Effect of Cations in Ionic Liquids on the Extraction Characteristics of 1,3-Propanediol by Ionic Liquid -based Aqueous Biphasic Systems

Separation of 1,3-propanediol (1,3-PDO) from fermentation broths becomes a bottleneck in biological production due to its high hydrophilicity and low concentration. Aqueous biphasic systems (ABS) composed of piperidinium-based ionic liquids (ILs) and K2HPO4 could be an alternative to extract 1,3-propanediol from fermentation broths. In this study, the ability of piperidinium-based ILs to form ABS with aqueous K2HPO4 solution was investigated. Binodal curves and tie-lines and tie-line length were evaluated by three parameter equation and mass balances for each components in top and bottom phases. The piperidiniumbased ILs was effective on promoting ABS formation in the presence of K2HPO4 and the forming ability of ABS increased with alkyl chain length of cations in ILs. The volume ratio to top and bottom phase decreased with K2HPO4 concentration and alkyl chain length of cations in ILs. However, above 20 wt % of K2HPO4, the partitioning of water into top phase is dominant, resulting in low phase volume ratio. The extraction efficiency of 1,3-PDO reached up to 95%. It is expected that piperidinium IL-based ABS is a prospective extraction media for the separation and concentration of 1,3-PDO.