Water repellents for the leaching control of heavy metals in municipal solid waste incineration fly ash

Suppression of heavy metal elution from municipal solid waste incineration (MSWI) fly ash by cement or geopolymer solidification was studied. When these approaches are implemented, however, the volume of the solidified body increases as a consequence of the solidifying agent addition. Considering that residual landfill disposal capacity is decreasing in the long term, a novel method to suppress the elution of heavy metals from MSWI fly ash without decreasing the disposal capacity is needed. We studied four different water repellents and the results indicated that heavy metal elution can easily be suppressed by impregnating the incineration fly ash with commercially available silane oligomers, alkyl alkoxysilane compounds, and water repellents like fatty acids.

Crystal Morphology Analysis for Heavy Elements in Municipal Solid Waste Incineration Fly and Bottom Ash by X-ray Characterization Techniques

The elemental and crystalline phase compositions of fly ash collected before and after spraying of the ash with slaked lime (first and second fly ash) and the bottom ash of municipal solid waste collected at an incineration plant were analyzed using powder briquette by X-ray fluorescence spectrometry and Rietveld refinement by X-ray diffraction. The crystalline and amorphous phase contents were quantified by adding 10% corundum as an internal standard. In the first fly ash, SiO2, Cl, and CaO were the main components, and several thousand ppm (μg/g) of Zn and Pb were detected. Anhydrite, gehlenite, and amorphous phases were the main phases in the first fly ash samples. The components of the first fly ash originated exclusively from the incineration of municipal solid waste in a furnace. The crystal morphologies of the heavy elements in the ash samples were estimated by determining the correlations among the concentrations of all the elements. The heavy elements in the bottom ash showed no strong correlations with other elements; therefore, the heavy elements in the bottom ash were present in an amorphous phase.