Application of micro-scale correlation analysis to estimate metal speciation and the matrix in municipal solid waste incineration fly ash

Micro-scale correlation analysis was applied to estimate metal speciation and the matrix in municipal solid waste incineration (MSWI) fly ash in this study. The results showed that dominant metal speciation and the bonding states with fly ash matrix are different in individual fly ash particle. Micro-scale correlation analysis also suggests metal behaviors in fly ash formation processes. Metal oxides likely react with and/or are trapped in Al/Ca/Si-based matrix such as aluminosilicate in the gas phase and then followed by KCl/NaCl adsorption on the surface. Zinc can possibly form other speciation depending on combustion condition. Zinc chlorides (ZnCl2 and/or K2ZnCl4) and Zn spinels (ZnAl2O4 and ZnFe2O4) are not trapped in Al/Ca/Si-based matrix, however, adsorbed on the surface together with KCl/NaCl-based aggregates. Because metal oxides basically combine with and/or are trapped in Al/Ca/Si-based matrix, metal leachability might be controlled by not only metal oxide leachability but also leachability of Al/Ca/Si-based matrix around metal oxides.