Isomer Distributions of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans Formed during De Novo Synthesis on Incinerator Fly Ash

• Published in: Environmental science & technology 1998-07, Vol.32 (13), p.1888-1893
• Main Authors: Addink, Ruud, Govers, Harrie A. J, Olie, Kees
• Format: Article
• Language: English
• Subjects: Analysis; Applied sciences; Atmospheric pollution; Combustion and energy production; COMPOSE ORGANOCHLORE; COMPUESTO ORGANICO DEL CLORO; Dioxins; Exact sciences and technology; Incineration; ORGANOCHLORINE COMPOUNDS; PCB; Pollution; Pollution sources. Measurement results; Polychlorinated biphenyls
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es971077z

Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) emitted from municipal waste incinerators appear to have a chlorination pattern that is quite constant across various samples and conditions. This suggested that these patterns may be controlled by thermodynamic properties of the individual PCDD/F congeners, such as the free Gibbs energy of formation (ΔG°f,T). This would make prediction of the isomer composition of a particular sample (and hence its TEQ value) possible, based on values of ΔG°f,T. A laboratory scale study was carried out with activated carbon on fly ash as the source of PCDD/F formation. Although it was found that the isomer distributions within homologues were independent of the reaction time (proof of thermodynamic control), other observations (lack of equilibrium/isomerization between isomers and lack of similarity between isomer distributions measured and predicted by ΔG°f,T) contradicted the possibility of thermodynamic control. Hence, this study could not confirm that de novo formation of PCDD/F could explain thermodynamically controlled isomer distributions in incinerators. Some recommendations for further worktime-based studies with precursors, isomerization studies with single congeners, and more data on ΔG°f,T values of PCDD/Fwere made.