Solubility Measurement and Calculation of the Quaternary System KCl–KBr–NaCl–NaBr–H2O at 323.15 K

With the increasing scarcity of underground brine, bittern has proven to be a better alternative source for bromine resources. Aiming at the comprehensive utilization of the bromine resources in bittern, solid–liquid equilibrium in the quaternary system KCl–KBr–NaCl–NaBr–H2O at 323.15 K was investigated experimentally by the approach of isothermal dissolution equilibrium. The phase diagram was drawn with the measured results and composed of an isothermal solubility curve and two crystallization zones of two solid solutions (K(Cl, Br)) and (Na(Cl, Br)). Using an improved model established based on the Pitzer model, the solubilities of the ternary subsystems NaBr–NaCl–H2O, KCl–KBr–H2O and the quaternary system KCl–KBr–NaCl–NaBr–H2O were calculated. The results showed that the computed solubilities agree well with the measured values.