Environ. Sci. Technol. 2000, 34, 4071-4075
Development of Semi- and Nonvolatile Organic Halogen as a New Hazardous Index of Flue Gas MIKA KATO, KOHEI URANO,* AND TOMOHIRO TASAKI Laboratory of Safety and Environmental Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Japan
It has been found that there are many unknown genotoxic compounds in flue gas, and some of them are expected to be semi- and nonvolatile organohalogen compounds. The measuring method of the semi- and nonvolatile organic halogen (SNVOX) as a new hazardous index was developed for controlling and monitoring of flue gas from various facilities, and the correlations among the concentrations of SNVOX and PCDDs/PCDFs or Cl4-6BZs were examined. The easy procedures and the conditions for the sampling, the extraction, the evaporation, and the concentration were determined for measuring SNVOX, which means organohalogen compounds having higher boiling points than ca. 240 °C. A correlation of I-TEQ values of PCDDs/ PCDFs and the concentration of SNVOX was found, and I-TEQ could be estimated approximately from SNVOX. It was found that the Cl4-6BZs were one of main semi- and nonvolatile organohalogen compounds in the flue gas, but SNVOX contains many other organohalogen compounds including unknown compounds, and some of them may have toxicity.
Introduction Many kinds of hazardous semi- and nonvolatile organohalogen compounds such as polychlorinated dibenzo-pdioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polychlorinated polyaromatic hydrocarbons (PCPAHs), polychlorinated naphthalenes (PCNs), polychlorinated phenols (CPs), and polychlorinated benzenes (CBZs) are emitted from waste incineration facilities, metal refinery and recovery facilities, etc. (1-9). It is necessary to develop the technical systems for controlling and monitoring these semi- and nonvolatile organohalogen compounds. However, much labor, high technical skills, and much cost are needed to measure these compounds individually because they have a very low concentration and contain many isomers and similar compounds. Furthermore, it has been found that there are many unknown genotoxic compounds in flue gas (10, 11), and some of them were expected to be semi- and nonvolatile organohalogen compounds such as PCPAHs and their substituted compounds (1). On one hand, the adsorbable organic halogen (AOX) is used widely as a hazardous index for water such as wastewater from pulp and paper mills and chlorinated drinking water (12). In this study, we developed a new measuring method * Corresponding author telephone/fax: +81-45-339-4001; e-mail:
[email protected]. 10.1021/es000881+ CCC: $19.00 Published on Web 08/26/2000
2000 American Chemical Society
of semi- and nonvolatile organic halogen (SNVOX) as a convenient hazardous index for controlling and monitoring of flue gas from waste incineration facilities.
Experimental Section Investigated Facilities. The concentrations of SNVOX were measured and compared to the concentrations of PCDDs/ PCDFs and polychlorinated benzenes having more than 4 chlorine atoms (Cl4-6BZs) in the flue gas in two incineration facilities of municipal solid wastes (MSW) equipped with a fluidized bed furnace or a stoker type furnace and five incineration facilities of industrial wastes (IW) equipped with a rotary kiln or a fluidized bed furnace. The characteristics of these facilities are summarized in Table 1. Sampling Method. The pollutants in the flue gas were collected by a sampling train as shown in Figure 1, which was a modified system of the EU Standard (13) for sampling of PCDDs/PCDFs. The pollutants were condensed with 200 mL of water and absorbed with 300 mL of diethylene glycol in 1-L bottles that were submerged sufficiently in a cooling box. It had been confirmed that PCDDs/PCDFs were collected completely by this sampling train (14). To investigating what compounds were recovered by this train, the XAD2 resin and the second diethylene glycol bottle were set after this sampling train. A cylindrical filter was used