Surfactant concentration-dependent effects of pH on the interfacial properties of a splittable surfactant

A systematic study was performed to explore the effects of pH on the emulsifying ability and interfacial tension-lowering activity of a commercial splittable surfactant Triton SP-175 at various concentrations. The findings indicate that the addition of inorganic acids had a pronounced influence on the stability of Triton SP-175-stabilized emulsions, and the influence was greatly enhanced with decreasing pH and surfactant concentration Moreover, the dynamic interfacial tension-lowering activity of the commercial Triton SP-175 surfactant was strongly inhibited by lowering the pH, resulting in a much slower relaxation in dynamic interfacial tension, with the extent depending on the surfactant concentration. However, its equilibrium interfacial tension-lowering activity was only slightly affected by acids. The data demonstrated that dramatic instability of emulsions stabilized by the splittable surfactant Triton SP-175 was induced by acids, along with considerably destroyed dynamic interfacial activity of the surfactant.