Multilayered ion-imprinted membranes with high selectivity towards Li ⁺ based on the synergistic effect of 12-crown-4 and polyether sulfone

High-selective multilayered Li ⁺ -imprinted membranes (Li-IIMs) with enhanced hydrophilicity and stability were developed based on polyether sulfone substrate membranes. The multilayered structure was prepared with polydopamine (pDA) as the interfacial adhesion layer, SiO ₂ nanoparticles as the hydrophilic layer and Li ⁺ -imprinted polymers as the imprinted layer. The selective “Li ⁺ -recognition sites” were formed using 12-crown-4 (12C4) as the adsorbing units. The optimal relative selectivity coefficients (α) of Li ⁺ /Na ⁺ and Li ⁺ /K ⁺ reached up to 1.85 and 2.07 with the imprinting factor (β) of 2.51, and the high permselectivity factors (γ) of Na ⁺ /Li ⁺ (7.39) and K ⁺ /Li ⁺ (9.86) were achieved on Li-IIMs. The Langmuir isotherm model and the pseudo-second-order kinetics model best fitted the rebinding data of Li-IIMs, as well as the rebinding capacities reached up to 90.3% of initial binding after 5 cycles of adsorption/desorption and just declined to 88.1% after another 5 cycles a month later. Therefore, the as-prepared Li-IIMs would have potential applications for the separation of lithium ions from salt lake brines.