before the bottles only in the case of high dust concentration. In this study, the sampling gas volumes were in the range of about 1-4 m3 N for analyses of not only SNVOX but also PCDDs/PCDFs and CBZs. Analytical Methods. The water and diethylene glycol were mixed together after the sampling. The probe and the bottles were rinsed carefully with ethyl alcohol and toluene of ca. 50 mL each. The rinsing solvents were mixed into the above mixture of water and diethylene glycol and extracted twice with 100 mL of toluene for 1-L each of the mixture. In this extraction procedure, the aqueous small particles in the toluene phase should be sufficiently separated in order to eliminate inorganic chlorine completely into the aqueous phase. After dewatering with sodium sulfate anhydride, this extract was evaporated to ca. 40 mL by an evaporator in a water bath at 40 ( 2 °C and adjusted to 50.0 mL with toluene. On one hand, the XAD2 resin was extracted by a Soxhlet extractor with toluene, and diethylene glycol in the third bottle, was extracted with toluene after the addition of 300 mL of pure water. These toluene extracts were mixed together and evaporated to ca. 40 mL and adjusted also to 50.0 mL. In this study, the sampling gas volumes were in the range of about 1-4 m3 N. The 5.0 mL of the evaporated extract was concentrated also exactly to 50-500 µL by nitrogen purge at ca. 600 mL/
FIGURE 1. Gas sampling apparatus. VOL. 34, NO. 19, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Characteristics of Investigated Facilities facility incinerator type waste feed ratea (kg/h) main composition of waste
A IW rotary kiln continuous 800-1200
B IW rotary kiln continuous 2500
C IW rotary kiln continuous 1900
D IW fluidized bed continuous 11000-12000
wastewater, waste oil, waste solvent
sludge, oil sludge, organic solid waste
wastewater, waste oil, waste solvent, sludge, oil sludge
steelworks dustb, waste paper waste paper ash, & wood, & wood, wastewater, waste plastics, waste plastics, sludge sludge, garbage waste oil, coal 950 800 700-800
combustion 800-950 850-1000 800-950 temp (°C) cyclone + flue gas cooling tower two steps cooling tower cooling tower treatment method + absorption tower of absorption + Ca(OH)2 + dry EP + + wet EP tower + absorption tower wet EP a
E IW fluidized bed continuous 9000
cyclone + BF
G MSW stoker batch (16 h) 2200
Ca(OH)2 + dry EP
Including auxiliary fuel. bContaining ca. 25% carbon.
TABLE 2. Analytical Conditions of SNVOX instrument electric furnace temp Ar gas O2 gas delay time of titration end point of electric potential electric potential range of end point titration injection volume at once
Mitsubishi Chemical Co. TOX-10 Σ 900 °C 300 mL/min (5 min hold) f inlet boat (1 min hold) f switch over O2 200 mL/min 6 min about 300 mV 0.3 mV 20 µL
FIGURE 2. Construction of TOX analyzer. min in a water bath at 10 ( 2, 35 ( 2, or 50 ( 2 °C for determination of optimum concentration conditions. The amounts of organohalogen compounds in the concentrated extract were analyzed as the chlorine converted concentrations with a total organic halogen analyzer (Mitsubishi Chemical Co., TOX analyzer Type Σ10), which is used widely to analyze the adsorbable organic halogen (AOX) in water. The diagram of the analyzer is shown in Figure 2, and the analytical conditions are shown in Table 2. The standard solutions of 12 CBZs and 8 PCDDs/PCDFs in toluene were used to examine the recoveries in the concentration procedure by the evaporation with the evaporator and the nitrogen purge. The standard solutions of 12 organochlorine compounds such as chlorobenzenes, chlorophenols, chloroanthraquinone, and chloroanthrathene in toluene were used also to examine the detection ratio and the reproducibility of the TOX analyzer. The standard solution or the concentrated extract from the flue gas was taken in a silica boat and put into the analyzer. At first, the solvent was vaporized at room temperature of the inlet part of the analyzer for ca. 5 min, and then it was introduced in the