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Mechanism and Kinetics Study of Manganese Sulfate Production from Low-Grade Minerals by Acid Digestion, Leaching and Antisolvent Crystallization

Mohagheghi, Mahdi | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58124 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Askari, Masoud; Sadrnezhaad, Khatiboleslam
  7. Abstract:
  8. In this research, the process of producing manganese sulfate from a low-grade manganese oxide ore through acid digestion-leaching and antisolvent crystallization was studied. First, a quantity of low-grade ore was prepared and concentrated using a shaking table. The resulting concentrate contained 39.25% manganese, 24.31% silica, and 4.01% iron, and was composed of quartz, pyrolusite, manganite, goethite, and lime. The processing of the concentrate via acid digestion-leaching was then investigated. Initially, the thermodynamics of the acid digestion of the concentrate was studied. Subsequently, the effects of digestion parameters—digestion temperature, digestion time, and the mass ratio of sulfuric acid to concentrate (A/C)—on the sulfation efficiency of manganese and iron were examined. The optimal digestion conditions in this study were determined as follows: A/C = 4.5, temperature = 300°C, and time = 3 hours. Under these conditions, 97% of manganese and 66% of iron were sulfated. Next, the precipitation of manganese sulfate from the solution obtained by leaching the digested concentrate was investigated. Precipitation was carried out using the antisolvent crystallization method. In a preliminary study, methanol was selected as the suitable antisolvent for this process, and its effectiveness in reducing the solubility of manganese sulfate was evaluated through modeling. The effects of parameters—initial manganese concentration, temperature, time, organic antisolvent-to-aqueous solution volume ratio (O/A), and seeding amount—on the precipitation efficiency of manganese sulfate were then studied. The optimal precipitation conditions were determined as follows: Initial Mn concentration = 115 g/L, Temperature = 50°C, Precipitation time = 5 minutes, O/A ratio = 3, and Seeding amount = 2%. Under these conditions, a manganese sulfate precipitation efficiency of 91% was achieved. The resulting precipitate contained 29.43% manganese in the form of MnSO₄•H₂O, which can meet the needs of the agrochemical industry. Finally, the crystallization kinetics was examined. The experimental data fitted well with the Avrami kinetic model. The calculated activation energy was 91 kJ/mol, indicating that the crystal growth process was controlled by surface integration
  9. Keywords:
  10. Leaching ; Antisolvent Crystallization ; Precipitation Modeling ; Manganese Sulfation ; Manganese Sulfate Precipitation ; Digestion Thermodynamics ; Acid Digestion ; Crystallization Kinetics

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