Selective separation of water–ethanol mixture through synthetic polymer membranes having carboxylic acid as a functional group

Separation of water–ethanol mixture through a membrane was carried out by pervaporation using a membrane which provided a hydrogen‐bonding interaction. A membrane obtained from poly(acrylic acid‐co‐acrylonitrile) was effective for a selective separation of water from aqueous ethanol solution by pervaporation technique. Spectroscopic and flux analyses verified that this high selectivity toward water was attributed to the hydrogen‐bonding interaction between water and acrylic acid (carboxylic acid) unit in the membrane. On the other hand, a membrane from poly(acrylic acid‐co‐styrene) preferentially permeated ethanol in the low water feed concentration region.