Volume reduction solidification technology for municipal solid waste incineration fly ash and evaluation of its long-term stability

Abstract Municipal solid waste incineration (MSWI) fly ash poses environmental risks due to its high soluble chloride content and heavy-metal leachability. Conventional organic chelation treatments often exhibit poor long-term stability and occupy large landfill volumes. To overcome these limitations, this study developed an inorganic mineralization and mechanical compaction treatment, and established a service-life prediction approach based on carbonation behavior. Chemical and mineralogical characteristics were analyzed using XRF, XRD, and SEM, while heavy-metal leaching tests were performed in accordance with GB 16889. The resulting volume-reduced solidified bodies (VRSB) exhibited a density of 2.0 t m −3 , a compressive strength of 4.19 MPa, and a volume reduction rate of 65%. Heavy-metal leachate concentrations were reduced below regulatory limits following treatment. Accelerated carbonation tests showed a carbonation depth of 2.6 mm after 28 days, and modeling predicted a natural carbonation depth of 21.2 mm after 100 years, equivalent to approximately 2.1% of the specimen dimension. These findings indicate that the VRSB maintain long-term heavy-metal immobilization and exhibit favorable durability under landfill conditions. Overall, the proposed method enhances landfill space efficiency, mitigates groundwater contamination risks, and provides a scalable and practical solution for long-term MSWI fly ash stabilization.