A novel method for solidification/stabilization of MSWI fly ash by graphene nanoplatelets synergistic alkali-activated technology

Municipal solid waste incineration (MSWI) fly ash with considerable heavy metals needs to be safely disposed of before landfill. In this study, graphene nanoplatelets (GNPs)/MSWI fly ash solidified body was prepared by alkali-activated technology, in order to improve the solidification ability of heavy metals and maximize the utilization of MSWI fly ash to cope with the scarcity of landfill. This paper studied the effect and mechanism of GNPs on heavy metal leaching characteristics. Results showed that solidified body with adding 0.05 wt% GNPs exhibited the highest compressive strength and the lowest heavy metals leaching concentration. Adding GNPs promoted heavy metals in solidified body to be converted into the residual state. Meanwhile, the microstructure and morphology characteristic analysis results indicated that GNPs promoted C-(A)-S-H gels formation. There were various kinds of solidification/stabilization (S/S) mechanisms including physical adsorption, physical encapsulation and chemical bonding in GNPs/MSWI fly ash solidified bodies. This study paves a potential new way for the application of nanomaterials in S/S MSWI fly ash through alkali-activated technology, and graphene is a more promising additive.