Phase Equilibria in the Quaternary Systems (KCl + CaCl2 + SrCl2 + H2O) and (LiCl + NaCl + SrCl2 + H2O) at 288.15 K and 0.1 MPa

Phase equilibria of the quaternary systems (KCl + CaCl2 + SrCl2 + H2O) and (LiCl + NaCl + SrCl2 + H2O) at 288.15 K and 0.1 MPa were studied using the isothermal dissolution method, and the phase diagrams of the two systems mentioned above were plotted. There are two invariant points and four crystallization regions in the quaternary system (KCl + CaCl2 + SrCl2 + H2O). Besides the crystallization regions of the minerals KCl, CaCl2·6H2O, and SrCl2·6H2O, the solid solution (Ca,Sr)Cl2·6H2O was found. The strontium and calcium salts can be separated from each other by avoiding crystallization in the solid solution region. There are two invariant points and four crystallization regions corresponding to NaCl, SrCl2·6H2O, SrCl2·2H2O, and LiCl·2H2O in the quaternary system (LiCl + NaCl + SrCl2 + H2O). Lithium chloride has a strong salting-out effect on NaCl and SrCl2·6H2O. The experiment results of the quaternary systems (KCl + CaCl2 + SrCl2 + H2O) and (LiCl + NaCl + SrCl2 + H2O) have a significant value for separating and purifying minerals from the oilfield brine in the Nanyishan Section of the Qaidam Basin.