Informing Ion-Exchange\nMembrane Design Targets for\nDonnan Dialysis-Mediated Lithium Brine Concentration

We assess the potential of a Donnan dialysis (DD) process\nfor lithium\nbrine concentration and prioritize material design opportunities from\na use-informed perspective. Bench-scale batch experiments were used\nto validate a kinetic process model, achieving lithium concentration\nfactors of 7.6–18.9× and recoveries of 22–74% for\nvarying dilute lithium feed streams and operating conditions. The\ncorresponding process model was used to assess DD performance for\ncontinuous pilot-scale concentrations of a representative lithium\nextraction eluate stream. Model outputs demonstrate that DD achieves\ncomparable lithium concentration and recovery targets with similar\nor lower membrane area requirements compared to reverse osmosis and\nelectrodialysis processes, respectively. A sensitivity analysis reveals\nthe relative importance of key parameters in ion-exchange membrane\ndesign for improving DD performance (water content > charge content\n≈ membrane thickness ≈ water permeability). The development\nof alkaline- and scaling-resistant cation exchange membranes has also\nbeen identified as a target material improvement to expand the solution\ncompatibility limits of the DD process.