Modification of Asymmetric Polysulfone Membrane Surfaces using Mixed Ar/O2 Plasma Technique

Abstract

Asymmetric polysulfone (PSF) membranes for gas separation were prepared via dry-wet phase inversion technique at different conditions such as coagulation bath temperature (CBT) and evaporation time (ET). The thickness of the dense layer that plays an important role on gas selectivity has been investigated by adjusting CBT and ET. Additionally, membranes were treated with mixed Ar/O2 DC glow discharge plasma in order to modify membrane wettability, surface roughness, and functional groups on the membrane surface. Scanning electron microscopy (SEM) was used to illustrate a cross sectional structure of PSF membranes. Hydrophilic properties of the membrane surfaces were analyzed via water contact angle (WCA) and surface energy measurements. Morphological structures of membrane surfaces, roughness and creation of functional groups were analyzed both before and after plasma treatment by atomic force microscopy and Fourier transform infrared spectroscopy, respectively. Experimental results show that CBT and ET can change porous voids size of the supporting layer and the dense layer thickness underneath of the membrane surface, while a mixed Ar/O2 gas plasma treatment can enhance hydrophilic properties of the asymmetric PSF membrane surfaces.