Al_2(SO_4)_3-Na_2SO_4-H_2O三元体系298.15K和323.15K相平衡研究

Phase equilibrium of ternary system of Al_2(SO_4)_3-Na_2SO_4-H_2O at 298.15 K and 323.15 K

采用等温溶解平衡法获取了Al_2(SO_4)_3-Na_2SO_4-H_2O三元体系298.15 K,323.15 K下的固液相平衡数据并绘制了溶解平衡相图。研究发现:该体系在2个温度下的平衡固相,均有3个盐出现,即:298.15 K为Na_2SO_4·10H_2O,Al_2(SO_4)_3·18H_2O和相称复盐Na Al(SO_4)_2·12H_2O;在323.15 K为Na_2SO_4,Al_2(SO_4)_3·18H_2O和相称复盐Na Al(SO_4)2·6H_2O。每个温度下的2个无变量点(2盐共饱点),以Na_2SO_4,H_2O,和Al_2(SO_4)_3的质量分数计,298.15 K为(1.75,69.38,28.87)和(2.62,70.76,26.62),323.15 K为(25.60,65.69,8.71)和(19.36,65.58,15.06)。结果表明:硫酸铝的固相均为十八水盐,且相区最小;硫酸钠和复盐在2个温度下分别为2种固体形式。复盐相区在相图中占最大相区,且随着温度的升高而明显加大。

Solid-liquid equilibrium（ SLE） data of the ternary system of Al_2（SO_4）_3-Na_2SO_4-H_2 O at 298. 15 K and323. 15 K were obtained via the isothermal solubility equilibrium method,and the phase diagram at each temperature was plotted. The results show that 3 solid salts occur in the ternary SLE system at each temperature respectively,those are Na_2SO_4·10H_2O,Al_2（SO_4）_3·18H_2O and one congruent double-salt Na Al（ SO_4）2·12H_2O at 298. 15 K,and Na_2SO_4,Al_2（SO_4）_3·18H_2O and congruent double-salt Na Al（ SO_4）2·6H_2O at 323. 15 K. Two invariant points（ two salts co-saturated points） existed in the ternary system were determined to be（ 1. 75,69. 38,28. 87）and（ 2. 62,70. 76,26. 62） at 298. 15 K,（ 25. 60,65. 69,8. 71） and（ 19. 36,65. 58,15. 06） at 323. 15 K,which was in the mass fraction recording of Na_2SO_4,H_2 O and Al_2（SO_4）_3. The results show that Al_2（SO_4）_3takes only one solid form and occupies a small solubility region at each temperature,Na_2SO_4 and the double-salt have two-type solid forms at two temperatures,respectively. The double-salt takes the largest solubility region in the phase diagram and can obviously enlarge with the temperature incerasing.