Heavy Metal Solidification and Environmental Risk Assessment During Co-Vitrification of Municipal Solid Waste Incineration Fly Ash with Coal Gasification Fine Slag and Coal Gangue

Vitrification is an effective method for treating municipal solid-waste incineration fly ash (MFA). However, the high melting temperature of MFA leads to substantial energy consumption and secondary volatilization of heavy metals. In this study, MFA was blended with coal gasification fine slag ash (FSA) and coal gangue ash (CGA) for co-vitrification. The influence of the blending ratio on heavy-metal solidification, vitreous-phase formation and environmental risk assessment of vitrified slags was investigated. Results indicated that when vitrified at 1300 °C, raw MFA achieved only ∼45% vitreous phase content, whereas blending with 50% FSA or CGA increased this value to >85%, successfully achieving complete vitrification. A 50% MFA + 50% FSA/CGA mixture exhibited higher solidification ratios for Cd, Pb, Zn, Ni and Cu than raw MFA. Cd, Cu, Pb and Zn predominantly existed in oxidizable and residual states within the vitrified slags, whereas Cr and Ni were almost exclusively in residual states. After co-vitrification with 50% FSA/CGA at 1300 °C, the comprehensive heavy-metal toxicity index dropped to ∼400, markedly lower than the 28700 value observed for MFA treatment.