Environ. Sci. Technol. 1982, 16, 53-56
Products from Laboratory Chlorination of Fly Ash from a Municipal Incinerator Gary A. Eiceman" and Hadl 0. Rghei
Department of Chemistry, New Mexico State University, Las Cruces, New Mexico 88003 Fly ash samples from a municipal incinerator were treated at 200 and 300 "C with chlorine gas for 1 h. Changes in composition of organic compounds in the samples were determined by using GC and GC/MS analysis of benzene extracts. Chlorination of fly ash produced a series of highly chlorinated aromatic hydrocarbons including hexachlorobenzene, decachlorobiphenyl, and nonachlorobiphenyl. Tentative identifications are also listed for other compounds with the following proposed molecular formulas: C7HOCl6,C6H302C13,CsC18, and (or CI3H8O2C&).Production of some of these CI2H4O3C& compounds is dependent upon chlorination of benzenesoluble -nonvolatile precursor which was present naturally in this fly ash. These results show that fly ash from municipal incinerators may undergo gas phase-particulate reactions under conditions of high temperature with a source of chlorine and that such reactions lead to the production of chlorinated organic compounds at trace concentration levels. ~
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Introduction Organic compounds have been found as complex mixtures with total concentration levels of 1-30 pg/g in fly ash samples from municipal incinerators (1-4). Typically, these mixtures are isolated from samples of fly ash through solvent extraction methods and include n-alkanes, polychlorinated benzenes (PCBzs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated phenols (PCPs), and others. Also present in extracts of these samples are polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins(PCDDs) at concentration levels of 1-10 ng/g of fly ash. Since some isomers of PCDDs are acutely toxic, teratogenic, and mutagenic (5-7), the formation and the environmental fate of PCDDs have been the center of several recent studies (8-10). Although precursors and mechanisms of formation of PCDDs in municipal and other incinerators are unknown, these and similar compounds may be formed during combustion processes (8). Laboratory studies have shown that thermal processes, including pyrolysis and burning of precursors such as PCBzs, PCPs, and polychlorinated biphenyls (PCBs), produce certain PCDDs and PCDFs (11-13). Results from these studies are consistent with theories of formation of PCDDs and other chlorinated compounds through combustion. However, organic compounds which are produced during incineration and which absorb on fly ash also may undergo reactions with gases during emission into the atmosphere. For example, some PAHs were rapidly oxidized on fly ash even in the absence of light (14),and similar gas-particulate reactions for other PAHs may be induced photochemically (14,15).In 1979, a model was proposed for reactions of PCDDs which are absorbed on particulate matter in effluent streams entering the atmosphere (16).In this oxidation/reduction model, individual PCDDs were in reversible equilibrium with higher and lower chlorine-substituted PCDDs, and constant ratios of PCDD classes were established in emission plumes independent of ratios or quantities at the point 0013-936X/82/0916-0053$01.25/0
source. Thus, substitution reactions involving these compounds on particulate matter lead to formation of new PCDDs. Although substitution reactions of halogens with aromatic hydrocarbons are known, such reactions for compounds including PCDDs on fly ash with a source of chlorine have not been described. In this paper, results are described from laboratory studies of changes in composition after chlorination of fly ash at temperatures of 200 and 300 "C. Although C12 is an unrealistic chlorination agent for modeling reactions in incinerator plumes or flues, complications in quantification of PCDDs was expected with use of HC1 in the treatment of fly ash (17). The intent of this work was to determine whether any reactions occur with PCDDs and with other organic compounds under conditions favorable for chlorination. Thus, while reactions using either HCl or C12will likely differ in mechanism and kinetics, final products in successful reactions using either reagent may be expected to contain increased chlorine content in aromatic or unsaturated hydrocarbons (18,19). Experimental Section Sample Storage, Extraction, and Treatment. Fly ash samples were received in closed glass jars, stored at room