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<p>Red mud is a major alkaline solid waste discharged from the alumina industry, the stockpiling of which causes environmental pollution and results in the waste of valuable elements such as Al and Fe.&#xa0;In this paper, a low-temperature ammonium sulfate-roasting–water-leaching process was proposed to extract Al and Fe from red mud.&#xa0;The effects of roasting temperature, time, and water-leaching conditions on the leaching behavior of these valuable elements were systematically investigated. The thermal decomposition behavior of the red mud and ammonium sulfate mixture was examined by TG-DSC, while phase transformations and morphological changes at different roasting temperatures were characterized using XRD and SEM. Based on the Box–Behnken response surface method, the optimal roasting parameters were determined as follows: a red mud to ammonium sulfate mass ratio of 1:1.51, a roasting temperature of 379.3°C, and a roasting time of 6.2 h. Under these conditions, an Al leaching rate of 89.98% was achieved. Furthermore, the leaching kinetics of aluminum and iron were studied using the shrinking core model. The results indicated that the leaching of Al and Fe followed mixed-control and chemical reaction-controlled models, with apparent activation energies of 24.59 kJ/mol and 45.50&#xa0;kJ/mol, respectively.</p>

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Using Ammonium Sulfate Roasting–Leaching for Recovery of Al and Fe from Red Mud

  • 期刊论文

  • 发表日期：

    2026年4月13日

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  • Wenxin Han,
  • Laishi Li,
  • Fang Ji,
  • Yusheng Wu,
  • Feng Liu

摘要

Red mud is a major alkaline solid waste discharged from the alumina industry, the stockpiling of which causes environmental pollution and results in the waste of valuable elements such as Al and Fe. In this paper, a low-temperature ammonium sulfate-roasting–water-leaching process was proposed to extract Al and Fe from red mud. The effects of roasting temperature, time, and water-leaching conditions on the leaching behavior of these valuable elements were systematically investigated. The thermal decomposition behavior of the red mud and ammonium sulfate mixture was examined by TG-DSC, while phase transformations and morphological changes at different roasting temperatures were characterized using XRD and SEM. Based on the Box–Behnken response surface method, the optimal roasting parameters were determined as follows: a red mud to ammonium sulfate mass ratio of 1:1.51, a roasting temperature of 379.3°C, and a roasting time of 6.2 h. Under these conditions, an Al leaching rate of 89.98% was achieved. Furthermore, the leaching kinetics of aluminum and iron were studied using the shrinking core model. The results indicated that the leaching of Al and Fe followed mixed-control and chemical reaction-controlled models, with apparent activation energies of 24.59 kJ/mol and 45.50 kJ/mol, respectively.