This paper describes a systematic study on the hydrodynamic and mass transfer performance of drops in liquid-liquid extra This paper describes a systematic study on the hydrodynamic and mass transfer performance of drops in liquid-liquid extraction of phenol pollutant from aqueous solutions using 1-hexyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide, [Hmim][NTf2] ionic liquid. Cumene, as a recommenced conventional solvent, was also used for precise comparison under identical conditions. Due to heavier and lighter solvent drops, relative to the aqueous continuous phase, different setups were employed to perform experiments with falling and rising drops in the columns. Based on different criteria, the generated drops were in circulating state and terminal velocities were comparable with the Grace model. By using the same nozzles, smaller drops were generated with the ionic liquid (2.28-3.01 mm) compared to cumene (2.85-4.32 mm), which was mainly due to lower interfacial tension of the ionic liquid system. Meanwhile, the corresponding mass transfer coefficients were within (7.4-16.2) and (56.3-164.4) mu m/s, respectively. The difference can be attributed to the much higher inherent viscosity of the ionic liquid. These findings imply that the ionic liquid, with environmental significance, is promising for the separation of phenol from aqueous solutions in large scale columns. Extraction of phenol pollutant from aqueous solutions using 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Hmim][NTf2] ionic liquid. Cumene, as a recommenced conventional solvent, was also used for precise comparison under identical conditions. Due to heavier and lighter solvent drops, relative to the aqueous continuous phase, different setups were employed to perform experiments with falling and rising drops in the columns. Based on different criteria, the generated drops were in circulating state and terminal velocities were comparable with the Grace model. By using the same nozzles, smaller drops were generated with the ionic liquid (2.28-3.01 mm) compared to cumene (2.85-4.32 mm), which was mainly due to lower interfacial tension of the ionic liquid system. Meanwhile, the corresponding mass transfer coefficients were within (7.4-16.2) and (56.3-164.4) mu m/s, respectively. The difference can be attributed to the much higher inherent viscosity of the ionic liquid. These findings imply that the ionic liquid, with environmental significance, is promising for the separation of phenol from aqueous solutions in large scale columns. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.