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<p>The efficient separation of fluorine from rare earths is a critical challenge in the recycling of both rare-earth molten salt electrolytic slag. In this work, a synergistic co-roasting strategy using ferroboron as a reactive additive was developed to enable simultaneous defluorination and resource recovery. Thermodynamic analysis confirmed that NdF<sub>3</sub> can react with boron in air to generate volatile BF<sub>3</sub> and neodymium borates, facilitating fluorine removal without alkali additives. Experimental results showed that direct roasting of NdF<sub>3</sub>–ferroboron mixtures at 800°C for 3&#xa0;h with a B:F molar ratio of 4:3 achieved a fluorine removal efficiency of 95.09%. In contrast, NaOH-assisted roasting led to the formation of water-insoluble NaNdF<sub>4</sub>, limiting defluorination to ~ 90% even after water leaching. XRD, SEM-EDS, and phase evolution analyses confirmed that direct roasting promotes the conversion of NdF<sub>3</sub> and ferroboron into Fe<sub>2</sub>O<sub>3</sub>, Nd(BO<sub>2</sub>)<sub>3</sub> or NdBO<sub>3</sub>, while effectively volatilizing fluorine as BF<sub>3</sub>. This study demonstrates a promising, alkali-free route for the collaborative treatment of REF-rich wastes, providing a foundation for sustainable and integrated rare-earth recycling technologies.</p>

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Investigation on the Defluorination and Transformation Mechanism of Neodymium Fluoride and Boron Iron During the Roasting Process

  • 期刊论文

  • 发表日期：

    2026年4月6日

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  • Senlin Ouyang,
  • Fei Niu,
  • Xiaolin Zhang,
  • Weihang Feng,
  • Youming Yang

摘要

The efficient separation of fluorine from rare earths is a critical challenge in the recycling of both rare-earth molten salt electrolytic slag. In this work, a synergistic co-roasting strategy using ferroboron as a reactive additive was developed to enable simultaneous defluorination and resource recovery. Thermodynamic analysis confirmed that NdF3 can react with boron in air to generate volatile BF3 and neodymium borates, facilitating fluorine removal without alkali additives. Experimental results showed that direct roasting of NdF3–ferroboron mixtures at 800°C for 3 h with a B:F molar ratio of 4:3 achieved a fluorine removal efficiency of 95.09%. In contrast, NaOH-assisted roasting led to the formation of water-insoluble NaNdF4, limiting defluorination to ~ 90% even after water leaching. XRD, SEM-EDS, and phase evolution analyses confirmed that direct roasting promotes the conversion of NdF3 and ferroboron into Fe2O3, Nd(BO2)3 or NdBO3, while effectively volatilizing fluorine as BF3. This study demonstrates a promising, alkali-free route for the collaborative treatment of REF-rich wastes, providing a foundation for sustainable and integrated rare-earth recycling technologies.