Novel PVA–silica nanocomposite membrane for pervaporative dehydration of ethylene glycol aqueous solution

To effectively suppress the swelling of poly(vinyl alcohol) (PVA) membrane, polymer–inorganic nanocomposite membranes composed of PVA and γ-mercaptopropyltrimethoxysilane (MPTMS) were prepared by in situ sol–gel technique for pervaporative separation of water–ethylene glycol (EG) mixtures. Effects of the types of catalyst for sol–gel process and MPTMS content on the physical and chemical structure of PVA–silica nanocomposite membranes (designated as PVA–MPTMS hereafter) were investigated by 29Si NMR, FTIR, SEM, XRD and TGA–DTA. Due to the formation of more compact crosslinked structure, nanocomposite membranes exhibited enhanced thermal stability. It was found that when 50 wt% of MPTMS was incorporated into PVA, the nanocomposite membranes possessed optimum pervaporation performance for 80 wt% EG aqueous solution at 70 °C. Unexpectedly, there was no improvement in the pervaporation performance of PVA–MPTMS nanocomposite membranes after mercapto group was oxidized into sulfonic group.