Recovery of Biobutanol from Aqueous Streams by Pervaporation Using Ionic Liquid Based Membranes

Butanol as a biofuel, can be produced by ABE (acetone-butanol-ethanol) fermentation. Pervaporation is a promising process, especially for the separation of biofuels from aqueous mixtures such as ABE mixtures which consists of 3:6:1 ratio of ABE solvents and water around 97%. In this study, ionic liquid-based membranes were developed for the recovery of butanol from aqueous mixtures. The active layer providing the selectivity was formed by using polydimethylsiloxane (PDMS) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) ionic liquid (IL). Porous polyvinylidenefluoride (PVDF) and polytetrafluoroethylene (PTFE) films were used as the support layers. Two different types of membranes were prepared, in which IL was mixed into PDMS and cast as a thin film on the support layer, and IL was impregnated into the pores of the support layers. The effects of feed concentration and temperature on separation performance were investigated. In addition, the membranes were prepared with and without IL, and the effect of IL on membrane performance was investigated. In general, an increase in flux and selectivity values was observed with the addition of IL in PDMS. Butanol selectivities in pervaporation experiments with different process parameters were found between 24.7 and 61.3 when PTFE support layer was used and between 22.5 and 48.6 when PVDF support layer was used. Especially with the use of IL in the membrane, the fluxes increased 2.5-5 times, resulting in a significant increase in fluxes. As a result, it has been shown that PDMS+IL/PVDF and PDMS+IL/PTFE membranes can be used for effective butanol recovery by pervaporation.