Enhanced dehydration performance of hybrid membranes by incorporating fillers with hydrophilic-hydrophobic regions

Abstract

In this study, sulfonated pitch (SP), composed of hydrophilic sulfonate groups and hydrophobic polycyclic aromatic hydrocarbons, was incorporated into sodium alginate (SA) membranes for ethanol dehydration via pervaporation. The morphologies and structures of the SP and hybrid membranes were confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), positron annihilation lifetime spectroscopy (PALS) and water contact angle measurement. Hydrophilic sulfonate groups in SP formed hydrophilic regions which can bind water molecules, ensuring sufficient water occupancy in the membranes, while the hydrophobic polycyclic aromatic hydrocarbons provided continuous transport “highways” for the water molecules. Meanwhile, the introduction of SP created more polymer-filler interface cavities, rendering the membrane with suitable free volume property for separation. Consequently, the membrane demonstrated a maximum permeation flux of 1879 ± 80 g/m2 h coupled with an optimal separation factor of 1913 ± 69 in separating 90 wt% ethanol aqueous solution. These resulted in an increase over the SA control membrane of 1.5-fold and 4-fold respectively. Moreover, the hybrid membranes exhibited good operation stability. The results suggested that incorporating fillers with hydrophilic-hydrophobic regions in the membranes can be an effective strategy to improve the performance of water-permselective membranes.