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<p>Heavy metal contamination, particularly Cr(VI), poses a significant environmental concern, as Cr(VI) is among the most prevalent heavy metals in contaminated soils. This study reports the development of a novel slag-phosphogypsum-based cementitious material (SPCM) synthesised from slag, phosphogypsum, and quicklime. The mechanical properties and micro-mechanisms of SPCM in solidifying Cr(VI)-contaminated silty clay were comprehensively investigated. The study evaluated the effects of SPCM on unconfined compressive strength (UCS), volumetric shrinkage, and Cr(VI) leaching concentration through mechanical performance tests and toxicity leaching tests. The solidification mechanism was further elucidated using Brunauer–Emmett–Teller (BET) specific surface area and pore size distribution tests, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrate that the optimal performance for stabilizing Cr(VI)-contaminated soil was achieved with a 20% SPCM dosage composed of 48.5% slag, 48.5% phosphogypsum, and 3% quicklime, resulting in a UCS of 2.881&#xa0;MPa and a Cr(VI) leaching concentration of 0.147&#xa0;mg/L, both of which comply with relevant standards. The hydration products, mainly ettringite and calcium silicate hydrate (C-S–H), were identified as the primary agents contributing to the solidification of the soil. This study provides a novel approach for utilizing solid waste materials and presents an environmentally friendly, cost-effective solution for the remediation of Cr(VI)-contaminated soils.</p>

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The Cementing Material Synthesized from Slag and Phosphogypsum for Solidifying Cr(VI)-Contaminated Silty Clay: Mechanical Properties and Solidification Mechanism

  • 期刊论文

  • 发表日期：

    2025年10月16日

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  • Tianyu Han,
  • Haijun Lu,
  • Xinghua He,
  • Yiqie Dong,
  • Jin Li,
  • Guanghui Shao

摘要

Heavy metal contamination, particularly Cr(VI), poses a significant environmental concern, as Cr(VI) is among the most prevalent heavy metals in contaminated soils. This study reports the development of a novel slag-phosphogypsum-based cementitious material (SPCM) synthesised from slag, phosphogypsum, and quicklime. The mechanical properties and micro-mechanisms of SPCM in solidifying Cr(VI)-contaminated silty clay were comprehensively investigated. The study evaluated the effects of SPCM on unconfined compressive strength (UCS), volumetric shrinkage, and Cr(VI) leaching concentration through mechanical performance tests and toxicity leaching tests. The solidification mechanism was further elucidated using Brunauer–Emmett–Teller (BET) specific surface area and pore size distribution tests, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrate that the optimal performance for stabilizing Cr(VI)-contaminated soil was achieved with a 20% SPCM dosage composed of 48.5% slag, 48.5% phosphogypsum, and 3% quicklime, resulting in a UCS of 2.881 MPa and a Cr(VI) leaching concentration of 0.147 mg/L, both of which comply with relevant standards. The hydration products, mainly ettringite and calcium silicate hydrate (C-S–H), were identified as the primary agents contributing to the solidification of the soil. This study provides a novel approach for utilizing solid waste materials and presents an environmentally friendly, cost-effective solution for the remediation of Cr(VI)-contaminated soils.