| The incineration treatment has been widely used for Municipal Solid Waste(MSW) treatment in the world. However, a great deal of fly ash has generated during the incineration progcess. Fly ashes from MSW incinerator (MSWI) contain high concentration leachable heavy metals (Pb, Cd, Cu, Zn). If the fly ash has been landfilled directly, the heavy metals would leached on large degree and polluted the underground water. Therefore, the safe and effective pre-treatment for incineration fly ash is becoming urgent for environmental problems.The carbonation progress for MSWI fly ash is a new technology in the world in recent years.This technology stabilize heavy metal in residue and involves the absorption and stabilization of CO2.In this study, preparation of the carbonated fly ash using self-made test system. The influence of two important parameter(liquid/solid ratio and reaction time)affecting the reactivity of CO2 on the extent and quality of carbonaton was evaluated. Studies have shown that the optimal carbonated liquid-solid ratio is 0.25. Evaluation of the ash mineralogy associated with the reaction revealed the disappearance of portlandite/calcium chloride hydroxide and the formation of calcite as carbonation proceeded. Furthermore, evaluation of the fly ash morphology revealed that the fly ash particles become compact following carbonation. The leaching properties of the carbonated ash were also examined following the Solid Waste Extraction Procedure for Leaching Toxicity (GB5086.1/2-1997). In general, the leaching of Pb, Cu and Zn decreased greatly following carbonation.After carbonation Pb concentration was reduced by 3 orders of magnitrdes to less than 10μg.L-1, Zn concentration was reduced by 1 order of magnitude, Cu concentration was reduced by 90%, As concentration was reduced 40%. Conversely, the leaching of Cd and Sb increased in response to carbonation. The optimum pH of the carbonated fly ash was 9.5-10.5 based on the leaching of the six heavy metals evaluated here. Furthermore, the release of soluble salts such as SO42-, Cl- and F- changed little following carbonation, and their release occurred independently of the pH. Taken together, these results indicate that carbonated fly ash has the potential to prevent the leaching of heavy metals.In this study,evaluation of influence of pre-treatment on the vaporization characterstics of heavy metals in MSWI fly ash during the calcination process was investigated, the test sample include the original fly ash, carbonated fly ash, carbonated fly ash after washing. Studies have shown that washing, carbonation combined washing pre-treatment change the sensitivity of metals to the temperature. Washing pretreatment reduce the volatilization of Pb and Cd. The carbonation combined washing pretreatment reduce the volatilization of Pb, Cd and Zn at 1100℃。The evaluation of changes in sample composition during the thermal process was investigated by using TG-DTA method and XRD analysis. Studies have shown that with the increase of content of heavy metals in sample, the weight loss of sample decreases for the samples containing the same kind of heavy metals. The comparison result of volatile percentage was that Pb﹥Cd﹥Cu﹥Zn for samples containing different types of heavy metals. The results are consistent with that of high-temperature tube furnace experiment. Finally, this study worked out the kinetic models of the volatilization of the samples by the TG-DTG results.
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