Strategies for heavy metals immobilization in municipal solid waste incineration bottom ash: a critical review

Incineration is an integral part of the waste management process to reduce the enormous volumes of municipal solid waste generated daily. Of the various incineration products, bottom ash makes up a major portion, which subsequently needs to be disposed or reused. Unavoidably, trace amounts of heavy metal content present in incineration bottom ash (IBA) can be leached out over time, ending up in water bodies and eventually entering the food chain. This can lead to toxic bioaccumulation of heavy metals in animals and humans. To minimize leaching, it is essential for heavy metals in IBA to be effectively immobilized. In this review, we critically evaluate the effectiveness of various heavy metal immobilization strategies to treat IBA in terms of their suppression of heavy metal leaching based on past research examples. Furthermore, these strategies are assessed for their medium to long term stabilities, potential impact on the environment, as well as challenges that may be faced in their successful implementation. Finally, some future directions in heavy metal immobilization efforts are proposed in light of the present climate crisis. Graphical abstract