Environ. Sci. Technol. 1994, 28, 267-276
Transformation of Dyes and Related Compounds in Anoxic Sediment: Kinetics and Products George L. Baughman' and Eric J. Weber
Environmental Research Laboratory, U.S. Environmental Protection Agency, College Station Road, Athens, Georgia 30605 The reactions of several azo, anthraquinone, and quinoline dyes were studied in settled sediments. Several l-substituted anthraquinones were lost from sediment with halflives less than 10days. For monosubstituted l-amino and l-methylamino (Disperse Red 9) compounds, the most stable product is the intramolecularly hydrogen-bonded anthrone. The 1,4-diaminoanthraquinone(Disperse Violet 1) and 1,4-diamino-2-methoxyanthraquinone(Disperse Red 11)were lost without formation of detectable products except for a demethylation product of the latter. Both the anthrone from Disperse Red 9 and the demethylation product of Disperse Red 11reacted with halflives of a few months, but other major products were not detected. An azo dye (Solvent Red 1)and a quinoline dye (Solvent Yellow 33) were transformed with half-lives of a few days and months, respectively. The azo dye reacted by reductive cleavage of the azo bond. Introduction
Textile dyes are of environmental interest because of their widespread use, their potential for formation of toxic aromatic amines and their low removal rate during aerobic waste treatment (1-6). Some disperse and solvent dyes are also of interest because of their dispersal in the environment through use as colorants in military smokes and signals. Also, the fate of dyes in environmental media has seldom been studied-especially with nonionic dyes. Although the majority of textile dyes are ionic, the nonionicdisperse dyes are the most heavily used (90million lbs in 1986) (7). Solvent dyes, like the disperse dyes, are hydrophobic but they are less widely used. Roughly 80 % of the dyes in use are azo compounds and, of the remainder, 15-20 7% contain the anthraquinone moiety. Probably because of analytical difficulties, dyes have seldom been reported in the environment, although dyerelated compounds have been reported in sediment (8) and in effluent from a manufacturing plant (9). The few reports of hydrophobic dyes in the environment have included disperse dyes in river water ( I O ) , sediment (IO), and fish (11). Recently, Yen et al. (12)reported Disperse Yellow 64 in sediment, and Maguire et al. (13) reported several disperse dyes in a Canadian river, including the most heavily used of all dyes, Disperse Blue 79 (DB 79). Until recently, the few studies relevant to the fate of dyes in natural systems showed that the formation of aromatic amines could result either from in vivo metabolism of azo dyes (1-3) or the action of bacteria in river water and soil (14). However, there have been many laboratory studies of microbial transformation, mostly in regard to waste treatment of anionic azo dyes (15-18). Also, the reduction of the dye resazurin has been used to measure dehydrogenase activity of sediments (19). Additionally, it is known from the chemistry of dyeing that many anthraquinone analogs are easily and reversibly reduced (20). Similar considerations strongly suggest that
reductive cleavage of azo dyes should result in irreversible formation of aromatic amine products as had been observed for other aromatic azo compounds (21). Also, solubilities of disperse and solvent dyes have been reported recently (22, 23) and as anticipated, these compounds are reduced in anoxic bottom sediments (12) where they are expected to accumulate (22). Facile sediment reduction of azo dyes (azo cleavage) and nitro groups in the laboratory has been reported (12,24),along with data showing the slower reaction of disperse anthraquinone dyes and the much greater stability of two quinoline disperse dyes. Other studies have reported the sediment reduction of benzidine- based azo dyes (25) and the loss of Disperse Yellow 42 from a pond system (26). Importantly, Maguire et al. (13)have reported a brominated aromatic product in river sediment that resulted from cleavage of the azo bond in DB 79. The present study is an extension of earlier work (12) on the reaction kinetics of disperse dyes under conditions expected in settled bottom sediments. In this case, particular emphasis is given to the anthraquinone dyes and to the reaction products. Also, some of the limitations in conducting and interpreting kinetic studies in compacted sediments are noted. Experimental Section
