Removing phenolic pollutants using Deep Eutectic Solvents

• Deep Eutectic Solvents based on menthol, thymol and organic acids were prepared. • The studied solvents present high extraction capability for phenolic compounds. • The best extraction results were obtained using menthol based mixtures. • The extraction efficiency follows the sequence: 2-chlorophenol >o-cresol >phenol. Phenolic compounds are present both in nature as components of fruits, coffee or tea, and in wastewaters of many different industries. The world organization WHO, list some of these phenolic compounds as priority pollutants due to their toxicity, so it is necessary to remove them, to a concentration below the legal limit (1 mg·L −1 ) before wastewater discharge. In this work, six new solvents, Deep Eutectic Solvents (DES) based on organic acids (dodecanoic acid, decanoic acid, octanoic acid) and menthol or thymol, were studied as extraction solvents for these pollutant compounds. Their physical properties (density, viscosity, refractive index and speed of sound) were measured, as well as their capability to remove phenolic compounds (phenol, o -cresol and 2-chlorophenol) from water using liquid-liquid extraction. The experimental data were compared with other results obtained for the extraction phenolic compounds from water using Ionic Liquids. The results obtained show that the use of these new solvents provide a good extraction method for phenolic compounds present in wastewaters. The best results were obtained for menthol based DES to extract o -cresol and 2-chlorophenol, getting extraction efficiencies upper than 85% for all initial concentration of phenolic compound.