FORMATION OF POLYCHLORINATED DIBENZO-P-DIOXINS DIBENZOFURANS ON FLY-ASH FROM PRECURSORS AND CARBON MODEL COMPOUNDS

In this article the formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) on waste incinerator fly ash is described. Model experiments were performed by heating organic-C-free fly ash with organic model compounds. Both chlorobenzenes and phenol form PCDD and PCDF via condensation reactions. Phenol is 10-540 times as reactive as the chlorobenzenes. A second (and separate) formation pathway is from oxidative breakdown of macromolecular carbon. This route was studied with hexane, toluene and three anthraquinone derivatives as carbon model compounds. Aliphatic, monocyclic aromatic and functionalized quinone parts of carbon may all contribute to PCDD and PCDF formation, but the latter pathway appears to be the most important. Functional groups play an important role in the potential of these various carbon parts to form PCDD and PCDF.