A thermodynamic model for molten salt-water solutions - Application to a thermodynamic optimization of the Ca(NO3)2-KNO3-H2O system

A new thermodynamic model has been developed for molten salt-water solutions. The model applies particularly to salt-rich solutions but may be applied over the entire composition range from anhydrous salts to pure H2O. The model is an extension of the two-sublattice Modified Quasichemical Model for molten anhydrous salt solutions with first-nearest-neighbour short-range ordering. The model assumes the existence of hydrated cations such as K(H2O)j+ and Ca(NO3)k2+ as well as “free” neutral H2O molecules. The model has been used in a complete critical evaluation and thermodynamic optimization of the three binary systems KNO3-Ca(NO3)2, KNO3-H2O and Ca(NO3)2-H2O and of the ternary system Ca(NO3)2-KNO3-H2O.