Identification of Trace Organic Compounds in Tire Manufacturing Plant Wastewaters Gregory A. Jungclaus, Larry M. Games, and Ronald A. Hltes" Department of Chemical Engineering, Massachuseffs Institute of Technology, Cambridge, Mass. 02 139
The organlc contamlnants In the effluents from two tlre manufacturing plants were analyzed by gas chromatographicmass spectrometry to determine If tire plants are potentlal point sources of hazardous organic compounds in the environment. One plant was emlttlng large amounts of fatty aclds (due to a lack of soap recycling) while the other was emittlng mostly benzothiazole and 2-mercaptobenzothiazole.
Most industries are now measuring only gross pollution parameters (biochemical and chemical oxygen demand and total organic carbon) in their wastewaters. These parameters are of little value for effluents which may contain small quantities of toxic or hazardous compounds. Computerized gas chromatographic mass spectrometry (GC/MS), however, is a powerful tool for identifying and quantitating such compounds. This paper presents the results of a GC/MS study of the organic pollutants in the wastewaters from two tire manufacturing plants. Tire plant wastewaters were investigated because of the large variety of chemicals used in tire formulations such as accelerators, antioxidants, and oils ( I ) . In addition, carbon black, which is known to contain a variety of carcinogenic polycyclic aromatic hydrocarbons ( 2 ) ,is used as a reinforcing agent for synthetic rubber, and significant quantities may escape into the aqueous environment.
EXPERIMENTAL Samples were collected in 1-gallon amber glass bottles, with Teflon-lined caps, which had been washed with soap and water, rinsed with distilled water, dried, and rinsed with Nanograde quality (Mallinckrodt) dichloromethane. Grab samples (3.5 1.) were collected at several drainage locations within each of the two tire plants and at points leading into and out of any wastewater treatment facilities. Biological degradation was minimized by acidification of the sample to pH 2 with hydrochloric acid and by the addition of approximately 250 ml of Nanograde dichloromethane (which immediately started the extraction). Upon return to the laboratory, a Teflon-covered magnetic stirring bar was added, and the samples were stirred for a minimum of 6 h. The dichloromethane extract was collected in a separatory funnel and concentrated by rotary evaporation. Some of the samples formed emulsions containing particles of carbon black; these emulsions were separated by centrifugation or by extraction with additional aliquots of solvent. The organic layer was dried with sodium sulfate (previously washed with solvent and heated to 550 "C) or by freezing out the water in a liquid nitrogen bath and decanting the organic layer to another container. Several of the extracted water samples were rendered alkaline with a concentrated KOH solution and extracted a second time with an additional 200 ml of dichloromethane; this isolated basic compounds that were not recovered in the initial extraction. Sam.ples found to contain fatty acids and phenols were treated with gaseous diazomethane to convert these polar compounds to their methyl esters. Preliminary gas chromatographic analysis was carried out on a Perkin-Elmer 900 gas chromatograph equipped with a flame ionization detector. A 180 cm X 0.32 cm 0.d. stainless steel column packed with 3% SP-2100 (a methyl silicone fluid) on 8O/lOO mesh Supelcoport was programmed from 70 to 300 "C at 16"/min for these analyses. The same column and conditions were later used for the GC/MS work. Final analysis was done on a dual source Hewlett-Packard 5982A GC/MS system interfaced with a H-P 5933A data system. The quadrupole mass spectrometer was coupled to the gas chromatograph via 1894
a glass-lined jet separator held a t 300 "C and was operated in the continuous scanning mode under control of the data system. Identification of compounds in the wastewater extracts was based on coincidence of gas chromatographic retention times and on equivalence of electron impact and chemical ionization mass spectra with those of authentic compounds.
