Interfacial properties of binary mixtures

Interfacial properties are important in many engineering applications throughout the chemical industry (i.e. distillation and extraction columns, piping used for adsorption and fluid flow). The variation of interfacial properties (interfacial tension, interfacial profiles, interfacial thickness and relative Gibbs adsorption of one component) with temperature and pressure strongly influences the mass transport between fluid phases. In this contribution the gradient theory is applied for modelling the interfacial properties of planar interface in different binary systems between two fluid phases. The Cahn–Hilliard theory was combined with the Peng–Robinson EOS or the original SAFT EOS in order to describe both the phase behaviour and the interfacial properties. The paper focuses on the experimental and theoretical investigation of the interfacial tension between the coexisting liquid phases. In the present study we find that for mixtures containing associating components the simultaneous correlation of both phase equilibria and interface properties with the SAFT EOS in combination with the Cahn–Hilliard theory is possible. For systems where only vapour–liquid equilibria are present, the simpler PR EOS can be used for the simultaneous modelling of phase and interfacial properties.