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<p>The similar physicochemical properties of Mn, Ca, and Mg make the efficient removal of Ca and Mg a major challenge in producing high-purity manganese-based materials. In this work, we develop a short-process and highly efficient method for preparing high-purity Mn<sub>2</sub>O<sub>3</sub> from impurity-containing MnSO<sub>4</sub> leach solutions by selectively enriching Ca and Mg impurities into a sulfite phase <i>via</i> sulfite precipitation. Under optimal conditions—8.13&#xa0;pct (NH<sub>4</sub>)<sub>2</sub>SO<sub>3</sub> in the precipitant, pH 7.5, 33.0&#xa0;°C, and 8&#xa0;minutes—the resulting Mn<sub>2</sub>O<sub>3</sub> contains less than 139&#xa0;μg&#xa0;g<sup>−1</sup> Ca and 99&#xa0;μg&#xa0;g<sup>−1</sup> Mg, meeting the high-purity standard (&lt;&#xa0;150&#xa0;μg&#xa0;g<sup>−1</sup>), with Ca and Mg removal efficiencies exceeding 98.80 and 99.89&#xa0;pct, respectively. Theoretical analysis reveals that the precipitation sequence in the sulfite system follows Ca &gt; Mn &gt; Mg, whereas in the carbonate system it follows Mn &gt; Ca &gt; Mg. Within pH 6–8, the equilibrium concentrations of Ca and Mg in the sulfite system are significantly lower than those in the carbonate system. Experimental results further confirm that increasing the dosage of (NH<sub>4</sub>)<sub>2</sub>SO<sub>3</sub> drives Ca and Mg impurities to concentrate progressively in the sulfite phase while reducing their presence in the carbonate phase. After calcination and rinsing, the sulfite phase converts into soluble sulfates and dissolves away, producing Mn<sub>2</sub>O<sub>3</sub> with a porous structure that exposes and hydrolyzes residual CaO and MgO, enabling deep purification. The resulting high-purity Mn<sub>2</sub>O<sub>3</sub> also exhibits excellent electrochemical performance: the synthesized LiMn<sub>2</sub>O<sub>4</sub> delivers an initial discharge capacity of 122.25&#xa0;mAh&#xa0;g<sup>−1</sup> and maintains 90.12&#xa0;pct capacity retention after 100 cycles. Overall, this study provides a green and efficient technological pathway for producing high-purity manganese-based materials. The process is simple, low-cost, and environmentally friendly, highlighting its strong potential for industrial application.</p> Graphical abstract <p></p>

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Integrated Process for Deep Removal of Ca/Mg Impurities via Sulfite Precipitation and High-Purity Mn2O3 Preparation

  • 期刊论文

  • 发表日期：

    2026年2月11日

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  • Juexi Chen,
  • Xue Li,
  • Junfeng Zhang,
  • Xingyan Wang

摘要

The similar physicochemical properties of Mn, Ca, and Mg make the efficient removal of Ca and Mg a major challenge in producing high-purity manganese-based materials. In this work, we develop a short-process and highly efficient method for preparing high-purity Mn2O3 from impurity-containing MnSO4 leach solutions by selectively enriching Ca and Mg impurities into a sulfite phase via sulfite precipitation. Under optimal conditions—8.13 pct (NH4)2SO3 in the precipitant, pH 7.5, 33.0 °C, and 8 minutes—the resulting Mn2O3 contains less than 139 μg g−1 Ca and 99 μg g−1 Mg, meeting the high-purity standard (< 150 μg g−1), with Ca and Mg removal efficiencies exceeding 98.80 and 99.89 pct, respectively. Theoretical analysis reveals that the precipitation sequence in the sulfite system follows Ca > Mn > Mg, whereas in the carbonate system it follows Mn > Ca > Mg. Within pH 6–8, the equilibrium concentrations of Ca and Mg in the sulfite system are significantly lower than those in the carbonate system. Experimental results further confirm that increasing the dosage of (NH4)2SO3 drives Ca and Mg impurities to concentrate progressively in the sulfite phase while reducing their presence in the carbonate phase. After calcination and rinsing, the sulfite phase converts into soluble sulfates and dissolves away, producing Mn2O3 with a porous structure that exposes and hydrolyzes residual CaO and MgO, enabling deep purification. The resulting high-purity Mn2O3 also exhibits excellent electrochemical performance: the synthesized LiMn2O4 delivers an initial discharge capacity of 122.25 mAh g−1 and maintains 90.12 pct capacity retention after 100 cycles. Overall, this study provides a green and efficient technological pathway for producing high-purity manganese-based materials. The process is simple, low-cost, and environmentally friendly, highlighting its strong potential for industrial application.

Graphical abstract