Solidification and leaching behaviours of heavy metal Pb in MSW incineration fly ash and its thermal stability at various thermal treatment temperatures

Abstract

The fly ash generated by municipal solid waste (MSW) incineration contains heavy metals, which pose a significant environmental threat. Thermal treatment emerges as a potential technique for reducing and detoxifying MSW incineration fly ash, but the optimal thermal treatment temperature remains unclear. This study explores the thermal stability of MSW incineration fly ash under various thermal treatment temperatures (1000 °C − 1500 °C). Additionally, the solidification and leaching behaviors of heavy metal Pb were investigated. The results revealed distinctive trends: the mass residual rate showed the fastest decline between 1200 °C and 1273 °C, while the volume residual rate showed the fastest decline between 1100 °C and 1200 °C. The solidification rate of heavy metal Pb decreased as the treatment temperature increased. With the decrease of specific surface area, the leaching rate of heavy metal Pb exhibited a gradual decline, but it sharply surged at the fluid temperature. This was because the encapsulation effect of Pb by calcium silicate iron manganese complex was weakened and an increase in kinds of Pb oxides(Pb2O3, Pb3O4) that can react with glacial acetic acid in the leachate. Thus, it was not advisable to treat the MSW incineration fly ash around the fluid temperature. The optimal thermal treatment temperature was suggested to be 1200 °C, as it achieves goals such as volume reduction, detoxification and low energy consumption. These provide useful theoretical guidelines for the thermal treatment of MSW incineration fly ash.