Extraction of adipic, levulinic and succinic acids from water using TOPO-based deep eutectic solvents

Organic acids are extremely useful as starting materials for chemical industry. Adipic, levulinic and succinic acids, are becoming in such interesting alternatives to petrochemical feedstock in the production of a wide range of compounds in many different industries such as polymer, pharmaceutical or food manufacture. The extraction process of these acids often use organic solvents which are environmental hazardous. In this paper, two hydrophobic trioctylphosphine oxide (TOPO)-based deep eutectic solvents (DESs) were studied as alternative solvents for the organic acid extraction. They were prepared and analysed using differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) to confirm the DESs formation and to check their stability in water. Density, speed of sound, refractive index and viscosity of the prepared TOPO-based DESs were determined from 293.15 to 343.15 K. Even though DES used to extract adipic, levulinic or succinic acid demonstrate high capacity to remove the above mentioned acids from aqueous solutions, TOPO is still exhibiting the best extraction capacity.