Layer-by-layer of graphene oxide-chitosan assembly on PVA membrane surface for the pervaporation separation of water-isopropanol mixtures

摘要

A graphene oxide/chitosan polyelectrolyte layer was used to modify the surface of a polyvinyl alcohol/tetraethyl orthosilicate membrane by layer-by-layer interfacial complexation and, thus, improve the pervaporation characteristics. The interfacial complexation between the chitosan and graphene oxide was confirmed by Fourier-transform infrared and X-ray photoelectron spectroscopy; the changes in surface hydrophilicity after layer-by-layer modification were examined by contact angle measurements, and the morphology of the layer-by-layer membrane was elucidated by field-emission scanning electron microscopy analysis. The pervaporation performance of the modified membranes was evaluated by performing the separation of water-isopropanol (IPA) azeotropes under different operating conditions. In the pervaporation experiments, the best performance was obtained using a membrane with 15 chitosan-GO layers (denoted 15L-L(CH-GO)). For this membrane, the flux increased from 13.6 to 76.4 g/m(2)h and the separation factor decreased from 56,720 to 4,001 as the feed temperature was varied from 30 to 60 degrees C for an 80: 20 (w/w) IPA/water feed. The apparent permeation activation energies were calculated and that of IPA (122.8 kJ/mol) was greater than that of water (47.4 kJ/mol).