| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 101 === The dynamic surface tension (DST) for anionic surfactant AOT in aqueous NaCl solution (10 mM and 500 mM) onto a clean air-water interface was measured by using a video-enhanced pendant bubble tensionmeter. The dynamic surface tension and the equilibrium surface tension for aqueous AOT solutions with 10 and 500 mM NaCl onto a freshly created air-water interface was obtained. Then the comparison was made for the equilibrium surface tension data and the ionic model predictions. We assume that the mass transport was diffusion-controlled for AOT molecules in 10 and 500 mM NaCl solution. For AOT in aqueous 10 mM NaCl solution, the values of the diffusivity of AOT molecules were around (3.55±0.6)×10-6 cm2/s estimated from the ionic-gF fitting of dynamic surface tension profiles. Because the value from Wilke-Chang equation (D= 4.63×10-6 cm2/s) is not for NaCl solution but pure water as the solvent, the actual value should be lower than 4.63×10-6 cm2/s, so it is reasonable to state that the mass transport for AOT in aqueous 10 mM NaCl solution was diffusion-controlled. For AOT in aqueous 500 mM NaCl solution, the diffusivity values for lower AOT concentrations match the value from Wilke-Chang equation, and the diffusivity values are around (1.95±0.3)×10-6 cm2/s for the AOT concentrations larger than 1.9×10-9 mol/cm3. These diffusivity values are lower than the value from Wilke-Chang equation so we fit the dynamic surface tension data for AOT concentrations larger than 1.9×10-9 mol/cm3 by a mixed controlled ionic-gF model. The fittings are great but the values of adsorption rate constants are not the same. So we do not believe that the parameters from the equilibrium surface tension fitting are good enough to fit the dynamic surface tension curves due to the higher equilibrium surface tension data cannot be obtained from experiments. That is the difficulty for us to decide the mass transport mechanism in this study.
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