Materials. Sources of chemicals and dyes are noted below. Dyes are listed with their Color Index (CI) constitution numbers (27). Six chemicals were purchased: l-aminoanthraquinone (97%), l-chloroanthraquinone (98%1, and Diazald from Aldrich Chemical Co. (Milwaukee, WI); l-hydroxyanthraquinone (98+ %) from TCI America (Portland, OR); sodium dithionite (purified) from Fisher Scientific (Atlanta, GA); and aluminum powder from EM Science (Gibbstown,NJ). Other chemicals were reagent or HPLC grade; water was deionized. Disperse Red 1(DR 1)(CI 11110),Disperse Red 9 (DR 9) (CI60505),DisperseViolet 1(DV 1)(CI61100),Disperse Red 11 (DR 11) (CI 620151, Solvent Red 1 (SR 1) (CI 12150) and Solvent Yellow 33 (SY 33) (CI 47000) were supplied courtesy of Atlantic Industries (Nutley, NJ). Disperse Blue 3 (DB 3) (CI 61505) and Disperse Blue 14 (DB 14) (61500) were used as components of Sublaprint Blue 70013, supplied courtesy of Keystone Aniline Corp. (Chicago, IL). Dye structures are given in Figure 1. Press cake samples of the dyes contained numerous components as shown by high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC). Thus, all of the dyes were initially recrystallized from ethanovwater solutions. The recrystallized dyes were then flash-chromatographed on silica gel (32-63 pm, Universal Adsorbents) (28). Due to the inability to obtain pure materials, DB 3 and DB 14 were used as the mixture
This article not subject to U S . Copyright. Published 1994 by the Amerlcan Chemical Society
Environ. Scl. Technol., Vol. 28, No. 2, 1994
267
\X
0
H 3
DR1 (mW=231) SR1 (mw = 278) CI
A
DR5 (mw = 378)
&ch
0
*
SY33 (mw = 273)
0
DR9 (mw = 237)
NH,
DV1 (mW = 238)
0
NH,
DR11 (mw-268)
0
HN/CH3
0
HN.
o$$
0 'C,H,OH DB3 (mw = 296)
OH
Quinizarin (mw = 240)
Figure 1. Dye structures.
isolated from Sublaprint Blue 70013. However, in the studies, each compound was resolved and measured separately. Sediments were obtained from four different lakes near Athens, GA. They were scraped from the top few centimeters of the lake bottom at a water depth of less than about 50 cm and sieved, at the lake, through a 0.5mm sieve. The sieved sediment (5-15 cm deep) was stored in the dark, under lake water, in sealed, 2-gal glass or plastic bottles until used. The water pH varied from 6.4 to 7.2 and was not buffered. Organic carbon content of sediments was determined at the University of Georgia Soil Testing Laboratory by the Walkley-Black method (29) and by three other combustion methods, including that of Lee and Macalady (30). In general, the methods gave comparable results. The percent organic carbon for each lake sediment was as follows: Beef Pond, 3.05 f 14% (n = 9); Herrick, 1.52 f 56% (n= 31);Kingfisher, 7.46f 45% (n= lO);Oglethorpe, 1.99 f 48% (n = 7). Equipment. The gel permeation chromatographic (GPC) apparatus (Bio-Rad Laboratories) consisted of a glass column (2.5 X 75 cm) containing approximately 45 cm (100g) of 200-400-mesh S-X12 Bio-Beads. Methylene chloride was pumped through the column at a rate of 1-2 mL/min by a Perkins-Elmer Series 100 HPLC pump. Under these conditions, the colors of the dyes and the humic material were clearly visible and most of the humic components eluted with a retention volume of 90 mL or less. HPLC measurements utilized isocratic elution of acetonitrile/water moblile phases from C18 columns at 1-1.3 268
Envlron. Scl. Technol., Vol. 28, NO. 2, 1994
mL/min. Columns were 4.6 mm in diameter and either 25 or 12.5 cm in length with guard columns and in-line prefilters. Columns with 30 % carbon loading (Phenomenex ultracarb 5 ODS) were used for the anthraquinone dyes. Programmed temperature gas chromatography was performed with a Hewlett-Packard gas chromatograph (Model 5890) equipped with Hewlett-Packard, bonded HP-1 or DB-5, fused-silica, Megabore columns. The columns were 12-30 m long. Electron impact mass spectra were acquired at 70 eV on a VG 70-SEQhigh-resolutionhybrid mass spectrometer, a Finnigan Model 4500 quadrupole mass spectrometer, or a Hewlett Packard Model 5970 mass selective detector. Fourier transform infrared spectrometry (GC-FTIR) data were obtained with a Digilab Model FTS-60 spectrometer, Model 3200 workstation, Model GC/C 32 light pipe-based interface and a narrow band mercury-cadmium telluride detector. NMR spectra were