Effect of milling material on characteristics and reactivity of mechanically treated fly ash to produce PCDD/F

Municipal solid waste incineration produces huge amount of fly ash containing chlorides, leachable heavy metals and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F or dioxins). High-intensity ball milling was applied to model fly ash (MFA) samples at 300 rpm (1 and 8 h) which were composed of silica, sodium chloride, activated carbon and doped with metal (0.2 wt.% Cu, Cr, Fe, Zn and Ca) chlorides. Effect of ball mill made of stainless steel and zirconia material was evaluated on characteristics and reactivity of MFA to produce PCDD/F. The characterization tests revealed that after milling treatment, MFAs with different metal catalysts showed similar changes in mass, distribution of metal catalysts, surface morphology, crystalline phases and graphitic structure of activated carbon. These changes were more pronounced in MFA milled with stainless steel material compared to zirconia. However, effect of milling material on the reactivity of MFA to form PCDD/F was almost similar in Cu-doped MFA, despite of homogenous dispersion of catalytic metal. The reactivity of all selected MFAs was greatly reduced after prolonged milling treatment and can be disposed of safely into landfills.

Automated summary

High-intensity ball milling was used to modify model fly ash samples, affecting their characteristics and reactivity in generating PCDD/F. The choice of stainless steel or zirconia as ball mill materials had varying influences on the fly ash samples, with more pronounced changes observed in those milled with stainless steel. However, the reactivity of all fly ash samples, particularly the Cu-doped ones, was significantly reduced after prolonged milling and could be safely disposed of in landfills.