Lead in various wastes is thought to cause serious pollution when the wastes are discarded in the environment. Therefore, its elution behavior from various kinds of ashes has so far been investigated. Here, mixing various wastes at optimum ratio is expected to result in the inhibition of its elution.
In the present study, first, elution behavior of lead, artificially added to the mixture of coal ash, municipal waste ash and flue gas desulfurization sludge was investigated by varying added amount of lead and mixing ratio. Remarkable inhibition effects by addition of flue gas desulfurization sludge to the mixture of the coal ash and municipal waste ash were found on the elution of lead. Second, the mechanism of the inhibition effects of lead was discussed by considering the effects of co-existing anions in the leachate. Chemical species of lead eluted were estimated by the stability of various lead complexes formed and their solubility products. It was suggested that lead carbonate formed by the reaction between lead ion produced from lead chloride added and carbonate ion eluted from the desulfurization sludge suppressed the elution of lead. Finally, the contribution of formation of ettringite or similar minerals during the curing process to the lead elution was discussed from the results on the effects of coal ash to municipal waste ash ratio on its elution.