The Efficient Removal of Calcium and Magnesium Ions from Industrial Manganese Sulfate Solution through the Integrated Application of Concentrated Sulfuric Acid and Ethanol

• Main Authors: Houyang Chen, Kaituo Wang, Xianquan Ming, Feng Zhan, Yaseen Muhammad, Yuezhou Wei, Weijian Li, Haiqing Zhan
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: Metals
• Subjects: OLI Stream Analyzer; high-purity MnSO₄; recrystallization; Ca²⁺ and Mg²⁺ removal
• Online Access: https://www.mdpi.com/2075-4701/11/9/1339
• ISSN: 2075-4701

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.