Development and Evaluation of Filtration Performance of ZnO-Doped PEI Composite Membranes

Polyetherimide (PEI)-based membranes were fabricated by phase inversion to examine the effects of zinc oxide (ZnO) nanoparticles and polyvinylpyrrolidone (PVP) on membrane structure, wettability, permeation, and fouling behavior. Six formulations comprising neat PEI, PEI/PVP, two ZnO loadings (0.5 and 1 wt.%), and the corresponding PVP/ZnO combinations were characterized by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), casting-solution viscosity, contact angle, water content, gravimetric porosity estimation, effective pore-radius estimation, and sequential distilled-water/lake-water filtration. The additives produced marked but non-monotonic changes in solution viscosity, morphology, and surface wettability. PEI/PVP/ZnO-0.5 exhibited the lowest contact angle (approximately 35°), whereas PEI/PVP/ZnO-1 showed the smallest lake-water flux decline and the lowest total (approximately 4%) and irreversible (approximately 1%) fouling ratios. The results indicate that the effects of ZnO loading depend strongly on the presence of PVP and that wettability alone does not explain the observed fouling response. Under the present short-term filtration conditions, PEI/PVP/ZnO-1 provided the most favorable antifouling performance among the formulations tested.