The role of metals in dioxin formation from combustion of newspapers and polyvinyl chloride in an incinerator

Article abstract of DOI:10.1016/j.chemosphere.2004.08.104

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 Cl_4-8-CDDs comprised 76-88% of the total Cl_1-8-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.

Full text of DOI:10.1016/j.chemosphere.2004.08.104

Chemosphere 58 (2005) 891–896
www.elsevier.com/locate/chemosphere
The role of metals in dioxin formation from combustion
of newspapers and polyvinyl chloride in an incinerator
a
Akio Yasuhara , Yuuka Tanaka , Takeo Katami , Takayuki Shibamoto
a
b
c,
*
a
Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies,
1
6-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan
b
Gifu Prefectural Institute for Bio-industrial Technology, 3481-2, Hachiya-cho, Minokamo-shi, Gifu 505-0004, Japan
Department of Environmental Toxicology, University of California, Meyer Hall, One Shields Avenue, Davis, CA 95616, USA
c
Received 3 April 2004; received in revised form 23 June 2004; accepted 18 August 2004
Abstract
Newspapers impregnated with NaCl mixed with various chloride metals (CuCl , MgCl , MnCl , FeCl , NiCl , and
2
2
2
3
2
2
CoCl ) 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
3
in the exhaust gases. The highest levels of PCDF isomers obtained were Cl
4.2ng/g (with NaCl + CoCl
2 2
) to 67.0ng/g (with NaCl + CuCl ). PCDFs composed 88–94% of the total dioxins formed
3
-CDF from the sample with NaCl + CuCl
14.8ng/g), Cl -CDF from the sample with NaCl + MgCl (12.3ng/g), and Cl -CDF from samples with NaCl + MnCl
2
(
(
2
2
1
2
12.6ng/g), with NaCl + FeCl
3
(11.8ng/g), and with NaCl + NiCl
2
(13.3ng/g), and with NaCl + CoCl
2
(8.62ng/g). The
7
total of Cl4–8-CDDs comprised 76–88% of the total Cl1–8-CDDs. In particular, Cl -CDDs had the highest levels except
for the sample with NaCl + NiCl . Total dioxins formed from samples of electric wire coated with PVC and PVC alone
2
were 38.3ng/g and 112ng/g, respectively, suggesting that the presence of copper reduced dioxin formation.
ꢀ
2004 Elsevier Ltd. All rights reserved.
1
. Introduction
ated in two places in an incinerator, a combustion
chamber and a chamber for exhaust gas treatment
such as an electric precipitator. In particular, it is
quite difficult to know precisely what the formation
mechanisms of dioxins in a combustion chamber are
because their formation varies over different combustion
conditions.
Major sources of dioxins (PCDDs, PCDFs, and
coplanar PCBs) in the environment are combustion
of waste materials and many other high-temperature
processes commonly used in industrial settings (Lust-
enhouwer et al., 1980). The chemical reactions involved
in dioxin formation are extremely complex and hetero-
geneous (Huang and Buekens, 1995). Dioxins are gener-
There are many reports on dioxin formation in the
presence of metals, such as Cu and Fe, at low tempera-
tures (200–500ꢁC) (Tuppurainen et al., 1998). For exam-
ple, it was hypothesized that the de novo synthesis at
300ꢁC from particulate carbon proceeds through a di-
rect ligand transfer of the halide, in which metal ions
(Cu, Fe) are involved (Stieglitz et al., 1991). The other
*
Corresponding author. Tel.: +1 530 752 4523; fax: +1 530
752 3394.
E-mail address: tshibamoto@ucdavis.edu (T. Shibamoto).
0
045-6535/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.chemosphere.2004.08.104

892
A. Yasuhara et al. / Chemosphere 58 (2005) 891–896
0
de novo experiment at 300ꢁC revealed that the order of
5,5 -H
Kanto Chemical Co., Inc. (Tokyo, Japan).
