Phase equilibria of AlCl3 + FeCl3 + H2O, AlCl3 + CaCl2 + H2O, and FeCl3 + CaCl2 + H2O at 298.15 K

Abstract

In the recovery of aluminum from coal fly ash, the phase equilibria of solid–liquid systems are important for purifying the aluminum salts. This research investigated phase equilibria of the ternary systems AlCl3 + CaCl2 + H2O, AlCl3 + FeCl3 + H2O, and FeCl3 + CaCl2 + H2O at 298.15 K using isothermal dissolution method. The corresponding phase diagrams and density diagrams were plotted. Both AlCl3 + CaCl2 + H2O and AlCl3 + FeCl3 + H2O systems had one invariant point, two univariate curves, two crystallization regions, and no double salts. The FeCl3 + CaCl2 + H2O system had two invariant points, three crystallization regions and a double salt (CaCl2·2FeCl3·8H2O) that formed at 298.15 K. There is no solid solution in all the three systems.