Nanofiltration membranes with fast water transport induced by controlled interfacial diffusion to enhance desalination and micropollutant removal

Abstract

Nanofiltration (NF) membranes offer tremendous potential in wastewater reuse, desalination, and resource recovery to alleviate water scarcity and environmental contamination. However, separating micropollutants and charged ions from wastewater while maintaining high water permeation remains challenging for conventional NF membranes. Customizing diffusion and interaction behavior of monomers at membrane-forming interfaces is promising for regulating interior pore structures and surface morphology properties for polyamide NF membranes, reaching efficient screening and retaining of solutes from water. In this work, photopolymerization occurred on two-phase interfaces of interfacial polymerization to modulate monomer diffusion toward reaction interfaces, accelerating reaction process and narrowing reaction area thus improving interior pore uniformity and free-volume regularity. Density distributions and interactive energies of monomers at the interface were explored to illustrate the effect of monomer diffusive behavior regulated by photopolymerization on membrane physicochemical properties and separation performance through molecular dynamics simulations. Pore size distributions were simulated to verify experimental results. Layers of nodules and rod-like structures appeared on the membrane surfaces. Membranes with interface photopolymerization exhibited a water permeability of 46.0 L·m⁻²·h⁻¹·bar⁻¹ more than five-fold that of the control, with improved monovalent and multivalent ions separation. Surface photopolymerized membranes with water permeation of 26.6 L·m⁻²·h⁻¹·bar⁻¹ (more than three times as high as the control) achieved excellent micropollutant and salt removal. This work provides a foundation for constructing NF membranes with specific separation functions for environmental applications.