Strategy for scale-up of SBS pervaporation membranes for ethanol recovery from diluted aqueous solutions

Ethanol is considered a green alternative to fossil fuels. Pervaporation (PV) is claimed to be an economical separation technique for ethanol recovery from fermentation broths. In this study, styrene-butadienestyrene (SBS) dense symmetric flat membranes were first prepared by solvent evaporation technique and applied for the pervaporative removal of ethanol from aqueous solutions. The results were compared with the performances of composite membranes made of SBS coated on a highly porous support of Fluoroplast F-42. In this case, an intermediate layer of PDMS (poly dimethyl siloxane) or PU (poly urethane) was used to improve the membrane performances. The results clearly evidenced the role of the intermediate layer (PU or PDMS) in improving the EtOH/H2O selectivity of the composite flat membranes in comparison to pure flat SBS membrane. Composite membranes were scaled-up in spiral-wound modules configuration and tested for the PV application of interest. A further increase in ethanol selectivity was observed (S.F.≈8) showing the superior performances of spiral wound modules with respect to their analogous membranes in flat sheet configuration. In all the PV tests carried out, the effect of ethanol concentration and feed temperature was investigated for each type of membrane.