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<p>This study addresses the treatment challenges associated with low-level radioactive residues (acid-insoluble slag) generated from rare earth metallurgy by developing a two-stage roasting-acid leaching process. This method facilitates the efficient recovery of strategic elements (rare earths, uranium, thorium, and barium) while significantly reducing the volume of radioactive waste. The results demonstrate that first-stage roasting at 500&#xa0;°C effectively decomposes organic carbon, achieving leaching efficiencies of 78.7% for rare earths, 93.3% for uranium, and 89.3% for thorium. The second-stage roasting (at 400&#xa0;°C, with a mass ratio of slag to NaOH of 1:0.9, and a CO₂ flow rate of 3 L/min) converts insoluble BaSO₄ into soluble barium salts, yielding a barium leaching efficiency of 96.9%. Subsequent extraction and fractional precipitation of the acid leachate achieved a recovery rate exceeding 99% for both uranium and thorium, while radium was effectively removed through barium-radium co-precipitation. This process resulted in a total waste volume reduction of 91.1%, concentrating <sup>226</sup>Ra in barium-radium slag at 7.90&#xa0;Bq/g, with the remaining slag falling below radioactivity exemption levels. This approach provides an effective technical solution for the resource recovery and safe disposal of low-level radioactive rare earth slag.</p>

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Experimental study on the two-stage roasting and acid leaching process for the reduction of low-level radioactive rare earth slag

  • 期刊论文

  • 发表日期：

    2025年7月15日

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  • An Guo,
  • Qiaofa Lan,
  • Xinjin Xiao,
  • Liusheng Ge,
  • Huijuan Wang,
  • Zhaohua Ke,
  • Li Xiao,
  • Di Wu,
  • Xiaoqiang Wen

摘要

This study addresses the treatment challenges associated with low-level radioactive residues (acid-insoluble slag) generated from rare earth metallurgy by developing a two-stage roasting-acid leaching process. This method facilitates the efficient recovery of strategic elements (rare earths, uranium, thorium, and barium) while significantly reducing the volume of radioactive waste. The results demonstrate that first-stage roasting at 500 °C effectively decomposes organic carbon, achieving leaching efficiencies of 78.7% for rare earths, 93.3% for uranium, and 89.3% for thorium. The second-stage roasting (at 400 °C, with a mass ratio of slag to NaOH of 1:0.9, and a CO₂ flow rate of 3 L/min) converts insoluble BaSO₄ into soluble barium salts, yielding a barium leaching efficiency of 96.9%. Subsequent extraction and fractional precipitation of the acid leachate achieved a recovery rate exceeding 99% for both uranium and thorium, while radium was effectively removed through barium-radium co-precipitation. This process resulted in a total waste volume reduction of 91.1%, concentrating 226Ra in barium-radium slag at 7.90 Bq/g, with the remaining slag falling below radioactivity exemption levels. This approach provides an effective technical solution for the resource recovery and safe disposal of low-level radioactive rare earth slag.