Informing ion exchange membrane design targets for Donnan Dialysis-mediated lithium brine concentration

Combining experimental studies and computational modeling, 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 show that DD achieves lithium concentration factors of 7.6-18.9× and recoveries of 22-74% for dilute lithium feed streams. The corresponding process model was adapted to assess DD performance for continuous pilot-scale operation on a representative direct lithium extraction product stream. Model outputs demonstrate that DD achieves comparable lithium concentration and recovery targets with similar or lower membrane area requirements than reverse osmosis and electrodialysis processes, respectively. A sensitivity analysis reveals the relative importance of key parameters in ion exchange membrane design (water content > charge content ≈ membrane thickness ≈ water permeability). The development of alkaline- and scaling-resistant cation exchange membranes is identified as a target material improvement to expand the solution compatibility limits of the DD process.