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COMPARISON OF HEAVY METALS LEACHABILITY FROM COMBUSTION WASTES USING BATCH LEACHING TESTS

Joanna Fronczyk

Abstract

Combustion wastes, such as fly ashes and slags, can be recycled primarily by using them in road construction. Nonetheless, their potential negative impact on the environment cannot be omitted. In practice, a number of methods are used for the leaching characterization of wastes, including the standards of the European and US Environmental Protection Agencies. The studies, the results of which are presented in this article, were performed for fly ashes and slags from coal combustion and for fly ashes from combustion of municipal sewage sludge. The materials tested were characterized by determining the pH and electrical conductivity of water eluates, and the contents of moisture, volatiles, ash and percentage of carbon. The aim of the study was the assessment of differences in the leachability of heavy metals from combustion wastes using ISO, DIN and US EPA methods. In the batch leaching tests, 0.01 mol/L CaCl2, demineralized water and 2.0N HNO3 were used as leachants, respectively. The concentration of cadmium, copper, lead, nickel and zinc in eluates was analyzed using atomic absorption spectrometry (iCE 3000). The results have shown that the pH of leachants had influence on the release of heavy metals. The highest concentrations of pollutants were obtained using the US EPA method and the HNO3 solution as the leachant. Moreover, the study has shown that according to European procedures, the concentrations of released pollutants (Cu, Ni, Pb and Zn) were characteristic for inert wastes.

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