Investigation of the impact of synthesized hydrophobic magnetite nanoparticles on mass transfer and hydrodynamics of stagnant and stirred liquid–liquid extraction systems

•Finest magnetite nanoparticles with high hydrophobicity characteristic were synthesized.•In the single drop experiments, extraordinary enhancement of mass transfer was found.•In stirred column, mass transfer augmentation of nanofluid was negligible.•Mass transfer enhancement of nanofluids decreased as the solute concentration increased. The impact of modified magnetite nanoparticles (MMNPs) on hydrodynamics and mass transfer in liquid–liquid extraction process was assessed using a ternary chemical system of toluene-acetic acid–water. The organic phase which contained toluene and acetic acid was dispersed through water, and the mass transfer of acetic acid between two phases was investigated. The hydrophobic modified magnetite nanoparticles (MMNPs) prepared through an optimized in-situ method were added to the dispersed phase at different concentrations (0.001−0.005 wt%). Two separate conditions were provided in the experiments, i.e. stagnant and stirred continuous phase. The latter case was provided by a rotor at two different speeds of 330 and 450 rpm. The effects of nozzle size and acetic acid concentration were also considered. The results showed that the as-prepared MMNPs decreased the terminal velocity and increased the liquid hold-up of the drops. Under the stagnant condition, an enhancement of 103.1% in overall dispersed-phase mass transfer coefficient was achieved at the optimum concentration of 0.001 wt% of MMNPs, whereas under stirred condition, the extraction fraction enhancement was not appreciable.