Reactions of dibenzofuran and 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin on municipal waste incinerator fly ash

Dibenzofuran (DF) on fly ash can be converted to polychlorinated dibenzofurans (PCDF) in a N-2/O-2/HCl atmosphere, yielding especially 2,3,7,8-substituted congeners. This is consistent with an electrophilic aromatic substitution mechanism. 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin (1,2,3,4,7,8-H6CDD) on fly ash can be chlorinated by HCl both in N-2 and O-2 atmospheres. Dechlorination and decomposition reactions are not important under these conditions, and isomerization reactions do not take place either. 1,2,3,4,7,8-H6CDD dechlorinates or decomposes on fly ash when no HCl is present. Only a limited number of dechlorination products are formed. Chlorination and dechlorination are separate processes, not occurring simultaneously.