Formation of dioxins from sodium chloride-impregnated newspapers by combustion

Full text of DOI:10.1007/s001280000010

Bull. Environ. Contam. Toxicol. (2000) 64:372-376
© 2000 Springer-Verlag New York Inc.
DOI: 10.1007/s001280000010
Formation of Dioxins from Sodium Chloride-Impregnated
Newspapers by Combustion
T. Katami,1 N. Ohno,2 A. Yasuhara,3 T. Shibamoto4
1 Gifu Prefectural Institute of Health and Environmental Sciences, l-l Fudogaoka, Naka,
Kakamigahara, Gifu 504-0838, Japan
2 Asahi University, 1851 Hozumi, Hozumi-cho, Motosu-gun, Gifu 501-0096, Japan
3 National Institute for Environmental Studies, 16-2, Onogawa, Tukuba,
lbaraki 305-0061, Japan
4 Department of Environmental Toxicology, University of California, Davis, CA 95616,
USA
Received: 11 October 1999/Accepted: 6 January 2000
Dioxins, in particular, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), are
Their contamination in the environment
the most potent man-made carcinogen.
has received much attention from the public because they form during the
combustion of waste materials as well as from many other high-temperature
processes commonly used in industrial settings (Lustenhower and Hutzinger,
1980; Tuppurainen et al., 1998). It is important to determine the formation
conditions of dioxins in high-temperature processes in order to reduce their role in
Therefore, intensive efforts have been made to
environmental contamination.
reduce dioxin formation during the above processes.
Many hypotheses about dioxin formation in combustion systems have been
advanced. but the chemical reactions involved are extremely complex and
heterogeneous (Huang and Buekens, 1995). In particular, the source of chloride
has been one of the major concerns in studies of dioxin formation in incinerators.
Organic chlorine (tetrachloroethylene) with a catalyst such as iron (III), tin (II),
and copper (II) promoted the formation of particle-bound dioxins in combustion
experiments. On the other hand, inorganic chlorine (sodium chloride) promoted
the formation of dioxins more effectively in the gas phase than in the particle
It appears that both organic and inorganic
phase (Halonen et al., 1995).
However, there are still
chlorides can be a precusor of dioxins in incinerators.
many unknown mechanisms of dioxins formation in high-temperature processes.
More experiments and theoretical studies to elucidate the details of dioxin
formation in a combustion is needed.
newspaper impregnated with sodium chloride was
combusted in an incinerator and the dioxins formed were analyzed by GUMS.
In the present study,
MATERIALS AND METHODS
A newspaper (top circulation in Japan) purchased from a local store was soaked in
a 3% sodium chloride solution for 20 min.
The newspaper was dried prior to use
in the experiment. The percentage of impregnated chlorine was 3.1 (w/w).
Four different samples were combusted in an incinerator diagramed in Figure 1.
1). Blank: Heavy oil A containing < 0.005% (w/w) chloride, 0.25% (w/w) sulfur,
and 0.02% nitrogen (w/w) was combusted for 4 h at the rate of 15 L/h. 2).
Five kilograms each of newspaper was combusted with heavy oil A (15 L/h) at 25
Five kilograms each of sodium chloride
min intervals for 4 h (total 55 kg). 3).
Correspondence to: T. Shibamoto
372

Incinerator used for combustion of newspaper samples.
impregnated-newspaper was cornbusted with heavy oil A (15 L/h) at 25 min
Figure 1.
intervals for 3 h and 55 min (total 50 kg).
newspaper was cornbusted with 0.5 kilograms each of polyvinyl chloride (PVC)
(40 x 28 cm and 0.2 mm thickness, soft PVC sheet) and heavy oil A (15 L/h) at 25
min intervals for 3 h and 20 min (total 28 kg).
35.7% (w/w).
4). Three kilograms each of
Chloride content in the PVC was
Exhaust gas samples for dioxin analyses were collected at the sampling port
located between the combustion chamber and cyclone (Figure 1).
The overall
sample collection apparatus used is diagramed in Figure 2.
Analysis of dioxins
in the collected exhaust gas was conducted according to the official method of the
Japan Ministry of Health and Welfare (JMHW, 1997).
Dust in the exhaust gas was trapped in an in-line silica-fiber thimble filter.
The
exhaust gas was next drawn into two 1 L-impingers each containing 150 mL of
water (washed with hexane prior to use) and an empty impinger connected in
series. The empty impinger was further connected to a column packed with 40 g
of XAD-2 resin which was interfaced to a 1 L-impinger containing 250 mL
diethylene glycol and an empty impinger connected in series. The impingers
were kept at 5 °C during sample collections in an ice-cooled water bath. The
exhaust gas was drawn using a.diaphagm vacuum pump with the flow rate as
same as that of exhaust gas in the duct (21 - 23 L/min).
The dust trapped in the silica-fiber thimble filter (apx., 1 g) was washed with 2
mol/L hydrochloric acid solution ( 20 mL), and combined with the XAD-2 resin.
The resin was extracted with toluene (200 mL) using a Soxhleit extractor for 16 h.
The water (500 mL) and diethylene glycol (250 mL) in the impingers, as well as
the water trapped (trace) in the empty impingers, were combined and extracted
with toluene (500 mL).
distillation using a rotary flash evaporator, and the combined samples were
cleaned with multilayer silicagel chromatography (JMHW, 1997).
was further cleaned using alumina column chromatography with a 120 mL
hexane/dichloromethane (1/1) solution.
After extraction, each extract was condensed by
The sample
The internal standards (0.5 ng each),
13
C -2,3,7,8-T4-CDD, 1,2,3,7,8-P5CDD, 1,2,3,6,7-H6CDD, 1,2,3,4,6,7,8-H7CDD,
12
13
1,2,3,4,6,7.8.9-O8CDD, C12-2,3,7,8-T4CDF, 1,2,3,7,8-P5CDF, 1,2,3,4,7,8-H6CDF,
1,2,3,4,6,7.8-H7CDF, and 1,2,3,4,6,7,8,9-O8CDF were used to spike the sample.
373