furnace at 900 °C. Because the introduction of too much solvent into the furnace causes explosion, this pre-evaporation procedure is very important, and the sample solution in the boat should be less than 20 µL at once. If it needs to be analyzed in low concentration, the concentrated extract adds twice as much or more to the boat after the vaporization of the solvent of the former injection at the low temperature part. About 5 min after the introduction to the furnace, the produced hydrogen halide was detected by a highly sensitive coulometric sensor, and the halogen amount as chlorine was computed and printed out. From the analyzed amounts X (µg of Cl), the concentration of SNVOX as chlorine (µg of Cl/m3 N) in the flue gas was calculated by the following equation:
SNVOX ) XV2/RV1V3 4072
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where V1 is the gas sampling volume (m3 N), V2 is the final concentration volume of extract (µL), V3 is the introduced volume of concentrated extract to analyzer (µL), and R is the fraction ratio of the evaporated extract for using the analysis of SNVOX. In this study, 5.0 mL of the 50.0 mL of evaporated extract was used to measure the SNVOX. The evaporated extract of 40.0 mL was evaporated again to 5 mL with an evaporator. And it was concentrated in a receiver of K-D concentrator exactly to 200 µL by nitrogen purge at 600 mL/min in water bath at 35 ( 2 °C for analyses of PCDDs/PCDFs. In this concentration process, the wall of the receiver was rinsed two or three times on the way. The concentrations of each homologue and toxic isomer of PCDDs/PCDFs were analyzed by GC/MS (Shimadzu QP5050A) after the purification with a multilayer silica column and alumina column chromatography by the JIS method (15) as in the U.S. EPA method (16). Another 5.0 mL of the evaporated extract was concentrated exactly to 300 µL by the nitrogen purge in a water bath at 35 ( 2 °C, and the concentrations of each CBZ isomer were analyzed by GC/MS after purification by a silica cartridge (Waters Sep-pak Light Silica).
Results and Discussion Detection Efficiencies and Determination Limit of TOX Analyzer. At first, the detection efficiencies of the TOX analyzer were confirmed three times by using the solution of the 12 standard compounds of 10 and 0.1 µg of Cl, and the results are shown in Table 3. All the chlorinated compounds, which were thought to be principal organohalogen compounds in the flue gas, were detected completely to the stoichiometric amounts by this TOX analyzer. The dispersion of the TOX analyses was examined 6-20 times by using the toluene solution of trichlorobenzenes of 0.05-2 µg of Cl, and the results are shown in Table 4. The standard deviation was considerably increased in amounts
TABLE 3. Detection Efficiencies of Organochlorine Compounds by TOX Analyzera compounds monochlorobenzene (Cl1BZ) monochlorophenol (Cl1P) o-dichlorobenzene (o-Cl2BZ) 2,4-dichlorophenol (2,4-Cl2P) 1,2,4-trichlorobenzene (1,2,4-Cl3BZ) 1,2,3,5-tetrachlorobenzene (1,2,3,5-Cl4BZ) 2,4,6-trichlorophenol (2,4,6-Cl3P) 1-chloronaphthalene pentachlorophenol (Cl5P) hexachlorobenzene (Cl6BZ) 1-chloroanthraquinone 9,10-dichloroanthracene a
boiling point (°C)
detection ratios (%)
132 175 180 210 213 246 246 263 310 325 sublimate
94.6 ( 4.9 96.4 ( 0.8 98.8 ( 2.4 99.0 ( 0.9 98.6 ( 0.9 100.6 ( 1.0 100.3 ( 2.3 96.5 ( 1.0 101.9 ( 1.2 101.5 ( 1.4 98.0 ( 1.3 106.5 ( 1.5
TABLE 5. Recoveries of Cl4-6BZs and SNVOX by Effective Sampling Train with Water and Diethylene Glycola Cl4-6BZs (µg/m3 N) by effective train by after adsorption/absorptionb total recovery by effective train (%)
1.9 0.0 1.9 100
31 5 36
53 9 62
73 13 86
60 7 67
86
85
85
90
SNVOX (µg of Cl/m3 N) by effective train by after adsorption/absorptionb total
68 17 85
recovery by effective train (%)
80
870 1104 1006 1112 21 56 55 34 890 1161 1061 1146 98
95
95
97
n ) 5. b Adsorption with XAD-2 resin and absorption of diethylene glycol after the effective sampling train. a
Concentration of standard components: 10 µg of Cl, n ) 3.
