PFSA-g-ZIF-L/CS-PVA mixed-matrix membrane for pervaporation desalination

Abstract

In this work, perfluorosulfonic acid (PFSA)-g-ZIF-L nanocomposites were prepared by grafting PFSA onto NH2-Co/Zn-ZIF-L at different mass ratios via substitution reaction. A series of PFSA-g-ZIF-L/chitosan (CS)-polyvinyl alcohol (PVA) composite membranes were prepared by solution coating method using different contents of PFSA-g-ZIF-L nanocomposites as nanofillers and polyacrylonitrile (PAN) membrane as the substrate. PFSA-g-ZIF-L nanocomposites and PFSA-g-ZIF-L/CS-PVA membrane were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. The application of composite membrane for pervaporation desalination was explored. The incorporation of PFSA-g-ZIF-L into the polymers introduced more water transport channels and hydrophilic groups, which improved the separation performance of membrane. The PFSA-g-ZIF-L/CS-PVA composite membrane loaded with 5 wt% PFSA-g-ZIF-L (PFSA:ZIF-L mass ratio of 5:1) showed excellent structural stability under continuous pervaporation desalination for 55 h. The water flux was about 15.4 kg·m−2·h−1 (2.3 times higher than that of CS-PVA membrane), and the rejection was as high as 99.99 % at 35 °C for 3.5 wt% aqueous NaCl solution.