Comparison of the effects of anionic and cationic surfactant concentration on mean drop size in a mixer-settler extractor

► In this study, the effect of Aniline and SDS surfactant on mean drop size was investigated in a mixer-settler. ► For this purpose, the effects of impeller speed and hold-up on the mean drop size were examined with and without surfactant. ► The results revealed that D32, in Aniline system is larger than D32 in SDS system. ► The system with Aniline surfactant has a better agreement with Hinze–Kolmogorov's theory. In this study, the effect of Aniline and SDS (Sodium Dodecyl Sulfate) surfactant on mean drop size, D32, was investigated in a horizontal mixer-settler. For this purpose, three series of experiments were conducted in a single stage mixer-settler on the liquid–liquid dispersion of a toluene–water system. At first, the effects of impeller speed and hold-up on the mean drop size were examined without any surfactant. Afterwards the same investigation was performed in the presence of SDS (Seri 1) and then in the presence of Aniline (Seri 2). The results revealed that D32 in Aniline system is larger than D32 in SDS system. In addition, the results show that D32 in the presence of Aniline depends on the impeller speed with a power low function, having an exponent of −1.11 which has a good agreement with Hinze–Kolmogorov's theory.