RESULTS AND DISCUSSION Tire Plant A produces 25 000 steel-belted radial tires and discharges 0.4 million gallons (1515 m3) of wastewater daily. The sources of wastewater include cooling water, washdown water from the stock preparation area, anti-tack dipping solution, water from wet particulate collectors in the tire grinding area (freed of solids in settling tanks), water from the pits under the tire forming presses, and oil and water mixtures from various plant processes and machinery. In this plant, the water from the different plant areas enters a main wastewater pipe and then passes through a catchment basin where some oil, grease, and suspended particles (carbon black) are collected. The wastewater then enters a lagoon with a 5-day retention time for settling and biological degradation. Before leaving the plant lagoon, it passes through a hay filter which collects some additional oil and grease. The lagoon area is quite smelly and is sometimes partially covered with an oily scum, part of which is removed with an oil skimmer. The gas chromatogram of the extract of the effluent from Tire Plant A was dominated by a single large peak. G U M S analysis of an esterified aliquot revealed that this peak consisted primarily of oleic and stearic acids, the total concentration of which was estimated to be about 56 mgA. The source of these compounds is the anti-tack dipping area of the plant. The anti-tack solution is prepared by saponifying commercially available oleic acid with aqueous sodium hydroxide, and 30
TIME ( m i n . ) Figure 1. Total ionization plot representing the gas chromatogram of the neutral fraction isolated from the organic compounds present in the wastewater of Tire Plant A. The GC conditions are given in the text. The enumerated peaks are identified in Table I
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Table I. Compounds Identified in the Wastewater from Tire Plant A No. (see Fig. 1) Compound 1
2-5 6-9 10-13,16,17 14 15
18 19 20 21-24 25-28 29 30 31 32 33 34 35 36 37,38 39 40 41 42-44
Approximate concn, mg/l.d
n-Decane C3 alkyl benzenes C4 alkyl benzenes C g alkyl benzenes Isophorone Naphthalene 2-Methyl naphthalene 1-Methyl naphthalene Benzothiazole Cz alkyl naphthalenes Cs alkyl naphthalenes C4 alkyl naphthalenes and methyl biphenyl" Diphenylamine and methylenediphenolb Cq alkyl naphthalenes Phenanthrene Propyldiphenylamine" Methyl phenanthrene 9,9-Dimethylacridan Di-ethyl-phthalate Cz alkyl phenanthrenes Fluoranthene Unknown Pyrene Unknown
Other compounds found in acidic extract
0.06 0.04-0.07 0.05-0.07 0.01-0.09 0.04 0.10 0.18
0.12 0.02 0.01-0.04 0.01-0.03 0.05 0.01
0.20 0.02 0.04 0.07 0.03 0.06 0.08 0.06 0.01 0.008 0.01 0.01 0.01 Approximate concn, mg/l.
Cyclohexylamine 2-n-Butoxy ethanol p-Nonyl phenol" 2,6-Di-tert-butyl-4-methylphenol Capric acid Lauric acid Myristic acid Pentadecanoic acid Palmitic acid Palmitoleic acid Heptadecanoic acid Stearic acid Oleic acid Linoleic acid Linolenic acid Arachidic acid Behenic acid Toluene Cz alkyl benzenes
0.01 0.03 0.06 0.04 0.2 0.5 2.8 0.4 7.2 6.1 2.7 10
46 0.3
0.2 1 1
10 0.5
Exact position of alkyl group on phenyl ring is not known. Orientation of phenol groups is not known. p-Nonyl phenol is a mixture in which the position of the phenol group varies along a linear nonyl chain. Errors are f30%. it is used to prevent sticking of the sheet rubber which is eventually cut and molded into tire components. At present, this solution is not recycled within the plant. A neutral fraction of the wastewater organics was obtained by removing the fatty acids from the dichloromethane extract with aqueous KOH solution. A total ionization plot of the resulting neutral fraction is shown in Figure 1. These compounds were present in such minor concentrations compared to the fatty acids that peaks representing most of them did not appear in the original analysis. The compounds identified in this neutral fraction and the concentrations of all compounds found in this wastewater are listed in Table I. In terms of relative importance to environmental concerns, the compounds found in this plant effluent can be roughly divided into two classes. The fatty acids found in the effluent have been thoroughly investigated in metabolic studies ( 3 ) and, unless ingested in huge amounts, offer no immediate hazard due to toxic effects. Most of the remaining compounds,
however, have not been extensively tested for toxicity, and their presence gives rise to somewhat more concern. The alkyl benzenes and naphthalenes in the plant effluent are components of an aromatic and naphthenic oil used to extend and soften rubber formulations. Many studies have shown that these compounds are toxic under acute and chronic loading conditions at high concentrations, both by inhalation and ingestion ( 4 ) .However, the effects of long term low level exposure have not been well-established. Several of the substances listed in Table I appear on the toxic substances list ( 5 ) . Many alkyl benzenes and naphthalenes, benzothiazole, isophorone, and cyclohexylamine are all listed, with LDso for oral ingestion by rats ranging from 710 mg/kg for cyclohexylamine to 2330 mg/kg for isophorone. These data may or may not provide insight into the effects of chronic ingestion of the small amounts found in the receiving waters of the tire industry. Diphenylamine, propyldiphenylamine, 9,9-dimethylac-
