Breaking through tradeoff of Polysulfone ultrafiltration membranes by zeolite 4A

•The tradeoff of Polysulfone ultrafiltration membrane was conquered by zeolite 4A.•The permeability was enhanced by fast flow paths in micro-channels.•The selectivity was kept high due to steric exclusion and Donnan effect.•The zeolite size must match the selective layer thickness.

Pressure-driven ultrafiltration by porous membrane often encountered a tradeoff between permeability and selectivity due to the transport mechanism based on pore dimension. This paper aims to break through the tradeoff of Polysulfone (PSf) ultrafiltration membranes by incorporating specific zeolite 4A. The influences of particle size, micro-channel dimension, zeta potential and content of zeolite 4A on tradeoff were discussed. The morphological evolution investigated by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) showed that zeolites 4A embedded in the selective layer within the depth of less than 1 μm increased the surface roughness and improved the hydrophilicity. Thermal and mechanical stability were also evaluated by thermal gravimetric analysis (TGA) and tensile testing respectively. The filtration experiments showed that both pure water flux and rejection were simultaneously improved due to the morphology regulation, abundant nano-scale water flow channels, negatively charged membrane surfaces and precise embedding position of zeolite 4A in the membrane selective layer.

Graphical abstractPolysulfone membranes (Pb-1, Pb-2 and Pb-3) doped with increasing zeolites 4A content showed increased pure water flux and rejection to pepsin and BSA simultaneously compared to control membranes (Pa-1, Pa-2 and Pa-3). The tradeoff between permeability and selectivity was sorted out by the embedding of zeolite 4A with abundant nano-scale water flow channels, negative charges in the membrane selective layer.Figure optionsDownload full-size imageDownload as PowerPoint slide