The high toxicity of Cr–Ca compounds generated during the heat treatment of solid waste will heavily threat the environment. In this work, a kind of Ca-rich river sludge which is bound with Ca and heavy metals was combusted with kaolin under 900 °C for 3 h in a muffle to study the transformation of Cr. The effects of kaolin on Cr transformation were investigated through sequential extraction, the risk assessment of heavy metals, and constant pH leaching test, also combined with crystal phase analysis of Ca–Al–Si minerals. The experimental results showed that the formation of Ca₁₀(SiO₄)₃(SO₄)₃Cl₂ was inhibited by the addition of 10% (mass fraction) kaolin and the released Cl promoted the evaporation of target elements in priority while 30% kaolin addition further inhibited the solidification of Cr. Furthermore, the effect of NaCl and CaCO₃ on the Cr solidification by kaolin were also explored by leaching procedure or XRD analysis of calcination products of their mixtures. It should be noticed that the addition of kaolin in Cr₂O₃–CaCO₃ mixture will directly react with CaCrO₄ and fixed the generated Cr₂O₃ into internal layered structure, preventing its re-oxidization by the free CaO. This work aims to help illustrate the Cr transformation with existence of Ca during sintering of Ca-rich solid wastes and reduce the Cr contamination in future.

固体废物热处理过程中产生的Cr-Ca化合物的高毒性将对环境造成严重威胁。在这项工作中，一种与 Ca 和重金属结合的富含 Ca 的河流污泥与高岭土在 900 °C 下在马弗炉中燃烧 3 小时，以研究 Cr 的转化。通过顺序提取、重金属风险评估和恒定 pH 浸出试验，并结合 Ca-Al-Si 矿物的晶相分析，研究了高岭土对 Cr 转化的影响。实验结果表明，Ca ₁₀ (SiO ₄ ) ₃ (SO ₄ ) ₃ Cl _{2 的形成}10%（质量分数）高岭土的加入抑制了Cr的凝固，释放的Cl优先促进了目标元素的蒸发，而30%的高岭土进一步抑制了Cr的凝固。此外，还通过浸出程序或对它们混合物的煅烧产物进行 XRD 分析，探讨了NaCl 和 CaCO ₃对高岭土对 Cr 固化的影响。需要注意的是，在Cr ₂ O ₃ –CaCO ₃混合物中加入高岭土会直接与CaCrO ₄反应，固定生成的Cr ₂ O ₃成内部层状结构，防止其被游离 CaO 重新氧化。这项工作旨在帮助说明在烧结富钙固体废物过程中存在 Ca 的 Cr 转化，并减少未来的 Cr 污染。