Incorporation of Multiwalled Carbon Nanotubes into Poly(vinyl alcohol) Membranes for Use in the Pervaporation of Water/Ethanol Mixtures

Multiwalled carbon nanotube (MWNT)/poly (vinyl alcohol) (PVA) blend membranes were prepared by the solution-casting method to determine the effect of MWNTs with nanoscale empty inner space along the tube length on the pervaporation performance of a PVA membrane in the separation of alcohol/water mixtures. The blend membranes were then characterized with several analytical methods such as transmission electron microscopy, differential scanning calorimetry, and X-ray diffractometry: Transmission electron microscopy showed that the MWNTs were homogeneously distributed through the PVA matrix. The glass-transition temperature of the PVA membrane was increased from 69.21 to 78.53 degrees C via blending with MWNTs. The crystallinity of the PVA matrix decreased with increasing MWNTs up to 5 wt % from 41 to 36%. The pervaporation properties of the blend membranes were completely different from those of the pure PVA membrane in the separation of water/ethanol mixtures. The flux of the membrane was increased with the amount of MWNTs, whereas the separation factor was maintained up to 1.0 wt % MWNTs. However, beyond that, it was reduced. These results Suggested that two factors, the crystallinity of the membrane and the diameters of the MWNTs, affected the performance of the membranes. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2186-2193, 2009