The Separation Of Magnesium From Manganese Sulfate In Hydrometallugical Process

As a worldwide problem, the separation of magnesium impurities from manganese sulfate in hydrometallugical process has been researched extensively but not in depth. It is necessary to research the thermodynamics properties of magnesium sulfate in manganese sulfate solution and design an effective separation method. In this work, the phase diagram of (NH4)2SO4-MgSO4-MnSO4-H2O system was simulated and predicted. The recrystallization method on the basis of thermodynamic simulation and the fluoride precipitation method of removing magnesium from manganese sulfate were studied.1) The Pitzer thermodynamic model is selected to simulate and predict the thermodynamic properties of the sub-binary systems (NH4)2SO4-H2O, MgSO4-H2O and MnSO4-H2O and the sub-ternary systems (NH4)2SO4-MgSO4-H2O,(NH4)2SO4-MnSO4-H2O, and MgSO4-MnSO4-H2O. The calculated results are good agree with the experiment data. The solid phases of these systems are also predicted accurately. The complete phase diagrams of these systems provide a theoretical basis to avoid the formation of double salts and the solid solutions in the hydrometallurgical process of manganese.2) Experiments of recrystallization of manganese sulfate solution have been carried out based on the complete solubility phase diagram predicted by the Pitzer thermodynamic model and the theory of solid solution. With the increase of the crystallization rate, the magnesium content in the crystals, the density and the pH value of the mother liquor decreases, while the magnesium content in the mother liquor increases. The highest removal rate of magnesium is80.9%.3) The method of magnisium fluoride precipitating magnesium from manganese sulfate solution have been studied, specifically including the choice of initiator, the dosage of precipitation agent, the reaction temperature, the reaction time and the pH value of the reaction system. And then, the optimal conditions of fluoride precipitation method have been determined:250%of the theoretical amount of NH4F, stirring time with1h at90℃without adjusting the pH value. The removal rate of magnesium could reach to92.3%. 4) Removing manganese sulfate from factory mixture solution was treated by the optimal conditions of recrystallization method and fluoride precipitation method. The result shows the removal rate of the magnesium impurities with fluoride precipitation method is better than the recrystallization method.