Abstract
Chemical treatment with liquid chelating agent is a common method to restrain leaching of heavy metals from melting furnace fly ash. However, the long-term stability of the metal chelate compounds in the treated fly ash could be a potential problem.
In this research, persistence of the metal chelate compounds in the samples excavated from an eight-year-old landfill site was evaluated by the n-butyl acetate extraction method. Concentration of metals in leachate by JLT-13 leaching test and in effluent of the landfill was measured. The research result shows that the persistence ratio of the lead chelate compound was very low. The extraction ratio of excavated samples from the landfill was equal to or less than 10% of the extraction ratio of the samples right after the treatment. Therefore, it is possible that the lead chelate compound was degraded after being buried in the landfill. However, lead concentrations in both the leachate by JLT-13 and in effluent water from the landfill were very low, with the maximum value of 0.031mg/L. The results from the pH-dependence test indicate that lead was transformed into some chemical compounds. These chemical compounds are very hard to dissolve, even in a strong alkali solution.
