The prospects of semi-crystalline poly(vinylidene fluoride) in biofuel separation via pervaporation: Membrane formation and fundamental studies

Abstract

The separation of acetone and ethanol binary mixture derived from the fermentation broth using pervaporation membranes is very challenging, most likely due to their small molecular size differences. In addition, the characteristics of acetone as a strong solvent which can easily swell and dissolve polymer materials, further increases the difficulty of separation. The present research adapted a mixed solvent system coupled with evaporation step prior to precipitation of the as-cast membrane in a coagulant bath to effectively suppress the formation of macrovoids and promote dense skin layer formation in PVDF membranes as compared to that of single solvent system. In addition, the porosity, pore size, crystalline phase as well as cell structure of membranes cast from mixed solvent systems can be further designed into the desired interconnected open cell structure rather than globular structure with weaker mechanical strengths by altering the membrane fabrication procedure. From the trade-off line of acetone/ethanol separation via pervaporation, it can be revealed that PVDF membranes cast from mixed solvent systems at higher evaporation temperatures exhibit superior separation factors with reasonably high fluxes as compared to those of pure NMP system. This separation performance is comparable or higher than that of commercially available PDMS membranes.