temperature, and protected from light. All samples were extracted and analyzed by using identical procedures. Approximately 15 g of sample was placed in a mediumporosity glass fritted extraction thimble. Samples were extracted for 6 h in a Soxhlet apparatus containing 200 mL of distilled-in-glass-grade benzene (Burdick and Jackson, Inc., Muskegon, MI). The extract was then reduced in volume to approximately 1mL by using a rotary evaporator and condensed to 100 pL by using a stream of nitrogen gas. A Soxhlet apparatus containing solvent but no fly ash was included as a procedure blank with the analysis of each set of samples. Fly ash from two batches was used in these chlorination studies: (1) fly ash from a municipal incinerator in Ontario (batch 1); (2) fly ash from the same incinerator but sampled on a different day (batch 2); (3) fly ash (batch 2) which was exhaustively extracted as above for three 24-h periods and dried for 3 days at room temperature (fresh benzene was used for each extraction); and (4) untreated glass beads, 100/120 mesh (Alltech Associates, Arlington Heights, IL). Samples which were treated with chlorine gas were first dry-packed into a 34-cm long X 1.6-cm i.d. borosilicate tube with a 6-cm section of 0.63-cm 0.d. X 0.4-cm i.d. tubing at one end. Fly ash was retained in the center of the 34-cm long tube by using glass wool as plugs. The tube was connected to a lecture bottle of high-purity chlorine (Matheson Co., LaPorte, TX) using 0.63-cm 0.d. glass tubing, stainless-steel Swagelock Unions (Albuquerque Valve and Fitting, Albuquerque, NM) with Vespel ferrules (Applied Science, State College, PA), and a stainless-steel control valve (Matheson Co.). A 500-mL glass impinger was inserted between the control valve and the reaction tube and was cooled to about 1OC in an ice and water bath. An electric furnace (Type 120-2, Hevi-Duty Electric Co., Milwaukee, WI) was placed around the tube, and the
0 1981 American Chemical Society
Environ. Sci. Technol., Vol. 16, No. 1, 1982 53
temperature raised to the appropriate setting (200 or 300 "C) by using a Variac. After 15 min, when the temperature of the oven was stable, chlorine gas was forced through the tube for 1 h at approximately 10 mL/min. After the treatment step, the tube was disconnected from the gas source and removed from the oven. When at room temperature, the tube was flushed with high-purity nitrogen gas at 50 mL/s for 10 min to remove any residual chlorine gas. The sample in the tube was then unpacked for extraction and analysis. Fly ash samples were also heated without chlorine gas treatment to monitor the effect of only heating on changes in composition. Other samples from the same batches were not heated or chlorinated for comparison to original composition of the fly ash. Analysis by Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GC/MS). Extracts were analyzed on a Hewlett-Packard Model 5880A GC (level 11) and a 5992A GC/MS. The GC was equipped with an automated splitless injector, a flame ionization detector, and a 25-m, OV-101, fused silica capillary column. The GC/MS was equipped with a manual splitless injector, a jet separator, and a 12-m, OV-101, fused silica column. The conditions for GC analysis were as follows: injector temperature, 250 "C; detector temperature, 250 "C; initial temperature, 75 "C; temperature program rate, 4 "C/min; final temperature, 250 "C; final time, 10 min; carrier gas He; carrier gas average velocity, 16 cm/s. The time for splitless injection was 30 s. The conditions for GC/MS analysis were as follows: injector temperature, 250 "C; initid temperture, 90 "C; temperature program rate, 4 "C/min; final temperature, 250 "C. The chromatographic conditions for GC/MS analysis were as follows: initial temperature 90 "C; temperature program rate 4 "C/min; final temperature, 250 "C; final time, 10 min; carrier gas, He; make up flow to jet separator, 20 mL/min; and time for splitless injection, 30 s. The conditions of the mass spectrometer during regular scanning GC/MS analyses were as follows: upper mass limit, 500 amu; lower mass limit, 45 m u ; scanning speed, 330 amu/s; electron multiplier voltage, 2000 V. Ions for PAHs and PCDDs were detected by using selected ion monitoring (SIM) analysis. Chromatographic conditions for SIM analyses were as described above, and exact values for m / e have been reported (3). Sample volumes used in GC and GC/MS analyses were 1.0 pL. Additional or different conditions for analysis are noted when necessary.
