Morphology and Filtration Characteristics of a Polysulfone Hollow Fiber Membrane

Abstract

Polysulfone (PSF) hollow fiber membranes incorporating a asymmetric microstructures suitable for ultrafiltration, were fabricated using dry–wet phase inversion method. The optimized dope solution contained PSF (25 wt%), polyethylene glycol (PEG-400; 22 wt%), and polyvinylpyrrolidone (PVP-K90, Mw ≈ 1,300 kDa; 0.3 wt%) dissolved in N,N-dimethylacetamide (52.7 wt%). The extruded nascent fibers coagulated in deionized water to form membranes with a dense selective skin layer supported by a porous substructure. Fourier Transform Infrared Spectroscopy (FT-IR) analysis confirmed the presence of the characteristic sulfone functional groups, indicating the chemical stability of the PSF matrix. Scanning Electron Microscopy (SEM) revealed a well-defined lumen structure with a diameter of 1.09 ± 0.05 mm and a wall thickness of 0.20 ± 0.01 mm. The membrane cross-section showed distinct finger-like macrovoids. These extended throughout the structure, indicating effective phase inversion and stable morphology. The membrane exhibited a porosity of 48.8 ± 2.1% and a pure water permeance of 70 ± 5 L m⁻² h⁻¹ bar⁻¹. The evaluation of ultrafiltration performance was done using bovine serum albumin (BSA, Mw ≈ 66 kDa). The membrane showed a rejection rate of 95 ± 1% at 2 bar pressure. This confirms its effective size-exclusion capability. Compared with reported PSF flat-sheet membranes, the present hollow fiber configuration demonstrated a more favourable balance between permeability and selectivity, attributed to PEG-400-driven rapid demixing and PVP induced pore interconnectivity. These findings showcase the potential of this minimalist dualadditive formulation for scalable, high-performance PSF hollow fiber membranes in aqueous separation applications.