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Molecular Simulation in Interface and Surfactant

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Computational and Theoretical Chemistry".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 19101

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Special Issue Editors

Key Lab of Colloid and Interface Chemistry, Shandong University, Jinan 250100, China
Interests: molecular simulation on polymer; surfactant; self-assembly
Special Issues, Collections and Topics in MDPI journals
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
Interests: physical chemistry of surfactant; computer simulation about surface science; molecular simulation on self-assemble system
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The application fields of colloid and interface chemistry are very wide, covering many aspects such as industrial and agricultural production, daily chemistry, enhanced oil recovery and so on. Traditional experimental analysis of colloid and interface chemistry system includes various instrumental analysis methods such as spectroscopy, rheometer, microscopes, etc. Recent decades molecular simulation has become an important research method in this field. It can investigate at molecular level and provide mechanisms or insights that is hard or impossible from experiment. Many applications of molecular simulation were reported in the literature, such as the behavior of surfactant, self-assembly, enhanced oil recovery, adsorption around interface, etc.

This special issue will include review articles on the application of molecular simulation in the field of colloid and interface chemistry, research articles on specific problems.

Prof. Dr. Shiling Yuan
Guest Editor

Mr. Heng Zhang
Assistant Guest Editor

Manuscript Submission Information

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Keywords

  • molecular dynamics simulation
  • surfactant
  • interface
  • self-assembly
  • aggregation

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Published Papers (9 papers)

