چكيده به لاتين
In this work, the SAFT-based equations of state (EOSs) have been extended to electrolyte solutions to predict the first and second order derivative thermodynamic properties. To predict the second order derivative properties, temperature and solution density dependent of long-range intermolecular contributions play an important role. In this study, the long-range interaction has been modified using modified version of static permittivity that has been extended using Onsager-Kirkwood-Frohlich theory. The results show that, using aforementioned theory, the standard thermodynamic properties of electrolyte solutions such as heat capacity, Gibbs free energy and enthalpy of hydration have been predicted up to high pressure and temperature without any additional adjustable paramter. Next, using standard properties, isobaric heat capacity has been predicted at various salt concentrations. On the other hand, the short-range interaction contribution between ions and solvent play a crucial role in phase behavior modeling of electrolyte solutions. The results show that, the dispersion contribution of PC-SAFT EOS is not capable to reproduce the soli-liquid equilibrium of mixed electrolytes. Therefore, the viarable potential function is utilized to account the ion-solvent short-range interaction. In this regard, the Morse potential function is utilized and the new SAFT-VR equation of state is introduced. The Monte Carlo molecular simulation is utilized to check the first and second order Helmhomtz free energy of Barker and Henderson pertuerbation theory. As well, the accurate solution of PY integral equation is used to improve the radial distribution function results especially in contact distance. Using SAFT-VR Morse EOS, the first and second order derivative properties of electrolyte solutions have been predicted. The optimized value of potentaial range (λ) between ion and solvent improves the prediction of phase behavior of mixd electrolyte. Finally, the excess isobaric heat capacity and enthalpy of electrolyte solutions have been predicted at various temperatures. The results show that the SAFT-VRE Morse EOS is able to predict the mixed electrolyte phase equilibrium in addition to second order derivative properties of electrolyte solutions over wide range of temperature and pressure.
Keyword: equation of state, electrolyte, phas equilibrium, heat capacity, enthalpy.