TABLE 4. Variation of the SNVOX Analysis of Tetrachlorobenzene added amt (µg)
n (-)
measd mean value (µg)
coeff of variation (%)
2.0 1.0 0.50 0.10 0.050
7 6 9 13 20
1.98 1.00 0.52 0.10 0.06
3.9 5.7 14 16 55
less than 0.1 µg of Cl. Therefore, the quantitative determination limit of the TOX analysis was estimated to be 0.1 µg of Cl in a CV of 16%. The determination limit of the SNVOX in flue gas Clim (µg of Cl/m3 N) is obtained by following eq 2 from eq 1 where the final concentration volume V2 is 200 µL and R is 1.0:
Clim ) 0.1 × 200/V1V3 ) 20/V1V3
FIGURE 3. Boiling point dependence of recovery in evaporation.
(2)
If the value of V1 is 1 (m3 N) and the maximum value of V3 is 60 (20 µL × 3 times injection) (µL), the determination limit of the SNVOX in flue gas was estimated as ca. 0.3 µg of Cl/m3 N. Since the concentrations of SNVOX were expected to be higher than 1.5 µg of Cl/m3 N in many cases of the flue gas from the waste incineration facilities as show in the following section, the sampling volume V1 can be decreased to smaller than ca. 0.2 m3 N. It means that the sampling time can be shortened by several 10-min intervals and the time variation of SNVOX can be monitored. Furthermore, the sampling train could be made much smaller than that in Figure 1, which is for the sampling of PCDDs/PCDFs. Collection Efficiencies of Pollutants by the Proposed Sampling Train. The collected amounts of the pollutants by the proposed sampling train, which was composed of two bottles with 200 mL of water and 300 mL of diethylene glycol, were examined. The collection efficiencies, which were obtained from the ratio of the collected amounts of SNVOX and isomers of Cl4-6BZs by the train to the total amounts with the following XAD2 and the secondary diethylene glycol, are shown in Table 5. It was found that Cl4-6BZs, whose boiling points were higher than ca. 240 °C, could be recovered over ca. 85% (average 89%). And the SNVOX were recovered over ca. 80% (average 93%) by the proposed sampling train. Best Concentration Procedure for SNVOX Measurement. Since some of the compounds in the extract may be lost in the evaporation and concentration procedures before the analysis, it was investigated as to what compounds were concentrated without loss and analyzed as the SNVOX.
FIGURE 4. Boiling point dependence of recovery in concentration by nitrogen purge at different final volumes. The relationship between the boiling points of the 12 CBZs and their recoveries in the evaporation with an evaporator in a water bath at ca. 40 °C when the final concentrating volume was ca. 5 mL is shown in Figure 3. The recoveries of the compounds, such as monochlorobenzenes and dichlorobenzenes, whose boiling points are lower than ca. 180 °C were decreased significantly, but the compounds whose boiling points are higher than ca. 240 °C, such as Cl4-6BZs, were recovered completely. The relationships between the boiling points of the compounds and the recoveries in the nitrogen purge at ca. 600 mL/min and ca. 35 °C when the final volumes were 50500 µL are shown in Figure 4. The recoveries of the compounds whose boiling points are lower than ca. 180 °C were decreased significantly. And the recoveries decreased with the final volume decrease though the compounds with a higher boiling point than ca. 240 °C. Consequently, the final volume should be more than 200 µL to get higher VOL. 34, NO. 19, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 5. Boiling point dependence of recovery in concentration by nitrogen purge at different temperatures.
FIGURE 7. Relationship between semi- and nonvolatile organic halogen (SNVOX) and I-TEQ of PCDDs/PCDFs in stack gas.
