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 also threatens the environment. This study investigates the influence of pre-addition of slaked lime during flue gas purification on the subsequent chelation and solidification treatment of MSWI fly ash. The research focuses on the impact of slaked lime dosage and purity on the stabilization efficiency of heavy metals in fly ash. Additionally, it elucidates the mechanism underlying heavy metal solidification by analyzing micro-structure, mineral composition, and the distribution of heavy metal morphology. The experimental results showed that the optimal solidification efficiency for most heavy metals was achieved when the slaked lime addition reached 8%. Specifically, the solidification efficiency of Zn, Se, and Cr(VI) reached 97.6%, 82.9%, and 53.3%, respectively. Moreover, the solidification efficiency of Cu, Pb, Cd and Ni reached 100%. The addition of slaked lime increased the leaching concentration of Ba and TAs, yet they still did not exceed the landfill detection limit. Notably, the use of high-purity slaked lime significantly reduced the leaching concentration of heavy metals, highlighting the crucial role of slaked lime purity in heavy metal stabilization. Micro-morphological analysis revealed that the addition of slaked lime compacted 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 morphology distribution analysis indicated that the distribution of heavy metals shifted to a more stable state, further indicating the benefits of slaked lime addition. This study emphasizes the importance of pre-addition of slaked lime during flue gas purification in influencing the subsequent chelation and solidification treatment of MSWI fly ash. The findings provide valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices. Close-