| Summary: | 碩士 === 東海大學 === 環境科學與工程學系 === 103 === The amount of municipal solid waste has significantly increased, leading to serious issues in waste management, environmental pollution and others. Current main way in treating municipal solid waste in Taiwan is incineration and the annual output of incineration fly ashes is approximately 300 thousand tons. Owing to its high concentration of leachable chloride and heavy metals, fly ashes in cement solidification are thought to be unstable in a long term. Further, space for landfill in Taiwan has been increasingly limited, thus, finding out proper recycling method for fly ashes is of high regard. Previous studies show that fly ashes contain mainly calcium, similar to cement, thus it is of great potential to recycle fly ashes as an additive in cement while solving the problem of fly ash treatment. But if not properly pre-treated, direct addition of fly ash in cement would lead to steel corrosion inside building structure and harm to human beings and environment.
To estimate the amount of chloride in incinerator fly ashes, this study develops a nearly complete digestion method with various combined acids and digestion temperature-ramping profiles. Chloride in the digests is quantified with ion chromatography. SEM-EDS pattern shows that the remaining chloride in digestion residue becomes negligible and the residue mainly consists of metal oxides and carbon increases. Results also indicate that the digestion efficiencies in the present study are greater than 90%, much better than what are obtained, about 50%, following the methods formulated by the ROC EPA and USEPA.
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