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Title: Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air

Abstract

For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends between each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [2];  [1]
  1. National Energy Technology Lab. (NETL), Pittsburgh, PA (United States)
  2. National Energy Technology Lab. (NETL), Pittsburgh, PA (United States); AECOM, South Park, PA (United States)
Publication Date:
Research Org.:
National Energy Technology Laboratory, Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org.:
USDOE; National Energy Technology Laboratory (NETL)
OSTI Identifier:
1366718
Report Number(s):
NETL-PUB-20956
Journal ID: ISSN 1520-6106; NETL-PUB-20956; TRN: US1703085
Grant/Contract Number:
E15PG00032
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 121; Journal Issue: 13; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Chong, Leebyn, Lai, Yungchieh, Gray, McMahan, Soong, Yee, Shi, Fan, and Duan, Yuhua. Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.6b13040.
Chong, Leebyn, Lai, Yungchieh, Gray, McMahan, Soong, Yee, Shi, Fan, & Duan, Yuhua. Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air. United States. doi:10.1021/acs.jpcb.6b13040.
Chong, Leebyn, Lai, Yungchieh, Gray, McMahan, Soong, Yee, Shi, Fan, and Duan, Yuhua. Wed . "Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air". United States. doi:10.1021/acs.jpcb.6b13040. https://www.osti.gov/servlets/purl/1366718.
@article{osti_1366718,
title = {Molecular Dynamics Study of the Bulk and Interface Properties of Frother and Oil with Saltwater and Air},
author = {Chong, Leebyn and Lai, Yungchieh and Gray, McMahan and Soong, Yee and Shi, Fan and Duan, Yuhua},
abstractNote = {For water treatment purposes, the separation processes involving surfactants and crude oil at seawater-air interfaces are of importance for chemical and energy industries. Little progress has been made in understanding the nanoscale phenomena of surfactants on oily saltwater-air interfaces. This work focuses on using molecular dynamics with a united-atom force field to simulate the interface of linear alkane oil, saltwater, and air with three surfactant frothers: methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE). For each frother, although the calculated diffusivities and viscosities are lower than the expected experimental values, our results showed that diffusivity trends between each frother agree with experiments but was not suitable for viscosity. Binary combinations of liquid (frother or saltwater)-air and liquid-liquid interfaces are equilibrated to study the density profiles and interfacial tensions. The calculated surface tensions of the frothers-air interfaces are like that of oil-air, but lower than that of saltwater-air. Only MIBC-air and terpineol-air interfaces agreed with our experimental measurements. For frother-saltwater interfaces, the calculated results showed that terpineol has interfacial tensions higher than those of the MIBC-saltwater. Here, the simulated results indicated that the frother-oil systems underwent mixing such that the density profiles depicted large interfacial thicknesses.},
doi = {10.1021/acs.jpcb.6b13040},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
number = 13,
volume = 121,
place = {United States},
year = {Wed Mar 15 00:00:00 EDT 2017},
month = {Wed Mar 15 00:00:00 EDT 2017}
}

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Free Publicly Available Full Text
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Cited by: 2works
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  • Separating oil from saltwater is a process relevant to some industries and may be aided by bubble and froth generation. Simulating saltwater–air interfaces adsorbed with surfactants and oil molecules can assist in understanding froth stability to improve separation. Here, combining with surface tension experimental measurements, in this work we employ molecular dynamics with a united-atom force field to linear alkane oil and three surfactant frothers, methyl isobutyl carbinol (MIBC), terpineol, and ethyl glycol butyl ether (EGBE), to investigate their synergistic behaviors for oil separation. The interfacial phenomena were measured for a range of frother surface coverages on saltwater. Density profilesmore » of the hydrophilic and hydrophobic portions of the frothers show an expected orientation of alcohol groups adsorbing to the polar water. A decrease in surface tension with increasing surface coverage of MIBC and terpineol was observed and reflected in experiments where the frother concentration increased. Relations between surface coverage and bulk concentration were observed by comparing the surface tension decreases. Additionally, a range of oil surface coverages was explored when the interface has a thin layer of adsorbed frother molecules. Finally, the obtained results indicate that an increase in surface coverage of oil molecules led to an increase in surface tension for all frother types and the pair correlation functions depicted MIBC and terpineol as having higher distributions with water at closer distances than with oil.« less
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  • We investigated the solvation and spectroscopic properties of SO2 at the air/water interface using molecular simulation techniques. Molecular interactions from both Kohn-Sham (KS) density functional theory (DFT) and classical polarizable models were utilized to understand the properties of SO2:(H2O)x complexes in the vicinity of the air/water interface. The KS-DFT was included to allow comparisons with sum-frequency generation spectroscopy through the identification of surface SO2:(H2O)x complexes. Using our simulation results, we were able to develop a much more detailed picture for the surface structure of SO2 that is consistent with the spectroscopic data obtained Richmond and coworkers (J. Am. Chem. Soc.more » 127, 16806 (2005)). We also found many similarities and differences between to the two interaction potentials, including a noticeable weakness of the classical potential model in reproducing the asymmetric hydrogen bonding of water with SO2 due to its inability to account for SO2 resonance structures. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less
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