obtained with a Bruker AC 250 and a Bruker AMX 400-MHz spectrometer. Methods. Product Studies. Product studies were conducted in covered beakers that contained 0.2-0.5 kg of sediment (4-10 cm deep) under 10-15 cm of water. Portions of the sediment were placed in 20-mL scintillation vials for sampling over time, as needed. Products were extracted by filtering the sediment to remove most of the water and then slurrying the resulting filter cake with acetonitrile (ACN). The slurry was again filtered, and the filtrate was rotovaped to remove ACN. The remaining water was extracted with methylene chloride (occasionally ethyl acetate) after pH adjustment, if necessary. This extract was rotovaped to a volume small enough (2-4 mL) for cleanup by GPC to eliminate most of the humic material. In most cases, eluates from GPC were evaporated and taken up in ACN for direct analysis by HPLC, GCMS, or GC-FTIR. In other cases, portions were taken up in ether for methylation with diazomethane that was generated using Diazald. Syntheses. Dithionite or aluminum reduction products were synthesized, based on information from Bradley and Maisley (32)and Hudlicky (321,respectively. Aluminum reductions were carried out by the addition of about 0.5 g of A1 filings to approximately 20 mL of gently stirred, concentrated sulfuric acid containing a small amount of dye (less than 1 mg). For dithionite reductions, about 1mg of dye was placed in approximately 10 mL of MeOH or EtOH. To this was added 1 pellet of KOH and 20-30 mL of water. The solution was stirred while sodium dithionite (up to about 0.1 g) was added and also during the reaction. Synthesis of 1,4-diamino-2-hydroxyanthraquinone (HA) was accomplished by demethylation of DR 9. The dye was stirred in concentrated H2S04 with gentle heating for 24 h. The empirical formula by high resolution mass spectrometry (HRMS) was C14H10N203. HA was also characterized by its UV-visible and fluorescence spectra in 60/40 ACN/H20 as follows. The UV-visible maxima are a t 256-258, 528-532, and 560-564 nm. The fluorescence spectrum has its exitation maximum at 256-260 nm and its emission maximum at 600-610 nm. The FTIR spectrum in KBr had only a weak carbonyl band at 1603 cm-1. Other infrared peaks were at 3460(s), 3345(w), 3244(w), 1735(w), 1571(s), 1462(m), 1373(m), and 1291(m) cm'.
Kinetics. Kinetic studies were conducted in unstirred containers using procedures similar to those described previously (12). Therefore, the method is only briefly described here. The desired amount of sediment (based on wet weight and moisture content of filter cake) in lake water was sealed and allowed to remain quiescent for 2-4 days prior to dye addition. During dye addition (in ACN) and mixing, the sediment was maintained under Nz until placement in 20-mL scintillation vials. No attempt was made to measure redox potentials in the compacted sediment of either kinetic or product studies. However, under the study conditions, the reddish Georgia clay sediment quickly became the light gray color that is characteristic of reducing environments. Vials were sacrificed for analysis by shaking, sonicating, and filtering. To a portion of the filter cake was added a volume of ACN equal to twice the sediment moist weight. The vial was then shaken and sonicated and the slurry was filtered. Control studies showed recoveries to be both high (>go%) and reproducible (f10%), with the exception of the demethylated product of DR 11. Recoveries of this compound were found to be only 24 % ,but measurement precision was similar to that of the other compounds. Therefore, results for this product were corrected accordingly. For all kinetic experiments, rate constants for dye loss, k ~ were , obtained as the slope of a regression of the logarithm of dye concentration versus time, i.e., from the logarithmic form of eq 5. In most cases, kinetic data were first order over at least 2 half-lives, and eight or more points were used in the regression. When this was not possible, the data either were rejected or were taken from an earlier, linear part of the plot. In a few such cases, as few as four or five points were used. In two cases, Arrhenius activation energies were estimated from the change in In k~ with respect to the reciprocal of absolute temperature for two or three temperatures. The slope was obtained algebraically for two points or by regression for three.
