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Updated: Jul 12, 2025
Extraction and Characterization of Surfactants from Atmospheric Aerosols
Published on: April 21, 2017
Surface Equation of State of Nonionic CE Surfactants
Shi-Yow Lin1, Ya-Chi Lee1, Ming-Wei Yang1
1Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Sec. 4, Taipei, 106 Taiwan, and Department of Chemical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei, 106 Taiwan.
Abstract:
The surface equation of state (γ vs Γ/Γref), based on the experimental data from rapid expansion of a pendant bubble, has been used on studying the adsorption kinetics for C12E6 (Pan et al. J. Colloid Interface Sci. 1998, 205, 213) and C14E8 (Lin et al. J. Colloid Interface Sci. 2001, 244, 372). In those studies, the relationship between surface tension γ and relative surface concentration Γ/Γref was applied, and the γ(Γ/Γref) data profiles were found very useful for the determination of the adsorption isotherm and its parameters. In this work, the value of Γref was evaluated from the equilibrium surface tension data γ(C) and the Gibbs adsorption equation. It was found that the dependence of γ vs Γ is more sensitive than γ(Γ/Γref) and brings more help to studying the adsorption kinetics. The role of γ(Γ) data was examined using the equilibrium γ(C) and dynamic γ(t) data of six nonionic polyoxyethylene surfactants CE and two alcohols. The γ(Γ) data play an important role on the determination of the adsorption isotherm, model parameters, and controlling mechanism, and also on the evaluation of surfactant diffusivity. Applying γ(Γ) data with γ(ln C) data does bring a much better result on studying the adsorption behavior. According to the γ(Γ) data, (i) the Langmuir isotherm clearly fails to describe the above nonionic surfactants, and (ii) the interaction between the adsorbed surfactant molecules is significant.
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