Adsorption Kinetics of Ionic Surfactants with Detailed Account for the Electrostatic Interactions
✍ Scribed by Petia M. Vlahovska; Krassimir D. Danov; Ammanuel Mehreteab; Guy Broze
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 272 KB
- Volume
- 192
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
perturbation: the larger the deviation from equilibrium ad-The problem of diffusion-controlled adsorption from a nonsorption, the larger the diffusion flux tending to eliminate micellar solution of an ionic surfactant in the absence of added the perturbation.
electrolyte is solved analytically for the case of small deviations While the adsorption kinetics from non-ionic surfactant from equilibrium. For that purpose the electro-diffusion equations solutions is comprehensively studied (1-10), the respective of the transport of surfactant ions and counterions are combined theory of adsorption from ionic surfactant solutions is somewith the Poisson-Boltzmann equation for the electrical field. The what behind. Indeed, there are theoretical studies describing resulting set of equations is linearized and Laplace transform the equilibrium state, i.e., the equation of state of the ionic is applied. Analytical expression for the Laplace image of the adsorption is obtained in terms of elementary functions. Simple surfactant adsorption monolayer (11)(12)(13)(14). However, the formulae for the short-time and long-time asymptotics of adsorptheoretical interpretation of data for adsorption kinetics of tion and surface tension relaxation are derived. To illustrate the ionic surfactants (15-22) meets some difficulties. The latter effect of the electrostatic interactions we calculated the theoretical originate from the non-linearity of the set of equations dedependence of the characteristic relaxation time on the bulk surscribing the electro-diffusion process. Three types of apfactant concentration and surface potential for aqueous surfactant proaches to this problem can be found in the literature: (i) solutions in contact with various non-aqueous phases (air, hepnumerical methods (23, 24), (ii) approximate analytical extane, decane, petroleum ether ) and two surfactants: SDS and pression derived by using an assumption for quasi-equilib-DTAB. The general trend is that the electrostatic effects decelerrium regime of surfactant adsorption (23, 25-28), and (iii) ate the process of adsorption, as it could be expected. The derived exact asymptotic expressions for the case of small deviations exact analytical expressions quantifying these effects can be directly applied for the interpretation of experimental data for the from equilibrium. The third is the approach we follow in kinetics of ionic surfactant adsorption. The reliability of our apthe present study.
proach is verified through a comparison with other available theo-
The characteristic extent of the electrical double layer is ries. ᭧ 1997 Academic Press determined by the Debye length, k 01 (see Eq. 9 below).