Membrane-enhanced lithium fluoride crystallization: A sustainable pathway for resource recovery from concentrated waste solutions

Sustainable recovery of critical raw materials is essential for a circular economy. Lithium fluoride (LiF), a key component in lithium-ion battery production, is usually recovered through energy-intensive methods. This study introduces a greener alternative using membrane-assisted crystallization with hydrophobic polypropylene membranes. By combining molecular dynamics simulations and experimental analysis, we investigated the effects of temperature (300–353 K) and concentration (5.8–8.9 M) on LiF crystallization from aqueous solutions. Simulations revealed that polypropylene (PP) membranes delay nucleation (e.g., induction time increases from 8.5 ns to 18.5 ns at 300 K) mainly by reducing local supersaturation and significantly restricting ion diffusion, up to 86 % for Li+ at 300 K. These effects lower nucleation rates and promote more ordered crystal growth. The optimal crystallization dynamics were observed at 5.8 M and 353 K, with activation energies of 36.7 kJ mol−1 for nucleation and 32.7 kJ mol−1 for growth. Experimental results confirmed the delayed onset and enhanced crystal regularity in membrane-assisted systems. Overall, the use of PP membranes enables spatial control of supersaturation and crystal formation without chemical additives or solvent loss. This membrane-assisted pathway offers a scalable, low-energy strategy for selective lithium recovery from concentrated waste solutions.