Recovery of Nonsteroidal Anti-Inflammatory Drugs from Wastes Using Ionic-Liquid-Based Three-Phase Partitioning Systems

Aiming at outlining new strategies for the valorization of solid pharmaceutical wastes as viable alternatives to incineration, this work proposes the use of ionic liquids-based three phase partitioning (IL-based TPP) systems. Ibuprofen, naproxen, and ketoprofen, all belonging to the class of nonsteroidal anti-inflammatory drugs (NSAIDs), were adopted as model compounds. An integrated process has been conceptualized based on three steps: (1) extraction and purification of NSAIDs using the IL-based TPP systems, (2) drug isolation by precipitation with antisolvents, and (3) recycling and reusing the solvents. With the optimization of steps 1 and 2 as objects of this investigation, aqueous biphasic systems (ABS) composed of three distinct ILs (tetrabutylammonium chloride, 1-butyl-3-methylimidazolium chloride, and benzyldimethyl(2-hydroxyethyl)ammonium chloride) and potassium citrate buffer were studied. The corresponding IL-based TPP systems were further applied in the purification of each NSAID, and different antisolvents (citric acid aqueous solutions for ibuprofen and naproxen and aluminum sulfate aqueous solutions for ketoprofen) were evaluated as precipitating agents to isolate each drug. The success of the process developed is demonstrated by extraction efficiencies higher than 83.8 ± 7.7% attained in step 1 and isolation efficiencies higher than 76.2 ± 1.8% in step 2. The stability of the three NSAIDs in IL-based aqueous matrices was additionally checked by using a protocol adapted from the OECD guidelines. The economic efficiency and environmental benignity of the process herein developed is underlined, based on not only the low cost of the solvents chosen but also the possibility of recycling and reusing the phase-forming components and antisolvents employed.