Results and Discussion GC Analysis. Effects of laboratory chlorination of fly ash are shown, in part, in Figure 1, which includes gas chromatograms from analysis of (a) fly ash chlorinated at 300 "C, (b) fly ash only heated at 300 "C, and (c) untreated fly ash. The fly ash used in these studies was from batch 1. The chromatogram from analysis of untreated fly ash is similar in pattern to results from earlier studies (4)and typical for sampIes from that incinerator. A mixture of over 100 components in the extract is evident from Figure IC. Since an approximate average value for detector response here was 80 ng full scale, concentrations per component are estimated at 30-500 ng/g. The procedure blank for this and all subsequent analyses was free of detectable contamination at retention times greater than 2 min. Results from heating this fly ash to 300 "C are shown in Figure lb. After only heat treatment, fly ash contained many of the same compounds but at concentration values reduced by 80-95%. Furthermore, fly ash heated at a lower temperature, 200 "C, showed less loss in mass than samples from the same batch heated at 300 "C. The fate of compounds lost during heating was not established. 54
Environ. Sci. Technol., Vol. 16, No. 1, 1982
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Figure 1. Chromatograms from GC analysis of (a) fly ash chlorinated at 300 "C, (6) fly ash heated only at 300 "C, and (c) untreated fly ash. Fly ash was from batch 1. Attentuatlon X4.
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Flgure 2. Chromatograms from GC analysis of (a) fly ash chlorlnated at 300 "C and (b) untreated fly ash. Fly ash was from batch 2. Attenuation X4.
Effects of treating fly ash from batch 1with chlorine and at 300 "C are shown in Figure la. Visual comparison of parts a and c of Figure 1shows major differences in fly ash composition after chlorination at 300 "C. At least 16 major components which are present after chlorinatjon were not detected or were present at very low concenttiitions in untreated or only-heated fly ash. Peaks $€h elution times of 16.5, 26.7,33.0,35.1,40.5,43.5,43.8, a6.6,54.8, and 58.0 min were all new major components producpd during chlorine treatment. These componknts were present at concentration values as large as any naturally present components in untreated fly ash and were estimated at values of 100-1000 ng/g.
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Figure 3. Chromatograms from GC analysis of (a) exhaustively benzene-extracted fly ash and (b) the same fly ash after chlorine treatment at 300 "C. Fly ash was from batch 2. Attentuation X4.
Chlorination of fly ash from batch 2 showed very similar results. A chromatogram for untreated fly ash from batch 2 is shown in Figure 2b. This untreated sample contained a different concentration and distribution of organic compounds in comparison to untreated fly ash from batch 1. However, qualitative results from identical chlorination procedures parallel earlier results from batch 1fly ash and are shown in Figure 2a. Some quantitative differences between chlorinated batches are apparent for components with elution times of 16.5 and 58.0 min. Batch 2 contained a higher concentration of the later-eluting component and a lower concentration of the earlier-eluting component than batch 1. Although the remaining patterns are similar, peak tailing for the component with a retention time of 33.0 rnin is indicative of unresolved components on this fused silica column. The peak shape of the component at a retention time of 58.0 min is typical of an overloaded column. Results from heat treatment of this sample were similar to those for batch 1and showed a major loss in concentration of compounds at high temperatures. Also, not shown here are results from chlorination at 200 "C which contained less of these new components and more of the naturally occurring compounds by concentration. The origin of these compounds which are apparently produced through chlorination may include (1) unaccounted contamination from the apparatus or during chlorination or after extractionjstorage, (2) chlorine substitution reactions from lower molecular weight material, (3) generation from nonvolatile, extractable precursors, and (4) generation from nonvolatile, nonextractable precursors. The first possibility was examined by chlorinating glass beads with identical treatment and analysis conditions. Chromatograms from that analysis showed no detectable contamination at elution times greater than 2 min. The second proposed origin is unlikely from a mass-balance comparison between components produced and components lost. The third possibility was studied through chlorination of exhaustively extracted fly ash. Fly ash from batch 2 was extracted in four separate extractions before the fly ash was dried. The chromatogram from GC analysis of this exhaustively extracted sample is shown in Figure 3b. No significant amounts of compounds were detected after a retention time of 2 min, although a very small, broad band is evident at 36 min. By comparison to results shown in Figure 2b, this sample was free of benzene-extractable components commonly seen in GC
