| HCl was used as extractant to leach Cd, Cr, Cu, Mn, Ni, Pb and Zn from municipal solid waste incinerator (MSWI) fly ash under traditional and microwave acid extraction conditions. The redistributions of heavy metals were determined using the sequential extraction procedure before and after extraction. The extraction efficiencies and speciation transformation of heavy metals were investigated. The result indicated that acid extraction can extract heavy metals effectively and extraction efficiencies of heavy metals following the sequence of Zn≈Pb>Cd>Mn>Cu>Cr>Ni. The microwave energy can improve the extraction efficiencies evidently. By the treatment with 1 mol/L HCl, 80.17% of Cd, 15.05% of Cr,58.25% of Cu，62.42% of Mn，8.88% of Ni，89.25% of Pb and 93.03% of Zn were extracted under the condition of L/S at 25 mL/g fly ash, radiation time at 7 min. The results of sequential extraction procedure reveal that fractions of exchangeable, carbonate, Fe-Mn oxide decreased significantly after acid extraction and the remaining heavy metals mostly bound to residual form. Acid extraction process can increase the environmental safety of fly ash. |
