Stabilization/solidification of municipal solid waste incineration fly ash via co-sintering with waste-derived vitrified amorphous slag

Municipal solid waste incineration (MSWI) fly ash (FA) is classified as hazardous waste and requires special treatment prior to landfilling due to its high levels of alkali chlorides and heavy metals. In this paper we presented and discussed a novel method of converting FA into an inert and non-hazardous material, by using the metastable state of vitrified amorphous slag (VAS). XRD results showed that VAS remained in the amorphous state when sintered at 700 and 800°C and were in the crystalline state at 900 and 1000°C. Heavy metals- and Cl-containing phases appeared during phase transformation process. The residual rates of heavy metals and Cl increased with the decrease of FA:VAS ratios. The prolonged leaching test and potential ecological risk assessment of heavy metals showed that the heavy metals were well immobilized into the sintered samples and presented no immediate threat to the environment. The results indicated that the immobilization of heavy metals was due to the reaction with silicate or aluminosilicate matrices within VAS and/or the incorporation into the new generated crystals. The proposed method can be considered as a potential promising technique for the stabilization/solidification of MSWI fly ash with high Cl content.