Apparatus used for collection of exhaust gas from combustion of
newspaper samples.
Figure 2.
After each sample was condensed using a rotary flash evaporator, the condensed
sample was dissolved into a minimum amount of n-nonane and then the volume
of the sample was adjusted to exactly 50 mL with n-nonane. The samples were
analyzed by gas chromatography/mass spectrometry (GCYMS) for dioxins.
A Hewlett-Packard (HP) model 5890 gas chromatograph (GC) interfaced to
Micromass double focus MS (Auto Spec ULTIMA, England) and equipped with a
60 m x 0.25 mm i.d. (df = 0.2 µm) SP-2331 bonded-phase fused-silica capillary
column (Supelco, Bellefonte, PA) for Cl4-6 dioxines or a 30 m x 0.25 mm i.d. (df =
0.25 µm) DB-5 bonded-phase fused-silica capillary column (J &W Scientific,
Folsom, CA) for Cl,, dioxins was used.
Gas chromatographic oven
temperatures were programmed from 130°C to 190°C at 20°C/min and then to
250°C at 2 °C/min for the SP-2331 column, and programmed from 130°C to
280°C at 10°C/min for the DB-5 column. The linear velocity of helium carrier
gas was 30 cm/set. The injector temperatures were 250°C for the SP 2331
column and 280°C for the DB-5 column.
250°C for the SP-2331 column and 289°C for the DB-5 column.
voltage was 35 eV.
MS ion source temperatures were
MS ionization
RESULTS AND DISCUSSION
Because a subsidiary combustion burner (Figure 1) was used, the temperature of
the combustion chamber was kept above 350°C during the combustion. The
average temperatures in the combustion chamber during combustion of the four
The recovery efficiencies of spiked standard
dioxins were 91% for C12-2,3,7,8-T 4CDD, 94% for 1,2,3,7,8-P5CDD, 103% for
samples ranged from 460 to 650°C.
13
1,2,3,6,7,8-H 6CDD, 82% for 1,2,3,4,6,7,8-H7CDD, 99% for 1,2,3,4,6,7,8,9-
13
O8CDD, 80% for C12-2,3,7,8-T4CDF, 97% for 1,2,3,7,8-P5CDF, 110% for
1,2,3,4,7.8-H 6CDF, 79% for 1,2,3,4,6,7,8-H7CDF, and 76% for 1,2,3,4,6,7,8,9-
O8CDF in the present study. Values are the average of two experiments.
Table 1 shows the results of analysis of the exhaust gas samples. The amount of’
dioxins formed according to the number of chlorides in isomers was Cl5 > Cl4>
C l6 > Cl7 > Cl8. In the case of benzofurans, the higher the number of chloride,
the less production of dioxin was observed.
in the samples were less than 0.005% for heavy oil A, 0.0064% for the blank
The calculated contents of chloride
374

newspaper. 3.1% for NaCl-impregnated newspaper, and 5.1% for newspaper with
It is obvious that the samples with a higher chloride content produced
more dioxins.
PVC.
Results of dioxin analysis in combusted newspaper samples.
Table 1.
Samples with inorganic chloride (NaCl) or with organic chloride (PVC) produced
significantly higher amounts of dioxins as compared with the blank newspaper.
There have been different reports on the promotion of dioxin formation by PVC.
In fires in public and industrial buildings where PVC materials were involved,
significantly higher levels of dioxins were found (Theisen et al., 1989; Marklund
et al., 1989). On the other hand, some investigators have reported that no
appreciable amounts of dioxins were formed from combustion of materials with
PVC (Karasec et al., 1983; De Fre, 1986).
sheathings were combusted, ppm levels of dioxins were formed (Christmann et al..
However, addition of PVC to urban wastes up to 10% did not produce
When PVC and PVC-cable
1989).
detectable concentrations of dioxins upon combustion (Giugliano et al., 1989).
There have been only a few reports on the possible formation of dioxins from a
reaction of‘ inorganic chloride such as sodium chloride with waste materials
during combustion. Some feed material generated dioxins when they were
combusted with sodium chloride in a pilot scale incinerator (Pandompatam et al.,
In the present study, both organic and inorganic chloride was shown to
be a source of chloride for dioxin formation.
1995).
It is hypothesized that HCl is
formed at first by high temperature from sodium chloride or PVC and
375

subsequently dioxins are produced (Takasuga et al., 1998). However. details of
the actual formation mechanisms are not yet well understood. Further
investigation of the formation mechanisms of dioxins from waste materials upon
combustion are in order to discover ways to reduce their formation in incinerators.
Acknowledgement. We thank Drs T. Yamamoto, T. Miyazaki, and T. Okuda for
their outstanding technical assistance.
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