Fly ash fro mmunicipal waste incinerators constitutes an environmental problem, as it is polluted with heavy metals. The heavy metals from fly ashes can partly be rmoved and possibly recovered by extracting with an acid solution. The remaining fly ash can be landfilled or used as ocnstructio neaterial. The controlling factor of this extraction process is generally the solubility of the metal salts on the fly ash. By adding ethlene diamine tetraacetic acid to the extractio solution the solubility restrictions can be avoided and the available heavy metals will dissolve even at high pH. Another possible application of the addition of EDTA to the leaching solution is as test method for the evaluation of the total availability of hte heavy metals on the fly ash. This is the portion of the metals that is not encapsulated in the mtrix structure or in insoluble oxides. By using EDTA, solubility rstrictions and the need for a low PH could be avoided. The evolution of the leaching efficiency as a function of the pH was investigated with and without addition of EDTA and those leaching efficiencies were compared. The experiments show that the leaching efficiency for several heavy metals increases when EDTA is added.
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