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Evolution of PCDD/F-signatures during mechanochemical degradation in municipal solid waste incineration filter ash

Zhiliang, Chen, Minghui, Tang, Shengyong, Lu, Jiamin, Ding, Qili, Qiu, Yuting, Wang, Jianhua, Yan
Chemosphere 2018 v.208 pp. 176-184
additives, chlorine, dechlorination, electrons, incinerators, mechanochemistry, municipal solid waste, oxygen, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, waste incineration
Mechanochemical degradation (MCD) is employed for the dechlorination of polychlorinated dibenzo-p-dioxins (PCDD) and -furans (PCDF) in filter ashes from municipal solid waste incinerators, respectively with the assist of six additive systems. The evolution of PCDD/F-signatures in all eleven samples are systematically monitored and studied at the level of individual congeners, and special attention is paid to CP-route congeners, 2,3,7,8-substitution, 1,9-substitution, and 4,6-PCDF. The PCDD/F-isomers distribution follows an analogous pattern, indicating the similar acting mechanism for all additives: additives transfer electrons to attack the CCl bond and then expulse chlorine. MC dechlorination is not favored for the chlorine on β-position (2,3,7,8-position). The oxygen with stronger electronegativity in PCDD/Fs negatively influences CCl bond to accept donated electrons, hindering the removal of chlorine on 1,9-position for PCDD, and chlroine on 4,6-position for PCDF. Finally, two fair dechlorination pathways for PCDD and PCDF are respectively proposed based on the detailed analysis of CP-route congeners. The evolution of PCDD-signatures is clear, yet obscure for PCDF-signatures, which still requires further investigations.