In this study, the effect of hydrophilic silica nanoparticles on mass transfer in liquid-liquid extraction process was experimentally investigated using the ternary chemical system toluene-acetic acid-water. In order to examine the dispersed phase drop sizes, single drop experiments with a range of nozzle diameters within 0.1-0.51 cm were carried out. Hydrophilic SiO2 nanoparticles with different volume concentrations of 0.005-0.1 vol% were added to the continuous phase. The results demonstrated that mass transfer coefficient reduced in presence of hydrophilic SiO2 nanoparticles and maximum deterioration of 22% was observed using 0.1 vol% silica nanofluid for drops generated by 0.2 and 0.4 cm nozzles. Viscosity increase, steric hindrance of nanoparticles at the liquid-liquid interface, reduction in both free volume of mass transfer path and liquid-liquid contact area because of solid nanoparticles presence are introduced as the main reasons of observed behavior. Moreover, it can be concluded from the experimental results that silica nanoparticles do not significantly influence hydrodynamic parameters of the extraction system. (C) 2016 Elsevier B.V. All rights reserved.