Abstract:Fly ash from municipal solid waste incineration (MSWI) is a hazardous waste that contains various toxic heavy metals, posing significant environmental risks if not properly treated. The leaching of these heavy metals restricts the resource utilization of fly ash and threatens the environment. This study investigates the influence of the slaked lime pre-addition during flue gas purification on the subsequent chelation and solidification treatment of MSWI fly ash. It focuses on the impact of slaked lime dosage and purity on the stabilization efficiency of heavy metals. Additionally, the mechanism of heavy metal solidification is elucidated by analyzing the micro-structure, mineral composition, and the distribution of heavy metal speciation. The experimental results indicated that the optimal solidification efficiency for most heavy metals was achieved when the slaked lime dosage reached 8%; specifically, the solidification efficiencies of Zn, Se, and Cr(Ⅵ) were 97.6%, 82.9%, and 53.3%, respectively. Moreover, the solidification efficiencies of Cu, Pb, Cd, and Ni reached 100%. The addition of slaked lime increased the leaching concentrations of Ba and As; however, these concentrations did not exceed the regulatory limts for landfill disposal. Notably, using high-purity slaked lime significantly reduced the leaching concentrations of heavy metals, highlighting the crucial role of lime purity in stabilization. Microstructural analysis revealed that the addition of slaked lime densified the internal structure of fly ash, promoting the solidification of heavy metals. Mineral composition analysis showed that the presence of alkaline substances enhanced heavy metal stabilization. Heavy metal speciation distribution analysis indicated that the distribution of heavy metals shifted to more stable forms, further demonstrating the benefits of slaked lime addition. This study emphasizes the importance of pre-addition of slaked lime during flue gas purification in enhancing the subsequent chelation and solidification treatment of MSWI fly ash. The findings provide valuable insights into optimizing lime dosage to improve heavy metal stabilization, contributing to more effective and sustainable waste management practices. Close-