I 0.1 M NaN03 o i = 30 sec
A
o
-
1
FRESHLY PRECIPITATED SOLID
I
I 0I M i 5 sec i = 30sec
’ SOLIDS AGED
‘6
NaN03-
Ihr
8
(6.8) 7
PH
Figure 4. Adsorption edges for cadmium adsorption onto freshly precipitated am-Fe2O3.H20under different mixing regimes.
Figure 5. Adsorption edges for cadmium adsorption onto aged (1 h) am-Fez03-Hz0under different mixing regimes.
h) solid for a given set of mixing conditions. Thus,_for reasonable mixing operations of complete mixing with t I30 s, the resulting solids show no differences in adsorption characteristics as measured by the adsorption of cadmium.
ditions are achievable with currently available commercial flash-mixing devices.
Conclusions We have shown that, for solid/solution contact times of 1 h, which are typical of common water and wastewater treatment schemes, a variation in residence times in the mixing vessel does not alter adsorption characteristics of cadmium on amorphous iron oxyhydroxide. Thus, presumably the physical/chemical characteristics of the solid are substantially the same in all cases. The two residence times used in this study differ by a factor of 6 but produce a well-mixed system under the chosen conditions. Equilibrium data for adsorption of cadmium onto freshly precipitated iron oxyhydroxide and iron oxyhydroxide aged 1 h indicate no differences in solid surface characteristics. As long as complete dispersion of the Fe(II1) feed solution in the mixing vessel occurs within 30 s, mixing conditions appear to be of minor importance in the removal of trace metals through adsorption onto the Fe(II1) flocs. These con-
Acknowledgment We thank Tony Naylor for his technical advice and assistance. Literature Cited (1) Leckie, James 0.;Benjamin, Mark M.; Hayes, Kim; Kaufman, Gary; Altman, Scott. “Adsorption/Coprecipitation of Trace Ele-
ments from Water with Iron Oxyhydroxide”, Electric Power Research Institute Final Report RP-910, Sept 1980. (2) Davis, James A.; Leckie, James Q. J . Colloid Interface Sci. 1978, 67,90-107. ( 3 ) Davis, James A.; Leckie, James 0.J . Colloid Interface Sci. 1980, 74,32-43. (4) Benjamin, Mark M. Ph.D. Thesis, Stanford University, Stanford, CA, 1978. (5) Gray, J. B. In “Mixing: Theory and Practice”; Academic Press: New York 1966; Vol. 1. (6) Levenspiel, Q.; Bischoff, K. B. Adv. Chem. Eng. 1963,4. (7) Holland, F. A,; Chapman, F. S. “Liquid Mixing and Processing in Stirred Tanks”; Reinhold: New York, 1966; pp 95-192. Received for review October 21,1980. Revised Manuscript Received April 14,1981. Accepted July 6,1981. This uork was partially supported by EPRI Contract EPRI-910.
Oxidation of Phenolic Antioxidants in a River System Viorica Lopez-Avila Midwest Research Institute, 425 Volker Boulevard, Kansas City, Missouri 641 10
Ronald A. Hites” School of Public and Environmental Affairs and Department of Chemistry, Indiana University, Bloomington, Indiana 47405
The phenolic antioxidants are very important commercial, organic chemicals. The two most well-known are 2,g-di-tertbutyl-4-methylphenol (also known as butylated hydroxytoluene or BHT) and 2- and 3-tert-butyl-4-methoxyphenol (also known as butylated hydroxyanisole or BHA). Both are widely used antioxidants in the polymer and food industries ( I ) . The environmental fate of phenolic antioxidants is of significance because of their abundance and their usage patterns. Thus, we have studied the fate of three such antioxidants which were being emitted in the wastewater of a facility which manufactures them. The compounds that we studied are 2,g-di-tert -butylphenol and the methyl and octadecyl esters of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid. These 1386
Environmental Science & Technology
antioxidants are produced by a small specialty chemicals plant located in Rhode Island ( 2 ) .The wastewater from this plant is biologically treated and released into the Pawtuxet River; we have previously reported that this plant was emitting (in 1976) -3 kglday of 2,6-di-tert-butylphenol, -25 kglday of the methyl ester, and -15 kg/day of the CISester (3).The purpose of this paper is to report on the fates of these compounds in the Pawtuxet River. Experimental Section The details of the sampling, isolation, and analytical procedures have been given elsewhere ( 2 , 3 ) .
