The preparation of polyamide/polyacrylonitrile thin film composite hollow fiber membranes for dehydration of ethanol mixtures

In this study, Polyamide (PA)/polyacrylonitrile (PAN) thin-film composite (TFC) hollow fiber membranes were fabricated to investigate the dehydration performances of ethanol mixtures by pervaporation. Amine monomers (ethylenediamine (EDA), 1, 6-hexanediamine (HDA), diethylenetriamine (DETA), and tetraethylenepentamine (TEPA)) with difference number of functional groups or chain length were selected to react with trimesoyl chloride (TMC) to prepare a PA dense thin-film onto the surface of asymmetric PAN hollow fiber membranes by way of interfacial polymerization. Attenuated total reflection infrared spectroscopy (FTIR-ATR), scanning electron microscope (SEM), atomic force microscope (AFM), light transmission, contact angle and positron annihilation spectroscopy (PAS) were used to characterize the physicochemical properties, morphologies and microstructure of the PA thin layer. The pervaporation performances of aqueous ethanol solution showed the permeation flux decreased while water content in permeate increased with increasing number of amine groups. The effects of monomer concentration and reaction time on the pervaporation performances of aqueous ethanol solution through TEPA-TMC/PAN TFC hollow fiber membranes were also investigated. A 342.0 ± 22.3 g/m2 h permeation flux and 97.6 ± 0.3 wt.% water content in permeate were obtained for the pervaporation of 90 wt.% aqueous ethanol solution at 25 °C through the PA/PAN TFC hollow fiber membrane which was fabricated by immersing PAN hollow fiber membrane into 2 wt.% TEPA aqueous solution for 1 min and then contacting 1 wt.% TMC solution for 0.5 min.