Interfacial Engineering of PES Mixed Matrix Membranes Using Green-Synthesized ZnO Nanoparticles for Enhanced Water Transport, Selectivity, and Antifouling Performance

Abstract

The incorporation of functional nanofillers into polymeric membranes offers a powerful pathway to overcome the inherent permeability–selectivity trade-off and fouling limitations of conventional mixed matrix membranes (MMMs). However, achieving uniform nanofiller dispersion while preserving membrane structural integrity and transport selectivity remains a critical challenge. In this study, green-synthesized zinc oxide nanoparticles (ZnONPs), produced using Calotropis gigantea leaf extract, were incorporated into polyethersulfone (PES) membranes via phase inversion to systematically engineer membrane interfacial properties and transport pathways. Structural and physicochemical characterization confirmed successful nanoparticle incorporation and revealed that ZnONPs significantly modified membrane hydrophilicity, pore architecture, and surface charge characteristics. The improved performance is attributed to nanoparticle induced acceleration of solvent–non-solvent exchange during phase inversion, resulting in enhanced pore connectivity, increased surface hydrophilicity, and optimized selective layer formation. Furthermore, the modified membranes demonstrated substantially improved antifouling behavior due to the formation of stable hydration layers and reduced foulant adhesion. These results demonstrate that green-synthesized ZnONPs can serve as effective interfacial modifiers to simultaneously enhance membrane permeability, selectivity, and fouling resistance, providing a sustainable and scalable strategy for advancing high-performance polymeric membranes for water purification