Separation of organic acids from water using ionic liquid assisted electrodialysis

Abstract

In this study, we present a system capable of concentrating, acidifying, and removing organic salts from aqueous solution through the use of ionic liquids in an electrodialysis stack. This system used a bipolar electrodialysis stack operating in batch mode with ionic liquids in the concentrate stream and an aqueous solution containing organic salts in the diluate stream. Sodium butyrate was used as our model organic salt. The desired organic product was successfully transferred from an aqueous phase to an ionic liquid phase through electrodialysis and then recovered from the ionic liquid. Bipolar electrodialysis produced butyric acid which allowed separation through distillation. Since ionic liquids possess no measurable vapor pressure, this process was able to recover organic acid at a recovery rate of 99% and recycle the ionic liquid back into the electrodialysis stack. This system also reduced separation energy requirements by 60% when compared to distillation from aqueous solution. The research presented has the potential to significantly improve upon current organic acid purification techniques by eliminating costly dehydration steps following fermentations and other typical organic acid production methods. By combining the versatility of ionic liquids with the energy efficiency of electrodialysis, a simple low-cost organic acid purification method has been developed.