Vapor–Liquid and Solid Equilibria of Mixed Aluminum–Calcium or Calcium Chlorides in Aqueous Solutions at Various Temperatures, Experimental Measurements, and Thermodynamic Modeling

Abstract

The vapor–liquid–solid equilibria and thermodynamic properties of mixed aluminum and calcium chlorides in aqueous solutions were studied at different temperatures. The experimental water activities for the ternary system AlCl3–CaCl2–H2O and the binary subsystem of CaCl2(aq) were measured from dilution to saturated solutions using the hygrometric method at various temperatures. From these measurements, the osmotic coefficients of water were determined for the salt-aqueous solutions. The related thermodynamic properties of CaCl2–H2O were evaluated by the developed models of Pitzer, extended ion interaction, and Clegg–Pitzer–Brimblecombe. The binary parameters of these models were obtained at different temperatures. For the mixed system of aluminum and calcium chlorides, the new ternary parameters of the ion interaction model were determined at various temperatures and used to calculate the activity coefficients. The solubility of CaCl2(aq) was carried out up to mmax = (10.987 to 13.245) mol kg–1 from (298.15 to 353.15) K. For {yAlCl3 + (1 – y)CaCl2}(aq), the solubilities in aqueous solutions were performed for different ionic-strength fractions at various temperatures. The X-ray diffraction analysis of the precipitates, obtained by filtration, allows us to identify the formed solid phases. The solubility products as LnKsp° of CaCl2(aq) and the mixed solutions of aluminum and calcium chlorides were also given at various temperatures.