DYNAMIC INTERFACIAL TENSION IN HEXADECANE/WATER SYSTEMS CONTAINING READY-MADE AND IN-SITU-FORMED SURFACTANTS

Dynamic interfacial tension (IFT) between two immiscible liquids has been investigated by the method of drop volume tensiometry. Hexadecane and water were employed for the measurements. In the case of the pure oil-water system, it was found that with hexadecane as the drop phase the IFT was very close to the published value (53.5 mN/m). When water acted as the drop phase the apparent IFT was about 20% higher, and a correction method was developed to account for the different geometry of droplet formation. A similar effect was observed when a surface active additive was present in either one or both phases. The effects of ready-made surfactants and their in-situ-formed equivalents were examined. It was found that both decreased the IFT between the two phases, but the in-situ-formed surfactant was more effective in that respect, It was also found that the IFT between acidic hexadecane and NaOH solution increased when ready-made surfactant was added to the alkaline solution. Addition of salt (NaCl) produced the expected decrease in IFT while the effect of added NaOH appeared to be more complex.