Novel polyelectrolyte complex membranes containing free sulfate groups with improved pervaporation dehydration of ethanol

• Synthesis of novel PEC membranes containing free SO3 (PECSMs).
• Both ESD and sorption selectivity of PECSMs increase with SO3 groups content.
• PECSMs containing free SO3 groups exhibit a good pervaporation performance.

Novel polyelectrolyte complexes containing free sulfate (SO3) groups (PECSs) were synthesized, with the sulfation of NH2 groups in the soluble chitosan (CS)/sodium carboxymethyl cellulose (CMC) complexes, and their membranes (PECSMs) were subjected to pervaporation dehydration of ethanol. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the chemical structure and the composition of PECSs. Zeta (ξ) potential and field emission scanning electron microscopy were used to investigate the surface charge density of the PECS particles and the morphology of their membranes. The effects of the chemical composition on the swelling degree, the hydrophilic property, and the pervaporation dehydration performance of PECSMs were determined. It was found that free SO3 groups were successfully incorporated into PECSMs. Both the flux and the separation factor of PECSMs increased with increasing SO3 groups. The permeation flux of PECSMs increased, and their selectivity was almost invariable with increasing temperature. A high separation performance of PECSMs was achieved in the dehydration of 10 wt% water–ethanol mixtures at 70 °C, yielding a flux and a separation factor for the PECSM-20 at 1385 g/m2 h and 1571, respectively. These results indicated that the introduction of free SO3 groups into PECSMs was an effective strategy to improve the pervaporation dehydration performance of PECSMs.