Surfactant-interlayer assisted interfacial polymerization for constructing Janus nanofiltration membranes: Enhanced Li+/Mg2+ separation efficiency

Nanofiltration (NF) technology shows significant potential for lithium extraction, but the limited Mg 2+ rejection of conventional negatively charged NF membranes constrains Li + /Mg 2+ selectivity. This work proposed a surfactant-interlayer assisted interfacial polymerization (SIAIP) methodology to convert a traditional NF membrane into a Janus membrane featuring dual-electrical properties. Sodium dodecyl sulfate (SDS) restricted the IP reaction region and modulated the interfacial diffusion behavior of amine monomers. The hydrophilic and negatively charged hyaluronic acid (HA) interlayer modified the substrate, enhancing membrane permeability. Under the combined influence of SDS and HA, more amine monomers were stored and diffused to the reaction interface, transforming the membrane surface into a positively charged region and forming a Janus structure with the negatively charged interlayer. The optimal SIAIP membranes possessed a homogeneous pore size distribution, with a high selectivity (S Li, Mg ) of 42.15 and superb permeability of 11.06 L m −2 h −1 bar −1 . This investigation furnishes an innovative approach for developing high-efficiency Li + /Mg 2+ separating NF membranes. • A surfactant-interlayer assisted interfacial polymerization (SIAIP) strategy was proposed to construct Janus membranes. • SDS restricted the IP reaction region, and the negatively charged HA interlayer modulated amine monomer release rate. • The SIAIP membranes exhibited a high S Li, Mg of 42.15 and excellent permeability of 11.06 L m −2 h −1 bar −1 .