Municipal solid waste circulating fluidized bed incineration (MSWCFBI) fly ash was a hazardous waste, maintaining challenges for disposal. One effective approach was stabilizing the toxic heavy metal ions in the fly ash structures in situ. This work proposed a fusion–hydrothermal method, including fusion pretreatment in nitrogen atmosphere and microwave-assisted hydrothermal process, to treat three MSWCFBI fly ash samples. Specifically, leaching tests were performed to demonstrate the heavy metal stabilization. Through the treatment of the fusion–hydrothermal process, the concentrations of Cd, Cu, Zn, Pb, Ni, and Cr ions leaching from the fly ashes were obviously less than those of the raw fly ash and the sample only treated by hydrothermal process. Meanwhile, the heavy metal ions migrating from the fly ash to the hydrothermal residual liquid were reduced. Importantly, lots of zeolites formed during the fusion–hydrothermal process, such as to bermorite and sodalite. The fusion pretreatment significantly facilitated the conversion of quartz into amorphous silicon and silicate salts. Then, the silicon dissolution was accelerated and zeolite formation was promoted. Eventually, the heavy metal ions could be trapped in zeolite frameworks, enhancing the stabilization of heavy metal. Moreover, the cation-exchange capability values of the three treated fly ash were 1.099, 1.168, and 1.188 meq g⁻¹, two-folder larger than those of the samples only treated by hydrothermal process. In summary, the fusion–hydrothermal method could facilitate the stabilization of heavy metal ions in the fly ash and the as-obtained solid product with high content of zeolite was promising for future applications.

中文翻译：

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熔融-水热法稳定城市生活垃圾循环流化床焚烧飞灰中的重金属

市政固体废物循环流化床焚烧（MSWCFBI）粉煤灰是有害废物，面临着处置方面的挑战。一种有效的方法是稳定粉煤灰结构中的有毒重金属离子。这项工作提出了一种熔融-水热法，包括在氮气气氛中进行熔融预处理和微波辅助水热法，以处理三个MSWCFBI粉煤灰样品。具体而言，进行浸出试验以证明重金属的稳定性。通过熔融-水热过程的处理，从粉煤灰中浸出的Cd，Cu，Zn，Pb，Ni和Cr离子的浓度明显低于未处理的粉煤灰和仅通过水热处理的样品。与此同时，从飞灰迁移到水热残留液的重金属离子被还原。重要的是，在熔融-水热过程中形成了许多沸石，例如绿沸石和方钠石。熔融预处理显着促进了石英向非晶硅和硅酸盐的转化。然后，加速了硅的溶解并促进了沸石的形成。最终，重金属离子可能被困在沸石骨架中，从而增强了重金属的稳定性。此外，三种处理后的粉煤灰的阳离子交换能力值为1.099、1.168和1.188meq g。熔融预处理显着促进了石英向非晶硅和硅酸盐的转化。然后，加速了硅的溶解并促进了沸石的形成。最终，重金属离子可能被困在沸石骨架中，从而增强了重金属的稳定性。此外，三种处理后的粉煤灰的阳离子交换能力值为1.099、1.168和1.188meq g。熔融预处理显着促进了石英向非晶硅和硅酸盐的转化。然后，加速了硅的溶解并促进了沸石的形成。最终，重金属离子可能被困在沸石骨架中，从而增强了重金属的稳定性。此外，三种处理后的粉煤灰的阳离子交换能力值为1.099、1.168和1.188meq g。^-1，比仅通过水热处理处理的样品大两倍。总之，熔融-水热法可以促进粉煤灰中重金属离子的稳定化，因此获得的具有高沸石含量的固体产物有望用于未来的应用。