7
CB was prepared. n-Nonane was bought from
the activity of metallic chlorides was KCl < CaCl <
FeCl
2
3
ꢀ CuCl
2
and the formation of PCDDs/PCDFs
The recovery efficiencies of standard dioxins (PCDDs,
PCDFs, and coplanar PCBs) were consistent with our
previous reports (Yasuhara et al., 2002, 2003). The
recoveries of both the sampling spike and the clean-up
spikes were satisfactory at values of over 82%.
significantly depended on the kind of metal (Kuzuhara
et al., 2003). However, there are only a few reports on
dioxin formation in a combustion chamber of incinera-
tors in the presence of metals at high temperatures
(
>500ꢁC) and the knowledge on the formation mecha-
nisms of dioxins in high-temperature processes is still
considerably limited. More experiments and theoretical
studies to elucidate the details of dioxin formation in
combustion are a pressing need.
2.2. Preparation and combustion of samples
Sample I:
Newspaper (5.029g) was soaked in an aqueous solution
It is important to determine the factors affecting the
formation of dioxins in high-temperature processes in
order to assess their environmental contamination. In
the present study, exhaust gas was collected at the outlet
of a small-scale, well-controlled incinerator in which
newspaper impregnated with NaCl mixed with various
chloride metals and electric wire coated with polyvinyl
chloride (PVC) were combusted. Samples collected were
analyzed for dioxins by gas chromatography/mass
spectrometry.
2 2
containing 14.6g of CuCl Æ 2H O and 85.9g of NaCl
and then dried in an oven at 110ꢁC (Cu con-
tent = 17lmol/g, Cl content = 1.13wt%). The sample
(5.129g) was combusted for 2h.
Sample II:
Newspaper (4.592g) was soaked in an aqueous solution
containing 18.6g of MgCl Æ 6H O and 92.8g of NaCl
2
2
and then dried in an oven at 110ꢁC (Mg con-
tent = 20lmol/g, Cl content = 1.34wt%). The sample
(4.703g) was combusted for 2h and 13min.
Sample III:
Newspaper (4.923g) was soaked in an aqueous solution
containing 15.5g of MnCl Æ 4H O and 78.2g of NaCl
2
. Experimental
2
2
and then dried in an oven at 110ꢁC (Mn con-
tent = 16lmol/g, Cl content = 1.06wt%). The sample
2
.1. Chemicals and reagents
(5.016g) was combusted for 2h and 2min.
Sample IV:
Newspaper (4.911g) was soaked in an aqueous solution
Copper(II) chloride dihydrate (CuCl
2
Æ 2H
Æ 6H O), manga-
Æ 4H O), iron(III)
chloride hexahydrate (FeCl Æ 6H O), nickel(II) chloride
2
O), mag-
nesium chloride hexahydrate (MgCl
nese(II) chloride tetrahydrate (MnCl
2
2
2
2
3 2
containing 21.6g of FeCl Æ 6H O and 80.6g of NaCl
and then dried in an oven at 110ꢁC (Fe con-
tent = 16lmol/g, Cl content = 1.14wt%). The sample
(5.013g) was combusted for 2h and 4min.
Sample V:
2
2
hexahydrate (NiCl
hexahydrate (CoCl
2
Æ 6H
2
O), and cobalt(II) chloride
2
O) were bought from Wako
2
Æ 6H
Pure Chemical Industries, Ltd. (Osaka, Japan).
Isotope-labeled PCDDs, PCDFs, and coplanar PCBs
non-ortho-PCBs and mono-PCBs) for internal stand-
Newspaper (4.935g) was soaked in an aqueous solution
(
2 2
containing 20.1g of NiCl Æ 6H O and 84.6g of NaCl
ards (10ng/ml n-nonane) were purchased from Cam-
bridge Isotope Laboratories, Inc. (Andover, MA). For
the solution of the sampling-spike recovery test, a 1ml
n-nonane solution containing 0.0005ng/ll each of
and then dried in an oven at 110ꢁC (Ni con-
tent = 17lmol/g, Cl content = 1.14wt%). The sample
(5.039g) was combusted for 2h and 1min.
