Vitrification of municipal solid waste incineration fly ash: An approach to find the successful batch compositions

Incineration is the most common way to reduce the mass and the volume of municipal solid wastes. One of the most dangerous by-products of the incineration process is fly ash that contains a considerable amount of heavy metals. Therefore, its treatment is crucial to prevent the leaching of heavy metals into the environment. In the present work, two different sources of municipal solid waste incinerator fly ash have been vitrified in order to inhibit the release of potentially toxic heavy metals. Two different sources of silica, i.e. silica sand and glass cullet, have been added to each type of fly ash in an attempt to obtain vitrifiable batches. The standard leaching test on vitrified products was performed according to EN12457-2 confirming no heavy metal leaching and, therefore, they all pass waste acceptance criteria to be classified as an inert material. Furthermore, the previously reported data for vitrification of fly ash was combined with the present work and their compositions were presented in the SiO2–Al2O3–CaO, and SiO2-ΣM2O3-Σ(MO + M2O) ternary phase diagrams to identify the region in which successful compositions are concentrated. This analysis could facilitate the attempt to find the right composition for vitrification of fly ash.