Phase Equilibria in the Ternary Systems Li2B4O7-MgB4O7-H2O and K2B4O7-MgB4O7-H2O at 273 K

Phase equilibria and phase diagram always play an important role to utilize the salt lake brine resources. In this paper, the phase equilibria in two ternary systems Li2B4O7-MgB4O7-H2O and K2B4O7-MgB4O7-H2O at 273 K were studied using the isothermal solubility equilibrium method. The densities and solubilities of the components in these systems listed above were measured. Based on the determined equilibrium data and the corresponding equilibrium solid phase, the phase diagram of the ternary systems were shown, respectively. The results show that the two ternary systems at 273 K are simple total saturated type and there are no complex salt and solid solution found. Besides, the phase diagrams of the two ternary systems are both constituted of a eutectic point, two univariant solubility curves, and two solid crystalline phase regions. The two equilibrium solid phases corresponding to the eutectic point of the Li2B4O7-MgB4O7-H2O ternary system are Li2B4O7 center dot H2O and MgB4O7 center dot 9H(2)O. In the K2B4O7-MgB4O7-H2O ternary system, K2B4O7 center dot 4H(2)O and MgB4O7 center dot 9H(2)O are the two equilibrium solid phases relevant to the eutectic point. Furthermore, the experimental results of densities were simply discussed, and the phase diagrams at different temperatures were compared.