Physico - chemical properties of (MgF2 - CaF2 - (LiF))eut - MgO system as a molten electrolyte for Mg electrowinning

Phase diagrams (solubility), density, electrical conductivity and viscosity of molten system (MgF2 - CaF2)(eut) MgO have been investigated. The phase diagram of (MgF2 - CaF2 - Uncut- MgO and (MgF2 - BaF2)(eut)- MgO and the density of (MgF2 - CaF2 - LiF)(eut) - MgO have been also investigated. The solubility of MgO was measured by means of thermal analysis, the density by means of a computerized Archimedean method, electrical conductivity by means of a tube-cell (pyrolytic boron nitride) with stationary electrodes and the viscosity of the melt by computerized torsion pendulum method. It was found that the all investigated properties varied linearly with temperature in all investigated mixtures. On the basis of density values, the molar volume of the melts and partial molar volume have been calculated. The coordinates of the eutectic systems has been established as follows: (CaF2 - MgF2)(eut)- MgO as 0.30 mol% at 972 degrees C; (CaF2 - MgF2 - LiF)(eut) - MgO as 0.20 mol% at 941 degrees C; and (MgF2 - Bez)(eut) - MgO as 0.25 mol% at 883 degrees C. The density of the molten system of (CaF2 - MgF2)(eut) - MgO was found to be at 1000 degrees C: 2.687 g . cm(-3) for the system with 0 mol% of MgO; 2.700 g . cm(-3) for the system with 0.30 mol% of MgO and 2.728 g . cm(-3) for the system with 0.50 mol% of MgO. The density of the molten system of (CaF2 - MgF2 - LiF)(eut) - MgO was found to beat 1000 degrees C; 2.875 g.cm(-3) for the system with 0 mol% of MgO; 2.690 g.cm(similar to 3) for the system with 0.20 mol% of MgO and 2.650 g.cm(-3) for the system with 0.30 mol% of MgO. The viscosity of basic eutectic mixture of (CaF2 - MgF2)(eut) at 1000 degrees C was found to be 7.806 mPa.s. (C) 2018 Published by Elsevier B.V.