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<p>Industrial solid wastes present severe disposal challenges, while hexavalent chromium [Cr(VI)]-contaminated wastewater threatens ecological and human health. This study developed a phosphogypsum-coal ash composite (MTPC) through synergistic mechanical-thermal activation to serve as a cost-effective impermeable liner for Cr(VI) environments. Orthogonal experiments assessed the influence of calcination temperature, duration, and Cr(VI) concentration on material’s performance. Optimal results were obtained at 700&#xa0;°C for 120&#xa0;min with a Cr(VI) concentration of 1&#xa0;mg/L. The 28-day compressive strength reached 36.80&#xa0;MPa, a 248.5% increase compared with the untreated samples. The Cr(VI) leaching concentration was reduced to 0.91&#xa0;µg/L, while permeability coefficients as low as 2.66 × 10<sup>− 8</sup> cm/s. Microstructural and chemical characterization was performed using scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Findings demonstrate that mechanical-thermal activation enhances the release and hydration reactions of active components in MTPC, promotes the formation of calcium silicate hydrate (C-S-H) gel and ettringite (AFt) crystals. These results highlight mechanical-thermal activation as an effective and practical approach to valorize industrial wastes into sustainable, high-performance cementitious materials for environmental protection.</p>

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Performance and microstructural assessment of mechanically-thermally activated phosphogypsum-coal ash composite for Cr(VI) wastewater environment

  • 期刊论文

  • 发表日期：

    2025年12月31日

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  • Tianyu Han,
  • Nachuan Zou,
  • Ke Wu,
  • Jun Xu,
  • Yiqie Dong,
  • Haijun Lu

摘要

Industrial solid wastes present severe disposal challenges, while hexavalent chromium [Cr(VI)]-contaminated wastewater threatens ecological and human health. This study developed a phosphogypsum-coal ash composite (MTPC) through synergistic mechanical-thermal activation to serve as a cost-effective impermeable liner for Cr(VI) environments. Orthogonal experiments assessed the influence of calcination temperature, duration, and Cr(VI) concentration on material’s performance. Optimal results were obtained at 700 °C for 120 min with a Cr(VI) concentration of 1 mg/L. The 28-day compressive strength reached 36.80 MPa, a 248.5% increase compared with the untreated samples. The Cr(VI) leaching concentration was reduced to 0.91 µg/L, while permeability coefficients as low as 2.66 × 10− 8 cm/s. Microstructural and chemical characterization was performed using scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Findings demonstrate that mechanical-thermal activation enhances the release and hydration reactions of active components in MTPC, promotes the formation of calcium silicate hydrate (C-S-H) gel and ettringite (AFt) crystals. These results highlight mechanical-thermal activation as an effective and practical approach to valorize industrial wastes into sustainable, high-performance cementitious materials for environmental protection.