Robust and water-selective natural-cellulose-nanofiber-reinforced polyvinyl alcohol composite membranes for pervaporation of isopropanol/water mixtures

Abstract

High-strength polyvinyl alcohol (PVA)–6-cellulose nanofiber (CNF) composite membranes for pervaporation separation of isopropanol (IPA)/water mixtures were produced using a solution casting method. Their morphological and physicochemical properties were evaluated using field emission scanning electron microscopy, atomic force microscopy, attenuated total reflection–Fourier-transform infrared spectroscopy, and X-ray diffraction. Upon the addition of various concentrations of CNF to PVA membranes, the tensile strengths of the PVA–CNF composite membranes increased with increasing CNF loading from 35.01 MPa for the pristine PVA membrane to 80.98 MPa for the membrane with an CNF loading of 10 wt% owing to the interactions between PVA and CNF. The effect of CNF loading was examined using pervaporation experiments, and the results indicated that the flux values of the membranes increased and their separation factors decreased with increasing CNF loading. The optimized membrane (PC-6 with a CNF loading of 6 wt%) presented stable pervaporation performance with a flux of 20-21 g/(m2h) and water content in the permeate of 20-21 g/m2h and 99.90±0.10 % after 120 h of operation at 40°C for a IPA/water feed of 85/15 (w/w). In summary, the high-strength water-selective PVA–CNF membranes fabricated in this study are promising for pervaporation separation of IPA/water mixtures.