0013-936X/81/0915-1386$01,25/0 @ 1981 American Chemical Society
w The environmental fates of several phenolic antioxidants which were emitted into a small river from a specialty chemicals manufacturing plant are discussed. Concentrations of 2,6-di-tert -butylphenol and 2,6-di-tert -butylbenzoquinone in four river sediment cores, plotted as the ratio of phenol to quinone vs. depth in core, may indicate the redox condition
a t any point in the sediment core. The presence in the river water of a quinone methide is due to the environmental oxidation of 3-(3,5-di-tert-butyl-4-hydroxypheny1)propionicacid esters, antioxidants which are manufactured a t the chemical plant.
Results and Discussion 2,6-Di- tert-butylphenol. We have previously reported that this dibutyphenol was easily oxidized to 2,6-di-tertbutylbenzoquinone in the river water ( 3 ) .
Clearly, 2,6-di-tert-butylphenol is being converted to the benzoquinone up to a certain depth in the sediment core; below this depth the opposite reaction is apparently taking place. The depth a t which this transition occurs is -18 cm near the plant and -36 cm downstream. When the given sedimentation rates are used, the transition depths correspond to -9 yr ago near the plant and -12 yr ago downstream. These times are in fair agreement with each other and suggest that the rate of phenol oxidation is about the same a t the two different sites. The reversal of the phenol/quinone ratio suggests that there is an oxidizing layer of sediment extending to a depth of 20-40 cm at which point the sediment becomes reducing. This agrees with earlier findings of Eglinton ( 4 ) ,who noted that, although most organic-rich sediments are reducing, there is an oxidizing zone in the upper layers where biological activity is strong. In the case of the Pawtuxet River, this layer of strong biooxidation is apparently 20-40 cm thick. We suggest that the phenol/quinone ratio vs. core depth could be a generally useful geochemical parameter which may indicate the redox condition a t any point in a core. Methyl and Octadecyl 3-(3,5-Di-tert-butyl-4-hydroxypheno1)propionates. An abundant (-20 ppb) compound was observed in the river water downstream from the chemical plant which had not been present in the wastewater ( 2 ) .Since this compound was probably the result of an environmental transformation, it was important to elucidate its structure. Figure 2 gives the mass spectrum of this unknown compound. High-resolution mass spectrometry indicated that the molecular ion a t mle 276 had the formula C17H2403, that mle
We report here on the behavior of this phenol in the river’s sediment. Sediment cores were taken in the Pawtuxet River by divers with a 6-cm i.d. X 80-cm long stainless-steel sampler a t two locations: next to the plant’s outfall and 1km farther downstream. At each location, the cores were taken in duplicate. The cores were sectioned into 3-cm layers, transferred to glass jars, and frozen until analyzed. The 2,6-di-tert -butylphenol and 2,6-di-tert -butylbenzoquinone concentrations were determined by gas chromatography for each section, and these values are given in Table I. While there is little trend in the absolute values of these concentrations (probably due to variations in inputs over time), the phenol-to-quinone concentration ratio vs. depth in these cores tells an interesting story. Plots of this ratio are given for the two locations in Figure 1. Each data point represents the average of the two replicate cores taken at that location. The sedimentation rate a t the near-plant site is 2 cm/yr, and a t the 1-km site it is 3 cm/yr ( 2 ) .Each fitted line is statistically significant; the correlation coefficients are given.
Table 1. Concentrations (in ppm) of 2,6-Di-ferf-butylphenol and 2,6-Di-ferf-butylbenzoquinone vs. Depth in Four Cores from the Pawtuxet River and Average Phenol-to-Quinone Ratio at the Two Sites core section, cmI
2,6-d1- terf-butylphenol near plant core no. b
0 3 6 9
12 15
ia 21 24 27 30 33 36 39 42 45 48 51 a
ds = downstream.
