Metal leachability and species analysis in municipal solid waste incinerator ashes

This study attempts to investigate the ashes morphology, metals leachability, and to speciate the metals species formation in the MSW incinerator ashes. Analysis for the percentage metals solubilities in flyashes indicate that the solubility of lead was relatively insoluble and cadmium was highly soluble. The solubilities of lead, cadmium, chromium, and zinc in bottom ashes were also highly soluble. In addition, the lead and chromium in reaction products present higher solubility than flyashes and bottom ashes. As a result, a high pH level of extraction and excess alkalinity of reaction products were significant factors of metals solubility. In this study, PbO and PbO₂ were the crystalline phase observed in the flyash sample; chromium silicide (CrSi₂), zincite (ZnO), silicon oxide (SiO₂), and calcium oxide (CaO) were detected in bottom ash. Besides, the metals species in the reaction products include sodium cadmium chloride (Na₂CdCl₄), lead arsenate hydroxide ((Pb₅(AsO₄)₃OH), and lead arsenate (Pb₄As₂O₉).