Sample VI:
1
3
C -1,2,3,4-T PCDD; 1,2,3,4,7,8-H CDF; and 1,2,3,
1
Newspaper (4.950g) was soaked in an aqueous solution
2
4
6
4
,6,7,8-H
7
CDF solution was prepared. For the solution
2 2
containing 19.3g of CoCl Æ 6H O and 81.0g of NaCl
of the clean-up-spike recovery test, a 100ll n-nonane
and then dried in an oven at 110ꢁC (Co con-
tent = 16lmol/g, Cl content = 1.07wt%). The sample
(5.050g) was combusted for 2h and 2min.
Sample VII:
1
3
solution containing 0.005ng/ll each of
CDD; 2,3,7-T CDD; 2,3,7,8-T CDD; 1,2,3,7,8-
CDD; 1,2,3,6,7,8-H CDD; 1,2,3,4,6,7,8-H CDD; 1,2,
C -2,3,7,8-T CDF; 1,2,3,7,8-
C -2,7-
12
D
2
3
4
P
5
6
1
7
3
3
,4,6,7,8,9-O CDD;
8cm · 1cm chips of double-core electric copper-wire
(1.6mm in diameter) coated with PVC (Cl con-
tent = 10.6wt%). The sample (948g) was combusted
for 1h and 4min.
8
12
4
P
5
CDF; 1,2,3,4,7,8-H
1
6
CDF; 1,2,3,4,7,8,9-H
0
7
CDF; 1,2,
0
3
0
3
3
2
,4,6,7,8,9-O CDF;
8
C
12-3,3 ,4,4 -T CB; 3,4,4 ,5-T
4
4
CB;
0
0
0
0
0
0
0
,3 ,4,4 ,5-P CB; 2 ,3,4,4 ,5-P CB; 3,3 ,4,4 ,5,5 -H CB;
5
5
6
0
0
0
0
0
0
,3 ,4,4 ,5,5 -H
6
CB; and 2,3,3 ,4,4 ,5,5 -H
7
CB was pre-
Sample VIII:
pared. For the solution of the internal standards, a 2ll
10cm chips of PVC removed from electric wire (Cl con-
tent = 17.1wt%). The sample (600g) was combusted for
1h and 4min.
1
3
n-nonane solution containing 0.25ng/ll each of
C
,3,6,8-T CDD; 1,2,3,7,8,9-H CDD; and 2,2 ,3, 4,4 ,
12
0
-
0
1
4
6

A. Yasuhara et al. / Chemosphere 58 (2005) 891–896
893
2
.3. Combustion conditions of incinerator
PVC was combusted (Sample VII). Samples were placed
into the incinerator at constant intervals.
Eight different samples were combusted in an inciner-
ator used previously (Yasuhara et al., 2001). The incin-
erator was equipped with two subsidiary combustion
burners (Kato Burner Co., Ltd., Gifu, Japan)—one at
the upper part of the combustion chamber (550mm
from grate) and the other near the grate (150mm from
grate)—with a heat supply of 30000 kcal/h. Propane
gas (97.6%), containing <0.0005% of Cl and 0.0008%
of sulfur, was used for fuel. The firebricks of the inside
walls and the fire clay of the grate were changed for each
experiment in order to avoid any contamination from
the previous experiment. The two subsidiary burners
were turned on 1h prior to combustion of the samples
in order to maintain a constant temperature. Air for
combustion was supplied from pipes located at the four
corners of the combustion chamber. The optimum com-
bustion was obtained by adjusting an air valve attached
to the pipes. The burner at the upper part of the com-
bustion chamber was always turned on. The burner near
the grate was turned on only when electric wire with
2.4. Sample collection, preparation, and analysis of
chemicals
Exhaust gases were collected using a previously re-
ported method (Katami et al., 2002; Yasuhara et al.,
2003). Gas samples were collected at the sampling port
located between the combustion chamber and the cyc-
lone. Sample preparation was conducted using a previ-
ously reported method (Yasuhara et al., 2002). Analyses
ꢁ
of Cl , CO, CO
2
, O
2
, PCDDs, PCDFs, and coplanar
PCBs were performed by the previously reported meth-
od (Yasuhara et al., 2002). Chloride compounds in ex-
haust gases were collected using an exhaust gas
collector, model NG-H-S (Nigorikawa Rikakogyo Co.,
Ltd., Tokyo, Japan). The combustion chamber and
flame temperatures were measured at the center of the
combustion chamber and at the grate by a LK-1200
thermo-couple conductor interfaced to a CT-1310 di-
gital thermometer (Custom Co., Ltd., Tokyo, Japan).
