Solid–Liquid Equilibrium Phase Diagram and Calculation in the Quaternary System (KBr + NaBr + MgBr2 + H2O) at 298 K

The solid–liquid equilibrium of the quaternary system (KBr + NaBr + MgBr2 + H2O) was accurately investigated at 298 K. The equilibrium phase diagram was obtained and consisted of seven dissolution isotherms, three co-saturated points and five solid crystallization regions under the condition of 298 K. The five solid crystallization regions contain four single salts NaBr·2H2O, NaBr, KBr, MgBr2·6H2O and one double salt KBr·MgBr2·6H2O, respectively. The largest crystallization region corresponds to KBr comprising more than half of the region of the equilibrium phase diagram. Using Pitzer’s model and mathematical calculation tools, the solubilities of the bromide minerals in this system were calculated; the calculation results are basically consistent with the experimental results. The research in this paper is of great significance in guiding the development of bromine resources of underground brines in the Western Sichuan Basin and providing fundamental thermodynamic data of bromine-containing systems.