298.2 K四元体系MgCl2+CaCl2+AlCl3+H2O 相平衡研究

为获取粉煤灰含铝溶浸液中铝与共存钙、镁之间的作用规律，采用等温溶解平衡法开展了298.2 K时四元体系MgCl₂+CaCl₂+AlCl₃+H₂O相平衡研究，测定了平衡液相组成及平衡液相密度，同时，绘制了该四元体系的干基相图、水图、密度-组成图。研究发现:298.2 K四元体系MgCl₂+CaCl₂+AlCl₃+H₂O 稳定相图由2个共饱点、4个结晶区以及5条单变量曲线组成，有复盐溢晶石（2MgCl₂·CaCl₂·12H₂O）生成，为复杂四元体系。4个结晶区分别对应3个单盐结晶区MgCl₂·6H₂O、CaCl₂·6H₂O、AlCl₃·6H₂O和1个复盐结晶区2MgCl₂·CaCl₂·12H₂O，结晶区按照AlCl₃·6H₂O、MgCl₂·6H₂O、CaCl₂·6H₂O、2MgCl₂·CaCl₂·12H₂O顺序依次减小，对应AlCl₃·6H₂O溶解度最小，2MgCl₂·CaCl₂·12H₂O溶解度最大。 

Phase Equilibria of Aqueous Quaternary System MgCl2+CaCl2+AlCl3+H2O at 298.2 K

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 MgCl₂+CaCl₂+AlCl₃+H₂O 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 MgCl₂+CaCl₂+AlCl₃+H₂O 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 MgCl₂·6H₂O, CaCl₂·6H₂O, AlCl₃·6H₂O and double salt 2MgCl₂·CaCl₂·12H₂O, respectively. The crystallization regions decreaseed in the order of AlCl₃·6H₂O, MgCl₂·6H₂O, CaCl₂·6H₂O and 2MgCl₂·CaCl₂·12H₂O, the solubility of AlCl₃·6H₂O was the smallest and the solubility of 2MgCl₂·CaCl₂·12H₂O is the highest.