Phase diagrams for the ternary system (NH4NO3 + CsNO3 + H2O) at 298.15 and 348.15 K and its application to cesium nitrate recovery from the eluent aqueous solution of ammonium nitrate

Abstract

A novel green process for CsNO3 separation from the eluent solution of NH4NO3 was developed based on the predictive phase diagrams of (NH4NO3 + CsNO3 + H2O) at 298.15 and 348.15 K, which were drawn using the Pitzer and its extended HW model. These single-salt parameters and the mixing ion parameters obtained either from the literature or fitted with the relevant experimental data in the literature were used to calculate the solubilities of the ternary system (NH4NO3 + CsNO3 + H2O) at two temperatures successfully. Based on phase diagrams at 298.15 and 348.15 K, a comparison of the ternary system diagrams shows that area of CsNO3 crystallized region is decreased obviously with the increasing temperature, which accounts for separating cesium nitrate from eluent by raising the temperature. Under the guidance of the predictive phase diagram at 298.15 and 348.15 K, the separating process of cesium nitrate from the eluent solution of ammonium nitrate by three fractional crystallization operations was established for the first time, and the material balance of the cyclic process is presented.