Correlation and prediction of interface tension for fluid mixtures: An approach based on cubic equations of state with t
- PDF / 170,938 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 89 Downloads / 200 Views
Basic and Applied Research: Section I
Correlation and Prediction of Interface Tension for Fluid Mixtures: An Approach Based on Cubic Equations of State with the Wong-Sandler Mixing Rule Andre´s Mejı´a, Hugo Segura, Jaime Wisniak, and Ilya Polishuk
(Submitted June 4, 2004; in revised form January 24, 2005) Concentration profiles, interface thickness, and interface tensions have been calculated for mixtures applying the gradient theory to the Peng-Robinson equation of state. The approach is based on an accurate local fit of vapor-liquid equilibrium (VLE) data, and, for this purpose, the flexibility of the original Wong-Sandler mixing rule has been taken into account. Correlation and prediction capabilities of experimental interfacial tension data are analyzed for the quadratic mixing rule and the present approach. The method, which is discussed in detail in this work, provides an improved scheme for calculating interfacial properties, both for polar and nonpolar mixtures. According to results, a better correlation and prediction of the interfacial tensions can be obtained from an adequate interpolation of the VLE, using simple cubic equations of state. Examples are presented for binary and ternary mixtures.
1. Introduction The interfacial tension () between phases is an important physical property because many physical and chemical processes take place at the interface of solids, liquids, and vapors. Typical cases in which the interfacial behavior plays a central role are the adhesion of surfaces, stability of foams, generation of drops and bubbles, wetting, coating, recovery of oil from wells, and phase behavior in porous media.[1] These processes differ considerably from those observed in the corresponding bulk phase and depend drastically on the magnitude of . Due to its technological importance, a theoretical approach that is able to correlate or predict as a function of temperature, pressure, and concentration is valuable from a practical viewpoint. One of the most successful approaches is the gradient theory (GT), originally developed by van der Waals, and reformulated later by Cahn and Hilliard.[2] Briefly, the GT describes a continuous evolution of the density of the Helmholtz energy along the interface, from which the interfacial concentration profile and can be calculated. Since then, many works have been devoted to improve the results of the GT by modeling the Helmholtz energy with different equations of state (EOS). A significant advantage of such an approach is that a common EOS model can be used to calculate and the phase equilibrium condition that promotes the coexistence of phases. As follows from the recent review of Kahl and Enders,[3] major work regarding the prediction of has been based on Andre´s Mejı´a and Hugo Segura, Departamento de Ingenierı´a Quı´mica, Universidad de Concepcio´n, P.O. Box 160-C-Correo 3, Concepcio´n, Chile; Jaime Wisniak, Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel; and Ilya Polishuk, the Department of Chemical
Data Loading...
