Solubilities of Salts in Quaternary System KBr–K2SO4–K2B4O7–H2O and Quinary System KCl–KBr–K2SO4–K2B4O7–H2O at 373 K

The underground brines are large reserves of valuable mineral resources. Aiming at the underground brines of western Sichuan Basin, the phase equilibria of quinary system KCl–KBr–K2SO4–K2B4O7–H2O and its quaternary subsystem KBr–K2SO4–K2B4O7–H2O were studied by using the method of isothermal dissolution equilibrium at 373 K. The phase diagrams, water content diagrams and density-composition relationship diagrams of above two systems were plotted by using the experimental data, respectively. The results show that the quaternary system KBr–K2SO4–K2B4O7–H2O belongs to a simple type; it consists of three univariant curves, one invariant point and three crystallization regions (K2B4O7⋅4H2O, K2SO4, and KBr). The equilibrium phase diagram (saturated with K2SO4) in the quinary system KCl–KBr–K2SO4–K2B4O7–H2O is a type of solid solution, and there are two crystallization regions (K2B4O7⋅4H2O, solid solution K(Cl,Br)) (saturated with K2SO4), one univariant curve and no invariant point.