Measurement and modeling of solubility of MgCl2 in 2-methylpropan-2-ol + water + glycerol + MgCl2 system: A solid-liquid equilibrium study based on symmetric eNRTL model and evaluation of thermodynamic functions of solutions

A comprehensive solid-liquid phase equilibrium to measure the solubility of MgCl2 in a 2-methylpropan-2-ol (2M2P) + water + glycerol system is investigated in the present study. The saturation concentrations of MgCl2 at different temperatures are reported for two different binary systems; 2M2P + MgCl2 and glycerol + MgCl2, a ternary system; 2M2P + water + MgCl2 and a quaternary system; 2M2P + water + glycerol + MgCl2 for a temperature range of 303.15-343.15 K at the local atmospheric pressure of 94.9 kPa. The thermodynamic functions of the solutions viz. Gibbs free energy change, dissolution enthalpy, dissolution entropy and isobaric heat capacity are evaluated by combining the modified Apelblat equation with the Clark-Glew equation to analyze the dissolution process at the molecular level. The molality based solubility product of MgCl2 in the different systems explored presently, is calculated using the mean ionic activity coefficients at different saturation temperatures. The experimental solubility data is fitted to the symmetric eNRTL model embedded in Aspen Plus in order to validate the thermodynamic consistency of the data. The high goodness of fit between experimental and predicted solubility data establishes the accuracy of the symmetric eNRTL model to represent the solid-liquid equilibria of MgCl2 in the 2M2P + water + glycerol + MgCl2 system. Hence, this model can suitably be adopted for the process modeling and simulation of aqueous as well as non-aqueous electrolyte solutions involving MgCl2.