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<p>This study systematically investigated the decomposition behavior of Baotou mixed rare-earth concentrate in potassium hydroxide (KOH) solution, with particular emphasis on the kinetic characteristics of the alkaline decomposition process and the subsequent acid leaching step, thereby elucidating the associated reaction mechanisms. The optimal operating conditions for potassium hydroxide decomposition were experimentally determined to be a reaction temperature of 220&#xa0;°C, a reaction time of 100&#xa0;min, a potassium hydroxide concentration of 70 wt%, and an ore-to-alkali mass ratio of 1:1. Under these conditions, the decomposition efficiency of the rare-earth concentrate reached 94.6%, while the fluorine conversion reached 91.2%. Kinetic analysis of the alkaline decomposition process indicated that, during the initial stage (0–20&#xa0;min), the reaction was jointly controlled by interfacial chemical reaction and mass-transfer diffusion, with an apparent activation energy of 18.58&#xa0;kJ/mol. In the subsequent stage (after 20&#xa0;min), the controlling mechanism gradually shifted to product-layer diffusion, corresponding to a lower apparent activation energy of 11.86&#xa0;kJ/mol. The acid-leaching kinetics further demonstrated that a segmented temperature-interval approach provides a more mechanistically appropriate description of the rare-earth leaching behavior. Specifically, in the temperature range of 30–50&#xa0;°C, rare-earth leaching was controlled by diffusion through the product layer, with an apparent activation energy of 8.464&#xa0;kJ/mol. In contrast, within the temperature range of 60–90&#xa0;°C, the leaching process was governed by the combined effects of interfacial reaction and diffusion, and the apparent activation energy increased to 27.434&#xa0;kJ/mol. This work systematically investigates the kinetic characteristics of potassium hydroxide decomposition and subsequent acid leaching of Baotou mixed rare-earth concentrate.</p> Graphical Abstract <p></p>

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Kinetic Study on the Liquid-Phase Potassium Hydroxide Decomposition and Leaching Behavior of Mixed Rare-Earth Concentrates

  • 期刊论文

  • 发表日期：

    2026年7月31日

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  • Xiaowei Zhang,
  • Likai Zang,
  • Feng Guo,
  • Wenjun Fan,
  • Yanhong Hu,
  • Jinxiu Wu,
  • Chuxuan Deng,
  • Xiaodong Wang

摘要

This study systematically investigated the decomposition behavior of Baotou mixed rare-earth concentrate in potassium hydroxide (KOH) solution, with particular emphasis on the kinetic characteristics of the alkaline decomposition process and the subsequent acid leaching step, thereby elucidating the associated reaction mechanisms. The optimal operating conditions for potassium hydroxide decomposition were experimentally determined to be a reaction temperature of 220 °C, a reaction time of 100 min, a potassium hydroxide concentration of 70 wt%, and an ore-to-alkali mass ratio of 1:1. Under these conditions, the decomposition efficiency of the rare-earth concentrate reached 94.6%, while the fluorine conversion reached 91.2%. Kinetic analysis of the alkaline decomposition process indicated that, during the initial stage (0–20 min), the reaction was jointly controlled by interfacial chemical reaction and mass-transfer diffusion, with an apparent activation energy of 18.58 kJ/mol. In the subsequent stage (after 20 min), the controlling mechanism gradually shifted to product-layer diffusion, corresponding to a lower apparent activation energy of 11.86 kJ/mol. The acid-leaching kinetics further demonstrated that a segmented temperature-interval approach provides a more mechanistically appropriate description of the rare-earth leaching behavior. Specifically, in the temperature range of 30–50 °C, rare-earth leaching was controlled by diffusion through the product layer, with an apparent activation energy of 8.464 kJ/mol. In contrast, within the temperature range of 60–90 °C, the leaching process was governed by the combined effects of interfacial reaction and diffusion, and the apparent activation energy increased to 27.434 kJ/mol. This work systematically investigates the kinetic characteristics of potassium hydroxide decomposition and subsequent acid leaching of Baotou mixed rare-earth concentrate.

Graphical Abstract