Abstract:
In order to obtain the interaction law between aluminum and coexisting calcium and magnesium in leaching solution containing aluminum of fly ash, the phase equilibria of the quaternary system MgCl
2+CaCl
2+AlCl
3+H
2O was investigated by isothermal dissolution method at 298.2 K. The composition of liquid phase and density were determined. Meanwhile, the phase diagram, water diagram and density vs composition diagram of the quaternary system were drawn, respectively. It was found that the stable phase diagram of the quaternary system MgCl
2+CaCl
2+AlCl
3+H
2O consisted of two invariant points, four crystallization regions and five univariate curves, which belonged to a complex system with the double salt of tachyhydrite formed. These four crystallization regions corresponded to single salts MgCl
2·6H
2O, CaCl
2·6H
2O, AlCl
3·6H
2O and double salt 2MgCl
2·CaCl
2·12H
2O, respectively. The crystallization regions decreaseed in the order of AlCl
3·6H
2O, MgCl
2·6H
2O, CaCl
2·6H
2O and 2MgCl
2·CaCl
2·12H
2O, the solubility of AlCl
3·6H
2O was the smallest and the solubility of 2MgCl
2·CaCl
2·12H
2O is the highest.
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