Determination of lead speciation in melting furnace fly ash by sequential chemical extraction

A procedure for sequential chemical extraction to determine the degree of speciation of Pb compounds in melting furnace fly ash was developed. Optimal solvent concentrations were determined individually for each extracting solvent by using standard Pb reagents. Sequential chemical extraction was performed to evaluate the selectivity of extraction procedures for each Pb compound using simulated melting furnace fly ash samples. The extraction of Pb was significantly inhibited by the formation of insoluble precipitates created by the combination of extracted Pb2+ with SO42-, Cl−, and OH− contained in melting furnace fly ash. To selectively extract each Pb compound, Pb2+ was sulfurized to prevent the formation of insoluble precipitates, and the solution pH was controlled to neutralize OH−. Consequently, by the parallel use of five extraction procedures, the concentration of Pb in simulated melting furnace fly ash samples was satisfactorily estimated with errors between 0.5% and 20%.