Surface tension of surfactant solutions in the presence of colloidal silica

The dynamic surface tension of pure surfacant solutions containing 20% colloidal SiO 2 was measured by the drop weight method. The equilibrium surface tension was precisely determined from the kinetic curves. The ionic surfactants used were sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromine (CTAB) and sodium dodecylbenzenesulphonate (SDBS). The nonionic surfactant used was a polyethoxylated alkylphenol. It was shown that the presence of colloidal SiO 2 reduced the surface tension changes in surfactant solutions, especially for CTAB which was explained in terms of surfactant adsorption onto the colloidal SiO 2 /solution interface.