Effect of Alcohol as Additives on the Morphology and Separation Performance of Polyethersulfone (PES) Hollow Fiber Ultrafiltration Membranes

Abstract

Hollow fiber ultrafiltration (UF) membranes were prepared usingPolyethersulfone (PES), alcohol (n-Propanol) as additive and N, N-dimethylacetamide(DMAc) as a solvent. Asymmetric hollow fiber UF membranes were spun by wet phaseinversion method from 17 wt% solids of PES/additive/NMP solutions. The alcoholadditive was n-Propanol while the external coagulant was water. Effects of n-Propanolconcentrations in the dope solution on morphology and separation performance of PEShollow fiber UF membranes were investigated. UF membranes were characterized interms of scanning electron microscope (SEM) while UF experiments were conductedusing polyethylene glycol (PEG20,000MW) and poly (vinyl pyrrolidone) (PVP40,000MW), as a solute. It was found that the PES UF membrane morphology changedfrom long two finger-like structure through a short two finger-like structure to the twovoid-like structure as n-propanol concentration in the dope solution increased from 5 to20 wt % using water as a bore fluid; pure water permeation fluxes (PWP) increased from47 to 201 L/m2.h.bar while rejections of PEG MW20,000 and PVP MW40,000 for wetspunPES hollow fiber membranes were decreased with the increasing of n-propanolconcentration up to 20%. Using above method, PES hollow fiber UF membrane withhigh pure water permeation flux could be prepared while the molecular weight cut-off ofPES hollow fiber membranes is approximately 20,000.