grams showed two major components that had molecular weights of 228 and 244. The spectrum and retention time of the MW 228 component matched that of the component from sediment. The MW 244 component must be due to either the hydroanthraquinone or its tautomeric oxyanthrone [mass spectrum: 244 (B), 209 (61), 181 (87), 163 (45), 152 (73), 76 (79)l. Selected ion mass scans showed that the other anthrone isomer coeluted with 1-CA and was thus hidden in the synthesis extracts. This product was not detected in sediment extracts. 1-CA is the only anthraquinone for which a hydroanthraquinone was detected, either from synthesis or in sediment. Dithionite reduction of 1-hydroxyanthraquinone resulted in product extracts that also indicated anthrone formation. In this case, the mass chromatogram showed that the isomers eluted on either side of the parent compound. However, 1-HAwas not examined in sediment. Disperse Red 9. By GC-MS analysis, the sediment reaction of DR 9 (mass 237) also was found to give two products (each with mass 223) eluting before and after the parent dye. Extracts of A1 metal reductions had only two major products, and they matched the retention times and mass spectra of the components from sediment. The component eluting after the dye was significantly less stable than the other (ANT),and often it was not observed in sediment extracts, presumably because of the time required for sample preparation and analysis. The compound, ANT, eluting before the dye was synthesized and purified by flash chromatography in sufficient quantity for HRMS analysis and for NMR and melting point (mp) determination. The HRMS obtained by a solid probe gave a mass of 223.100, consistent with the formula C15H13NO. The spectrum also confirmed that the major fragment peak at mass 206.098 was due to the loss of OH. This suggests, but does not prove, that the earlier eluting product is the hydrogen-bonded isomer (Scheme 2). Scheme 2 o\bH' I,
r?
/R
Q..Jk 3
N
Results Product Studies. 1-Chloroanthraquinone. In initial experiments without GPC sample cleanup, the detection of reaction products by GC-MS was not possible. Therefore, one of the first compounds examined was 1-CA on the premise that C1 would serve as a tracer in the mass spectra. The resulting mass chromatogram showed a C1containing component that eluted before 1-CAand which had an apparent molecular weight 14 less than the parent compound (MW 242). Based on the mass spectrum [(rnle (I): 193 (B), 228 (421,165 (541,163 (38),97 (24), 82 (57)1, this component was presumed to be an anthrone (Scheme
..1).
Scheme 1
R = CH, R=H
DRQ (mw = 237) 1-AA (mw= 223)
ANT (mw = 223) (mw = 209)
(mw = 223) (mw = 209)
The mp at 115-117 "C was higher than the 111-113 OC reported for 1-methylamino(9,lOH)anthraceneone(31). However, Bradley and Maisey (31) made their isomer assignment based on synthesis, so we conducted further work to obtain a positive identification. Isomer confirmation was obtained by GC/FTIR of the extracts. The FTIR spectrum of DR 9 has carbonyl stretching peaks at 1686 (m) and 1643 (m) c m l corresponding to the free and intramolecularly hydrogen-bonded carbonyl groups, respectively. It also has an N-H stretching peak at 3308 (w) cml. The spectrum of the first eluting peak, ANT, has only one carbonyl stretching peak [1644 (s) cmll and an N-H stretching peak at 3307 (w) cml. The mass and infrared spectra combined provide proof that the first eluting product, ANT, is the hydrogen-bonded isomer, 1-rnethylamino(9,lOH)anthraceneone. A similar analysis shows that the peak eluting after the dye [mass spectrum: 223 (B), 208 (771, 194 (16), 181 (lo), 165 (311, 152 (12)l is the non-hydrogen bonded anthrone, l-methylamino-
&-&+& \
\
0
0 1-CA (mw-242)
[mw = 228)
(mw = 228)
The reduction of 1-CA with sodium dithionite or A1 resulted in reaction mixtures for which mass chromato-
Environ. Sci. Technol., Vol. 28, No. 2, 1994
269
