Municipal solid waste incinerator (MSWI) fly ash is defined as hazardous waste, which is difficult to be handled due to its complicate composition. At present, all of them are treated by solidification/stabilization and then landfill in Taiwan. But the specimen occupied the landfill site and the heavy metals re-leaching in long-term still are the problems. Ball milling to super-fine particle could enhance the chemical reaction in the treatment, applying it on the stabilization of the heavy metals in fly ash, is anticipative to promote the opportunity of recovery and reusing.
The study is to research the characteristic of water extracted fly ash followed by wet ball milling. By using of Particle Size Analyzer, X-ray Diffraction, Scanning Electron Microscope to identify the property of fly ash, then use toxicity characteristic leaching process (TCLP) and sequential extraction procedure (SEP) to analyze the leaching characteristics and bonding pattern of heavy metals.
The results showed that, water-extraction could effectively reduce the chloride content, and leaching potential of Pb in fly ash. The optimum grinding condition in the experiment is：solid of slurry by weight is 10 %, rotation rate of milling jar is 93 rpm, and the milling dispersion solution is alcohol, the mixing ratio of milling media is 1:1(diameter of milling media is 5 and 15 mm respectively). After milled, particle size of water-extracted fly ash reduced gradually to micrometer grade detected by Ultra Particle Analyzer, but based on SEM observations, these micro-particles actually composed of smaller motes. The peak intensity of XRD decreased as increasing of milling time. In addition, leaching potential of Pb could be reduced to fit TCLP regulation after milling operation; it proved that the milling operation has the ability to stabilize Pb in fly ash. Appling phosphoric acid solution as the milling fluid and analyzing the product by SEP, the results showed that Pb can be stabilize as hard-to-leaching bounding type.