Removal of Acetaminophen (Paracetamol) from Water Using Aqueous Two-Phase Systems (ATPSs) Composed of Choline-Amino Acid Ionic Liquids

Abstract

Emerging contaminants, such as pharmaceutical compounds, are often bioaccumulative and can have toxic effects on the environment; therefore, there is a need to find efficient techniques to extract these hazardous species from water bodies. In this work, five aqueous two-phase systems (ATPSs) composed of choline-amino acid ionic liquids (CAAILs) and phosphate salts were studied to remove acetaminophen (a common active pharmaceutical ingredient, API), constituting a sustainable extraction approach. The CAAILs cholinium l-alaninate ([Ch][Ala]), cholinium glycinate ([Ch][Gly]), cholinium leucinate ([Ch][Leu]), and cholinium l-serinate ([Ch][Ser]) were successfully synthesized, and their chemical structures were confirmed by infrared spectroscopy and density measurements. Partitions of acetaminophen were performed in the systems {[Ch][Ala] or [Ch][Gly] or [Ch][Ser] (1) + K2HPO4 (2) + water (3)} and {[Ch][Ala] or [Ch][Leu] (1) + K3PO4 (2) + water (3)}, at 298.15 K and 0.1 MPa. Of these, four ATPSs showed good results in the extraction of acetaminophen: {[Ch][Ala] or [Ch][Gly] (1) + K2HPO4 (2) + water (3)} and {[Ch][Ala] or [Ch][Leu] (1) + K3PO4 (2) + water (3)}. Acetaminophen migrated preferentially to the top (IL-rich) phase, obtaining partition coefficients (K) higher than unity and extraction efficiencies (E) larger than 90%. The most promising extraction efficiencies (E) were attained for the largest tie-line lengths (TLLs) of {[Ch][Ala] or [Ch][Gly] (1) + K2HPO4 (2) + water (3)}, with E = 97.5% for TLL = 82.18 m % and E = 79.3% for TLL = 85.05 m %, respectively, while {[Ch][Ala] or [Ch][Leu] (1) + K3PO4 (2) + water (3)} only obtained E = 97.9% for TLL = 75.35 m % and E = 97.50% for TLL = 85.23 m %, respectively.