Abstract
In the process of preparing high-purity MnSO4 from industrial MnSO4 solution, it is difficult to remove Ca2+ and Mg2+ due to their closely similar properties. In this study, thermodynamic software simulation and experimental procedures were combined to remove Ca2+ and Mg2+ from industrial MnSO4 solution to obtain high-purity MnSO4. The simulation model was applied to predict the trend of the crystallization of different ions in the solution upon the addition of H2SO4, which revealed that, at a volume ratio of H2SO4 to MnSO4 solution of more than 0.2, MnSO4 started to crystallize and precipitate. The experimental results further verified the simulation results, and the yield of MnSO4 increased with the increasing ratio of H2SO4, while the removal rate of Ca2+ and Mg2+ decreased gradually. Keeping the economic aspect in mind, the 0.3 ratio of H2SO4 was selected at which the yield of MnSO4 reached 86.44%. The removal rate of Ca2+ and Mg2+ by recrystallization reached 99.68% and 99.17% respectively after six consecutive cycles. The recrystallized sample was washed twice with anhydrous ethanol (volume ratio of ethanol to MnSO4 solution of 0.5) and dried for 6 h at 120 °C, and the purity of MnSO4·H2O reached the battery grade requirements with the final yield as high as 80.54%. This study provides important guideline information for the purification of MnSO4·H2O from industrial MnSO4 solution via a cost-effective, simple and facile approach.
Highlights
Among the many impurities like K+, Na+, Ca2+ and Mg2+, the chemical properties of manganese are closely similar to the calcium and magnesium present in MnSO4 solu
The density of the industrial MnSO4 solution used in this experiment was 1.3127 ± 0.0004 g/cm3, and the density calculated by the OLI Stream Analyzer software was 1.2982 g/cm3, it could be concluded that the OLI Stream Analyzer software could be used to simulate and calculate the industrial MnSO4 solution
When the ratio of H2SO4 reached 6% and 10%, the scaling trend of MnSO4·H2O and CaSO4 in the solution reached 1 [28], which indicated that MnSO4·H2O and CaSO4 were saturated and had reached the precipitation condition
Summary
MnSO4, as a base manganese salt, is used in the preparation of various advanced manganese-based alloys and products [1–4]. Recrystallization includes evaporative concentration, high temperature and pressure crystallization [19–21], where it uses MnSO4 solubility, which shows a sharp decrease at temperatures of over 100 ◦C, and the MnSO4 crystals are obtained by heating the solution in the high-pressure reactor. This process is very stringent on the material and quality requirements of the equipment, otherwise it can affect the normal safe operation of the system [22,23]. Ethanol was recovered via a rotary evaporator (EYELA-1300D-WB, Tokyo Japan), while solution pH was tested via a pH meter provided by Shanghai San-Xin Instrumentation, China
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