FIGURE 6. Preparation method for determination of SNVOX. recoveries than ca. 85% for the compounds with higher boiling points than ca. 240 °C. Furthermore, influence of the temperature of the water bath for the nitrogen purge at ca. 600 mL/min is shown in Figure 5. The concentration times for toluene from ca. 5 mL to 200 µL could be shortened to ca. 40 min at 50 °C from ca. 60 min at 35 °C and ca. 160 min at 10 °C. However, the recoveries at 50 °C were much lower than those at 35 and 10 °C, and the recoveries at 10 °C were unstable. Therefore, the concentrating temperature was decided at ca. 35 °C. Besides, the WHO proposed that the compounds having a higher boiling point than 240-260 and 380-400 °C be called semivolatile compounds (SVOC) and particular organic matters (POM), respectively (17). Namely, the semi- and nonvolatile compounds in this study are the compounds whose boiling points are higher than ca. 240 °C in consideration of the above recoveries of the sampling, evaporation by an evaporator, and concentration by nitrogen purge. The determined measuring procedure of the SNVOX is shown in Figure 6. Relationship between Concentrations of SNVOX and PCDDs/PCDFs. The logarithmic relationships between the SNVOX (µg of Cl/m3 N), the I-TEQ (ng of I-TEQ/m3 N), and the total concentration of PCDDs/PCDFs (ng/m3 N) are shown in Figures 7 and 8 for various waste incineration facilities whose systems for the incineration and the flue gas treatment were different widely. The SNVOX were in the range from ca. 1.5 to ca. 1200 µg of Cl/m3 N. Namely, the concentrations of SNVOX were 1000 times different among the facilities. On one hand, the total concentrations of PCDDs/PCDFs were in the range from ca. 10 to ca. 10 000 ng/m3 N, and the I-TEQ 4074
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FIGURE 8. Relationship between semi- and nonvolatile organic halogen (SNVOX) and total PCDDs/PCDFs in stack gas. values were in the range from ca. 0.05 to ca. 100 ng of I-TEQ/ m3 N. Their relationships could be approximated by eqs 3 and 4 for the five and six facilities in the wide concentration ranges, although there was a little scatter:
[I-TEQ] ) 0.060[SNVOX]1.0
r ) 0.91
[PCDDs/PCDFs] ) 4.6[SNVOX]0.95
r ) 0.89
(3) (4)
From these correlations, the I-TEQ and the concentrations of PCDDs/PCDFs could be estimated approximately from the SNVOX. Kawamoto (18) reported that TOX (total organic halogen) includes water-soluble and volatile compounds that were collected with a water drain, and four activated carbon columns were proposed as an index for PCDDs/PCDFs in flue gas. But the recoveries of volatile compounds by his
to form from these aromatic compounds. Takasuga et al. (7) tried to determine halogenated aromatic hydrocarbons from an incineration facility of MSW. But the accurate concentrations of the compounds whose standard substances could not be obtained were not clear because their concentrations were converted to the PCDFs concentrations. They reported that the main halogenated aromatic hydrocarbons abounded in the following order: CPs > CBZs > PCNs > PCBs, PCDFs > PCDDs > PCPAHs. And they mentioned that most of the SNVOX was composed of the above halogenated aromatic hydrocarbons, although details of the measurement method were not shown. From these reports, it was estimated that most of SNVOX formed from aromatic compounds. Some of these aromatic halogenated compounds seemed to be toxic. Yoshino et al. (2) reported that the mutagenic activities increased with the concentration of SNVOX of the flue gas from nine incineration facilities of MSW. Consequently, the concentration of SNVOX, which could be measured easily by a nonspecialist, is thought to be one of the useful indices for monitoring and controlling hazardous pollutants in flue gas from the waste incineration facilities. FIGURE 9. Relationships between concentrations of Cl4-6BZs or PCDDs/PCDFs converted to Cl and SNVOX in stack gas. sampling method might be insufficient. His correlation of TEQ with TOX