Preparation and characterization of chitosan-poly (vinyl alcohol)/polyvinylidene fluoride hollow fiber composite membranes for pervaporation dehydration of isopropanol

A new hollow fiber composite membrane of chitosan-poly (vinyl alcohol)/polyvinylidene fluoride (CS-PVA/PVDF) was prepared by casting the solution of CS and PVA on PVDF hollow fiber support for pervaporation dehydration of isopropanol. The composite membranes were crosslinked with glutaraldehyde (GA) and sulfuric acid. The microstructure and physicochemical properties of the membranes were characterized by scanning electron microscope (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetry (TG) and contact angle measurements. Results from SEM images showed that dense separation layers were successfully coated onto the supports, and the ATR-FTIR results showed that GA had crosslinked the composite membranes. Results of TG and contact angle showed the thermostability of membranes increased and the hydrophilicity decreased after blending CS and PVA. The swelling degree of composite membranes increased with increasing CS content and water content. Effects of the content of CS and GA in solution on membrane separation performance were investigated. The pervaporation experiments for dehydration of isopropanol showed that the membrane with 60 wt% CS and 0.1 wt% GA had a good separation performance. The permeate flux was 306 g/(m²·h) and the separation factor was 2140 for the feed solution containing 90% isopropanol at 60 °C. When the water content increased from 3 wt% to 15 wt%, the permeate flux increased from 207 g/(m²·h) to 346 g/(m²·h) while the separation factor decreased from 2406 to 1876. The separation factor and permeation flux increased with feed temperature.