Phase behavior of sodium and potassium salts in their aqueous solutions: Experiment and computational thermodynamics

Abstract With the rapid development of the semiconductor industry, the demand for ultraclean and high‐purity electronic chemicals, especially ultrapure water as a general solvent for cleaning semiconductor chips, has increased dramatically. The distillation process is a good choice for large‐scale production of ultrapure water that can be used to clean semiconductor chips, but there is a lack of basic thermodynamic theory for removing ionic impurities. In this work, the temperature and vapor–liquid phase composition of sodium and potassium salts aqueous solutions at vapor–liquid equilibrium (VLE) were investigated by experiments. The microstructure of each inorganic salt aqueous solution was explored by molecular dynamics simulation and quantum chemical calculation, and the interaction between each ion and water molecule was analyzed. A volatilization mechanism of inorganic salts was proposed, and it was found that the volatilization of inorganic salts in an aqueous solution was affected by the strength of interaction between the dissociated anions and cations and water molecules. Finally, the conductor‐like screening model segment activity coefficient (COSMO‐SAC) model predicted the VLE values of inorganic salt aqueous solutions. The prediction at low concentrations ( x s < 0.06) was in good agreement with the experimental data.