Permeation of Succinic Acid through Supported Ionic Liquid Membranes

Succinic acid, which is a bio-based product produced by biomass conversion processes and utilized in biorefineries, has come into focus because of the concerns surrounding renewable and green energy sources. Large-scale application of succinic acid as a bio-based compound is receiving much attention to find potential production processes. Ionic liquids, which have negligible vapor pressure and whose solubility in the surrounding phases can be minimized by the appropriate selection of anions and cations, have potential application as supported ionic liquid membranes (SILMs) to separate succinic acid. We found that succinate successfully permeated through an SILM containing Aliquat 336 and observed the uphill transport. By examining the effects of pH and sodium chloride concentration on the permeability and distribution ratio, we explained the permeation mechanism of succinate using the solution-diffusion model. We found that the succinate di-anion reacted with quaternary ammonium salt in the membrane during the SILM process.