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<p>Municipal solid waste incineration fly ash (MSWI-FA) is an urgently treatable hazardous waste in China. High-temperature melting is a promising resource utilization technology for global solid waste. This study examines physicochemical properties of grate furnace incineration fly ash from northern and southern China, finding Cd, Pb, and Zn leaching toxicity exceeds national standards by 9.14, 8.59, and 1.09 times for northern samples, and 17.58, 7.13, and 1.25 times for southern samples, respectively. Clinker ignition loss during melting reaches approximately 40% for both fly ash types. Heavy metal migration (Pb, Zn, Cd, Cr, Cu, Ni) was analyzed across 200–1600 °C. Cr and Ni, predominantly in the slag phase, exhibited low volatility (∼20% at 1600 °C). Fe and Cu showed moderate volatility, exceeding 70% at 1600 °C. Pb, Cd, and Zn demonstrated high volatility, surpassing 90% at 1200 °C. The volatilization sequence is Cd &gt; Pb &gt; Zn &gt; Cu &gt; Ni &gt; Cr. XRD, SEM, TGA analyses revealed melting behavior and vitrification mechanisms. Heavy metals accumulate in secondary fly ash mainly as chlorides (PbCl<sub>2</sub>, ZnCl<sub>2</sub>, ZnCdCl<sub>4</sub>). Slag minerals transition from low-temperature CaCl<sub>2</sub>, CaClOH, NaCl, KCl to high-temperature chlorinated (Ca<sub>5</sub>Al<sub>2</sub>SiO<sub>8</sub>Cl<sub>4</sub>) and non-chlorinated (Ca<sub>5</sub>Al<sub>2</sub>SiO<sub>10</sub>) calcium aluminum silicates. However, no glass peaks were observed in XRD spectra of both fly ashes at 1600 °C. Thermodynamic analysis points to high CaO content as the main cause of elevated melting points. To achieve vitrification below 1500 °C, the optimal SiO<sub>2</sub>:CaO:Al<sub>2</sub>O<sub>3</sub> ratio should be approximately (3.5–9.0):(0–4.0):(0–3.5).</p>

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Migration behaviour of heavy metals and vitrification characteristics in melting of municipal solid waste incineration fly ash

  • 期刊论文

  • 发表日期：

    2026年1月20日

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  • Quanming Li,
  • Yajie Gao,
  • Chao Geng,
  • Xianfeng Shi,
  • Hong Zhang,
  • Cheng Chen,
  • Yukai Wang,
  • Jiaqi Chang,
  • Yajie Wang,
  • Ziyi Ding

摘要

Municipal solid waste incineration fly ash (MSWI-FA) is an urgently treatable hazardous waste in China. High-temperature melting is a promising resource utilization technology for global solid waste. This study examines physicochemical properties of grate furnace incineration fly ash from northern and southern China, finding Cd, Pb, and Zn leaching toxicity exceeds national standards by 9.14, 8.59, and 1.09 times for northern samples, and 17.58, 7.13, and 1.25 times for southern samples, respectively. Clinker ignition loss during melting reaches approximately 40% for both fly ash types. Heavy metal migration (Pb, Zn, Cd, Cr, Cu, Ni) was analyzed across 200–1600 °C. Cr and Ni, predominantly in the slag phase, exhibited low volatility (∼20% at 1600 °C). Fe and Cu showed moderate volatility, exceeding 70% at 1600 °C. Pb, Cd, and Zn demonstrated high volatility, surpassing 90% at 1200 °C. The volatilization sequence is Cd > Pb > Zn > Cu > Ni > Cr. XRD, SEM, TGA analyses revealed melting behavior and vitrification mechanisms. Heavy metals accumulate in secondary fly ash mainly as chlorides (PbCl2, ZnCl2, ZnCdCl4). Slag minerals transition from low-temperature CaCl2, CaClOH, NaCl, KCl to high-temperature chlorinated (Ca5Al2SiO8Cl4) and non-chlorinated (Ca5Al2SiO10) calcium aluminum silicates. However, no glass peaks were observed in XRD spectra of both fly ashes at 1600 °C. Thermodynamic analysis points to high CaO content as the main cause of elevated melting points. To achieve vitrification below 1500 °C, the optimal SiO2:CaO:Al2O3 ratio should be approximately (3.5–9.0):(0–4.0):(0–3.5).