A modified electrolyte-Uniquac model for computing the activity coefficient and phase diagrams of electrolytes systems

Abstract A modified electrolyte-Uniquac model describing the behaviour of single and multicomponent electrolyte systems was developed. The thermodynamic properties of electrolyte solutions are considered to be the sum of two contributions: the long-range represented by Debye–Huckel contributions and the local-composition expression (modified Uniquac type) that have been applied to account for short-range contributions. The local mole fractions are calculated based on the assumptions proposed by Chen and coworkers. The model has been tested on 86 aqueous electrolyte solutions at 298.15 K and results have been compared with those obtained from the Pitzer and electrolyte-NRTL models. The modified electrolyte-Uniquac model led to the accurate calculation of individual activity coefficient of ion. This new model can also be used to predict the excess properties and the salt solubility in aqueous multielectrolyte solutions with the interaction parameters obtained from binary data.