Extraction of aromatic compounds by water-rich aqueous two-phase system comprising surface-active ionic liquid and cationic surfactant

Aqueous two-phase system (ATPS) has been considered a promising alternative to traditional water-organic systems in liquid-liquid extraction. In this study, extractions of L-tryptophan (Trp), L-tyrosine (Tyr), vanillin (Van) and theophylline (Thp) under various conditions were investigated using the ATPS formed by 1-(2hydroxyethyl)piperazinium laurate ([HEP][C11CO2]) and dodecyldimethylbenzylammonium chloride (DDBAC). Pseudo-ternary phase diagrams were obtained for the DDBAC/[HEP][C11CO2]/brine systems at 25.0 degrees C. In all the ATPSs, the extracts migrated to the top phase, which exhibited higher hydrophobicity than the bottom phase. Due to the increased hydrophobicity difference between two phases, increasing water content from 0.70 to 0.96 resulted in a decrease of the recovery (R) of Van from 96 % to 84 %, while the R values of Trp, Tyr and Thp markedly decreased by at most 54 %. The highest partition coefficient (K) was observed with Van. Increasing the molar ratio of DDBAC to [HEP][C11CO2] resulted in higher R values of Trp and Van, while the initial concentration of extract and the extraction temperature showed limited effects on the partition behavior. NaCl addition effectively expanded the ATPS region in the phase diagram, due to the enhanced salting-out effect. However, it negatively impacted the recovery of Trp and Van, primarily due to the volume expansion of the bottom phase. The results suggested that the water-rich SAIL-ATPS was suitable for the extraction of highly hydrophobic compounds such as Van.