Pervaporation performance of unfilled and filled PDMS membranes and novel SBS membranes for the removal of toluene from diluted aqueous solutions

In this study, the influence of downstream pressure on the pervaporative removal of toluene from water was investigated. An unfilled and CBV 3002-filled PDMS membranes were compared with novel dense and porous SBS membranes. Experiments were performed by varying the downstream pressure from 1 to 40 mbar. The effect of fillers incorporation into the polymeric network of PDMS-based membranes was also studied. It was found that the performance factors of all examined membranes were dependent on downstream pressure. Both the water and toluene flux decreased with increasing downstream pressure, the former being more pronounced, resulting in increased membrane separation factors. Moreover, the partial fluxes of all examined membranes were linearly dependent on the vapor pressure difference between permeate and feed. From the analysis of the intrinsic membrane properties it was found that toluene sorption was enhanced at higher downstream pressures. This resulted in membrane swelling, and hence higher water permeability than expected; nevertheless increased the membrane selectivity. Incorporation of the CBV 3002 fillers into the PDMS network enhanced both toluene removal rate and separation performance as well as intrinsic membrane properties. For the porous SBS membrane the highest toluene flux and permeability was obtained, but the lowest separation efficiency. The dense SBS membrane showed similar separation factors as the PDMS-based membranes, although a significantly higher toluene removal rate was observed.