| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 100 === The dynamic surface tension (DST) for anionic surfactant SDS in aqueous NaCl solution onto a clean air-water interface was measured by using a video-enhanced pendant bubble tensionmeter. The electrostatic interaction between ionic molecules plays an important role in the adsorption kinetics. Relaxation profiles of surface tension for various aqueous SDS solutions with 30, 100 and 300 mM NaCl onto a freshly created air-water interface for were obtained. Comparison was made for the entire relaxation period of the tension data and the ionic model predictions. If the mass transport was diffusion-controlled, values of the diffusivity of SDS molecules was estimated from dynamic surface tension profiles and values of D= 0.4–1.5 (10-6 cm2/s) and D=1–4 (10-6 cm2/s) were obtained for solutions with 100 and 300 mM NaCl, respectively. These diffusivities are significantly lower than what the Wilke-Chang equation predicts (D = 5.78×10-6 cm2/s). However, the mixed controlled tension profiles of SDS solutions with D = 5.78×10-6 cm2/s and an ionic generalized model predicted the dynamic surface tension pretty well. Therefore, the adsorption of SDS was concluded to be of mixed diffusive-kinetic controlled.
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