analysis. Results from chlorination of this fly ash sample at 300 "C are shown in Figure 3a. The chromatogram shows a large number of lower molecular weight compounds between 2 and 26.7 min, including three compounds with elution times matching those detected in chlorination studies with unextracted fly ash. However, many of the other compounds in Figures 2a and l a were not detected, and the major product at 58.0 rnin is at low concentration by comparison to Figure 2a. These results show that treatment of fly ash at high temperatures in the presence of a source of chlorine lead to production of organic compounds through gas phaseparticulate reactions. These compounds do not appear to result from simple thermal rearrangements of compounds already present on the fly ash. Furthermore, a benzenesoluble precursor is suggested since production of certain of these compounds is greatly reduced or not detected in exhaustively extracted fly ash. The reproducibility of retention times and peak heights from three replicate gas-chromatographic analyses averaged 0.1% and 3% relative standard deviation, respectively. The reproducibility of peak heights from triplicate analyses including extraction of samples from the same batch averaged better than 10% relative standard deviation. Thus, these results are outside analytical error. GC/MS Analysis. Total ion chromatograms (TICS) from scanning GC/MS analysis of untreated fly ash samples were similar to chromatograms from GC analysis, although many of the minor components were not detected in the TICs. Major components in each sample were identified by using mass spectra and included unsaturated alkanes, tetrachlorobenzenes, pentachlorobenzene, and hexachlorobenzene. Other compounds such as PAHs and chlorinated phenols were not detected in the TICs. Visual comparison of TICS and gas chromatograms for chlorinated samples also showed similar distributions and patterns for components. Mass spectra for compounds which were produced during chlorination showed intense ions at high mass, little fragmentation, and isotope patterns for compounds containing 3-10 chlorine atoms. Certain of these compounds are structurally simple and were favorably matched with standard spectra (20). These compounds included the following (referring to Figure l a for retention times): 20.8 min, C6HCls, pentachlorobenzene; 26.7 min, C6C16, hexachlorobenzene; 58.0 min, Cl2Cll0, decachlorobiphenyl; and 46.5 min, C12HC19,nonachlorobiphenyl. Mass spectra for other compounds produced through chlorination also showed strong molecular ions for chlorinated aromatic compounds. Although molecular formulas and reasonable structures have been proposed for these compounds, identifications are tentative pending availability of standards and standard spectra. These compounds are as follows: 28.0 min, C7HOCls, tetrachlorobenzoyl chloride; 33.0 min, a mixture of CsH302C12, trichlorocatechol, and C9H402C16,tetrachlorodihydrocumene; 35.1 min, C8C13,perchlorostyrene; and 46.5 min, C12H403Ch or C,H802C&, unknown. Analysis by SIM was used to determine whether these new components were naturally present as minor components in the untreated fly ash but masked by coeluting or larger peaks. None of the compounds produced in the laboratory except pentaand hexachlorobenzenes were detected as naturally abundant components. Treated and untreated samples also were analyzed by SIM for PAHs and PCDDs. Since standards were available for PAHs, results may be considered quantitative. However, since standards for PCDDs were not available, results are useful for comparison of relative concentrations Environ. Sci. Technol., Vol. 16, No. 1 , 1982 55
only. Biphenyl and anthracene were the most abundant PAHs at approximately 10 ng/g each in batches 1 and 2 and together comprised over 90% by concentration of other PAHs detected here. After only heat treatment at 300 “C, concentration levels of all PAHs including fluorene, pyrene, and phenanthracene were reduced by over 50% of original values. By comparison, chlorinated samples contained similar or slightly lower values for all PAHs except biphenyl. The concentration for biphenyl in batch 2 was 7 times higher after chlorination than concentrations on untreated fly ash and 10 times higher than on fly ash heated to 300 “C without chlorine treatment. These results were confirmed by using scanning GC/MS which also showed biphenyl at approximately 100 ng/g and corresponded to the first major peak at a retention time of 16.5 min in the gas chromatograms. In addition, the concentration of biphenyl on fly ash, chlorinated at 300 OC, was greater than that on the same sample chlorinated at 200 “C. The original of these differences and the apparent production of biphenyl through chlorination are unknown. Similar losses in concentration from heating only were also observed for PCDDs. Each class of PCDD was detected by SIM in untreated fly ash, and relative ratios and estimated values were similar to prior studies. Heating fly ash to 300 “C led to 90-99% reduction in the concentration of PCDDs, but the percent loss was greater for octachlorodibenzo-p-dioxins and heptachlorodibenzo-pdioxins than less-chlorinated isomers. Since PCBs which were produced through chlorination were major sources of interference in SIM determination of PCDDs, one original objective was not clearly established. Results showed only that no single PCDD or series of PCDDs were produced in large (over 100-200%) concentrations during chlorination of fly ash in the laboratory. Compounds with retention times between 6.0 and 26.7 min in Figure 3a were identified as.polychlorinated benzenes including isomers of di- through hexachlorobenzenes. Although nonachloroand decachlorobiphenyls were also present in that sample, the origin of these additional chlorinated benzenes may be a result of known chlorination of residual benzene which was used in the exhaustive extraction process.
