Tailoring polyamide membranes via dynamic interfacial manipulation with functional Fe₃O₄ nanoparticles for elevated Nanofiltration performance

This study investigates the enhancement of thin-film-composite polyamide (TFC-PA) membranes for nanofiltration (NF) by conducting direct interfacial polymerization (IP) at a substrate-free water/n-hexane interface. Fe₃O₄ nanoparticles, stabilized with surfactants sodium laurate (SL) and hexadecyltrimethylammonium bromide (CTAB), were employed to dynamically influence the diffusion of piperazine (PIP) monomers. The incorporation of these nanoparticles enabled the modulation of the IP process, yielding membranes with distinct morphologies and performance characteristics. Specifically, membranes with SL-stabilized Fe₃O₄ (SLF) demonstrated enhanced cross-linking and superior salt rejection capabilities for divalent cations, with MgCl₂ and CaCl₂ rejection rates notably increasing to 95.5 % and 93.4 % respectively. Conversely, CTAB-stabilized Fe₃O₄ (CTABF) membranes, characterized by smoother surfaces and a looser structure, exhibited increases in water permeance up to 140 % relative to controls, but with a significant reduction in salt rejection efficacy as nanoparticle concentration increased. This study highlights the crucial impact of surfactant-stabilized nanoparticle modifications in manipulating the IP process and tailoring the filtration properties of PA membranes, offering promising avenues for optimizing NF membrane technology.