Change search
ReferencesLink to record
Permanent link

Direct link
Thermal degradation of PCDD/F in municipal solid waste ashes in sealed glass ampules
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2005 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 10, 3872-3877 p.Article in journal (Refereed) Published
Abstract [en]

Due to their high concentrations of toxic organic compounds such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), metals, and water-soluble salts, fly ashes are classified as hazardous waste in the European Union and are required to be deposited in controlled landfills. We have shown here that the tetra- to octachlorinated PCDD/F in fly ash can be degraded by thermal treatment. The temperature needed for total degradation of PCDD/F depends on the composition of the fly ash. Its concentrations of unburned carbon and alkaline compounds were found to be important in this respect. Experimental design was used to investigate the effects of varying the temperature, residence time, and atmosphere on the degradation of PCDD/F in three different types of fly ash. The results showed that the three ashes clearly showed different degradation potentials for PCDD/F during thermal treatment. The concentrations of unburned carbon, alkaline species such as CaO and Na2O, and metals such as copper and iron strongly influenced the degradation of PCDD/F. However, the different combinations of pH and amounts of native PCDD/F, unburned carbon, metals (Cu, Fe, Sn and Na), and sulfur in the ashes made it difficult or even impossible to conclude that any single parameter was responsible for the degradation of PCDD/F in these thermal treatment experiments. The decreases observed in all of the experiments are due to dechlorination and/or destruction of PCDD/F: depending on the temperature and ash composition, either of these processes may be the more important.

Place, publisher, year, edition, pages
Washington: American Chemical Society , 2005. Vol. 39, no 10, 3872-3877 p.
URN: urn:nbn:se:umu:diva-2646DOI: 10.1021/es0485513OAI: diva2:140872
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2011-03-14Bibliographically approved
In thesis
1. Formation and degradation of PCDD/F in waste incineration ashes
Open this publication in new window or tab >>Formation and degradation of PCDD/F in waste incineration ashes
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The disposal of combustible wastes by incineration is a controversial issue that is strongly debated by both scientists and environmental activists due to the resulting emissions of noxious compounds, including (inter alia) polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), heavy metals and acid gases like sulfur dioxide. Currently available air pollution control devices are capable of effectively cleaning flue gases, and PCDD/F emissions to air from modern municipal solid waste (MSW) incinerators are low. However, the PCDD and PCDF end up in ash fractions that, in Sweden, are usually deposited in landfills.

The European Union has recently set a maximum permitted total concentration of 15 µg TEQ/kg for PCDD/F species in waste. Fly ash from municipal solid waste (MSW) incineration containing PCDD/Fs at concentrations above this limit will have to be remediated to avoid disposing of them in landfills; an expensive and environmentally unfriendly option. Therefore, effective, reliable and cost-effective methods for degrading PCDD/F in fly ash are required, and a better understanding of the behavior of PCDDs and PCDFs during thermal treatment will be needed to develop them.

In the studies this thesis is based upon both the formation and degradation of PCDDs and PCDFs in ashes from MSW incineration were studied.

The main findings of the investigations regarding PCCD/F formation were:

- The concentrations of PCDD and PCDF in fly ash increased with reductions in the temperature in the post-combustion zone.

- The homologue profile in the ash changed when the temperature in the post-combustion zone changed.

- The final amounts of PCDD and PCDF present were affected by their rates of both formation and degradation, and the mechanisms involved differ between PCDDs and PCDFs.

The main findings from the degradation studies were:

- The chemical composition of ash has a major impact on the degradation potential of PCDD and PCDF.

- The presence of oxygen during thermal treatment can enhance the degradation of PCDD and PCDF.

- Thermal treatment is a viable option for degrading PCDD and PCDF in ashes from MSW.

- Shifts in chlorination degree occur during thermal treatment.

- Rapid heat transfer into the ash is a key factor for ensuring fast degradation of PCDD and PCDF.

- Degradation of other chlorinated organic compounds, e.g. PCB and HCB, also occurs during thermal treatment of ash.

- Reductions in levels of PCDD and PCDF were not solely due to their desorption to the gas phase.

- Differences between the behavior of 2378-substituted congeners of PCDD and PCDF and the other congeners during thermal treatment were observed.

- Differences in isomer patterns of both PCDD and PCDF were observed between the ash and gas phases after thermal treatment at both 300 and 500 oC.

Overall, the results show that the formation and degradation mechanisms of PCDDs differ substantially from those of PCDFs. Thus these groups of compounds should be separately considered in attempts to identify ways to reduce their concentrations.

Place, publisher, year, edition, pages
Umeå: Kemi, 2007. 59 p.
MSW, fly ash, remediation, ash, PCDD, PCDF, formation, degradation, destruction, dechlorination, thermal treatment
National Category
Environmental Sciences
urn:nbn:se:umu:diva-1395 (URN)978-91-7264-411-3 (ISBN)
Public defence
2007-11-09, N320, Naturvetarhuset, Umeå Universitet, Umeå, 13:00
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2011-03-10Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text
By organisation
Department of Chemistry
In the same journal
Environmental Science and Technology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 34 hits
ReferencesLink to record
Permanent link

Direct link