Table 1
Analytical results of exhaust gases and combustion conditions
Combustion samples
I
II
III
IV
V
VI
VII
VIII
a
NP + CuCl
2
NP + MgCl
2
NP + MnCl
2
NP + FeCl
3
NP + NiCl
2
NP + CoCl
2
Wire + PVC PVC
Chlorine
content (wt%)
1.13
1.34
2.12
1.06
2.51
1.14
2.51
1.14
2.52
1.07
2.03
10.6
0.89
17.1
0.56
Amt. combustion 2.56
kg/h)
(
Grate temp. (ꢁC)
Range
Average
509–844
675
453–739
595
510–779
664
491–802
660
515–749
645
498–800
673
1003–1059
1029
989–1038
1010
Chamber temp.
(
ꢁC)
Range
569–757
662
473
659–763
689
456
679–765
710
515
547–758
659
481
687–745
705
517
614–708
664
476
721–809
787
646
725–780
763
639
Average
Av. ext.
gas temp. (ꢁC)
Amt. dry ext.
3
gas (m N/h)
240
14.7
4.9
222
15.9
4.0
217
15.6
4.2
206
14.6
5.0
218
15.6
4.2
226
15.2
4.4
214
12.2
5.9
223
12.6
5.8
Av. oxygen
conc. (%)
Av. CO
2
conc. (%)
Av. CO conc.
350
6.5
400
5.6
300
5.0
310
7.3
400
5.4
350
5.2
12
13
b
(ppm)
Water content
in ext. gas (%)
Cl ion conc.
11.1
480
10.0
490
200
120
240
170
250
120
3
b
(
mg/m N)
a
Newspaper.
Relative to 12% oxygen.
b

8
94
A. Yasuhara et al. / Chemosphere 58 (2005) 891–896
The highest levels of PCDF isomers obtained were
Cl -CDF from Sample I (14.8ng/g), Cl -CDF from
3
. Results and discussion
3
2
Table 1 shows the combustion conditions and analyt-
ꢁ
Sample II (12.3ng/g), and Cl
(12.6ng/g), IV (11.8ng/g), V (13.3ng/g), and VI
1
-CDF from Samples III
ical results of O , CO , CO, H O, and Cl in exhaust
gases. When samples (I–VI) were combusted with only
one burner (upper), the average grate temperature was
2
2
2
(8.62ng/g). The total of Cl4 -CDDs comprised 76–
ꢁ8
88% of the total Cl1ꢁ8-CDDs. In particular, Cl
7
-CDDs
over 660ꢁC except in the case of MgCl
2
Æ H
2
O (595ꢁC).
had the highest levels—ranging from 0.424 (Sample V)
to 0.944ng/g (Sample I)—in all metal chloride samples
except NiCl Æ 6H O sample (Sample VI).
