A strategy for characterizing the surface layer at the liquid-vapor interface of binary liquid mixtures containing non-ionic surfactants: An approach from Gibbs adsorption isotherm

Meza, Manuel S. Páez; Cantero-López, Plinio; Sotelo, Dairo E. Pérez; Arias, Francisco J.; Varilla, L. A. Alcalá

doi:10.1016/j.fluid.2021.113090

Cited by 2 publications

(2 citation statements)

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“…To further explain the role of Span 20 in stabilizing water droplets, we calculated the average area A occupied by each Span 20 molecule based on the surface excess concentration at the interface, as shown in Table : A = 1 N normalA normalΓ N A denotes the Avogadro constant. Table shows the area occupied at the interface by a single Span 20 molecule at various bulk concentrations.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Oil-Soluble/Water-Soluble Surfactants on the Stability of Water-in-Oil Systems, an Atomic Force Microscopy Study

Xiao

Gong

et al. 2023

Langmuir

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The stabilization mechanism of water-in-oil (W/O) emulsions has been studied by measuring the interactions between two water droplets in n-tetradecane using atomic force microscopy. The effects of water-soluble surfactants (SDS/CTAB/Tween 80), an oil-soluble surfactant (Span 20), and the coexistence of the water and oil-soluble surfactants on the stability of water droplets in oil were investigated separately. It is found that the addition of oil-soluble surfactants (Span 20) prevents the coalescence of water droplets in oil. To discuss the role of an oil-soluble surfactant, we analyzed the force curve by applying the theoretical model. The results demonstrate that the oil-soluble surfactant (Span 20) stabilizes dispersed droplets by adsorbing onto the interface and forming a relatively tighter layer with the increase in surfactant concentration, which hinders film rupture. This behavior of the surfactant could also be properly characterized by steric hindrance. A further step was taken by introducing another water-soluble surfactant. It is found that the addition of either SDS or CTAB into the water phase is futile in inducing droplet coalescence in the presence of Span 20. In contrast, Tween 80 was found to be effective in destabilizing water droplets, which could be due to the competitive adsorption between Tween 80 and Span 20 at the interface. By characterizing the interfacial adsorption of Tween 80 and Span 20 with a theoretical adsorption isotherm model, the result indicates that interface replacement would result in a loose adsorption layer that is insufficient to hinder droplet coalescence. Our study provides an intriguing understanding of the role of surfactants in the stabilization and destabilization of water-in-oil emulsions.

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Section: Resultsmentioning

confidence: 99%

“…To further explain the role of Span 20 in stabilizing water droplets, we calculated the average area 35 A occupied by each Span 20 molecule based on the surface excess concentration at the interface, as shown in Table 3:…”

Section: ■ Results and Discussionmentioning

confidence: 99%