Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane–Benzene Sulfonate–Tetradecane–Water System

Paredes, R.; Fariñas-Sánchez, Ana Isabel; Medina-Rodriguez, Bryan X.; Samaniego, Samantha; Aray, Yosslen; Álvarez, Luis Javier

doi:10.1021/acs.langmuir.7b03719

Cited by 17 publications

(8 citation statements)

References 43 publications

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“…To further elucidate the effects of polar components on IFT, we analyze the hydrogen bond density between polar compounds and water in the interfacial regions ρ HB , which is defined as where A xy is the cross-sectional area of the x–y plane (nm 2 ) and “2” appears in the denominator since there are two interfaces in the system. The interfacial region is estimated by the “90–90” criteria . The hydrogen bond is recognized when the donor–acceptor distance is less than 0.35 nm and the angle between the vectors of donor-hydrogen and hydrogen-acceptor is less than 30° .…”

Section: Resultsmentioning

confidence: 99%

“…The interfacial region is estimated by the "90−90" criteria. 97 The hydrogen bond is recognized when the donor−acceptor distance is less than 0.35 nm and the angle between the vectors of donor-hydrogen and hydrogen-acceptor is less than 30°. 98 N and S in N-and S-bearing compounds only serve as acceptors, whereas the OH group in O-bearing compounds acts as both acceptor and donor.…”

Section: Resultsmentioning

confidence: 99%

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Effects of Salinity and N-, S-, and O-Bearing Polar Components on Light Oil–Brine Interfacial Properties from Molecular Perspectives

Nan

Wen

et al. 2019

J. Phys. Chem. C

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Oil–brine interfaces play an important role in oil recovery and oil–brine separation, in which the effects of salinity on interfacial tension (IFT) have been much of debate in the past in experiments and modeling studies owing to complex oil compositions. In this work, we use molecular dynamics (MD) simulations to study the oil–brine interfacial properties by designing seven systems containing different oil compositions (decane with/without polar compounds) and the salinity in brine of up to ∼14 wt %. We carefully investigate the salinity and polar component effects by analyzing IFTs, density profiles, orientation parameters, hydrogen bond densities, and charge density profiles. The results indicate that O-bearing compounds (phenol and decanoic acid) can significantly reduce the oil–brine IFT and exhibit the highest Gibbs surface excess relative to water, while the others, including N-bearing compounds (pyridine and quinoline) and S-bearing compounds (thiophene and benzothiophene), only slightly decrease the oil–brine IFTs and show a relatively small Gibbs surface excess. Increasing salinity can slightly increase the oil–brine IFT except in the system containing phenol, which shows a decrease. Phenol and decanoic acid incline to be perpendicular to the interface and generate numerous hydrogen bonds with water in the interfacial region, while others prefer to be parallel to the interface with much fewer hydrogen bonds with water. On the other hand, salinity has an insignificant effect on the orientation of polar molecules and hydrogen bond density in the interfacial region. The charges at the interfaces on the brine and oil sides are negative and positive, respectively, and the polar compounds disturb the arrangement of water molecules in the interfacial regions, while the addition of salt ions result in the higher peak values of charges in terms of water and system. Our study should provide new insights into the oil–brine interfacial issues and clarify some unsettled disputes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Effects of Salinity and N-, S-, and O-Bearing Polar Components on Light Oil–Brine Interfacial Properties from Molecular Perspectives

Nan

Wen

et al. 2019

J. Phys. Chem. C

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“…Studying surfactants assemblies is affected by the time scales accessible to the simulations. Paredes et al 25 showed that to predict the interfacial tension for the water-tetradecane interface in the presence of sodium hexadecane benzene sulfonate surfactants, it is necessary to conduct simulations for several s. This length scale far exceeds that of most MD simulation studies reported to quantify the properties of surfactant aggregates, including those from our group.…”

