Tunable interlayer spacing of composite graphene oxide-framework membrane for acetic acid dehydration

Minute amount of poly(vinyl alcohol) (PVA) was used to cross-link graphene oxide (GO) nanosheets to prepare composite graphene oxide-framework (GOF) membranes with a nacre-like structure. The PVA provided additional increase in viscosity of GO suspension which made the solution casting of a large-area composite GOF membrane possible. The membranes were applied to separate an acetic acid-water mixture through pervaporation. The ATR-FTIR and XPS analyses confirmed the covalent bonding between GO and PVA as ether bonds were formed. This influenced the changes in water contact angle where it increased from 40.8 degrees (pristine GO) to 62.7 degrees (GO-PVA(8wt%)). X-ray diffraction showed that d-spacing of GOF was higher than GO due to the intercalation of PVA. The d-spacing of GO layer from dry to wet state has a difference of 2.59 angstrom but addition of PVA lowered the difference to 0.38 angstrom. The newly formed covalent bonds between GO and PVA might suppressed the stretching of d-spacing. It shows that the swelling was prevented and the interlayer spacing can be tuned. The composite GO-PVA(8wt%) membrane has a short d-spacing and provided an outstanding pervaporation performance at 80 degrees C with a permeation flux of 463.9 g m(-2) h(-1) and water concentration in permeate of 97.7%. (C) 2017 Elsevier Ltd. All rights reserved.