Effect of divalent ions on the dynamics of disjoining pressure induced by salinity modification
| Autor: | Vahid Niasar, Omar E. Godinez-Brizuela |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Disjoining pressure Thermodynamics Ionic bonding 02 engineering and technology Electrolyte 010402 general chemistry 01 natural sciences Ion Physics::Fluid Dynamics Electrokinetic phenomena symbols.namesake Materials Chemistry Physical and Theoretical Chemistry Spectroscopy Debye length Surface force 021001 nanoscience & nanotechnology Condensed Matter Physics Atomic and Molecular Physics and Optics 0104 chemical sciences Electronic Optical and Magnetic Materials Condensed Matter::Soft Condensed Matter Ionic strength symbols 0210 nano-technology |
| Zdroj: | Journal of Molecular Liquids. 291:111276 |
| ISSN: | 0167-7322 |
| DOI: | 10.1016/j.molliq.2019.111276 |
| Popis: | Disjoining pressure is defined as the net difference between the pressure in a water film and that of the bulk fluid. It is known that disjoining pressure in water films is one of the thermodynamic aspects that control wettability, and is itself locally determined by short-range and long-range surface forces. Modifying the ionic strength and composition of water films leads to alteration of local electrostatic/electrokinetic forces, which results in the variation of disjoining pressure. This has been of particular interest in industrial applications such as enhanced oil recovery technology. In low salinity waterflooding, the variation of disjoining pressure has been linked to alteration of wettability, however, there are still many unanswered questions in this regard, such as the role of ion valency in the dynamics of disjoining pressure. In this work, we carried out a numerical study of the relation between ionic composition and disjoining pressure in a water film, induced by the reduction of the ionic strength in the bulk fluid. We compared systems composed of electrolytes of different valencies, with the aim of studying the impact of divalent ions and the role of charge symmetry on disjoining pressure. We simulate the initial equilibrium conditions under high ionic strength by solving the Poisson-Boltzmann equation. Then, we reduce the ionic strength at the boundary of the domain and use the Poisson-Nernst-Planck equations to model the transient re-distribution of ions within the film. In order to investigate the impact of ionic composition on the ionic transport and pressure dynamics, all simulations are implemented at the same initial ionic strength, but different ion pairs (1:1, 1:2 and 2:1), and different finite film thicknesses. We discuss the impact of system scaling factors in the total disjoining pressure, such as the ratio between film thickness and Debye length, as well as the relation between the electrostatic and osmotic pressure effects. |
| Databáze: | OpenAIRE |
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