Thin and uniform polyamide membrane constructed via histidine-assisted hydrous-ZrO2 for efficient Li+/Mg2+ separation

Membrane separation technology serves as an essential approach for the efficient and sustainable extraction of lithium from salt-lake brines, whose effectiveness crucially depends on the selective Li + /Mg 2+ separation performance. However, conventional nanofiltration (NF) membranes remain constrained by the trade-off between water permeability and ion selectivity. In this study, we proposed a two-step fabrication strategy that couples solution deposition with interfacial polymerization (IP), successfully constructing a positively charged Zr-His/PTF composite NF membrane with a thin selective layer and uniform pore size. Hydrated zirconia clusters (hydrous-ZrO 2 ) derived from inorganic zirconium salts were utilized to regulate the distribution of reaction sites via electrostatic anchoring, while the amphipathic structure of histidine was employed to restrict the diffusion of aqueous monomers. These two components synergistically modulated the IP process, enabling the precise regulation of the selective layer microstructure while significantly reducing organic reagent consumption. Under a high Mg 2+ /Li + mass ratio of 30:1, the modified membrane achieved a synchronous enhancement in Li + /Mg 2+ separation selectivity (29.57) and water permeance (21.7 L·m −2 ·h −1 , 6 bar). Moreover, the membrane maintained stable separation performance and structural integrity across a wide Mg 2+ /Li + mass ratio range (1:1 to 100:1) and throughout 100 h of continuous operation. Through the integration of fabrication methods, this study provides a straightforward, low-cost and environmentally friendly strategy for fabricating high-performance NF membranes.