Interfacial Properties of the Hexane + Carbon Dioxide + Brine System in the Presence of Hydrophilic Silica

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4 Scopus citations

Abstract

Molecular dynamics simulations were performed to understand the interfacial properties of brine (up to 5.4 mol/kg NaCl) and brine + silica systems in the presence of CO2, hexane, and their equimolar mixture under geological conditions. Simulation results of brine + CO2, brine + hexane, and brine + CO2 + hexane systems agree reasonably well with the theoretical results predicted using the density gradient theory based on the cubic-plus-association equation of state (with Debye–Hückel electrostatic term). In all these systems, the interfacial tension (IFT) increases linearly with increasing NaCl concentration. Here, simulated slopes of the NaCl concentration dependence of IFT are about 1.99 mN/(m mol kg–1), under all conditions. We observe a negative surface excess for NaCl, which may explain the increase in IFT with increasing NaCl concentration. The contact angle (CA) of H2O + CO2 + silica and brine + CO2 + silica systems increases with pressure and decreases with temperature. However, the CA of H2O + hexane + silica and brine + hexane + silica systems is nearly independent of temperature and pressure. These CAs are not significantly affected by the presence of CO2. An important result is that in all investigated systems, the CA increases with increasing salt content. Our simulated CA is in the ranges of 51.4–95.0°, 69.1–86.0°, and 72.0–87.9° for brine + CO2 + silica, brine + hexane + silica, and brine + CO2 + hexane + silica systems, respectively. The density profiles indicate that the positively charged hydrogen atom of the surface hydroxyl group attracts Cl– ions to the surface. In all investigated systems, the adhesion tensions decrease with increasing NaCl concentration.
Original languageEnglish (US)
JournalIndustrial & Engineering Chemistry Research
DOIs
StatePublished - Aug 21 2023

Bibliographical note

KAUST Repository Item: Exported on 2023-08-31
Acknowledged KAUST grant number(s): 5028 CRG2022
Acknowledgements: This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. 5028 CRG2022. R.C. and A.K.N.N. would like to thank KAUST for providing computational resources of the Shaheen II supercomputer. This work is also partly supported by the National Natural Science Foundation of China (Grant No. 42203041), the Natural Science Foundation of Jiangsu Province (Grant No. BK20221132), and the China Postdoctoral Science Foundation (Grant No. 2022M723398).

ASJC Scopus subject areas

  • General Chemical Engineering
  • General Chemistry
  • Industrial and Manufacturing Engineering

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