Informing Ion-Exchange Membrane Design Targets for Donnan Dialysis-Mediated Lithium Brine Concentration

We assess the potential of a Donnan dialysis (DD) process for lithium brine concentration and prioritize material design opportunities from a use-informed perspective. Bench-scale batch experiments were used to validate a kinetic process model, achieving lithium concentration factors of 7.6–18.9× and recoveries of 22–74% for varying dilute lithium feed streams and operating conditions. The corresponding process model was used to assess DD performance for continuous pilot-scale concentrations of a representative lithium extraction eluate stream. Model outputs demonstrate that DD achieves comparable lithium concentration and recovery targets with similar or lower membrane area requirements compared to reverse osmosis and electrodialysis processes, respectively. A sensitivity analysis reveals the relative importance of key parameters in ion-exchange membrane design for improving DD performance (water content > charge content ≈ membrane thickness ≈ water permeability). The development of alkaline- and scaling-resistant cation exchange membranes has also been identified as a target material improvement to expand the solution compatibility limits of the DD process.