Pervaporation membranes were produced comprising a 4:1 sodium-alginate:poly(vinyl-alcohol) polymer
blend selective layer with a plasticizing agent (glycerol). Membranes were supported on a poly(acrylonitrile)
mesoporous support layer and non-woven fabric base. Pervaporation separation of ethanol/water
mixtures was carefully followed as a function of film thickness and time. It was found, contrary to what
might be expected from literature, that these films showed increased selectivity and decreased flux as
film thickness was reduced. It is argued that the morphology and structure of the polymer blend changes
with thickness and that these structural changes define the efficiency of the separation in these
conditions.