Background: Bioethanol as a renewable energy resource plays an important role in alleviating energy crisis and environmental protection. Pervaporation has achieved increasing attention because of its potential to be a useful way to separate ethanol from the biomass fermentation process. Results: This overview of ethanol separation via pervaporation primarily concentrates on transport mechanisms, fabrication methods, and membrane materials. The research and development of polymeric, inorganic, and mixed matrix membranes are reviewed from the perspective of membrane materials as well as modification methods. The recovery performance of the existing pervaporation membranes for ethanol solutions is compared, and the approaches to further improve the pervaporation performance are also discussed. Conclusions: Overall, exploring the possibility and limitation of the separation performance of PV membranes for ethanol extraction is a long-standing topic. Collectively, the quest is to break the trade-off between membrane permeability and selectivity. Based on the facilitated transport mechanism, further exploration of ethanol-selective membranes may focus on constructing a well-designed microstructure, providing active sites for facilitating the fast transport of ethanol molecules, hence achieving both high selectivity and permeability simultaneously. Finally, it is expected that more and more successful research could be realized into commercial products and this separation process will be deployed in industrial practices in the near future. Graphical

In order to improve separation performance of pervaporation membranes, we explored, for the first time, using tree bark biochar (BB) as filler for preparing polydimethylsiloxane (PDMS) composite membranes to separate ethanol from water. The composite membranes prepared by adding BB fillers obtained from different temperatures had different pervaporation performances. It was found that the addition of the three types of modified BB particles could all significantly improve pervaporation performance of the composite membranes. However their effects on permeation flux and separation factor were varied. Compared to BB obtained at 300 °C and 900 °C, BB obtained at 600 °C resulted in the membrane with the highest pervaporation performance with a separation factor of 9.92 and a permeation flux of 219.20 g m⁻² h⁻¹ at 40 °C in 10% ethanol solution. This study demonstrates the promise of biochar as a novel type of biomass-derived nanoparticles suitable for applications in pervaporation separation membranes.

In this article, response surface methodology was used to optimize the preparation conditions of fumed silica filled polydimethylsiloxane/cellulose acetate composite membranes. The silica loading, polydimethylsiloxane concentration, and NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio were considered as factors. Two regression equations, which described the effects of the three factors on the permeation flux and selectivity of the membranes, were derived from the results of 20 experiments by using a statistical software Design-Expert 7.1.4. The results revealed that the three factors had important effects on the permeation flux and the selectivity. The obtained regression equations were confirmed with another four groups of experiments. According to the regression equations, for the separation of an ethanol aqueous solution with the concentration of 10 wt%, the maximum selectivity of the membrane, 11.5 could be obtained at the feed temperature of 40°C, and the corresponding permeation flux was 197.3 g · m⁻² · h⁻¹. The preparation conditions for making the composite membrane with the above separation performances were: the silica loading was 5.21 wt%, the polydimethylsiloxane concentration was 13.36 wt%, and the NH₂-C₃H₆-Si(OC₂H₅)₃/silica weight ratio was 0.59.

In this work, polydimethylsiloxane (PDMS) polymeric membranes were fabricated by incorporating fumed silica nanoparticles which were functionalized with two silane coupling agents—NH₂(CH₂)₃Si(OC₂H₅)₃(APTS) and NH₂(CH₂)₂NH(CH₂)₃Si(OC₂H₅)₃(TSED)—for selective removal of ethanol from aqueous solutions via pervaporation. It was demonstrated that large agglomerates were not observed indicating the uniform distribution of modified silica throughout the PDMS matrices. It is noted that the ethanol diffusivity and the water contact angles were both increased remarkably, being beneficial to the preferential permeation of ethanol through the membranes. The pervaporation results showed that the addition of the two types of modified silica nanoparticles dramatically enhanced both the permeability and selectivity of hybrid membranes. Compared to APTS, silica modified by TSED at the concentration of 4 wt. % resulted in the optimum pervaporation membranes with the maximum separation factor of 12.09 and the corresponding permeation flux of approximately 234.0 g·m⁻²·h⁻¹in a binary aqueous mixture at 40°C containing 10 wt. % ethanol. The observation will benefit the choice of coupling agents to improve the compatibility between hydrophilic fillers and hydrophobic polymers in preparing mixed matrix membranes.