Solidification/stabilization and risk assessment of heavy metals in municipal solid waste incineration fly ash: A review

Incineration is currently the most common method of treating municipal solid waste. Municipal solid waste incineration fly ash (MSWI FA) contains a high concentration of toxic heavy metals (HMs), making it a hazardous waste. A series of detoxification treatments are required to reduce the toxicity of fly ash. Furthermore, the environmental risk of MSWI FA after treatment is becoming a cause of concern. This paper reviews the primary ash properties, pH, liquidsolid ratio, and other factors (microorganism, type of leaching agents, etc.) that affect the leaching of HMs from MSWI FA, compares and summarizes the most widely applied solidification/stabilization (S/S) techniques. In particular, models and methods for the environmental risk assessment and prediction of HMs are classified and described in detail. Finally, the inadequacy of current S/S techniques for MSWI FA is pointed out, which may be useful for upcoming studies on this topic.