Stabilization of Fly Ash from Municipal Incinerators

Municipal solid waste incinerator by-products include fly ash and air pollution control residues. In order to transform these wastes into reusable species, soluble alkali chlorides must be separated and toxic trace elements must be stabilized. In this paper, alkali chlorides can be extracted efficiently in an aqueous extraction step combining a calcium phosphate gel precipitation. In such a process, sodium and potassium chlorides are obtained free from calcium salts, and the trace metal ions are immobilized in the calcium phosphate matrix. Fly ash spiked with copper ions and treated by this process shows improved stability of metal ions. Leaching tests with water or EDTA reveal a significant drop in metal ion dissolution.