(SH,lO)anthraceneone, which also has only one carbonyl peak (1683 cml). The FTIR spectra of these and related compounds will be published separately. The proton NMR spectrum of ANT shows a broad N-H resonance at 9.51 ppm with singlets at 4.23 and 2.95 ppm for the (2-10 methylene group and the methyl group of the amine, respectively. The other downfield signals are from the aromatic hydrogens and are between 6.5 and 8.5 ppm. All 15 carbon signals are present in the 13C spectrum, and DEPT 135 indicates the methyl group at 29.4 ppm, the methylene carbon at 33.2 ppm, and seven CHs between 107 and 134 ppm. The carbonyl carbon is located at 186.8 ppm. The complex pattern of aromatic hydrogens was resolved in a C-H correlation experiment into the expected four doublets and three triplets. A “-COSY experiment indicates coupling between the aromatic hydrogens but also shows some coupling between the protons of the methylene group and the aromatic protons. Based on the above experiments, the following assignments are proposed (ppm) [proton, carbon]: C-1, 153.0; C-2 [6.58 d, 107.91; C-3 i7.35 t, 134.31; C-4 r6.59 d, 114.41; C-4a r139.41; C-5 [7.34 d, 127.51; C-6 r7.49 t, 131.81; C-7 [7.40 t, 126.61; C-8 18.25 d, 126.81; (2-9, 186.8; C-10, 33.2; C-loa, 142.9; C-8a, 133.1; C-ga, 114.4, CH3, 29.4. Carbons 9 and 10 were assigned on the basis of the NMR studies of Tomano and Koketsu (33). In sediment, there was no evidence of N-demethylation of DR 9 (Le., no 1-aminoanthraquinone (1-AA) was detected) even though the possibilitywas always examined. Similarly, the 4-hydroxy compound was never detected as more than a trace component. Further, the 2-hydroxyanthraquinones are too involatile for GC and, hence, would not have been detected from either 1-AA or DR 9. These findings are quite different from results on metabolism in sheep, which have an anaerobic rumen. In that case, metabolites were 1-aminoanthraquinone, its 2- and 4-hydroxy derivatives and their glucuronides (34). 1 -Arninoanthraquinone. Results with 1-AA were similar to those with DR 9. GC-MS analysis showed 1-AA (mass 223) to react in sediments with the formation of one anthrone (mass 209). The other anthrone could not be detected. Reduction of 1-AA with aluminum resulted in the formation of both anthrones, one of which eluted on either side of the parent compound. Like the other anthrones, both isomers have the molecular ion as the base peak in the mass spectrum. Also, the second and third largest peaks (masses 180 and 152,respectively) are the same in both spectra. Other peaks were in the background. By analogy with the anthrones from DR 9 (Scheme 21, the first eluting peak for 1-AA was assumed to be the hydrogen-bonded isomer. This was also confirmed by GCFTIR based on the following infrared spectral data: 1-AA 3501 (w), 3074 (w), 1683 (m), 1654 (m), 1606 (m), 1278 (9); H-bonded anthrone 3508 (w), 3342 (w), 3064 (w), 1653 (m), 1601 (s), 1461 (m), 1281 (9); non-H-bonded isomer 3487 (w), 3407 (w), 3076 (m), 2879 (w), 1682 (s), 1622 (m), 1468 (m), 1306 (9). The above data suggest that, for mono 1-substituted anthraquinones in anoxic sediments, the initial transformation step is the reduction to anthrones. Also in the case of DR 9 and 1-AA,the hydrogen-bonded isomers are stable but the non-hydrogen-bonded isomers break down rather easily. The more highly substituted compounds behaved quite differently as shown below. 270
Envlron. Scl. Technol., Vol. 28. No. 2, 1994
Disperse Violet 1 . Upon chemical reduction, DV 1 (Figure 1)can be converted to the “leuco”form of the dye, 1,4-diamino-2,3-dihydroanthraquinone (DDA) (mass 240) (35). DDA, however, is reported to be unstable toward hydrolysis, the products of which react with ferric ions to produce a fluorescent compound (36, 37). Bradley and Maisey (311 also reported that chemical reduction of DV 1(followedby aeration) yields quinizarin, MW 242. Quinizarin is probably the compound reacting with ferric ions to produce the fluorescent product noted by Salinas et al. (36). Thus, quinizarin can also be anticipated to undergo metal complexation and reduction to leuco-quinizarin in sediments. Many different sediment experiments were conducted with DV 1 in attempts to identify products, especially DDA. Unfortunately, only two products were identified with certainty-quinizarin and 1-hydroxyanthraquinone. Both compounds were identified by comparison of GCMS retention times and spectra with those of purchased material. Also, quinizarin was identified by HPLC with fluorescence detection. Both