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<p>Excavation and retreatment of landfilled chelated incineration fly ash (CIFA) is an important pathway to recovering landfill capacity and improving waste management, but its potential risks remain unclear. This study investigates the secondary release behaviors of chloride and heavy metals during water washing of landfilled CIFA. Under the optimal water washing conditions-liquid–solid ratio of 8.3:1, 50&#xa0;min, and 63&#xa0;°C-soluble chlorides were effectively leached, yielding a chloride removal of 86.95%; the residual soluble Cl content dropped below 1 wt%, meeting the requirement for direct high-temperature thermal treatment. Water washing promoted the release of heavy metals into the aqueous phase predominantly as hydroxo-complex anions, while the remaining metals in the solid occurred mainly in the oxidizable and residual fractions. The risk assessment indices for the Washed CIFA (WCIFA) indicated that the potential risk of Pb escalated from "low" to "medium", necessitating continued attention during subsequent thermal treatment. Nevertheless, the synthetic toxicity index and hazard index for heavy metals suggested that the overall environmental risk of the WCIFA was low. Overall, water washing not only efficiently extracts soluble chlorides from CIFA but also mitigates the overall risk of heavy metals, thereby validating the process as an effective pretreatment step for its subsequent management.</p> Graphical abstract <p></p>

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Flow and distribution of chlorine and heavy metals during water washing of landfilled chelated fly ash

  • 期刊论文

  • 发表日期：

    2026年3月10日

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  • Zheyu Chen,
  • Minrui Huang,
  • Yi Chen,
  • Yuqiang Yang,
  • Huanlin Huang,
  • Dongsheng Shen,
  • Yuyang Long

摘要

Excavation and retreatment of landfilled chelated incineration fly ash (CIFA) is an important pathway to recovering landfill capacity and improving waste management, but its potential risks remain unclear. This study investigates the secondary release behaviors of chloride and heavy metals during water washing of landfilled CIFA. Under the optimal water washing conditions-liquid–solid ratio of 8.3:1, 50 min, and 63 °C-soluble chlorides were effectively leached, yielding a chloride removal of 86.95%; the residual soluble Cl content dropped below 1 wt%, meeting the requirement for direct high-temperature thermal treatment. Water washing promoted the release of heavy metals into the aqueous phase predominantly as hydroxo-complex anions, while the remaining metals in the solid occurred mainly in the oxidizable and residual fractions. The risk assessment indices for the Washed CIFA (WCIFA) indicated that the potential risk of Pb escalated from "low" to "medium", necessitating continued attention during subsequent thermal treatment. Nevertheless, the synthetic toxicity index and hazard index for heavy metals suggested that the overall environmental risk of the WCIFA was low. Overall, water washing not only efficiently extracts soluble chlorides from CIFA but also mitigates the overall risk of heavy metals, thereby validating the process as an effective pretreatment step for its subsequent management.

Graphical abstract