3268-87-9Relevant academic research and scientific papers
The formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon model mixtures containing ferrous chloride
Ryan, Shawn P.,Altwicker, Elmar R.
, p. 1009 - 1014 (2000)
The potential to form polychlorinated dibenzo-p-dioxins/furans (PCDD/F) was investigated in carbon model systems containing ferrous chloride tetrahydrate and a matrix representative of that found in particle emission from the catalytic extraction process (CEP) for wastes. Various types of carbons were used resulting in different PCDD/F yields but, with one exception, similar homologue distributions. Due to the similarity between the turbostratic structure of the carbon in the representative CEP dusts and the carbon blacks used in the model system, experiments were performed using two carbon blacks (termed CBA and CBB). On a mass basis, CBB was more reactive over the temperature range of 275-325°C and reaction times of 20-60 min in the formation of PCDD/F; as well as more adsorptive in terms of the desorption of PCDD/F. On a volume basis, the reactivities and adsorptivities were similar. A maximum in PCDD/F formation occurred at an oxygen concentration of 2% in nitrogen. (C) 2000 Elsevier Science Ltd.
Myeloperoxidase-catalyzed formation of PCDD/F from chlorophenols
Wittsiepe, Juergen,Kullmann, Yvonne,Schrey, Petra,Selenka, Fidelis,Wilhelm, Michael
, p. 963 - 968 (2000)
Chlorophenols (CP) are transformed in vitro to polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/F) by a biochemical-catalyzed oxidation. This is shown for 2,4,5-tri-, 2,3,4,6-tetra-and pentachlorophenol with myeloperoxidase recovered from human leucocytes in the presence of hydrogen peroxide. The yield, the reaction, and the PCDD/F-pattern found depend on the CP. The formation rates are in the μmol-per-mol range for all substrates. The experiments confirm the suspicion that a biochemical formation of PCDD/F from precursors such as CPs can take place in the human body and that this metabolic pathway may lead to a higher inner exposure with PCDD/F than is now assumed. (C) 2000 Elsevier Science Ltd.
Formation of PCDD/Fs in the sintering process: Influence of the raw materials
Xhrouet, Celine,De Pauw, Edwin
, p. 4222 - 4226 (2004)
The sintering process is among the major sources of PCDD/Fs in the environment. This research studies the influence of the raw materials in this type of industrial plant on the amounts of PCDD/Fs generated. Particular interest is given to coke, which constitutes the principal source of carbon for the de novo synthesis of PCDD/Fs, and to the dust collected in the electrostatic precipitator (E.S.P. dust), usually recycled in the raw materials. The de novo synthesis of PCDD/Fs is simulated at the laboratory scale by thermal treatments of the samples. The use of a particular coke as a fuel does not drastically reduce the formation of PCDD/Fs. Actually, the global amounts of PCDD/Fs generated from the graphite and the two cokes tested are very similar. Only modifications in the fingerprint are observed. On the other hand, the addition of 10 wt % dust collected in the electrostatic precipitator leads to the formation of amounts of PCDD/Fs multiplied by a factor larger than 103. These results imply caution against the recycling of this E.S.P. dust in the raw materials.
The role of metals in dioxin formation from combustion of newspapers and polyvinyl chloride in an incinerator
Yasuhara, Akio,Tanaka, Yuuka,Katami, Takeo,Shibamoto, Takayuki
, p. 891 - 896 (2005)
Newspapers impregnated with NaCl mixed with various chloride metals (CuCl2, MgCl2, MnCl2, FeCl3, NiCl2, and CoCl2) and electric wire coated with polyvinyl chloride (PVC) were combusted in a well-controlled incinerator. Exhaust gas samples collected at the outlet of the incinerator were analyzed for dioxins (PCDDs, PCDFs, and coplanar PCBs) by gas chromatography/mass spectrometry. The amount of total dioxins formed from newspaper samples ranged from 34.2 ng/g (with NaCl + CoCl2) to 67.0 ng/g (with NaCl + CuCl2). PCDFs composed 88-94% of the total dioxins formed in the exhaust gases. The highest levels of PCDF isomers obtained were Cl3-CDF from the sample with NaCl + CuCl2 (14.8 ng/g), Cl2-CDF from the sample with NaCl + MgCl2 (12.3 ng/g), and Cl1-CDF from samples with NaCl + MnCl2 (12.6 ng/g), with NaCl + FeCl3 (11.8 ng/g), and with NaCl + NiCl2 (13.3 ng/g), and with NaCl + CoCl 2 (8.62 ng/g). The total of Cl4-8-CDDs comprised 76-88% of the total Cl1-8-CDDs. In particular, Cl7-CDDs had the highest levels except for the sample with NaCl + NiCl2. Total dioxins formed from samples of electric wire coated with PVC and PVC alone were 38.3 ng/g and 112 ng/g, respectively, suggesting that the presence of copper reduced dioxin formation.
Photochemistry of Polyhaloarenes. 4. Phototransformations of Perchloro-o-phenoxyphenol in Basic Media
Freeman, Peter K.,Srinivasa, Remanujan
, p. 3939 - 3942 (1986)
Irradiation of the sodium salt of the conjugate base of perchloro-o-phenoxyphenol (PreD-Na+) in methanol (300 nm) in the presence of sensitizer m-methoxyacetophenone generates ether cleavage products and mono- and di-dechlorination with no cycliozation to OCDD.In the presence of sensitizer and excess triethylamine, irradiation of perchloro-o-phenoxyphenol leads to OCDD as a major product with ether cleavage and dechlorination products representing important reaction pathways.Photodecomposition of the conjugate base of perchloro-o-phenoxyphenol in methanol reveals a small amount of cyclization, while irradiation in methanol in the presence of a 10-fold excess of triethylamine increases the quantum yield for cyclization 17-fold.The photolytic transformations of the conjugate base of perchloro-o-phenoxyphenol in the presence of excess triethylamine are dependent upon solvent polarity with the quantum yield for cyclization increasing strongly in methanol or water/acetonitrile (70:30) relative to that in dibutyl ether.These results are interpreted in terms of electron transfer to PreD- to form a radical dianion.
