Co-treatment of municipal solid waste incineration fly ash and alumina-/silica-containing waste: A critical review

Municipal solid waste incineration fly ash (MSWI-FA) is a hazardous by-product of the incineration process, characterized by elevated levels of heavy metals, chlorides, and dioxins. With a composition high in calcium but low in silicon/aluminum, MSWI-FA exhibits a poor immobilization effect, high energy demands, and limited pozzolanic activity when it is disposed of or reutilized alone. Conversely, alumina-/silica-containing waste (ASW) presents a chemical composition rich in SiO₂ and/or Al₂O₃, offering an opportunity for synergistic treatment with MSWI-FA to facilitate its harmless disposal and resource recovery. Despite the growing interest in co-treatment of MSWI-FA and ASW in recent years, a comprehensive evaluation of ASW's roles in this process remains absent from the existing literature. Therefore, this study endeavors to examine the advancement in the co-treatment of MSWI-FA and ASW, with the focus on three key aspects, i.e., elucidating the immobilization mechanisms by which ASW improves the solidification/stabilization of MSWI-FA, exploring the synergies between MSWI-FA and ASW in various thermal and mechanochemical treatments, and highlighting the benefits of incorporating ASW in the production of MSWI-FA-based building materials. Additionally, in the pursuit of sustainable solid waste management, this review identifies research gaps and delineates future prospects for the co-treatment of MSWI-FA and ASW.