Facile design of a crown ether-functionalized polymeric membrane for highly efficient lithium and magnesium separation during electrodialysis

Efficient separation of magnesium and lithium is essential for the extraction of lithium resources from salt-lake brines. However, the current membrane separation technologies are challenged by the membrane permeability-selectivity trade-off. Herein, we demonstrated a facile and practical approach to fabricate crown ether-functionalized polymeric membranes with excellent Li⁺/Mg²⁺ separation performance by incorporating 12-crown-4 rings into the cellulose triacetate polymer network. The tightly and regularly arranged polymer chains anchored the crown ether rings firmly in the membrane structure, thereby facilitating the formation of stable and highly selective cation transport channels inside the membrane. As a result, the prepared membrane achieved an ultrahigh Li⁺/Mg²⁺ separation factor of ∼872 and Li⁺ flux of 22.6 μmol m⁻² s⁻¹, which was much superior to that of commercial CIMS and reported membrane separation technologies. The good long-term stability of the fabricated membrane is promising for achieving efficient magnesium-lithium separation in large-scale industrial applications.