Homogenous polyelectrolyte complex membranes incorporated with strong ion-pairs with high pervaporation performance for dehydration of ethanol

Solution-processable polyelectrolyte complexes (PECs) incorporated with both sulfate (OSO3) groups and carboxylic acid groups (COOH) were prepared from sulfated sodium carboxymethyl cellulose (SCMC) and poly(diallydimethylammonium chloride) (PDDA). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were utilized to characterize the chemical structures of SCMC and the compositions of SCMC/PDDA PECs. Membranes were made from PECs (SPECMs), and their surface properties were studied by field emission scanning electron microscopy and contact angle characterizations. Moreover, SPECMs were subjected to pervaporation dehydration of aqueous ethanol solution. Effects of SPECMs’ chemical compositions and operation conditions on pervaporation performance were studied and discussed in terms of membrane structures. It was found that OSO3 groups were incorporated into SPECMs in the form of sulfate–amine ion-pairs, and they improved both the selectivity and flux in the dehydration of aqueous ethanol solution. For instance, the flux and water content in permeate for SPECM-0.34 in dehydration of 10 wt% water–ethanol mixture at 70 °C were 1760 g m−2 h−1 and 98.7 wt%, respectively, both of which were much higher than those for pristine PEC membranes with no sulfate groups. Moreover, the high separation performance of SPECMs was stable and both the tensile strength and elongation at break increased with increasing strong ion-pairs content. For instance, the SPECM-0.34 tensile strength and elongation at break were 64.5 MPa and 9.33%.

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► Preparation of sulfated CMC and its complex membranes (SPECMs).
► ESD and sorption selectivity of SPECMs increase with OSO3 group content.
► SPECMs exhibit higher flux and selectivity than those for pristine PEC membranes.