Kerosene–water system is widely used in liquid–liquid extraction investigations. This study aimed to examine the effect of cetyltrimethyl ammonium bromide (CTAB) surfactant and different size silica nanoparticles (NPs) on the interfacial tension (IFT) of kerosene–water at 298.2 K and ambient pressure. Based on the experimental results, CTAB with concentrations up to 5.0 × 10−4 mol dm−3 was positively adsorbed while no sensible adsorptionwas observed in the case of NPs alone. However, the surfactant adsorption could significantly improve in the presence of only 1.00 × 10−4 wt% of NPs, leading to a significant decrease in the IFT. In addition, aqueous phase pH variation indicated strong effects under alkaline pHs. The obtained experimental IFT data for CTAB concentrations were considerably reproduced by the well-known Frumkin adsorption isotherm under the critical micelle concentration. Accordingly, a decrease was appeared in the saturated interface excess with pH while adsorption equilibriumconstant could increase. Finally, both higher saturated interface excess and lower adsorption equilibrium constant were recognized as appropriate for the larger size NPs.
