Separation of Zn/Pb/Cu from municipal waste incineration fly ash: A phase change-driven method with molten salt...

Municipal solid waste incineration fly ash (MSWI FA), although classified as hazardous waste, is characterized by high levels of non-ferrous metal elements with recycling potential. In this study, a method is proposed to achieve the conversion of Zn/Pb/Cu into volatiles (gas), chlorides into molten salt (liquid) and calcium-containing slag into the molten slag (liquid) from MSWI FA (solid) with molten salt assistance. The process achieved the melting of MSWI FA in molten salt within 600 s, with a chloride separation rate of 99.1 %. The separation efficiencies for Zn, Pb, and Cu from MSWI FA were up to 85.6 %, 74.7 %, and 84.1 %, respectively. Furthermore, key factors affecting the separation efficiency were explored. Increasing the temperature promoted the release of Zn and Pb from fly ash, while Pb volatilization was influenced by residence time. Additionally, an increase in CaO content in molten salt caused Zn/Pb/Cu to migrate to the solid phase, but the introduction of CaCl₂ alleviated this effect. Finally, the dioxin content and leaching toxicity of the product were analyzed, and methods for recovering each component in different phases were also discussed. This study presented a promising approach for the separation of Zn/Pb/Cu from fly ash and the recovery of multiple components.