(514o) Heavy Metal Solidification Via CO2 Injection in Municipal Solid Waste Incineration Fly Ash(MSWI FA) Stabilization By Leaching Using Various Solvents

manufacturing or consuming of the products, especially, the increase of municipal solid waste

(MSW) is one of the main problems of the national and civil authorities. Conventionally, the

MSW was usually disposed by landfill. However, it requires the massive lands to cover the

wastes, and the hazardous components can be leached out by the water in the soils.

Therefore, except the recycling, most of MSW is treated by incineration nowadays.

Incineration also produces the by-products, such as municipal solid waste incineration (MSWI)

ashes. The MSWI ashes are classified to bottom and fly ash. MSWI bottom ash (MSWI BA)

can be reused as construction materials or disposed, since its properties are similar with the

ordinary materials, and the allowable amount of the hazardous components, such as the heavy

metals, is leached out to the environment. However, MSWI fly ash (MSWI FA) must be

stabilized before the disposal, the higher amount of the heavy metal components can be leached

out than MSWI BA. To prevent the pollution by MSWI FA, several methods are applied or researched for the

environmental prevention systems. Among them, acid leaching is the most prevalent and

widely used in the industries, due to higher efficiency of the removal of the heavy metals than

other methods, recovery of the valuable metals, and decrease of the volume of the MSWI FA.

Also, in table 1, various types of the acid can be used as leaching solvent. However, this

method produces the pollutants, H2 gas and wastewater containing the heavy metals, it requires

the additional treatment. Furthermore, the evaluation at equal experimental conditions is

required, the leaching and stabilization/solidification properties of the strong and weak acids.

Therefore, in this study, we performed the revised acid treatment with following acid solutions.

To evaluate the effect of the different anions and cations, we selected 0.5 M HCl, H2SO4, HNO3

for the strong, NH4Cl, (NH4)2SO4, and NH4NO3 for the weak acid solutions. After mixing these

solutions with MSWI FA, the solidification is performed by following methods. The pH of

these mixtures is relatively basic, by the alkali properties of the MSWI FA, so the solids can be

produced by CO2 uptake, to fix the metal cations in the aqueous phase in solids for easier

handling. In previous study, by adopting this method, the heavy metal components in the

leachate were reduced, and additional processing was not required. To confirm the

properties of solids and solutions, and the reduction of the heavy metal components, following

analysis was used: X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Scanning Electron

Microscope images (SEM), and analyzed Inductively Coupled Plasma Optical Emission

Spectroscopy (ICP-OES).