Nesting doll-inspired double-layered nanofiltration membranes for highly efficient PFAS removal and natural water purification

Tailoring the surface pleat morphology of polyamide nanofiltration (NF) membranes allows for targeted modulation of their performance, thereby optimizing membrane functionality for diverse application scenarios. This approach has emerged as a critical research direction in membrane technology, particularly industrial applications. In this study, the precise modulation of the polymerization rate, molecular diffusion behavior, and interfacial reaction kinetics was achieved by adding LiCl. By leveraging the synergistic effects of Li⁺ coordination with carbonyl groups and the interfacial thermal phenomena, a nesting-doll structure featuring multiple filtration interfaces was successfully engineered. This significantly enhances the separation efficiency of NF membranes. Consequently, the prepared NF membranes exhibit notable advantages in natural surface water treatment. Specifically, the uniquely designed nesting-doll membrane (PIP–Li@3) achieved 89.5 % and 95.9 % removal rates for dissolved organic carbon and fluorescent organics, respectively. The PIP-Li@3 demonstrated exceptional efficacy in treating complex and difficult-to-remove per- and polyfluoroalkyl substances. Compared to NF270, the PIP-Li@3 exhibits superior removal performance for PFAS of varying molecular weights, achieving a rejection rate of 98.4 % for perfluorooctanoic acid. This work presents a green and efficient method for removing PFAS from surface water by preparing NF membranes with a unique nesting-doll morphology by regulating the two-stage IP reaction rate.