The influence of sodium dodecyl sulfate (SDS) and magnetite nanoparticles (NPs), individually and simultaneously, on the interfacial tension of n-hexane−water was studied over the temperature range from (288.2 to 308.2) K. Results show that SDS in the range from (0 to 2.00·10−4) mol·dm−3 is adsorbed positively; while, NPs in the mass fraction range from (0 to 5.00·10−4) are adsorbed negatively and cause interfacial tension to rise. Interestingly, with the presence of both SDS and NPs, interfacial tension is reduced more than with SDS only, because the repulsive interactions between SDS molecules are weakened in the presence of positively charged NPs. An almost linear decrease in interfacial tension with temperature is also relevant in all cases. The experimental data, below the critical micelle concentration of SDS, were nicely reproduced by the Szyszkowski adsorption isotherm. Accordingly, obtained SDS saturated interface excess is reduced with NPs mass fraction, and on the other hand, adsorption tendency increases with temperature and NPs mass fraction.
