Subcritical hydrothermal treatment of municipal solid waste incineration fly ash: A review

Municipal solid waste incineration fly ash (MSWI-FA) is a hazardous waste generated from the incineration process, and the harmless treatment of MSWI-FA has attracted widespread attention. Subcritical hydrothermal treatment is competitive in achieving the harmless treatment and resource recycling of MSWI-FA. It exhibits excellent performance in degrading dioxins, stabilizing heavy metals, and converting MSWI-FA into zeolite or tobermorite at low tempera-tures. This paper clearly introduces the characteristics of MSWI-FA, roundly summarizes the current research status of treating MSWI-FA by subcritical hydrothermal methods, and deeply clarifies the mechanisms of dioxins degrada-tion, zeolite/tobermorite synthesis, and heavy metals stabilization. Considering the research status of handling MSWI-FA by subcritical hydrothermal methods, future research directions are proposed. Owing to the advantages of high efficiency, energy-saving, and environmental sustainability, subcritical hydrothermal treatment of MSWI-FA ex-hibits promising prospects for industrialization.