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ridan, and 2,6-di-tert-butyI-l-methyl phenol (BHT) are all used by the tire industry as antioxidants (4,6,7). Diphenylamine, the most abundant compound in the neutral extract, can cause asthenia, wasting, and occasionally death when administered orally to rabbits in doses of 500-2000 mg/kg over a period of 15-20 days (4).B H T has "practically no systemic toxicity" and is approved for food use (8). Unfortunately, there are no toxicity data available far propyldiphenylamine or 9,Q-dimethylacridanalthough acridan itself has a LDsO(in the mouse by subcutaneous injection) of 4 mg/kg (9) which indicates that it is a highly toxic compound. The presence of isophorone (3,5,5-trimethyl-2-cyclohexenone) is somewhat of a surprise. Although it may also be used as an antioxidant, its main industrial use appears to be as a solvent in the lacquer and plastics industry (4). Both the isophorone and diphenylamine have been shown (4, 10) to cause kidney damage when inhaled over long periods in relatively high doses (300 ppm), but again no information about low level chronic ingestion is available. Tire Plant B discharges about 2.4 million gallons (9090 m3) of wastewater per day into a creek which drains into a small river, and it produces 20 000 to 22 000 passenger tires per day. Most of the discharge is cooling water, about 60% of which is reused after each cycle. The primary functional difference between Tire Plant B and Tire Plant A is that this plant recycles the anti-tack solution; in addition, the anti-tack solution consists of a claywater mixture rather than a saponified fatty acid solution. The wastewater from this tire production facility is colorless and odorless before and after the holding lagoon, which is the only provision for the treatment of the effluent. The lagoon, in fact, is used for recreation. The only compounds found in this plant effluent in appreciable quantities were benzothiazole and 2-mercaptobenzothiazole present a t concentrations of 0.06 mg/l. and 0.03 mg/l., respectively. Both of these compounds [or precursors of them such as 2,2'-dithiobis(benzothiazole)] are used as vulcanization accelerators. The plant wastewater was found to contain less organic matter than the creek into which it discharges. The creek apparently receives considerable agricultural runoff since it contained fatty acids and some nitrogen-containing compounds such as N,N- dimethylurea. The benzothiazole in the plant effluent persists in the creek, and 60-90% of this potentially toxic compound still is present several miles from the plant where the creek enters a river. Toxicity data for these two compounds are limited. For
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benzothiazole, there is no reported LDb0 for oral ingestion. The 2-mercaptobenzothiazole may be absorbed through the skin (11) but its toxicity has been measured only for oral feeding to rats [LD50 = 2160 mg/kg ( 5 ) ] .Absent from this discussion is any information about the effects of long term exposure to either compound, since no work has been done in this perhaps more critical area.
CONCLUSIONS The difference between these two tire plants indicates the need to study the specific organic compounds being emitted by several representatives of a given type of industry before drawing conclusions about the overall pollution potential of that industry. Although one of the two plants studied was emitting 800 times more organic material, the nature of the largest part of the organic compounds present (fatty acids) made this less significant from the viewpoint of human health than it might have been. The exact effect on human health of chronic exposure to low levels of the other compounds cannot be established until more sophisticated toxicology information is available. LITERATURE CITED (1) "Development Document for Effluent Limitation Guidelines and New Source
Performance Standards for the Tire and Synthetic Segment of the Rubber Processing Point Source Category", Environmental Protection Agency, EPA-440/1-74-013-a, February, 1974. (2) A. Gold, Anal. Chem., 47, 1469 (1975). (3) H. R. Mahler and E. H. Cordes, "Biological Chemistry", 2d ed., Harper and Row, New York, 1971. (4) L. T. Fairhall, "Industrial Toxicology", 2d ed., Hafner Publishing Co., New York. 1969. (5) H.-E.'Chrktensen, Ed., "The Toxic Substances List (1973)", U.S. Department of Health, Education, and Welfare (NIOSH), 1973. (6) A. M. Merrill, "Materials and Compounding Ingredients for Rubber and Plastics", Bill Brothers Publishing Corp., New York. 1965. (7) R. C. Elderfield, Ed., "Heterocyllic Compounds, Volume 4: Quinoline, Isoquinoline, and Their Benzo Derivatives", John Wiley and Sons, New York, 1952. (8) P. G. Stecher, Ed., "Merck Index, Eighth Edition", Merck and Co., Rahway, N.J., 1968. (9) W. S. Spector, Ed., "Handbook of Toxicology, Volume I: Acute Toxicities of Solids, Liquids and Gases to Laboratory Animals", W. B. Saunders Co., Philadelphia, Pa., 1956. (IO) E. Browning, Toxicity and Metabolism of Industrial Solvents", Elsevier, New York, 1965. (1 1) D. Dittmer, Ed., "Handbook of Toxicology, Volume V: Fungicides", W. B. Saunders Co., Philadelphia, Pa., 1959.
RECEIVEDfor review June 10,1976. Accepted July 26,1976. We are grateful to the Research Applied to National Needs program of the National Science Foundation for support (grant number AEN75-13069).
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