2019 Fiscal Year Annual Research Report
Thermal treatment of polybrominated diphenyl ethers (PBDEs) and the formation of dioxins
|Research Institution||Kyoto University |
高岡 昌輝 京都大学, 工学研究科, 教授 (80252485)
|Foreign Research Fellow
ZHANG MENGMEI 京都大学, 工学(系)研究科(研究院), 外国人特別研究員
|Project Period (FY)
2019-10-11 – 2022-03-31
|Keywords||Organohalogen pollutants / PBDE / Deca-BDE / PVC / undesirable by-products / PXDD/F / thermal treatment|
|Outline of Annual Research Achievements
Approximately 75% of the polybrominated diphenyl ethers (PBDE) congeners used as flame retardants are Deca-BDE making it important to understand its degradation and decomposition behavior. Firstly, the quantitative analysis method for measuring Deca-BDE using gas chromatography/mass spectrometry (GC/MS) was established. Then decomposition tests on Deca-BDE were conducted at 400 and 850 ℃ in synthetic air. The destruction efficiency (DE) of >99.999% and destruction removal efficiency (DRE) of >99.9999% were achieved at 850 ℃. The qualitative analysis method of 27 PBDE congeners (including Deca-BDE) was built up. Based on this method, debromination behavior of Deca-BDE during thermal process was observed.
PVC has been reported to be the largest end-use of PBDE flame retardant plastic. Experimental work was paid to study its thermal characteristics during combustion, formation behavior of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), etc. All these results provide as foundation for future study on investigating the influence of PBDE on emission of undesirable by-products from thermal treatment of PBDE-containing plastic and the reaction mechanisms.
PBDE are widely used in numerous types of daily goods and easily spilled and emitted during disposal of end-of-life consumer products. Experimental work was also paid on analysis of residue and soil samples collected from an open burning site of municipal solid waste (MSW). Measurements on concentration and chemical forms of halogens (Cl and Br) and content of various metals (Cu, Zn, Sb, Pb, etc.) were finished.
|Current Status of Research Progress
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Currently, three aspects concerning the theme of this research are progressing simultaneously:
(i)Thermal degradation of PBDE, in which specific PBDE (especially Deca-BDE) are studied for their decomposition behavior, and by-products are characterized and used for evaluating DE and DRE and speculating the debromination/degradation pathways of PBDE;
(ii)Characterization on formation behavior of toxic and undesirable by-products, e.g., polyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/F), chlorobenzene (CBz) and bromobenzene (BBz), halogenated polycyclic aromatic hydrocarbons (Cl-/Br-PAH), etc., during thermal treatment of PBDE-containing plastic and exploration of the reaction mechanisms;
(iii)Investigation on emission of PBDE and other organohalogen pollutants to environment through preliminary ways of waste disposal (e.g., open burning) and interplay of specific metals and halogens in forming these dioxin-related compounds, and estimation of the exposure risk to local residents.
For aspect (i), the evaluation of DE and DRE has been finished. The quantitative analysis method of 27 typical Mono- to Deca-BDE congeners will soon be established based on the existing qualitative analysis method. For aspect (ii), the fundamental study on side of PVC has been finished and one journal paper was prepared for submission. For aspect (iii), characterization on halogens and metals has almost been completed. Overall, the research project is progressing gradually and smoothly.
|Strategy for Future Research Activity
In the next fiscal year, the work on this research project will be conducted around the theme and continued in three main aspects (as mentioned above). For aspect (i), firstly, the internal-standard method for quantitatively measuring Mono- to Deca-BDE congeners will be established and tested for its level of precision and accuracy. Based on this method, the by-products produced from thermal treatment of Deca-BDE will be analyzed for all measurable PBDE congeners. The degradation and debromination pathways of Deca-BDE under thermal stress are expected to be revealed. For aspect (ii), one more paper unveiling the reaction mechanisms of PXDD/F from combustion of PVC is to be prepared and submitted at first, based on the previously attained data. Then combustion experiments using various PBDE-containing plastic standard will be carried out, with the aims of observing the emission behavior of individual PBDE congeners and formation characteristics of undesirable by-products (PXDD/F, CBz, BBz, Cl-/Br-PAH, etc.). For aspect (iii), PBDE and PCDD/F in residue and reference soil samples collected from the MSW open burning site will be measured for their concentration and distribution of homologues and isomers. On the basis of the previously acquired data of characterizing metals and halogens (contents and chemical species) in these samples, the interplay between metals and halogens will be investigated by statistical analysis. The results will throw more light on formation mechanisms and emission of organohalogen pollutants from open burning of waste.
Research Products (2 results)