A predictive model for the excess gibbs free energy of fully dissociated electrolyte solutions



In this work, we show that the mean activity coefficient, osmotic coefficient, and vapor pressure of aqueous electrolyte solutions can be successfully predicted through combining the Pitzer-Debye-Hückel model for long-range interactions and the modified COSMO-SAC model for short-range interactions. This method contains only a small number (13) of universal parameters to describe various types of interactions between different species, such as ions, hydrogen-bonding species, and non-hydrogen bonding species. This approach does not require any pair interaction parameters between species and does not contain any ion specific parameter other than the element radius. We have examined this method for the properties of three types of systems, including a single salt in water, mixture salts in water, and a single salt in solvent mixtures containing water and alcohols. The predicted results are found to be in good agreement with those from experiments over wide ranges of concentration and temperature. This model is, in principle, applicable to all types of electrolyte solutions and is especially useful for property estimation for cases when no experimental data are available. © 2010 American Institute of Chemical Engineers AIChE J, 2011