The average chamber temperature of six metal chlorides
combustion was 680ꢁC. The average concentrations of
CO from the metal chloride samples ranged from 300
2
2
In our previous study (Yasuhara et al., 2002), the
total dioxins formed and the TEQ value from NaCl-
impregnated newspaper (Cl content 1wt%), which was
combusted without any metals under the same condi-
tions as the present study, was 80.8ng/g and 1.08ng-
TEQ/g, respectively. Therefore, it is obvious that the
addition of metal chlorides (17–20lmol/g) decreased
the formation of dioxins from NaCl-impregnated news-
paper upon combustion. The effects of different metals
were, in decreasing order, Cu > Mg > Mn > Fe > Ni >
Co. In the experiments that involved heating chloro-
phenols with metals or their oxides at 200–500ꢁC, Cu,
CuO, NiO, ZnO, Al O , Fe, and Fe O increased dioxin
(
Sample III) to 400ppm (Samples II and V), which were
somewhat high levels. On the other hand, the average
CO concentrations of the samples (VII and VIII) com-
busted with two burners were less than 13ppm. These
differences may be due to the grate and chamber temper-
atures and the combustion rate of samples. For example,
the grate temperature for Sample VII (1029ꢁC) was
much higher than that for Sample V (645ꢁC).
Table 2 shows the results of dioxin analyses of the ex-
haust gas samples obtained from the incinerator along
with their toxicity equivalency quantity (TEQ), obtained
using previously reported methods (Van den Berg et al.,
2
3
2
3
1
998). In the case of metal chloride samples (I–VI), the
amount of total dioxins formed ranged from 34.2ng/g
Sample VI) to 67.0ng/g (Sample I). PCDFs comprised
8–94% of the total dioxins formed in the exhaust gases.
formation (Gullett et al., 1990, 1992).
In the case of electric wire coasted with PVC sam-
ple (Sample VII), total PCDFs composed 85% of the
total PCDDs/PCDFs formed. The concentration of
(
8
Table 2
Analytical results of PCDDs, PCDFs, and coplanar PCBs in exhaust gases from combustion of samples
Dioxins
Combustion samples (ng/g)
II III
I
IV
V
VI
VII
VIII
PCDDs
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
1
2
3
4
5
6
7
8
-CDDs
-CDDs
-CDDs
-CDDs
-CDDs
-CDDs
-CDDs
-CDDs
0.093
0.278
0.442
0.680
0.836
0.914
0.944
0.674
4.86
0.025
0.023
0.108
0.026
0.144
0.032
0.034
0.161
0.203
0.480
0.554
0.595
0.723
0.700
3.44
0.156
0.108
0.130
0.155
0.326
0.600
0.474
1.97
0.120
0.154
0.228
0.386
0.564
0.663
0.584
2.81
0.141
0.131
0.156
0.139
0.214
0.424
0.691
1.92
0.215
0.251
0.284
0.331
0.430
0.527
0.395
2.58
0.119
0.334
1.03
0.183
0.515
1.89
2.14
3.09
6.42
7.04
0.753
0.582
0.593
0.565
4.01
Total PCDDs
PCDFs
Cl -CDFs
21.3
1
3.32
1.69
12.6
11.8
13.3
8.62
7.98
6.18
3.27
1.68
0.971
0.990
1.09
2.22
4.24
5.63
6.42
4.45
2.68
2.44
4.43
2.09
4.61
6.43
9.20
Cl
2
-CDFs
-CDFs
-CDFs
-CDFs
-CDFs
-CDFs
-CDFs
12.3
14.8
12.3
8.23
5.17
2.68
1.52
1.55
2.47
2.94
7.46
4.56
2.75
2.49
2.03
1.94
2.32
8.59
5.47
2.83
1.56
1.05
1.18
1.32
Cl
Cl
Cl
Cl
Cl
Cl
3
4
5
6
7
8
8.49
8.11
5.13
2.77
2.09
2.12
9.37
7.20
4.91
3.51
3.57
11.4
15.6
19.8
19.7
88.7
Total PCDFs
59.0
3.14
67.0
42.7
1.06
47.2
37.2
0.511
39.7
35.2
0.719
38.7
35.3
0.601
37.8
30.8
0.783
34.2
32.5
1.79
38.3
Coplanar PCBs
a
Grand total
Toxicity equivalency quantity (ng-TEQ/g)
1.53
112
1.6
0.62
0.44
0.19
0.28
0.16
0.17
0.39
a
Grand total = total PCDDs + total PCDFs + total coplanar PCBs.

