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<p>Fluorite (CaF<sub>2</sub>) sludge in this research was from a chip-producing industry with a CaF<sub>2</sub> content of about 88%. However, the sludge also contained about 1.82 wt% of sulfur in the form of sulfate which made it unsuitable for reuse as flux in iron smelting. This study focused on desulfurization of the sludge. Na<sub>2</sub>CO<sub>3</sub> and sodium D-gluconate were employed as replacement and chelating reagents respectively to replace sulfate with carbonate or transfer CaSO<sub>4</sub> into calcium D-gluconate. Results showed that, at a solid/liquid ratio of 30&#xa0;g/L and molar ratio of Na<sub>2</sub>CO<sub>3</sub>:S of 1.2:1, after reaction of 4&#xa0;h, the S content of CaF<sub>2</sub> sludge decreased from the original 1.82 wt% to around 0.10 wt%. For sodium D-gluconate, the optimal condition is solid/liquid ratio of 30&#xa0;g/L, molar ratio of 2.0:1, and reaction time of 60&#xa0;min. A desulfurization efficiency of more than 88.9% was achieved. S contents in the treated sludge dropped to 0.20 wt%. CaF<sub>2</sub> contents after desulfurization reached 95%. Characterization of sludge after desulfurization showed that desulfurization process did not significantly change the physical structure of CaF<sub>2</sub> particles. Results from this research provide two effective methods for potential recycle of CaF<sub>2</sub> sludge.</p>

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Desulfurization of calcium fluoride sludge for reuse by selective removal of gypsum using replacement and chelating reagents

  • 期刊论文

  • 发表日期：

    2025年3月27日

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  • Weifang Chen,
  • Jingjing Yan,
  • Yifan Chen,
  • Yimo Sun,
  • Yegui Wang

摘要

Fluorite (CaF2) sludge in this research was from a chip-producing industry with a CaF2 content of about 88%. However, the sludge also contained about 1.82 wt% of sulfur in the form of sulfate which made it unsuitable for reuse as flux in iron smelting. This study focused on desulfurization of the sludge. Na2CO3 and sodium D-gluconate were employed as replacement and chelating reagents respectively to replace sulfate with carbonate or transfer CaSO4 into calcium D-gluconate. Results showed that, at a solid/liquid ratio of 30 g/L and molar ratio of Na2CO3:S of 1.2:1, after reaction of 4 h, the S content of CaF2 sludge decreased from the original 1.82 wt% to around 0.10 wt%. For sodium D-gluconate, the optimal condition is solid/liquid ratio of 30 g/L, molar ratio of 2.0:1, and reaction time of 60 min. A desulfurization efficiency of more than 88.9% was achieved. S contents in the treated sludge dropped to 0.20 wt%. CaF2 contents after desulfurization reached 95%. Characterization of sludge after desulfurization showed that desulfurization process did not significantly change the physical structure of CaF2 particles. Results from this research provide two effective methods for potential recycle of CaF2 sludge.