Thermal separation of heavy metals from municipal solid waste incineration fly ash: A review

Municipal solid waste incineration (MSWI) fly ash is categorized as a hazardous waste owing to the presence of heavy metals. The thermal separation of heavy metals from MSWI fly ash has the potential to not only purify the fly ash, but also enable the recovery of heavy metals. The main thermal separation methods include calcination thermal separation (700-1200℃), chlorination thermal separation (700-1000℃), reduction thermal separation (700-1000℃) and molten salts thermal separation (600-800℃). This paper presents a comprehensive review of these four thermal separation methods, comparing them in terms of separation effectiveness, economic feasibility, technical maturity, and environmental impact, etc. Additionally, the possibility of urban mining from MSWI fly ash was evaluated, and the results indicated that while it may be less cost-effective, it could bring significant environmental and social benefits. Finally, the limitations of the existing thermal separation methods and the focus of further research, including both mechanisms and experimental investigations were outlined.