Effect of Temperature on Aqueous Two-Phase Systems Based on Acetonitrile and Protic Ionic Liquids: Phase Diagram and Partitioning of Commercial Biomolecules Present in Clove Oil

Abstract

Recently, ionic liquids (ILs) have been applied in extraction and separation processes due to their chemical and physical properties arising from the cations and anions that form these liquids. In aqueous two-phase systems (ATPSs), ILs can be used as phase formers and assist in the separation and purification processes of biomolecules, such as phenolics and terpenes present in clove oil. In this work, the effect of temperature (288.2, 298.2, and 308.2 K) and the alkyl chain size of protic ionic liquid (PIL) anion in ATPSs based on PIL + acetonitrile (ACN) + water at 101.2 kPa is evaluated. The NRTL and UNIQUAC models were used to predict the LLE data. The increase in the temperature and the alkyl chain compressed the biphasic region of the phase diagram. In the proposed systems, partitioning data were obtained for commercial biomolecules present in clove oil (eugenol, eugenyl acetate, and α-humulene). Phenolics (eugenol and eugenyl acetate) were partitioned to the PIL-rich phase. In contrast, α-humulene (terpene) was partitioned into the ACN-rich phase. It was observed that increasing temperature increases or maintains almost constant the recovery of biomolecules in the bottom phase (R_B) from similar tie-line length (TLL). Additionally, eugenol and eugenyl acetate can be partially isolated (selectivity: S = 2.17) at 298.2 K. Finally, the highest values achieved for bottom phase recoveries for the target biomolecules were achieved using ATPS formed by [2HEA][Bu] + ACN + water (TLL ≈ 53 and 57.57 < R_B < 93.54). PILs can be used as a salting-out agent to form biphasic phase systems with acetonitrile and separate biomolecules where reasonable recovery rates were verified.