Liquid-liquid extraction of phenolic compounds from aqueous solution using hydrophobic deep eutectic solvents

This work evaluates the efficiency of extracting phenolic compounds (phenol, guaiacol, eugenol and pyrocatechol) from aqueous solution using Hydrophobic Deep Eutectic Solvents (HDESs). Four solvents were selected by screening HDESs database using the predictive model COSMO-RS (Conductor like Screening Model for Real Solvent): menthol: dodecanoic acid [2:1], decanoic acid: dodecanoic acid [2:1], octanoic acid: menthol [2:1] and thymol: menthol [1:1]. Experimental liquid–liquid equilibria of ternary systems {water – HDESs – phenolic compounds} measured at 298.15 K under atmospheric pressure were used to determine the distribution coefficient and selectivity values. Experimental data were used to determine the interaction parameters of the thermodynamic Non-Random Two-Liquid model (NRTL). NRTL model represents with good accuracy experimental data. COSMO-RS model predicts well the ternary systems containing phenolic compounds except those containing pyrocatechol. Finally, extraction of the four phenolic compounds from synthetic oil and kinetics study were performed. The extraction process using HDES: octanoic acid: menthol [2:1] exhibits the highest efficiency and more than 85 % of phenolic compounds are extracted after 5 min.