(574h) New SAFT Eos for Electrolyte Solution

In this study, the electrolyte Statistical Associating Fluid Theory (SAFT) equation of state (EOS) has been considered to represent solid liquid equilibrium of aqueous electrolyte solutions. In this regard, the SAFT-VR Morse and ePC-SAFT models were developed and modified respectively for this purpose. In the modified electrolyte PC-SAFT model, the modified version of static permittivity was utilized to consider the electrostatic effect of charged particles in solvent dielectric constant. In the case of electrolyte SAFT-VR Morse, the robust variable range potential was used to consider the short-range interaction between ion-ion and ion-solvent. For aforementioned models, the ion-specific parameters were obtained from the fitting of mean ionic activity coefficient and solution density (or apparent molar volume) data of several 1:1, 1:2 and 2:1 types binary electrolyte, simultaneously. Using single electrolyte parameters solid liquid equilibrium were predicted in some simple mixed electrolyte solution, however to have an accurate estimation of thermodynamic properties of mixed electrolyte solutions an additional parameter was needed to improve the cross dispersion energy between unlike particles. Therefore, the binary interaction parameters (BIPs) have been introduced to improve the model prediction results. The results showed that, for the case of SAFT-VR Morse model smaller absolute value of BICs compared to ePC-SAFT is required to predict the solid-liquid equilibrium (SLE) of mixed electrolyte solutions. It is indicated that, the suitable short-range interaction between charged and uncharged particles can improves the model capability especially in mixed electrolyte solutions. In addition, the Gibbs free energy of hydration and hydration enthalpy were predicted at 298.15 K and 1bar. The results were in good agreement with experimental data. The results showed that in the case of Gibbs free energy and enthalpy of hydration, two mentioned models give comparable values but in SLE of mixed electrolyte solutions, the SAFT-VRE Morse EOS gives accurate results using smaller correction parameters (BIPs).