Effects of electric field on vapor–liquid equilibrium of binary mixture

Abstract

Previous studies showed that electric fields could change the boiling point and vapor pressure of the vapor–liquid equilibrium (VLE) state of pure substances and mixtures. This is an important feature in controlling the separation of mixtures. In this paper, based on the principle of phase equilibrium, together with the formulas of chemical potential including the effect of electric field and the dielectric pressure, the Raoult’s law was extended to include the effect of electric field to describe VLE of a mixture under an external electric field. The effects of electric field on VLE can be calculated by combining the extended Raoult’s law and the Dalton’s law of partial pressure, and then, the effect of electric field on the relative volatility can also be calculated. Numerical calculations showed that the effects of an electric field on VLE depend on both the magnitude and the direction of the electric field, and the effects become obvious until the field strength is greater than 10\(^{7}\) V/m. When the direction of the electric field is parallel to the gas–liquid interface, the vapor pressure decreases; the equilibrium temperature, the mole fractions of the volatile component, and the relative volatility increase. While, when the direction of the electric field is perpendicular to the gas–liquid interface, the opposite changes in these properties appear. The shifting of the equilibrium curves caused by the electric field indicates that the electric field can cause the vapor–liquid phase transition and change the amount of the phase material.