Mechanochemical treatment of fly ash and de novo testing of milled fly ash

Mechanochemical (MC) treatment has been widely proposed to degrade chlorinated organics in various matrix materials. In this study, fly ash from municipal solid waste incineration was grinded without any addition, using an all-dimensional planetary ball mill. The treated fly ash samples were characterised using X-ray diffraction, Raman spectra, scanning electron microscopy and X-ray energy-dispersive spectroscopy. The residual content of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was monitored, as well as polycyclic aromatic hydrocarbons (PAH), a potential precursor of PCDD/F and amorphous carbon or graphite. Finally, de novo formation experiments were performed to test the chemical reactivity of the treated fly ash. The PCDD/F in milled samples was compared to those resulting from de novo tests on these same samples. The results suggest that both milling as well as de novo tests significantly alter the PCDD/F signature, suggesting substantial differences in the mechanisms of formation and destruction.