In Situ Formed Soot Deposit as a Carbon Source for Polychlorinated Dibenzo-p-dioxins and Dibenzofurans
Wikstroem, Evalena,Ryan, Shawn,Touati, Abderrahmane,Gullett, Brian K.
, p. 2097 - 2101 (2004)
The aim of this study was to investigate the role of in situ formed soot deposits generated during a combustion process for the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs). In situ formed soot deposits were generated in an entrained flow reactor by using a sooting methane (CH4) flame (sooting phase), with or without chlorine doped into the flame, and fly ash added into the gas phase. The presence of fly ash in the soot deposit was found to be critical, as a catalyst for formation and/ or a chlorinating agent. The presence of chlorinated aromatic structures in the soot matrix was not enough to promote de novo formation of PCDDs/Fs without the presence of fly ash. PCDFs were formed via direct release of the molecule backbone structure from the soot. PCDDs were formed via a similar mechanism as well as an equally important formation pathway of condensation reactions of C6 compounds. The formation rate of the soot/ash deposit was still at half its original activity 34 h after the deposits were formed, suggesting a persistent de novo formation occurring for a long time after the sooting incidences (memory effect).
Formation of Dioxins from Incineration of Foods Found in Domestic Garbage
Katami, Takeo,Yasuhara, Akio,Shibamoto, Takayuki
, p. 1062 - 1065 (2004)
There has been great concern about the large amounts of garbage produced by domestic households in the modern world. One of the major sources of dioxins (PCDDs, PCDFs, and coplanar PCBs) in the environment is the combustion of domestic waste materials. Exhaust gases from an incinerator, in which mixtures of 67 food items-including fruits, vegetables, pasta, seafoods, meats, and processed foods and seasoned foods-were analyzed for dioxins. Gases collected at the chimney port (9.15 ng/g) contained less total dioxins than those collected at the chamber port (29.1 ng/g). The levels of Cl1-Cl 6-PCDDs and Cl1-Cl5-PCDFs were much lower in the gas collected at the chimney port than in the gas collected at the chamber port. The levels of Cl7-Cl8-PCDDs and Cl 6-Cl8-PCDFs were higher in the gas collected at the chimney port than in the gas collected at the chamber port. A total of Cl 4-Cl8-PCDDs (1.84-3.04 ng/g) comprised over 80% of the total PCDDs formed (2.24-4.00 ng/g). Total PCDFs (16.2-22.6 ng/g) comprised 78-86% of the total dioxins formed (18.9-29.1 ng/g). The PCDFs formed in the greatest amounts were M1CDFs (9.68-10.7 ng/g). Mixtures of commonly consumed food items produced ppb levels of total dioxins in exhaust gases upon combustion, suggesting that incineration of domestic food wastes is one of the sources of dioxins in the environment. A mixture containing some seasoned foods, such as mayonnaise spread on bread, produced more dioxins (29.1 ng/g) than a mixture without seasoned foods did (18.9 ng/g).
Dioxin production during the thermal treatment of meat and bone meal residues
Conesa, Juan A.,Fullana, Andres,Font, Rafael
, p. 85 - 90 (2005)
Safe animal by-product disposal is a priority target as a result of the Bovine Spongiform Encephalopathy crisis in the European beef industry. One such disposal option is the incineration of by-product material such as meat and bone meal residues (MBM) for the purpose of energy recovery. Although currently applied, the thermal decomposition of MBM wastes has not been scientifically studied until now. A series of experiments has been performed to study the thermal behavior of MBM both in inert (N2) and reactive atmosphere (air), both by thermogravimetry and in a horizontal laboratory furnace. As a general trend, MBM gives low PCDD/F values, compared with incineration of other wastes. Maximum yield of pollutants is observed at a nominal temperature between 700 and 800°C.
The effects of temperature and oxygen content on the PCDD/PCDFs formation in MSW fly ash
Chang, Moo Been,Huang, Tsai Fei
, p. 159 - 164 (2000)
In this study, the effects of the temperature, oxygen content in the gas stream and carbon content in ash particles on PCDD/Fs formation on the fly ash surface were investigated. The optimum temperatures for dioxin formation were found at 350°C for boiler
Understanding the Role of Iron Chlorides in the De Novo Synthesis of Polychlorinated Dibenzo-p-dioxins/Dibenzofurans
Ryan, Shawn P.,Altwicker, Elmar R.
, p. 1708 - 1717 (2004)
The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was investigated for mixtures of carbon black and iron chloride supported on a ceramic glass powder matrix in a low (2%) oxygen environment. Three iron chloride types (iron(II) chloride tetrahydrate, iron(III) chloride hexahydrate, and iron(III) oxychloride) were studied to gain some insights into their role in de novo formation. The importance of iron(II) and iron(III) chlorides both as chlorinating agents and promoters of low-temperature carbon gasification was observed. Iron(III) oxychloride was shown to be a very effective promoter at 325 °C and above; its conversion to iron(III) chloride was suggested as a key step. The predominant product was octachlorodibenzofuran. The oxide support matrix was found to be an important parameter.