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Research

15 pages, 5912 KiB  
Article
Molecular Dynamics Simulation for the Demulsification of O/W Emulsion under Pulsed Electric Field
by Shasha Liu, Shiling Yuan and Heng Zhang
Molecules 2022, 27(8), 2559; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27082559 - 15 Apr 2022
Cited by 4 | Viewed by 1767
Abstract
A bidirectional pulsed electric field (BPEF) method is considered a simple and novel technique to demulsify O/W emulsions. In this paper, molecular dynamics simulation was used to investigate the transformation and aggregation behavior of oil droplets in O/W emulsion under BPEF. Then, the [...] Read more.
A bidirectional pulsed electric field (BPEF) method is considered a simple and novel technique to demulsify O/W emulsions. In this paper, molecular dynamics simulation was used to investigate the transformation and aggregation behavior of oil droplets in O/W emulsion under BPEF. Then, the effect of surfactant (sodium dodecyl sulfate, SDS) on the demulsification of O/W emulsion was investigated. The simulation results showed that the oil droplets transformed and moved along the direction of the electric field. SDS molecules can shorten the aggregation time of oil droplets in O/W emulsion. The electrostatic potential distribution on the surface of the oil droplet, the elongation length of the oil droplets, and the mean square displacement (MSD) of SDS and asphaltene molecules under an electric field were calculated to explain the aggregation of oil droplets under the simulated pulsed electric field. The simulation also showed that the two oil droplets with opposite charges have no obvious effect on the aggregation of the oil droplets. However, van der Waals interactions between oil droplets was the main factor in the aggregation. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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13 pages, 54241 KiB  
Article
Demulsification of Heavy Oil-in-Water Emulsion by a Novel Janus Graphene Oxide Nanosheet: Experiments and Molecular Dynamic Simulations
by Yingbiao Xu, Yefei Wang, Tingyi Wang, Lingyu Zhang, Mingming Xu and Han Jia
Molecules 2022, 27(7), 2191; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27072191 - 28 Mar 2022
Cited by 4 | Viewed by 2214
Abstract
Various nanoparticles have been applied as chemical demulsifiers to separate the crude-oil-in-water emulsion in the petroleum industry, including graphene oxide (GO). In this study, the Janus amphiphilic graphene oxide (JGO) was prepared by asymmetrical chemical modification on one side of the GO surface [...] Read more.
Various nanoparticles have been applied as chemical demulsifiers to separate the crude-oil-in-water emulsion in the petroleum industry, including graphene oxide (GO). In this study, the Janus amphiphilic graphene oxide (JGO) was prepared by asymmetrical chemical modification on one side of the GO surface with n-octylamine. The JGO structure was verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), and contact angle measurements. Compared with GO, JGO showed a superior ability to break the heavy oil-in-water emulsion with a demulsification efficiency reaching up to 98.25% at the optimal concentration (40 mg/L). The effects of pH and temperature on the JGO’s demulsification efficiency were also investigated. Based on the results of interfacial dilatational rheology measurement and molecular dynamic simulation, it was speculated that the intensive interaction between JGO and asphaltenes should be responsible for the excellent demulsification performance of JGO. This work not only provided a potential high-performance demulsifier for the separation of crude-oil-in-water emulsion, but also proposed novel insights to the mechanism of GO-based demulsifiers. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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19 pages, 61524 KiB  
Article
Screening and Demulsification Mechanism of Fluorinated Demulsifier Based on Molecular Dynamics Simulation
by Xiaoheng Geng, Changjun Li, Lin Zhang, Haiying Guo, Changqing Shan, Xinlei Jia, Lixin Wei, Yinghui Cai and Lixia Han
Molecules 2022, 27(6), 1799; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27061799 - 09 Mar 2022
Cited by 5 | Viewed by 1938
Abstract
In order to solve the problem of demulsification difficulties in Liaohe Oilfield, 24 kinds of demulsifiers were screened by using the interface generation energy (IFE) module in the molecular dynamics simulation software Materials Studio to determine the ability of demulsifier molecules to reduce [...] Read more.
In order to solve the problem of demulsification difficulties in Liaohe Oilfield, 24 kinds of demulsifiers were screened by using the interface generation energy (IFE) module in the molecular dynamics simulation software Materials Studio to determine the ability of demulsifier molecules to reduce the total energy of the oil–water interface after entering the oil–water interface. Neural network analysis (NNA) and genetic function approximation (GFA) were used as technical means to predict the demulsification effect of the Liaohe crude oil demulsifier. The simulation results show that the SDJ9927 demulsifier with ethylene oxide (EO) and propylene oxide (PO) values of 21 (EO) and 44 (PO) reduced the total energy and interfacial tension of the oil–water interface to the greatest extent, and the interfacial formation energy reached −640.48 Kcal/mol. NNA predicted that the water removal amount of the SDJ9927 demulsifier was 7.21 mL, with an overall error of less than 1.83. GFA predicted that the water removal amount of the SDJ9927 demulsifier was 7.41mL, with an overall error of less than 0.9. The predicted results are consistent with the experimental screening results. SDJ9927 had the highest water removal rate and the best demulsification effect. NNA and GFA had high correlation coefficients, and their R2s were 0.802 and 0.861, respectively. The higher R2 was, the more accurate the prediction accuracy was. Finally, the demulsification mechanism of the interfacial film breaking due to the collision of fluorinated polyether demulsifiers was studied. It was found that the carbon–fluorine chain had high surface activity and high stability, which could protect the carbon–carbon bond in the demulsifier molecules to ensure that there was no re-emulsion due to the stirring external force. