Embedding of FeOOH Nanorods in the Fabrication of 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 TFN membranes has emerged as a promising route to alleviate the inherent permeability–selectivity trade off and durability constraints of conventional polyamide RO membranes. However, the role of the nanomaterial dispersion phase—a key factor regulating interfacial properties—remains underexplored. Here, cost effective FeOOH nanorods were incorporated into TFN membranes by dispersing them in either the aqueous (TFN A) or organic (TFN O) phase. The FeOOH nanorods modulated interfacial tension and stability, which in turn tailored 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 performance, mechanical strength, and chemical stability compared to the pristine thin film composite (TFC) membrane. Specifically, TFN A achieved a remarkable 355.7% increase in water flux with minimal flux decline under high pressure, while TFN O maintained NaCl rejection with only a 2.0% reduction after exposure to 10,000 ppm·h chlorine. These results not only demonstrate how FeOOH nanorods regulate interfacial properties to engineer polyamide structure, but also establish a phase-dependent tuning strategy for integrating hydrophilic nanoporous materials into high-performance RO membranes.