Aqueous two-phase system formed by alkanolammonium-based Protic Ionic Liquids and acetone: Experimental data, thermodynamic modeling, and Kraft lignin partition

[Display omitted] •Phase-forming abilities of Protic Ionic Liquids with acetone were evaluated;•The biphasic system formation is influenced by the anion/cation structure of PILs;•Partition of lignin depends on the interactions between PILs-water-lignin-acetone.•The highest lignin partition coefficient was found for glycolate-based PIL. Aqueous two-phase systems (ATPS) formed by Protic Ionic Liquids (PILs) are a potential alternative to recovery PILs after their use in pretreatment step and valorization of lignocellulosic biomass. Besides, ATPS based on PILs may be applied to Kraft lignin fractionation toward a more sustainable environment. In this study, nine alkanolammonium-based PILs were synthesized using organic acids (formic, acetic, propionic, lactic, and glycolic) as precursors. These PILs were combined with acetone to form ATPS at low temperatures, and the partition of Kraft lignin was tested using these same systems. The presence of an extra hydroxyl group in the PILs’ anionic part increased their ability to form ATPS, due to the increase in their acidity. Also, increasing the alkyl chain length of the PILs’ anionic part impairs the formation of ATPS. In contrast, the behavior was observed for the cationic part, due to the increase in the PILs’ hydrophobicity nature. Regarding the partition of Kraft lignin applying 2-hydroxyethylammonium-based PILs, the increase in the alkyl chain length of the PILs’ anionic part leads to stronger PILs-lignin interactions, which favored the lignin’s migration to the bottom phase (PILs-rich phase), and lower partition coefficient values, as follows: formate