Novel graphite-filled PVA/CS hybrid membrane for pervaporation of benzene/cyclohexane mixtures

Novel kind of hybrid membrane was prepared by filling carbon graphite (CG) into poly (vinyl alcohol) (PVA) and chitosan (CS) blending mixture, in hopes of improving the separation performance of the membranes by the synergistic effect of blending and filling. The membranes were characterized through SEM, FTIR, XRD, DMA and PALS. The results showed homogenous distribution of graphite particles, considerable alteration of hydrogen bonding interaction, remarkable decrease of crystallinity degree, dramatic enhancement of mechanical properties and significant increase of free volume in CG-PVA/CS hybrid membranes. Sorption studies indicated that the degree of swelling of CG-PVA/CS hybrid membranes increased with graphite content increasing and the separation factor of benzene/cyclohexane was dominated by solubility selectivity rather than diffusivity selectivity. The concentration-averaged diffusion coefficients of benzene were larger than those of cyclohexane in all CG-PVA/CS hybrid membranes with different graphite loading. The pervaporation properties of CG-PVA/CS hybrid membranes for separation of benzene/cyclohexane mixtures were investigated through varying graphite content and mass ratio of PVA to chitosan in hybrid membranes. Higher permeation flux and separation factor of CG-PVA/CS hybrid membranes were desirably obtained, comparing to PVA and PVA/CS membranes. In particular, CG06-PVA60/CS40 membrane exhibited the highest separation factor of 59.8 with a permeation flux of 124.2 g/(m2 h) at 323 K, 1 KPa.