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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12 pages, 3473 KiB  
Article
DPD Simulation on the Transformation and Stability of O/W and W/O Microemulsions
by Menghua Li, Haixia Zhang, Zongxu Wu, Zhenxing Zhu and Xinlei Jia
Molecules 2022, 27(4), 1361; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27041361 - 17 Feb 2022
Cited by 10 | Viewed by 2371
Abstract
The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. [...] Read more.
The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. Inverse W/O microemulsion transform to O/W microemulsion by decreasing the ratio of oil-water from 3:1 to 1:3. The stability of O/W and W/O microemulsion is controlled by shear rate, inorganic salt and the temperature, and the corresponding results are analyzed by the translucent three-dimensional structure, the mean interfacial tension and end-to-end distance of H1T1. The results show that W/O microemulsion is more stable than O/W microemulsion to resist higher inorganic salt concentration, shear rate and temperature. This investigation provides a powerful tool to predict the structure and the stability of various microemulsion systems, which is of great importance to developing new multifunctional microemulsions for multiple applications. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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8 pages, 286 KiB  
Article
Self-Diffusion in Simple Liquids as a Random Walk Process
by Sergey A. Khrapak
Molecules 2021, 26(24), 7499; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26247499 - 11 Dec 2021
Cited by 13 | Viewed by 1806
Abstract
It is demonstrated that self-diffusion in dense liquids can be considered a random walk process; its characteristic length and time scales are identified. This represents an alternative to the often assumed hopping mechanism of diffusion in the liquid state. The approach is illustrated [...] Read more.
It is demonstrated that self-diffusion in dense liquids can be considered a random walk process; its characteristic length and time scales are identified. This represents an alternative to the often assumed hopping mechanism of diffusion in the liquid state. The approach is illustrated using the one-component plasma model. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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12 pages, 3847 KiB  
Article
MHD Stagnation Point on Nanofluid Flow and Heat Transfer of Carbon Nanotube over a Shrinking Surface with Heat Sink Effect
by Mohamad Nizam Othman, Alias Jedi and Nor Ashikin Abu Bakar
Molecules 2021, 26(24), 7441; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26247441 - 08 Dec 2021
Cited by 6 | Viewed by 1683
Abstract
This study is to investigate the magnetohydrodynamic (MHD) stagnation point flow and heat transfer characteristic nanofluid of carbon nanotube (CNTs) over the shrinking surface with heat sink effects. Similarity equations deduced from momentum and energy equation of partial differential equations are solved numerically. [...] Read more.
This study is to investigate the magnetohydrodynamic (MHD) stagnation point flow and heat transfer characteristic nanofluid of carbon nanotube (CNTs) over the shrinking surface with heat sink effects. Similarity equations deduced from momentum and energy equation of partial differential equations are solved numerically. This study looks at the different parameters of the flow and heat transfer using first phase model which is Tiwari-Das. The parameter discussed were volume fraction nanoparticle, magnetic parameter, heat sink/source parameters, and a different type of nanofluid and based fluids. Present results revealed that the rate of nanofluid (SWCNT/kerosene) in terms of flow and heat transfer is better than (MWCNT/kerosene) and (CNT/water) and regular fluid (water). Graphically, the variation results of dual solution exist for shrinking parameter in range λc<λ1 for different values of volume fraction nanoparticle, magnetic, heat sink parameters, and a different type of nanofluid. However, a unique solution exists at 1<λ<1, and no solutions exist at λ<λc which is a critical value. In addition, the local Nusselt number decreases with increasing volume fraction nanoparticle when there exists a heat sink effect. The values of the skin friction coefficient and local Nusselt number increase for both solutions with the increase in magnetic parameter. In this study, the investigation on the flow and heat transfer of MHD stagnation point nanofluid through a shrinking surface with heat sink effect shows how important the application to industrial applications. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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12 pages, 3656 KiB  
Article
