Research On Stable Equilibria In Quinary System Mn²⁺,Mg²⁺,NH₄⁺//Cl^-,SO₄^2--H₂O And Its Sub-systems

In the production process of Electrolytic manganese,a lot of waste residue,waste water and leachate will be produced,which will pollute the environment greatly.There are a lot of soluble bivalent manganese,magnesium and ammonia nitrogen in the wastewater and leachate.The effective recovery of them can not only solve the environmental pollution but also recycle the resources.In addition,manganese,magnesium and ammonium are indispensable elements in the process of plant growth,and the effect of compound fertilizer on plant growth is higher than that of single fertilizer.Therefore,the utilization of Mn2+,Mg2+,NH4+//Cl-,SO42--H2O phase diagram is involved in both the treatment and recovery of electrolytic manganese wastewater percolate and the production of compound fertilizer.Therefore,it is of great significance to study the solid-liquid equilibrium of water salt system of five element system Mn2+,Mg2+,NH4+//Cl-,SO42--H2O.In this paper,the solubility and physicochemical properties(?,?,nD,pH)of the equilibrium supernatant of five ternary subsystems and two quaternary subsystems in water salt system Mn2+,Mg2+,NH4+//Cl-,SO42--H2O were determined by means of isothermal dissolution equilibrium and wet slag method at 303.15 K.According to the experimental results,the phase diagram and physicochemical property composition diagram of each systems are drawn.There are two simple systems of Mn2+,Mg2+//SO42+-H2O and Mn2+//Cl-,SO42--H2O in the five ternary systems.There is a common saturation point,two univariant curves and three crystal regions.The other three ternary systems are Mn2+,NH4+//SO42--H2O?Mg2+,NH4+//SO42---H2O and Mn2+,NH4+//Cl-,H2O which have two co saturation points,three univariant curves and five crystallization zones.For the quatemary system Mn2+,Mg2+,NH4+//SO42--H2O,there are three common saturation points and five crystal regions,which are three pure substance crystal regions(MnSO4?MgSO4?(NH4)2SO4)and two double salt crystal regions((NH4)2Mn(SO4)2·H2O?(NH4)2Mg(SO4)2·H2O)respectively.For the interactive quaternary system Mn2+,NH4+//Cl-,SO42-,H2O,it contains four cosaturation points and six crystallization zones,which are four pure substance crystallization zones(MnSO4?MnCl2?NH4Cl?(NH4)2SO4)and two double salt crystallization zones((NH4)2Mn(SO4)2-H2O?NH4Cl-MnCl2-4H2O)respectively.Based on the phase equilibrium data,the "translation method" is used to predict the phase diagram of multi-element system.The phase diagrams of Mn2+,Mg2+,NH4+//Cl-,SO42--H2O were obtained.The system consists of nine cosaturation points,twenty-eight univariant curves and fourteen crystal regions.In addition,the phase diagrams of Mn2+,NH4+//SO42--H2O and Mg2+,NH4+//SO42--H2O in the ternary system at 303.15 K were analyzed by isothermal evaporation and variable temperature crystallization.The crystallized substances(MnSO4?(NH4)2Mn(SO4)2-H2O and(NH4)2Mg(SO4)2-H2O)in each process were obtained,which can effectively improve the crystallization rate in theory.In this paper,the solubility and salting out law of the five component system Mn2+,Mg2+,NH4+//Cl-,SO42--H2O are studied and predicted,which provides a theoretical basis for the recovery and production of effective substances(MnSO4?(NH4)2Mn(SO4)2·H2O and(NH4)2Mg(SO4)2·H2O).