Sequential extraction procedure for the speciation of elements in fly ash samples

A five-stage sequential leaching procedure, developed in this work, was successfully applied to fly ash samples collected at several emission sources. The solvent leaching experiments, together with solid phase examinations carried out by X-ray powder diffraction, provide information on the possible environmental impact of particle-associated pollutants. The partitioning of paticulate metals was achieved for Cd, Cr, Cu, Pb, Zn, and V into various fractions: (1) exchangeable, (2) bound to carbonate, (3) bound to Fe/Mn oxides, (4) bound to sulfide compounds, and (5) residual fraction. The concentration of the metals in the leaching solutions was determined by atomic absorption spectrometry. The solid residues of the fractions were analyzed by X-ray powder diffraction. The leachabilities of the metals proved to be different, so various distribution patterns have been achieved. II was found that the difference in the partitioning depends considerably on the properties of the raw material and the operation conditions. It is emphasized that fly ash samples collected at different sources should be individually investigated. (C) 1996 Academic Press, Inc.