Embedding of FeOOH nanorods in the fabrication of a thin film nanocomposite (TFN) membrane for enhanced desalination

Abstract

The phase (aqueous versus organic) in which FeOOH nanorods are dispersed during interfacial polymerization critically governs the structure and performance of thin-film nanocomposite (TFN) reverse osmosis (RO) membranes. Embedding inorganic nanoporous materials into thin-film nanocomposite (TFN) membranes has emerged as a promising route to alleviate the inherent permeability–selectivity balance and durability constraints of RO membranes. A critical yet underexplored factor is the dispersion phase of nanomaterials during interfacial polymerization, which governs interfacial properties and, consequently, the membrane structure and performance. Here, cost-effective FeOOH nanorods were introduced into TFN membranes via dispersion in either the aqueous (TFN-A) or organic (TFN-O) phase. By modulating interfacial tension and stability, FeOOH nanorods altered the physicochemical structure of the polyamide layer, leading to increased crosslinking density, enhanced hydrophilicity, and distinct morphological features. Both TFN-A and TFN-O membranes exhibited superior desalination, mechanical, and chemical stability compared to the pristine thin-film composite (TFC) membrane. In particular, the TFN-A membrane achieved a 355.7% increase in water flux with minimal flux decline under pressure, while the TFN-O membrane maintained NaCl rejection with only a 2.0% reduction after exposure to 10 000 ppm h chlorine. These findings highlight how FeOOH nanorods regulate interfacial properties to tailor the polyamide structure, offering new design strategies for integrating hydrophilic nanoporous materials into high-performance RO membranes.