Simultaneous adsorption of CTAB surfactant and magnetite nanoparticles on the interfacial tension of n-hexane–water

Abstract

Simultaneous adsorption of CTAB surfactant and different size magnetite nanoparticles (NPs) on the interfacial tension of n-hexane–water was investigated. Different methods were used to characterize the NPs and aqueous suspensions. Interfacial tension measurements were performed at 293.2K and ambient pressure of 83.5kPa. Results indicate that CTAB, with concentrations up to 7.50×10−4moldm−3, was positively adsorbed whereas no significant adsorption was relevant for NPs alone within (10−4–10−2) wt%. It was while CTAB adsorption was significantly improved in the presence of NPs and more effective with the small size particles. Accordingly, either alkaline or acidic solutions were more effective than neutral pH due to the provided attractive or repulsion interactions. The provided data were nicely reproduced by the well-known Frumkin adsorption isotherm. Accordingly, the saturated interface excess was decreased under alkaline or acidic conditions; whereas adsorption equilibrium constant showed a slight decrease with pH up to neutral pH and then sharply increased. With respect to the size of particles, it was revealed that higher saturated interface excess and lower adsorption equilibrium constant were appropriate to the large size particles.