71925-16-1Relevant academic research and scientific papers
Comparison of 2,4,6-trichlorophenol conversion to PCDD/PCDF on a MSWI- fly ash and a model fly ash
Hell,Altwicker,Stieglitz,Addink
, p. 995 - 1001 (2007/10/03)
We performed experiments on two different matrices with 2,4,6- trichlorophenol as precursor to Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD)/F. A municipal solid waste incinerators (MSWI) and a model fly ash were spiked in two different ways. The experiments demonstrated a three times higher formation potential of the trichlorophenol to PCDD on MSWI fly ash compared with the model fly ash used. For both fly ashes the PCDD yield was higher when gaseous trichlorophenol was fed continuously compared to mixing the fly ashes prior to the experiments with the total amount of the precursor. Despite dilution of the fly ashes tenfold with an inactive matrix the conversion of the chlorophenol was very high. (C) 2000 Elsevier Science Ltd.
Isomer distributions of polychlorinated dibenzo-p-dioxins/dibenzofurans formed during de novo synthesis on incinerator fly ash
Addink, Ruud,Govers, Harrie A. J.,Olie, Kees
, p. 1888 - 1893 (2007/10/03)
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. 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.
Isomer-Specific Separation of 2378-Substituted Polychlorinated Dibenzo-p-dioxins by High-Resolution Gas Chromatography/Mass Spectrometry
Buser, Hans Rudolf,Rappe, Christoffer
, p. 442 - 448 (2007/10/02)
All polychlorinated dibenzo-p-dioxin (PCDD) isomers containing four and more chlorine substituents were prepared by micropyrolysis of chlorophenolates.The synthesis included the preparation of all 22 tetra-, 14 penta-, 10 hexa-, 2 hepta-, and octachlorinated species (tetra- to octa-CDD).The gas chromatographic and mass spectrometric properties of these isomers were studied.High resolution gas chromatography (HRGC) on a 55-m Silar 10c glass capillary column allowed the separation of many of these isomers and allowed the unambiguous assignment of the toxic and environmentally hazardous 2378-substituted isomers (2378-tetra-, 12378-penta-, 123478-, 123678-, and 123789-hexa-CDD).Analyses were carried out to determine the occurence of these isomers in environmental samples and in fly ash from municipal incinerators.
