Dynamics of Surfactant Adsorption from Solution Considering Aggregation within the Adsorption Layer

Abstract

The theory of diffusion-controlled adsorption kinetics is developed for adsorption layers of surfactant molecules able to form two-dimensional aggregates. It is shown that the formation of such aggregates within the adsorption layer results in a deceleration of the surface tension decrease and in a reduction of the dynamic surface pressure when the system is far from the equilibrium state. If no aggregation of adsorbed molecules is considered, then any decrease in adsorption rate is ascribed usually to the existence of an adsorption barrier. However, assuming this two-dimensional aggregation, the diffusion model provides a much better description of phenomena that actually take place. A good correspondence is found between the experimental dynamic surface tensions and theoretically calculated dependencies for the solutions of 1-decanol for a mean aggregation number of 2.5 within the monolayer. The same aggregation number was estimated for decanol equilibrium monolayers.

Helical poly(N-propargylamide)s with functional catechol groups: Synthesis and adsorption of metal ions in aqueous solution

“…Within the concentration range, it was found that with an increase in the concentration of Fe(III), the adsorption capacity of poly(1 0.1 -co-2 0.9 ) toward Fe(III) ascended gradually, while only little change was seen for Cu(II) and Ni(II). The adsorption of poly(1 0.1 -co-2 0.9 ) toward Fe(III), Cu(II) and Ni(II) showed obvious Langmuir adsorption characteristics, among which monodisperse layer adsorption occupied absolute predominance [39]. Thus, it is demonstrated that the present adsorptions followed Langmuir model.…”

Equilibrium and dynamic surface properties of trisiloxane aqueous solutions. Part 2. Theory and comparison with experiment

“…(5) and (9) that at such surface pressures Γ 1 >>Γ 2 . Hence, in this range we can neglect the adsorption in the state 2 and investigate adsorption behaviour of trisiloxanes using already know earlier theoretical models of aggregation processes [10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

“…In [9,[20][21][22][23] such kind of phase transitions were treated using the quasi-chemical approach based on the analysis of chemical potentials of the components in the surface layer. When aggregates are formed at the surface (interface), the equilibrium between monomers and n-mers can be described by the following equation [9,20]:…”

“…If the dynamic surface tension of a surfactant aggregating in the surface layer is studied, then above the critical adsorption of aggregates formation one should expect retardation of the surface pressure dependence on time expressed by the dynamic curve [16,21]. The dynamic curves calculated assuming the aggregation in the monolayer exhibit (for the not too large values of Π)…”

Adsorption of surfactants at air/solution interfaces: theoretical description of adsorption equilibrium based on a model of clustering of the surfactant molecules at the air/solution interface

“…For instance, these experimental data can be perfectly described by assuming that small aggregates (dimers and trimers) are formed in the adsorption layer. 10,13 It was also shown that for sodium dodecylsulfate (SDS) the aggregation model predicts dimer formation at the airasolution interface. Correspondingly, the formation of small aggregates was also indicated for the ¯uid state of Langmuir monolayers.…”