Interfacial properties of the aromatic hydrocarbon plus water system in the presence of hydrophilic silica

YF Yang and AKN Nair and MFAC Ruslan and SY Sun, JOURNAL OF MOLECULAR LIQUIDS, 346, 118272 (2022).

DOI: 10.1016/j.molliq.2021.118272

Molecular dynamics simulations and density gradient theory are used to get insights into the interfacial behavior of the aromatic hydrocarbon + H2O and aromatic hydrocarbon + H2O + silica (hydrophilic) systems under geological conditions. Four aromatic hydrocarbons are considered, namely, benzene, toluene, ethylbenzene, and o-xylene. The increase in the IFT with increasing pressure for the aromatic hydrocarbon + H2O system may be explained by a negative surface excess of the aromatic hydrocarbon. These surface excesses follow the order benzene < toluene < ethylbenzene < o-xylene and are directly correlated with the aromatic- aromatic interactions. The simulated contact angles of water are in the range of about 81-93 degrees (in many instances "degree" sign is not in the superscript) for the aromatic hydrocarbon + H2O + silica system and are almost similar for all studied aromatic hydrocarbons. Furthermore, the interfacial behavior of, for example, the aromatic hydrocarbon + H2O + silica system is compared with that of the hexane + H2O + silica system. The IFT of the hexane + H2O system is much higher than that of the aromatic hydrocarbon + H2O system. The effect of pressure on the IFT of the hexane + H2O system is much stronger than that of the aromatic hydrocarbon + H2O system. The simulated contact angle of water for the hexane + H2O + silica system is in the range of about 58-77 degrees and is lower than that of the aromatic hydrocarbon + H2O + silica system. Interestingly, in all studied systems, thin water films are found at the silica surface in the hydrocarbon-rich region. (C) 2021 Elsevier B.V. All rights reserved.

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