the sample peak and quinizarin had exitation and emission maxima at 490 and at 565-570 nm, respectively. In all cases, the product peaks were very small. Other products tentatively identified by GC-MS were leuco-quinizarin and 1-aminoanthraquinone. Many anthraquinones and related compounds were difficult to identify with certainty at trace levels by GC-MS because the molecular ion is the base peak in the mass spectrum and other peaks are often of low intensity. The reaction of DV 1 with dithionite resulted in two major products. These were identified as quinizarin and leuco-quinizarin as expected. Identification was based on GC-MS, HPLC, and TLC for quinizarin. GC-MS of the reaction mixture shows quinizarin (mass 240) and the leuco compound (mass 242). HRMS of these components resulted in molecular weights of 240.043 and 242.059, corresponding to C ~ ~ H and S O C14Hl~O4, ~ respectively. These results strongly suggest that Disperse Violet 1is transformed in sediment to products, perhaps including DDA, that are converted to compounds containing OH groups in place of “2. This conclusion is consistent with recent work on the nucleophilic substitution of NH2 groups in DDA and DV 1(38). As noted above, such products are likely to reoxidize during workup. Also, the complexation by metals in sediment could adversely affect extraction (recovery) of quinizarin and other 1-hydroxy compounds. The addition of large amounts of EDTA, however, did not result in increased recovery of quinizarin. Disperse Red 1 1 . Experiments with DR 11showed the presence of a major product that (1) was not cleanly separable from the parent dye by HPLC, (2) was not amenable to GC-MS analysis, (3) could not be extracted from aqueous alkali, and (4) had a diode array spectrum (UV-vis) very similar to that of DR 11. The electron impact mass spectrum [254 (B), 223 (31), 169 (13), 127 (8)] is typical of an anthraquinone with MW 254 and was tentatively ascribed to 1,4-diamino-2-hydroxyanthraquinone (HA), the 0-demethylation product (Figure 2). To verify the identity of this reaction product, the methyl group was cleaved from the parent dye with cold concentrated sulfuric acid to give a red compound that could not be extracted from basic aqueous solutions. The HPLC/ TLC retention characteristics, diode array and mass spectra matched that of the sediment transformation
1-amino-2-methoxyanthraquinone
Disperse Red 11
0 M
0
YH2
\
C
w
H
3
- & /I ( /1 J B
I1
0 MW 253
MW 265 A
1
&\cH,
Slow
NH,
0
“2
1
Fast
Fast
C
Slow Slow
II
0 MW 254
HA
MW 239
I-amino-2-hydroxyanthraquinone
Flgure 2. Proposed reaction pathway for Disperse Red 11.
product. The HRMS spectrum is consistent with the empirical formula C14HloNz03. HRMS also confirmed the expected fragmentation as mle 254, molecular ion; mle 226, M - CO; and m/e 197,M - NHzCzOH. This compound has not been reported previously in the chemical literature. HA was also examined by NMR (lacand lH). The spectra show the presence, for the same ring, of an alcohol proton at 11.5 ppm and an aromatic proton at 6.6 ppm. Two additional sets of aromatic protons are located at 8.2 ppm (C-5 and C-8 protons) and at 7.7 ppm (C6 and C7 protons). Only 13 carbon signals are present in the 13Cspectrum since there is a high intensity peak at 125.7 ppm due to two carbon resonances. The carbon bearing the hydroxyl group resonates at 153.4 ppm. The DEPT 45 spectrum has five signals due to the five aromatic CHs. The parent compound, containing a methoxy group at C-2,shows only the aromatic protons and the methyl signal at 3.1 ppm. There are no other resonances downfield of 8.0 ppm. These NMR results unequivocally established HA as the 1,4-diamino-2-hydroxy compound. The FTIR spectrum is also consistent with this conclusion. No other products were verified, either from DR 11 or from its daughter product, HA, though many attempts were made. It is probable, however, that products are formed from either the dye or HA as a result of the replacement of one or more of the amino groups with protons or a hydroxy group. For example, quinizarin was identified tentatively in several product runs but at concentrations too low for confirmation. The above facts are consistent with the observation that the reaction between dithionite (or aluminum) and the dye results in the formation of 1-amino-2-methoxyanthraquinone as the major product. Similar reduction of HA resulted in the analogous 2-hydroxy compound. As noted earlier, anthraquinones having a hydroxyl group in
