This paper describes a systematic study on the hydrodynamic and mass transfer per-formance of drops in liquid–liquid extra This paper describes a systematic study onthe hydrodynamic and mass transfer performance of drops in liquid–liquid extrac-tion of phenol pollutant from aqueous solutions using 1-hexyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide, [Hmim][NTf2] ionic liquid. Cumene, as a recommencedconventional solvent, was also used for precise comparison under identical conditions. Dueto heavier and lighter solvent drops, relative to the aqueous continuous phase, differentsetups 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 veloc-ities were comparable with the Grace model. By using the same nozzles, smaller dropswere 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) m/s,respectively. The difference can be attributed to the much higher inherent viscosity of theionic liquid. These findings imply that the ionic liquid, with environmental significance, ispromising 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 compar-ison under identical conditions. Due to heavier and lighter solvent drops, relative to theaqueous continuous phase, different setups were employed to perform experiments withfalling and rising drops in the columns. Based on different criteria, the generated dropswere in circulating state and terminal velocities were comparable with the Grace model. Byusing the same nozzles, s
