Content and fractionation of Cu, Zn and Cd in size fractionated municipal solid waste incineration bottom ash

• The contents of Cu, Zn, Cd in bottom ash are related with their volatility.
• The thermodynamic nature of Cu, Zn, Cd affects their fractionation in bottom ash.
• Fine ash contains higher amounts of unstable volatile metal Cd than the large ash.
• Large ash contains higher amounts of unstable lithophilic metal Cu than the fine ash.

Municipal solid waste incinerator (MSWI) bottom ash was size fractionated into six fractions, with the respective particle size of <0.45 mm, 0.45–1 mm, 1–2 mm, 2–4 mm, 4–8 mm and >8 mm. The contents and fractionation of Cu, Zn, Cd in the size fractionated MSWI bottom ash were investigated. The results showed the contents and fractionation of Cu, Zn and Cd varied among the different particle sizes, which were related to their thermodynamic characteristics. High content of Cu was found in the bottom ash with the particle size of <0.45 mm and >4 mm, due to its lithophilic property and the function of entrainment. The content of Zn showed a relatively even distribution among the various particles. The content of Cd showed a decreasing trend with the increase of the particle size, due to its high volatility. Besides, the carbonate bound fraction of Cd showed a decreasing trend with the increase of the particle size, while the carbonate bound fraction of Cu showed an increasing trend. The organic matter bound fraction of Cu increased when the particle size increased. The results also showed the fine ash contained a higher level of unstable Cd than the large ash, while the large ash had a higher level of unstable Cu comparatively.