the 2-position seem not be amenable to analysis by GC. These observations are based on analysis by GC-MS and HRMS of both the product mixtures from synthesis and their methylated derivatives. Methylation of sediment extracts prior to GPC was not attempted because of their complexity. Ifthe above conclusion is correct, other products may still not have been detected because (1) they are not amenable to GC-MS analysis, (2) they cannot be extracted because they are good complexing agents, or (3) their chromatographic peaks were hidden behind those of the sediment background components. Solvent Red 1. Products of the azo dye, SR 1, were expected to be o-anisidine and 1-amino-2-naphthol resulting from reductive cleavage of the azo bond. However, these compounds could not be identified by HPLC because they coeluted. After GPC cleanup, each product was detected by GC-MS with both spectra and retention times identical to those of purchased materials. Several other azo dyes have been studied in sediment systems (12,21,24). In all cases, the primary products are amines resulting from nitro group reduction and/or cleavage of the azo bond. This conclusion is also consistent with environmental data on DB 79 (24) in that one of its cleavage products recently has been reported in river water (13). Thus, we can confidently conclude that reductive cleavage of azo groups is general in anoxic environments. Solvent Yellow 33. Although the kinetics of this quinoline dye were studied in three different sediments, the dye was so unreactive that a product was only identified from Herrick Lake sediment that had been standing with dye for almost 2 years. Detection of the product was prompted on discovering that reduction of SY 33 (mass 273) with aluminum resulted in the formation of a minor, stable product having a molecular weight of 275 (mass spectrum [mle (I): 133 (B), 246 (801,275(40),77 (40), 105 (30), 248 (20)l. Selected ion GC-MS analysis of the sediment extract after GPC cleanup showed the presence of a very small amount of a compound having the same retention time and mass spectrum. GC-HRMS of the product gave a molecular weight of 275.098 corresponding to ClaH13N0~.GC-FTIR analysis of the synthetic product shows a strong carbonyl frequency at 1802cm-l (reasonable for a five-membered ring) and a weak aliphatic CH at 2932 cm-l. The parent dye has no aliphatic CH and its carbonyl frequency is 1815cm’ . The spectrum of neither compound has an OH band. Many attempts were made to reduce SY 33 in sufficient quantity for NMR. However, the yield was always low, and the compound decomposed on flash chromatography. HPLC, with diode array detection, of a small amount of purified material showed that the product has no absorption maximum in the visible region. A reaction pathway consistent with the above information is given in Scheme 3. Scheme 3
SY 33 (mw = 273)
(mw = 275)
Kinetics. Rate Constants. Kinetic data for dyes in sediment are summarized in Table 1. The half-lives of the dyes vary from 0.1 to 140 days or about 1000-fold. However, except for SY 33, only the two anthraquinone Environ. Sci. Technol., Vol. 28, No. 2, 1094
271
Table 1. Kinetic Data for Dyes in Sediment-Water Systems
sediment'
Dob (mg/kg)
DilDo'
k (h-l)d
ANT form. ANT loss 1-AA
H K K K K H
3-4 5-31 12
0.90 0.89 0.80
2.4 X (85) 1.8 X [531 1.7 X l t 3(8) 1.1 X [78] 3.3 X lo4 [351 2.0 x 10-2
SY 33
K 0
dye DR 9
1-CA
DV 1 DR 11
HA form. HA loss DB 3 DB 14 DR 1 DR 5
H B H K H B 0 H K K K K K K K K K H H H
H K SR 1
H
K
8-15
0.84
14-18 0.5-13 0.7-1.2 15 7-10
0.6 0.7 0.5
2.2
6-9 9 9 10-30
1.2 x 10-2
6.5 X [551 1.9 x 10-3 (17) 4.5 X [15] 2.7 X (6) 2.4 X (66) 7.0 X [281 7.3 x 10-4 (4) 1.5 X (1) 5.2 X [41] 5.9 X 1W (25) 6.0 X (18) 4.1 X lo4 [46] 1.1 X [361 1.9 X [45] 9.3 x 10-2 9.4 x 10-2 2.8 X 10-1 1.6 X 10-1 2.2 x 10-1 (94) 7.2 X lo3 [621 1.3 X [78]
12
200 50 10-60
0.87 1.0 0.6
10-98 10-23
1.3 0.8
4 3
x 10-2
1.1
0.63 0.93
1.2 1.6 1.7 0.65 87 1.4 1.3 82 180 200 2.4
