Abstract
Ball milling is investigated as a method of reducing the leaching concentration (often termed stablilization) of heavy metals in municipal solid waste incineration (MSWI) fly ash. Three heavy metals (Cu, Cr, Pb) loose much of their solubility in leachate by treating fly ash in a planetary ball mill, in which collisions between balls and fly ash drive various physical processes, as well as chemical reactions. The efficiency of stabilization is evaluated by analysing heavy metals in the leachable fraction from treated fly ash. Ball milling reduces the leaching concentration of Cu, Cr, and Pb, and water washing effectively promotes stabilization efficiency by removing soluble salts. Size distribution and morphology of particles were analysed by laser particle diameter analysis and scanning electron microscopy. X-ray diffraction analysis reveals significant reduction of the crystallinity of fly ash by milling. Fly ash particles can be activated through this ball milling, leading to a significant decrease in particle size, a rise in its BET-surface, and turning basic crystals therein into amorphous structures. The dissolution rate of acid buffering materials present in activated particles is enhanced, resulting in a rising pH value of the leachate, reducing the leaching out of some heavy metals.
Highlights
Municipal solid waste incineration (MSWI) fly ash has been classified as hazardous waste because of the presence of contaminants such as heavy metals and dioxins
Fly ash was taken from the bag filter of a circulating fluidized bed (CFB) MSWI plant located in Hangzhou, Zhejiang Province, China
The main cations, anions, and heavy metals of raw fly ash, MFA and washed fly ash (WFA) were analysed by X-rayatdiffraction room temperature (XRF)
Summary
Municipal solid waste incineration (MSWI) fly ash has been classified as hazardous waste because of the presence of contaminants such as heavy metals and dioxins. Treatment of fly ash has become an urgent environmental issue in China. The most common method of fly ash elimination is landfill disposal, after cement-based solidification of heavy metals. Cement addition does not degrade polychlorinated dibenzo-p-dioxins (PCDD) and –furans (PCDF). The volume of fly ash significantly increases after treatment, which rapidly reduces existing landfill capacity. New landfill sites are often opposed to by local residents. It is important to develop novel methods to render
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