Adsorption from Surfactant Solutions under Diffusion Control

Kralchevsky, Peter A.; Radkov, Y. S.; Denkov, Nikolai D.

doi:10.1006/jcis.1993.1478

Cited by 25 publications

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“…The quantitative interpretation of the MBPM data demands one to take into account the fact that the surfactant adsorbs at an expanding interface. ,,,− The cinematography of bubble growth provides direct evidence for the time dependence of the bubble surface area, A ( t ). The latter dependence is different for apparatuses of different constructions of the gas supply system.…”

Section: Introductionmentioning

confidence: 99%

Maximum Bubble Pressure Method: Universal Surface Age and Transport Mechanisms in Surfactant Solutions

et al. 2006

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Here, based on the theoretical analysis of results for two ionic surfactants, sodium dodecyl sulfate (SDS) and dodecyl trimethylammonium bromide (DTAB), we develop a new approach for quantitative interpretation of data from the maximum bubble pressure method. A given tensiometer is characterized by an apparatus function, A(t), and by an apparatus constant. The former represents the time dependence of the bubble surface area, whereas the latter is expressed through integrals of A(t). The experiment indicates that both of them are independent of the surfactant type and concentration. Moreover, if a certain criterion is satisfied, the experimental results depend on the surface dilatation only through the apparatus constant. This makes the data interpretation much easier. The knowledge of the apparatus constant gives a general time scale (universal surface age) that makes the results independent of the specific bubble-pressure setup and produces dynamic surface tension curves that are universal characteristics of the investigated solutions. A new equation for data processing is proposed, which provides excellent fits of the dynamic surface tension. In the case of micellar solutions, the data analysis enables one to identify the kinetic regime of adsorption (among four possible regimes). For the investigated surfactant solutions, the diffusion regime "BC" was identified, for which the fast micellar process is equilibrated, whereas the slow micellar process is negligible. Upgraded with the developed approach for quantitative data interpretation, the bubble-pressure tensiometry could be a useful tool for a detailed analysis of the adsorption processes in more complex systems.

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Section: Introductionmentioning

confidence: 99%

Maximum Bubble Pressure Method: Universal Surface Age and Transport Mechanisms in Surfactant Solutions

et al. 2006

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Section: Effect Of Surfactant On Thin Film Drainage and Hydrodynamic ...mentioning

confidence: 99%

“…Additionally, for single interfaces the hydrodynamic problem requires one to find the surfactant distribution in the vicinity of the interface. For this purpose one can use a model profile for the surfactant concentration [35][36][37] or a concentration boundary layer. 36 Note that the quasi-stationary approximation might be inadequate for description of some dynamic processes, i.e., the time derivatives cannot be neglected in the equation describing the surfactant balance on the surface (see, e.g., eq 3.9).…”

Section: Effect Of Surfactant On Thin Film Drainage and Hydrodynamic ...mentioning

confidence: 99%

Role of Surface Diffusion for the Drainage and Hydrodynamic Stability of Thin Liquid Films

Stoyanov

Denkov

2001

Langmuir

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The dynamics of thin liquid films is analyzed taking into account the dependence of the surface diffusion coefficient of the adsorbed surfactant molecules on the density of the adsorption layer. The analysis shows that the Gibbs elasticity disappears from the final equations describing the drainage and hydrodynamic stability of thin liquid films. Thus from a theoretical viewpoint, no correlation between the Gibbs elasticity and the dynamic properties of the thin foam and emulsion films is expected. This conclusion is valid also for a variety of other dynamic processes (in a quasi-stationary regime) where the concentration Marangoni effect is important, such as the motion of drops and bubbles in a liquid medium, and rheology of foams and emulsions. The theory predicts that the main factors governing these processes are (i) the density of the adsorption layer and (ii) the surface friction coefficient of the adsorbed molecules.

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“…In such a case there is no general analytical expression for the dynamic surface tension σ ( t ) since the adsorption isotherms (except that of Henry) are nonlinear. In this case one can use either a computer solution , or apply the von Karman's approximate approach. , Moreover, analytical asymptotic expressions for long times ( t → ∞) can be obtained. Hansen derived the long-time asymptotics of the subsurface concentration, c 1s ( t ), of a nonionic surfactant: Equation 1.4 has been utilized and generalized by many authors. − The validity of eq 1.4 was reexamined and confirmed by Filippov .…”

Section: Introductionmentioning

confidence: 99%

Adsorption Kinetics of Ionic Surfactants after a Large Initial Perturbation. Effect of Surface Elasticity

et al. 2000

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This theoretical study is devoted to the relaxation of surface tension of an ionic surfactant solution for submicellar concentrations. The effects of added nonamphiphilic electrolyte and counterion binding are taken into account. We consider a large initial deviation from equilibrium, which is defined as the formation of a new interface: there is no adsorbed surfactant and electric double layer at the initial moment. Next, the surfactant solution and its interface are allowed to relax without any subsequent perturbation. The electrodiffusion equations, which describe the adsorption kinetics, are nonlinear, and it is impossible to find a general analytical solution, especially in the case of large initial deviations. Nevertheless, the problem can be linearized in the asymptotic case of long times. The derived theoretical expressions show that the relaxation times in the cases of large and small initial perturbations are numerically close to each other. For that reason the relaxation time can be considered as a general kinetic property of the adsorption monolayer. The theory predicts also the slope of the experimental plot of dynamic surface tension vs inverse square root of time; this makes the theory useful for interpretation of experimental data. The theoretical expressions involve the surface (Gibbs) elasticity, whose definition for adsorption monolayers of soluble ionic surfactants is discussed in detail. The Gibbs elasticity of such monolayers is found to increase strongly with the rise of salt concentration. The derived asymptotic expressions are verified against an exact computer solution of the electrodiffusion problem, and excellent agreement is found.

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Adsorption from Surfactant Solutions under Diffusion Control

Cited by 25 publications

References 0 publications

Maximum Bubble Pressure Method: Universal Surface Age and Transport Mechanisms in Surfactant Solutions

Maximum Bubble Pressure Method: Universal Surface Age and Transport Mechanisms in Surfactant Solutions

Role of Surface Diffusion for the Drainage and Hydrodynamic Stability of Thin Liquid Films

Adsorption Kinetics of Ionic Surfactants after a Large Initial Perturbation. Effect of Surface Elasticity

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