Computational Investigations of a pH-Induced Structural Transition in a CTAB Solution with Toluic Acid
by Tingyi Wang, Hui Yan, Li Lv, Yingbiao Xu, Lingyu Zhang and Han Jia
Molecules 2021, 26(22), 6978; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26226978 - 19 Nov 2021
Viewed by 1437
Abstract
In this work, molecular dynamics simulations were performed to study the pH-induced structural transitions for a CTAB/p-toluic acid solution. Spherical and cylindrical micelles were obtained for aqueous surfactants at pH 2 and 7, respectively, which agrees well with the experimental observations. [...] Read more.
In this work, molecular dynamics simulations were performed to study the pH-induced structural transitions for a CTAB/p-toluic acid solution. Spherical and cylindrical micelles were obtained for aqueous surfactants at pH 2 and 7, respectively, which agrees well with the experimental observations. The structural properties of two different micelles were analyzed through the density distributions of components and the molecular orientations of CTA+ and toluic acid inside the micelles. It was found that the bonding interactions between CTA+ and toluic in spherical and cylindrical micelles are very different. Almost all the ionized toluic acid (PTA) in the solution at pH 7 was solubilized into the micelles, and it was located in the CTA+ headgroups region. Additionally, the bonding between surfactant CTA+ and PTA was very tight due to the electrostatic interactions. The PTA that penetrated into the micelles effectively screened the electrostatic repulsion among the cationic headgroups, which is considered to be crucial for maintaining the cylindrical micellar shape. As the pH decreased, the carboxyl groups were protonated. The hydration ability of neutral carboxyl groups weakened, resulting in deeper penetration into the micelles. Meanwhile, their bonding interactions with surfactant headgroups also weakened. Accompanied by the strengthen of electrostatic repulsion among the positive headgroups, the cylindrical micelle was broken into spherical micelles. Our work provided an atomic-level insights into the mechanism of pH-induced structural transitions of a CTAB/p-toluic solution, which is expected to be useful for further understanding the aggregate behavior of mixed cationic surfactants and aromatic acids. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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8 pages, 2310 KiB  
Article
Adsorption of Mussel Protein on Polymer Antifouling Membranes: A Molecular Dynamics Study
by Fengfeng Gao
Molecules 2021, 26(18), 5660; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26185660 - 17 Sep 2021
Cited by 3 | Viewed by 1946
Abstract
Biofouling is one of the most difficult problems in the field of marine engineering. In this work, molecular dynamics simulation was used to study the adsorption process of mussel protein on the surface of two antifouling films—hydrophilic film and hydrophobic film—trying to reveal [...] Read more.
Biofouling is one of the most difficult problems in the field of marine engineering. In this work, molecular dynamics simulation was used to study the adsorption process of mussel protein on the surface of two antifouling films—hydrophilic film and hydrophobic film—trying to reveal the mechanism of protein adsorption and the antifouling mechanism of materials at the molecular level. The simulated conclusion is helpful to design and find new antifouling coatings for the experiments in the future. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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14 pages, 2276 KiB  
Article
Determination of Minimum Miscibility Pressure of CO2–Oil System: A Molecular Dynamics Study
by Ding Li, Shuixiang Xie, Xiangliang Li, Yinghua Zhang, Heng Zhang and Shiling Yuan
Molecules 2021, 26(16), 4983; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26164983 - 17 Aug 2021
Cited by 5 | Viewed by 2175
Abstract
CO2 enhanced oil recovery (CO2-EOR) has become significantly crucial to the petroleum industry, in particular, CO2 miscible flooding can greatly improve the efficiency of EOR. Minimum miscibility pressure (MMP) is a vital factor affecting CO2 flooding, which determines [...] Read more.
CO2 enhanced oil recovery (CO2-EOR) has become significantly crucial to the petroleum industry, in particular, CO2 miscible flooding can greatly improve the efficiency of EOR. Minimum miscibility pressure (MMP) is a vital factor affecting CO2 flooding, which determines the yield and economic benefit of oil recovery. Therefore, it is important to predict this property for a successful field development plan. In this study, a novel model based on molecular dynamics to determine MMP was developed. The model characterized a miscible state by calculating the ratio of CO2 and crude oil atoms that pass through the initial interface. The whole process was not affected by other external objective factors. We compared our model with several famous empirical correlations, and obtained satisfactory results—the relative errors were 8.53% and 13.71% for the two equations derived from our model. Furthermore, we found the MMPs predicted by different reference materials (i.e., CO2/crude oil) were approximately linear (R2 = 0.955). We also confirmed the linear relationship between MMP and reservoir temperature (TR). The correlation coefficient was about 0.15 MPa/K in the present study. Full article
(This article belongs to the Special Issue Molecular Simulation in Interface and Surfactant)
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