Ternary PES/CNC–ZnO nanocomposite ultrafiltration membrane with enhanced hydrophilicity and antifouling properties for methylene blue removal

In this study, a novel sustainable membrane material that integrates adsorption and filtration was developed to treat dye-polluted wastewater. The membrane, a ternary nanocomposite ultrafiltration membrane, was fabricated via non-solvent induced phase inversion by incorporating zinc oxide-functionalized cellulose nanocrystals (CNC-ZnO) into a polyethersulfone (PES) matrix. The resulting PES/CNC-ZnO membrane was characterized using SEM, FTIR, water contact angle, porosity, water uptake, and mechanical analyses. The PES/CNC-ZnO membrane exhibited a highly asymmetric, sponge-like porous cross-section with suppressed macrovoid formation. Surface hydrophilicity increased substantially, with the water contact angle decreasing from 92.4° (pristine PES) to 55.9°. Mechanical properties (tensile strength and elongation at break) improved synergistically, surpassing both pristine PES and binary PES/CNC or PES/ZnO membranes. Pure water flux was 72 L m -2 h -1 at 2 bar, nearly six times that of pristine PES. Hydraulic resistance decreased accordingly, with the PES/CNC-ZnO membrane showing the lowest resistance among all formulations. The ternary membrane achieved a flux recovery ratio of approximately 88% after the first cycle and >60% after the third cycle. Fouling resistance analysis revealed a total fouling ratio of 68.2% but a remarkably low irreversible fouling ratio of only 12.1%, indicating that most fouling was reversible. The hybrid CNC-ZnO scaffold imparts superior hydrophilicity, mechanical reinforcement, and fouling reversibility, making the PES/CNC-ZnO membrane a promising adsorptive ultrafiltration platform for the removal of cationic dyes from water. This study demonstrates that the synergistic combination of CNC and ZnO within a PES matrix transforms irreversible fouling into predominantly reversible fouling, providing a sustainable adsorptive ultrafiltration platform for cationic dye removal.