Mixed matrix membranes (MMMs) for ethanol purification through pervaporation: current state of the art

Over the last few decades, different polymers have been employed as materials in membrane preparation for pervaporation (PV) application, which are currently used in the preparation of mixed matrix membranes (MMMs) for ethanol recovery and ethanol dehydration. The ethanol-water and water-ethanol mixtures are, in fact, the most studied PV systems since the bioethanol production is strongly increasing its demand. The present review focuses on the current state of the art and future trends on ethanol purification by using MMMs in PV. A particular emphasis will, therefore, be placed on the enhancement of specific components transport and selectivity through the incorporation of inorganic materials into polymeric membranes, mentioning key principles on suitable filler selection for a synergistic effect toward such separations. In addition, the following topics will be discussed: (i) the generalities of PV, including the theoretical aspects and its role in separation; (ii) a general overview of the methodologies for the preparation of MMMs; and (iii) the most recent findings based on MMMs for both ethanol recovery and ethanol dehydration for better evolution in the field. From the last decade of literature inputs, the poly(vinyl alcohol) has been the most used polymeric matrix targeting ethanol dehydration, while the zeolites have been the most used embedded materials. Today, the latest developments on MMM preparation declare that the future efforts will be directed to the chemical modification of polymeric materials as well as the incorporation of novel fillers or enhancing the existing ones through chemical modification.