A. Yasuhara et al. / Chemosphere 58 (2005) 891–896
4
-CDFs was the highest level (6.42ng/g) among the Acknowledgement
895
Cl
PCDFs formed. Cl4 -CDDs comprised 88% of the
ꢁ8
total PCDDs formed. The total PCDDs/PCDFs was
We thank Y. Amano for her assistance in prepara-
tion of the combustion samples.
3
8.3ng/g and the TEQ value was 0.39ng-TEQ/g. The
electric wire was composed of 37.6% copper wire and
2.4% coated PVC. Therefore, the calculated value of
the total PCDDs/PCDFs without copper wire was
1.1ng/g and the calculated value of TEQ without cop-
per wire was 0.63ng-TEQ/g. In the case of PVC alone
Sample VIII), PCDFs comprised 80% of the total
6
References
6
Addink, R., Olie, K., 1995. Mechanisms of formation and
destruction of polychlorinated dibenzo-p-dioxins and di-
benzofurans in heterogeneous systems. Environ. Sci. Tech-
nol. 29, 1425–1435.
(
PCDDs/PCDFs formed in the exhaust gas. The higher
the number of chlorides, the more PCDF was produced.
The amount of PCDF isomers ranges from 2.09ng/g
Gullett, B.K., Bruce, K.R., Beach, L.O., 1990. The effect of
metal catalysts on the formation of polychlorinated di-
benzo-p-dioxin and polychlorinated dibenzofuran precur-
sors. Chemosphere 20, 1945–1952.
(
Cl
1
-CDF) to 19.8ng/g (Cl
7
-CDF). Cl4ꢁ8-CDDs com-
prised 96% of the total PCDDs formed. The total
PCDDs/PCDFs formed (112ng/g) and the TEQ value
(
1.6ng-TEQ/g) from Sample VIII were the highest
Gullett, B.K., Bruce, K.R., Beach, L.O., Drago, A.M., 1992.
Mechanistic steps in the production of PCDD and PCDF
during waste combustion. Chemosphere 25, 1387–1392.
Huang, H., Buekens, A., 1995. On the mechanisms of dioxin
formation in combustion processes. Chemosphere 31, 4099–
among the samples combusted in the present study.
Based on these values, the presence of copper wire is
seen to reduce dioxin formation by 30% from PCDDs,
5
8% from PCDFs, and 55% from the total dioxins.
The residual blue–green material collected from the
4
117.
Inui, T., Otowa, T., Tsutcihashi, K., Takegami, Y., 1982.
Complete oxidation of active carbon at low temperatures by
composite catalysts. Carbon 20, 213–217.
grate after the combustion of electric wire coated with
PVC (Sample VII) was copper oxide (CuO). It was,
therefore, estimated that both 1.0mol of vinyl chloride
monomer and 0.59mol of CuO were present during
the combustion of electric wire coated with PVC. These
results are consistent with a previous study reporting
that dioxin formation was reduced corresponding to a
decrease of the PVC/CuO mol ratio (Shibata et al.,
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(
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pounds during combustion and consequently reduced
dioxin formation in the exhaust gases. In addition,
TEQ values of the samples (I–VI) combusted with vari-
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wire coated with PVC (Sample VII) was much less than
that of PVC alone (Sample VIII) in the present study.
The mechanisms of dioxin formation and degrada-
tion under presence of metals are still not completely
understood. However, the results obtained in the present
study clearly indicate that metals reduce dioxin forma-
tion during the combustion of paper and PVC. There-
fore, the addition of metals may be one way to reduce
dioxin contamination caused by exhaust gases from
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