Section: Possible Simulation Approaches To Study Surfactants Adsorptionmentioning

confidence: 99%

Studying surfactants adsorption on heterogeneous substrates

Striolo¹

2019

Current Opinion in Chemical Engineering

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Surface active compounds are continually designed and formulated to advance a large number of modern applications. In the past, the key design principle was the amount of surfactants adsorbed on a surface, because most attention was on changing the substrate wettability. As technology progresses, this is no longer sufficient, and the community is interested in preparing uniform surfactant films on a variety of substrates, typically characterized by surface roughness, both geometric and chemical. Much of our understanding on surfactant films is due to advanced experimental techniques that function best on chemically homogeneous atomically smooth surfaces. Simulations studies have also been conducted on similar substrates, often achieving results in apparent agreement with experimental observations. However, mounting evidence suggests that surface heterogeneity strongly affects the properties of adsorbed surfactant aggregates. To probe using computational approaches systems relevant for experimental investigations, one requires a combination of atomistic and coarse-grained approaches, both implemented using advanced algorithms. We discuss here a few possible approaches that could be used to study surfactant films adsorbed on heterogeneous surfaces, and how they could be combined with experimental investigations. Some recent trends that attempt to predict surfactant performance are also briefly highlighted.

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“…Studies on the molecular arrangement of surfactants at the vacuumwater interfaces [1,2] have found the formation of molecular aggregates of surfactants at the interfacial region when they have relatively high concentrations of surfactants. Recently, molecular dynamic simulations of 8-phenyl hexadecane sulfonate, located at the n-tetradecane/water interface, have reported similar aggregation of surfactants at low concentration [2]. In that work, Paredes et al concluded that the interface equilibrium time (several microseconds) is orders of magnitude greater than the obtained in other systems simulated.…”

Section: Introductionmentioning

confidence: 99%

“…In that work, Paredes et al concluded that the interface equilibrium time (several microseconds) is orders of magnitude greater than the obtained in other systems simulated. In fact, there was convincing indication that this slow equilibration process is due to surfactant aggregation at the interfacial region [2]. Therefore, the understanding of the nature of the aggregation in this type of molecules is fundamental and would have strong consequences on their simulation times.…”

Section: Introductionmentioning

confidence: 99%

Exploring the nature of the interactions between the molecules of the sodium dodecyl sulfate and water in crystal phases and in the water/vacuum interface

Aray

Parra

Paredes

et al. 2020

Heliyon

Self Cite

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The nature of the interaction between the molecules of the sodium dodecyl sulfate surfactant forming two crystal phases, one anhydrous, NaC 12 H 25 O 4 S and the other, NaC 12 H 25 O 4 S.H 2 O, hydrated with one water molecule for unit cell, has been studied in detail using the quantum theory of atoms in molecules and a localized electron detector function. It was found that for the anhydrous crystal, the head groups of the surfactant molecules are linked into a head-to-head pattern, by a bond path network of Na-O ionic bonds, where each Na þ atom is attached to four SO À 4 groups. For the hydrated crystal, in addition to these four bonds for Naþ, two additional ones appear with the oxygen atoms of the water molecules, forming a bond paths network of ionic Na-O bonds, that link the Na þ atoms with the SO À 4 groups and the H 2 O molecules. Each H 2 O molecule is bonded to two SO À 4 groups via hydrogen bonds, while the SO À 4 groups are linked to a maximum of four Naþ atoms. The phenomenon of aggregation of the sodium dodecyl sulfate molecules at the liquid water/vacuum interface was studied using NVT molecular dynamics simulations. We have found that for surfactant aggregates, the Naþ ions are linked to a maximum of three SO 4 groups and three water molecules that form Na-O bonds. Unlike hydrated crystal, each of the O atoms that make these Na-O bonds is linked to only one Naþ ion. Despite these differences, like the crystal phases, the surfactant molecules tend to form a head-to-head network pattern of ionic Na-O bonds that link their heads. The present results indicate that the clustering of anionic surfactant at the water/vacuum interface is a consequence of the electrostatic alignment of the cationic and anionic groups as occurs in the crystalline phases of sodium dodecyl sulfate.

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Dynamics of Surfactant Clustering at Interfaces and Its Influence on the Interfacial Tension: Atomistic Simulation of a Sodium Hexadecane–Benzene Sulfonate–Tetradecane–Water System

Cited by 17 publications

References 43 publications

Effects of Salinity and N-, S-, and O-Bearing Polar Components on Light Oil–Brine Interfacial Properties from Molecular Perspectives

Effects of Salinity and N-, S-, and O-Bearing Polar Components on Light Oil–Brine Interfacial Properties from Molecular Perspectives

Studying surfactants adsorption on heterogeneous substrates

Exploring the nature of the interactions between the molecules of the sodium dodecyl sulfate and water in crystal phases and in the water/vacuum interface

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