Separation properties of supported ionic liquid polydimethylsiloxane membrane in pervaporation process

Pervaporation separation properties of water Á butan-1-ol binary mixtures were measured with the use of three supported liquid membranes at 378C, namely PDMS, 1-ethenyl-3-ethyl-imidazolium hexafluorophosphate Á PDMS, and tetrapropyl-ammonium tetracyanoborate Á PDMS membranes. An ultrafiltration ceramic module from TiO2 with 60 nm pore size was used as a support. The diffusion coefficients of butan-1-ol in IL-PDMS were much higher than in PDMS only. However, the sorption isotherms were identical for all three measured membranes. Higher permeation flux and enrichment factors of butan-1-ol in IL-PDMS membrane were probably caused by higher diffusion coefficient. The supported ionic liquid membranes were stable during all measurements.

The removal of butan-1-ol from aqueous solution has a practical application in biotransformation processes such as fermentation of Clostridium acetobutylicum [16]. The diffusion coefficient of butan-1-ol is much higher in IL-PDMS than in the PDMS membrane. However, with higher relative pressure of butan-1-ol the diffusion coefficients in IL-PDMS decreased exponentially. The sorption isotherms were identical for IL-PDMS and PDMS membranes. The higher permeation flux and enrichment factor in IL-PDMS membranes was most probably caused by much higher diffusion coefficient of butan-1-ol at low relative pressure. Especially noteworthy is the fact that IL-PDMS membranes have significantly better separation properties than PDMS membrane itself.