三元体系MgSO_4-FeSO_4-H_2O的相平衡研究

Metastable phase equilibrium in the aqueous ternary system MgSO_4-FeSO_4-H_2O

从钛白废酸与磷矿浮选尾矿中提取的铁、镁反应制备硫酸亚铁镁,反应主要涉及Mg^(2+),Fe^(2+)//SO_4^(2-)三元体系,因此开展该体系相平衡研究对综合利用工业废料,并使其转化成环保且具有经济价值的复合肥料意义重大。文中采用等温溶解平衡法测定了三元体系MgSO_4-FeSO_4-H_2O在293.15,303.15,313.15 K下的溶解度数据以及平衡溶液液相的密度,采用化学分析和X射线衍射法对结晶湿渣进行了分析,并依据相平衡数据绘制了相图。实验发现:在293.15,303.15,313.15 K下,该三元体系不存在单盐区和复盐区,固溶体[(Fe,Mg)SO_4·7H_2O]占据了整个相区。在固溶体[(Fe,Mg)SO_4·7H_2O]中,Mg^(2+)与Fe^(2+)在晶体中可以任意比例互换,形成完全类质同像系列物。因此,在293.15,303.15,313.15 K下很难采用单一的蒸发结晶方法从硫酸亚铁镁溶液中分离出硫酸镁和硫酸亚铁晶体;同时,若要获得单一配比的硫酸亚铁镁晶体,需要严格控制原料液中的Mg/Fe比例。

The titanium white waste acid and phosphate rock flotation tailings were changed into Mg^（2＋）,Fe^（2＋）/ / SO_4^（2-） ternary system after the iron and magnesium were crystallized and separated,and the phase equilibrium research on the ternary system MgSO_4-FeSO_4-H_2O was essential to convert industrial wastes to environmentally friendly compound fertilizer which also had significant economic value. The metastable phase equilibrium in the ternary system MgSO_4-FeSO_4-H_2O was investigated at 293. 15 K,303. 15 K and 313. 15 K using an isothermal evaporation method. The solubilities and densities of the equilibrated solution were measured. The crystalloid forms of the solid phase were determined using chemical analysis and an X-ray diffraction method. The results show that the ternary system belongs to the complete isomorphous series,and double salts are not found at the investigated temperature.The crystallization region of the solid solution [（ Fe,Mg） SO_4·7H_2O] occupies the entire phase region. In the solid solution,Mg（2＋）and Fe（2＋）can be interchanged in any proportion. Thus,it is difficult to separate epsomite from ferrous sulfate solution by only using evaporation and crystallization methods at 293. 15 K,303. 15 K and 313. 15 K. During the preparation of a fixed ratio of ferrous sulfate magnesium crystals,the Mg / Fe ratio in raw material liquid should be strictly controlled.