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<p>Red mud is massively produced in the aluminium refining industry and commonly disposed as hazardous waste in storage dams. Herein, red mud containing 4.4% Ti, 11.9% Fe, 12.1% Al, 15.2% Ca and 10.7% Si, was recovered by a combined acid leaching, hydrothermal and chemical precipitation route. Results showed that over 90% Ti, Fe, Al and Ca were leached from the red mud when treated with hydrochloric acid and sulfuric acid in sequence, which was higher than the rate when using either acid alone. The generated leachate was heated to 80&#xa0;°C with 10&#xa0;g/L urea, resulting in about 99.7% of Ti being hydrolysed as anatase nanoparticles and Fe, Al and Ca losses of 2.3%, 2% and 0.12%, respectively. After separating the Ti-rich deposit, the rest supernatant was also collected and then heated to 150&#xa0;°C with the addition of 0.5&#xa0;g/L nitrate. Approximately 99.4% of Fe was separated as hematite nanoparticles with an average diameter of 100&#xa0;nm, and 0.8% Al and 0.3% Ca were lost. In the supernatant, Ca was precipitated as gypsum by adjusting the sulphate concentration to 0.3&#xa0;M and the remaining Al was directly collected as nordstrandite by adjusting the supernatant pH to 5. The treatment successfully purified the waste red mud into four products: anatase (64.5% Ti), hematite (57.3% Fe), gypsum (40.1% Ca), and nordstrandite (47.1% Al). These products serve as commercial catalysts, paint/dye, or building/environmental materials, widely utilized in various industries and for environmental protection. This work developed a novel hydrometallurgy strategy to separate Ti, Fe, Ca and Al from red mud.</p> Graphic abstract <p></p>

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Non-extractant recycling of Ti, Fe, Ca and Al as value-added anatase, hematite, gypsum and nordstrandite from waste red mud

  • 期刊论文

  • 发表日期：

    2025年6月23日

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  • T. Su,
  • S. Li,
  • R. Bian,
  • Y. Lin,
  • S. Zhu

摘要

Red mud is massively produced in the aluminium refining industry and commonly disposed as hazardous waste in storage dams. Herein, red mud containing 4.4% Ti, 11.9% Fe, 12.1% Al, 15.2% Ca and 10.7% Si, was recovered by a combined acid leaching, hydrothermal and chemical precipitation route. Results showed that over 90% Ti, Fe, Al and Ca were leached from the red mud when treated with hydrochloric acid and sulfuric acid in sequence, which was higher than the rate when using either acid alone. The generated leachate was heated to 80 °C with 10 g/L urea, resulting in about 99.7% of Ti being hydrolysed as anatase nanoparticles and Fe, Al and Ca losses of 2.3%, 2% and 0.12%, respectively. After separating the Ti-rich deposit, the rest supernatant was also collected and then heated to 150 °C with the addition of 0.5 g/L nitrate. Approximately 99.4% of Fe was separated as hematite nanoparticles with an average diameter of 100 nm, and 0.8% Al and 0.3% Ca were lost. In the supernatant, Ca was precipitated as gypsum by adjusting the sulphate concentration to 0.3 M and the remaining Al was directly collected as nordstrandite by adjusting the supernatant pH to 5. The treatment successfully purified the waste red mud into four products: anatase (64.5% Ti), hematite (57.3% Fe), gypsum (40.1% Ca), and nordstrandite (47.1% Al). These products serve as commercial catalysts, paint/dye, or building/environmental materials, widely utilized in various industries and for environmental protection. This work developed a novel hydrometallurgy strategy to separate Ti, Fe, Ca and Al from red mud.

Graphic abstract