An axisymmetric model for the analysis of dynamic surface tension

Arias, S.; Fernández, José R.; García‐Río, Luis; Mejuto, J. C.; Muñiz, M. C.; Núñez, Cristina

doi:10.1039/c4ra10845k

Cited by 4 publications

(1 citation statement)

References 31 publications

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“…The numerical methods to solve the Ward–Tordai equation were explicitly described in the literature. − C s i is assumed to be linear in each small time interval ( t n – j – t n – j –1 ). Unlike the previous numerical methods, − the time step adopted in the current model has been modified to be quadratic instead of being uniform. This modification, which is balanced by some reduction in accuracy, however, improved the computation speed and simplified the computation steps.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Modeling the Multicomponent Compositional Effects of Asphaltenes on Interfacial Phenomena

2020

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The polydisperse nature of asphaltenes is not usually considered in studies of asphaltenes adsorption effects at interfaces, e.g., water–oil interfaces. We recently proposed a methodology that takes into account the mixture nature of asphaltenes and showed that a binary mixture model for diffusion-limited adsorption at water–oil interfaces could describe qualitatively all of the features of asphaltenes’ interfacial dilatational rheology [LiuF. Liu, F. 10.1021/acs.langmuir.6b03958Langmuir20173319271042]. On the quantitative side, however, use of only two pseudocomponents did not adequately predict some other aspects of their behavior, such as dynamic interfacial tension over the full range of time scales. To address these limitations, a methodology for calculating interfacial rheological properties for an n-component mixture was first developed [LiuF. Liu, F. 10.1016/j.colsurfa.2017.05.080Colloids Surf. A2017532140143]. To capture, first, the interfacial tension behavior and then the rheological properties within the same methodological structure, we discuss here an approach using a multicomponent model that inversely solves the Ward–Tordai equations and extracts the properties of individual pseudocomponents (concentration and adsorption coefficient) from dynamic interfacial tension measurements. Using ternary mixture models proves sufficient to capture the data obtained for asphaltenes over large adsorption time scales (up to 24 h) and large frequency range. Quaternary mixture models do not significantly improve the predictions. Another feature revealed by this methodology is the aggregation behavior of the different pseudocomponents. For dilute solutions, the calculated sum of the pseudocomponents’ concentrations falls in the range of the actual asphaltenes concentration. As the actual asphaltenes concentration is increased, the calculated concentration of the most surface-active pseudocomponents levels offs, indicating that the most surface-active asphaltenes are also the most prone to aggregate due perhaps to π–π interactions. This result would be expected as asphaltenes adsorption at the water–oil interface appear to be driven by the interactions of the π electrons of their aromatic cores as previously demonstrated [RaneJ. P. Rane, J. P. 10.1021/acs.energyfuels.5b00179Energy Fuels20152935843590]. Finally, the result obtained by this model indicates that the presence of a very small fraction of extremely surface-active asphaltenes components could explain both the “everlasting” interfacial tension decay observed and the apparent irreversibility of adsorption during washout experiments.

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