancing overall process sustainability within the battery materials supply chain.