Conclusion The relationships between these results and actual chemistry in incinerator plumes are unknown. However, in addition to production of chlorinated aromatic compounds in flame chemistry, the possibility of a second mechanism of production, namely, gas phase-particulate reactions, has been demonstrated here. Further investigations using conditions more closely resembling actual incinerators are needed.
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Acknowledgments
The fly ash used in this study was a gift from Professor F. W. Karasek, University of Waterloo, Ontario, Canada. Literature Cited (1) Olie, K.; Vermenlen, P. L.; Hutzinger, 0. Chemosphere 1977, 6 , 455. (2) Buser, H. R.; Bosshardt, H.-P.; Rappe, C. Chemosphere 1978, 7, 165. (3) Eiceman, G. A.; Clement, R. E.; Karasek, F. W. Anal. Chem. 1979, 51, 2343. (4) Eiceman, G. A,; Clement, R. E.; Karasek, F. W. Anal. Chem. 1981, 53. ( 5 ) Schwetz, B. A,; Norris, J. M.; Sparschu, G. Lo;Rowe, V. K.;
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Gehring, P. J.;Emerson, J. L.; Gerbig, C. G. Enuiron.Health Perspect. 1973, 5, 87. Sparschu, G. L.; Dunn, F. L.; Rowe, V. K. Food Cosmet. Toxicol. 1971, 9, 405. Seiler, J. P. Experimentia 1973, 29, 622. The Chlorinated Dioxin Task Force, Michigan Division, Dow Chemical Co., U.S.A., Midland, MI, “The Trace Chemistries of Fire-A Source of and Routes for the Entry of Chlorinated Dioxins into the Environment”, 1978. Young, A. L.; Calcagni, J. A.; Thalken, C. E.; Tremblay, J. W. “The Toxicology, Environmental Fate and Human Risk of Herbicide Orange and Its Associated Dioxin”, Report DEHL TC-78-92; USAF, Occupational and Environmental Health Laboratory, Aerospace Medical Division: Brooks Air Force Base, TX, 1978. Lamparski, L. L.; Nestrick, T. J. Anal. Chem. 1980,52,2045. Buser, H. R.; Busshardt, H.-P.; Rappe, C. Chemosphere
1978, 78, 109. (12) Buser, H. R. Chemosphere 1979,8, 415. (13) Rappe, C.; Marklund, S.; Buser, H. R.; Bosshardt, H.-P. Chemosphere 1978, 7, 269. (14) Korfmacker, W. A.; Natusch, D. F. S.; Taylor, D. R.; Mamantov, G.; Wehry, E. L. Science 1980,207,763. (15) Nojima, K.; Kanno, S. Chemosphere 1977, 6 , 371. (16) Townsend, D. I. “Abstracts of Papers”, 178th National
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Meeting of the American Chemical Society, Washington, DC, Sept 9-14, 1979; America1 Chemical Society: Washington, DC, 1979; No. 80. Kooke, R. M. M.; Lustenhouwer, J. W. A.; Olie, K.; Hutzinger, 0. Anal. Chem 1981,53, 461. Sconce, J. S. “Chlorine: Its Manufacture, Properties, and Uses”; Robert E. Krieger Publishing Co.: Huntington, NY, 1972; pp 430-40. March, J. “Advanced Organic Chemistry Reactions, Mechanisms, and Structure”; McGraw-Hill: New York, 1968; pp 580, 610. Environmental Protection Agency/National Institutes of Health, Mass Spectral Data Base, U.S. Government Printing Office, Washington, D.C., 1978.
Received for review April 20,1981. Accepted September 28,1981.
