Distribution of pigments in the aqueous two-phase system formed with piperazinium-based ionic liquid and anionic surfactant

Abstract In this work, phase behaviors and pigment extraction performance of the ionic liquid-based aqueous two-phase system (IL-ATPS) formed by 1-ethylpiperazinium tertrafluoroborate ([C2pi][BF4]) + sodium dodecyl sulfonate (SDS) and 1-phenylpiperazinium tertrafluoroborate ([Phpi][BF4]) + sodium dodecyl benzene sulfonate (SDBS) are investigated. Phase composition of ATPS is determined, revealing ion exchange between conjugated phases. Mixing the piperazinium-based IL with the anionic surfactant produces a weakly acidic environment of ATPS which is suitable for the separation of curcumin. The influences of surfactant/IL mass ratio, pigment concentration and temperature on extraction efficiency and distribution coefficient are evaluated. The separation mechanism of ATPS is further explored by DLS, TEM and FTIR. The packing effect induced by the re-assembly of micelles formed mainly by IL cations and surfactant anions are the driving force for the preferable separation of curcumin, while carmine distributes in both phases with similar concentrations due to its high water solubility.