Unusual trend of increasing selectivity and decreasing flux with decreasing thickness in pervaporation separation of ethanol/water mixtures using sodium alginate blend membranes

► Mechanically stable sodium alginate based membrane with high flux and selectivity. ► Reduced relaxational effects through control of glass composition of membrane. ► Increased selectivity of membrane as thickness decreases. ► Increased crosslinking of membrane polymer as thickness decreases due to longer periods of solvent evaporation. ► Results in increased hydrophobicity of membrane as thickness decreases which explains improved selectivity.