Ultrathin nanofiltration membrane based on MXene interlayer for efficient Li+/Mg2+ separation

Nanofiltration (NF) membranes with sub-nano structure are promising for the extraction of lithium from brine resources, yet often face a trade-off between separation efficiency and permeation rate. Here, the ultrathin nanocomposite membranes (TFN AM ) with high Li + /Mg 2+ selectivity and permeability are prepared by introducing the positive aminated-MXene interlayer in the process of interfacial polymerization (IP). This interlayer modulates the diffusion behavior of amine monomers and reduces the thickness of the polyamide (PA) layer by six times; meantime, it provides excellent positive charge on the membrane surface. The aminated-MXene interlayer endows the high positive charge density of TFN AM enhancing the Donnan exclusion effect on the improvement of Li + /Mg 2+ selectivity. As a result, the TFN AM exhibits a high permeability of 12.5 L m −2 h −1 bar −1 and a Li + /Mg 2+ selectivity of 17.5, while maintaining performance over 100 h. This work proposes a facile and effective strategy to address the challenge of NF membrane limitations and advance lithium recovery technologies from brines.