was shown only in a narrow range with large scatter. By the above correlations, it is possible to use the SNVOX for controlling PCDDs/PCDFs as well. However, it is more important to use the SNVOX for monitoring and controlling unknown hazardous halogenated compounds and not only PCDDs/PCDFs. Composition of SNVOX. The logarithmic relationships between the SNVOX (µg of Cl/m3 N) and the concentrations as chlorine (µg of Cl/m3 N) of PCDDs/PCDFs and Cl4-6BZs are shown in Figure 9 for six facilities. The PCDDs/PCDFs were estimated to contribute ca. 0.1-0.5% of the SNVOX, and the Cl4-6BZs were estimated to contribute ca. 2-20% of the SNVOX. Namely, it was found that the Cl4-6BZs were one of main organohalogen compounds in the flue gas. However, there were many other semi- and nonvolatile organohalogen compounds including unknown compounds in the flue gas from waste incineration facilities. Many kinds of hazardous semi- and nonvolatile organohalogen compounds such as polychlorinated dibenzo-pdioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polychlorinated polyaromatic hydrocarbons (PCPAHs), polychlorinated naphthalenes (PCNs), polychlorinated phenols (CPs), and polychlorinated benzenes (CBZs) are emitted from waste incineration facilities (1-9). Jay and Stieglitz (6) reported that 227 individual organic compounds corresponding to ca. 42% of the total organic carbon (TOC) in flue gas from an incineration facility of MSW were determined, and ca. 3% of the TOC consisted of halogenated compounds. Almost all of the identified halogenated compounds were volatile compounds, and all of the identified semi- and nonvolatile halogenated compounds were aromatic compounds. Besides, 7% of the TOC was aromatic hydrocarbons and 3% of the TOC was phenols. It was reported that these aromatic hydrocarbons were chlorinated easily (2). Therefore, most of SNVOX was estimated
Literature Cited (1) Yoshino, H.; Urano, K. Toxicol. Environ. Chem. 1996, 57, 123136. (2) Yoshino, H.; Urano, K. Toxicol. Environ. Chem. 1997, 63, 233246. (3) Tiernan, T. O.; Taylor, M. L.; Garett, J. H.; Van Ness, G. F.; Solch, J. G.; Wagel, D. J. Chemosphere 1983, 12, 596-606. (4) Yoshikazu, G.; Yoshiaki, N.; Masahiro, U. Organohalogen Compd. 1999, 41, 477-480. (5) Tsuji, M.; Nakano, T.; Okuno, T. Chemosphere 1987, 16, 18891895. (6) Jay, K.; Stieglitz, L. Chemosphere 1995, 30, 1249-1260. (7) Takasuga, T.; Inoue, T.; Ohi, E.; Ireland, P.; Suzuki, T.; Takeda, N. Organohalogen Compd. 1994, 19, 41-44. (8) Imagawa, T.; Tamashita, N.; Miyazaki, A. J. Environ. Chem. 1993, 3, 221-230. (9) Nakano, T.; Umeda, H.; Okuno, T. Organohalogen Compd. 1994, 20, 315-320. (10) Yoshino, H.; Urano, K. Sci. Total Environ. 1995, 162, 23-30. (11) Kamiya, A.; Ose, Y. Sci. Total Environ. 1987, 61, 37-49. (12) U.S. EPA. National Emission Standards for Hazardous Air Pollutants for Source Category; Pulp and Paper Production; Effluent Limitations Guidelines, Final Rules. Code of Federal Regulations, Parts 63, 261, and 430, Title 40, 1998. (13) European Committee for Standardization. Stationary Source Emissions-Determination of the Mass Concentration of PCDDs/ PCDFs; EN1948-1; 1996. (14) Kato, M.; Urano, K. J. Jpn. Soc. Waste Manage. Experts 2000, 11, 155-163. (15) Japanese Industrial Standards Committee. Method for Determination of Tetra- Through Octa-Chlorodibenzo-p-Dioxins, Tetra- Through Octa-Chlorodibenzofurans and Coplanar Polychlorobiphenyls in Stationary Source Emissions; JIS K 0311; Japanese Standards Association: Tokyo, 1999. (16) U.S. EPA. Tetra-Through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS; Method 1613; Office of Water Engineering and Analysis Division: Washington, DC, 1994; Revision B. (17) WHO Indoor Air Quality, Organic Pollutants; Euro Reports and Studies 111; WHO: Geneva, 1987. (18) Kawamoto, K. Organohalogen Compd. 1999, 40, 157-160.
Received for review January 7, 2000. Revised manuscript received July 3, 2000. Accepted July 17, 2000. ES000881+
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