I
IV
2 4 9 0.5 16 12 12
13 9 1a0 a4 12 10 39 5 14
a a
V
a
13 15 15
2,6-dl- ferf-butylbenzoquinone
1 km d s a
33 17 5 ND
NA NA
260 410 1a0 22 66 570 1a0 380 90 36 10 6 20 6 11
near plant
Not analyzed.
near plant 1 km ds a
VI
I
IV
V
VI
70 760 410 370 370 77 11 41 270 20 120 23
1 2
NA
a
2 3 42
1
40
10 14 14 11 11 10 10 10
NA
7 38 32 50 34 9 3 7 36 25 28 2a 39 15 12 17 12 ND
a 4 4 24 11 ND
See Figure 1 in ref 2
phenollquinone
1 kmdsa
34 58 15 24 7 15
a 2 ND
NA
21 60 33 4 10 a0 34 a7 49 12 42 49 27
a a
4’3 2.5 2.7
}
15 13 7.1
1.3 1.6 0.58 0.77 0.53 0.66 1.2 1.9 1.a 2.5
8.2 7.0 5.1 6.5 6.4 2.6 3.1 1.9 0.23 0.20 0.54 1.1 1.2
Not detected. ~~~
~~~~
V o l u m e 15, Number 11, N o v e m b e r 1981
1387
205
I 175
I
L-
near plant 2 cm/yr
189
~
217
downstream 3 cm/yr
Flgure 2. Electron impact mass spectrum of a compound subsequently identified as 2,6-di-fert-butylbenzoquinone 4-(carboxymethyl)methide. This mass spectrum was obtained at 70 eV on a Hewlett-Packard5982 G U M S system.
& 6
Core Depth lcml
CH,CH&OOR
I
CH,CHEOOH
I
CHCH2COOH
II
12 18 2L 30 36 1 2 18
Core Depth (cml
Figure 1. Plot of the ratio of 2,6-di-tert-butylphenol to 2,6-di-tertbutylbenzoquinone (average of two replicates) vs. core depth (in cm) at two sites in the Pawtuxet River (Rhode Island); see Table I. The sedimentation rates and correlation coefficients are given.
205 was C12H1303, and that mle 217 was C15H210. Furthermore, this unknown compound and the propionic acid were formed in an independent experiment by stirring a sediment sample containing various esters of 3-(3,5-di-tert-butyl-4hydroxypheny1)propionic acid in high-purity water for 2 weeks. These data suggest that the unknown was a quinone (carboxymethy1)methideof the following structure:
OH R = CH, or C,,H,,
!
OH
0
This identification of a quinone methide as an environmental oxidation product of a phenolic compound is unique. On the basis of this finding and of the observation of other facile phenol oxidations, we suggest that the general environmental fate of phenolic antioxidants is their transformation to quinones or quinone methides. Acknowledgment The cooperation of the company officials and plant personnel in obtaining the wastewater samples is gratefully acknowledged. Literature Cited (1) “Kirk-Othmer Encyclopedia of Chemical Technology”, 3rd ed.;
Since this compound (2,6-tert-butylbenzoquinone 4-(carboxymethy1)methide) was structurally related to the propionic acid but had two fewer hydrogen atoms, it is likely that oxidation of this acid had taken place in the river water. The source of the propionic acid is probably hydrolysis of the methyl ester; the C18 ester is less likely to hydrolyze because of its strong tendency to adsorb to the river sediment (2).
Wiley: New York, 1978; Vol. 3, p 139. (2) Lopez-Avila, V.; Hites, R. A. Environ. Scz. Technol. 1980, 14, 1382. (3) Jungclaus, G. A,; Lopez-Avila, V.; Hites, R. A. Environ. Sei. Technol. 1978,12,88. 141 , , Eelinton. G.. Ed. “Environmental Chemistrv”: The Chemical Soiety: United Kingdom, 1978; Vol. 1,Special”Report No. 35. Received for reuiew February 9,1981. Accepted July 16,1981. This work has been supported by the U.S. Environmental Protection Agency (Grant No. R806350) and by the National Science Foundation (Grant No. ENV-75-13069).
Removal of Elemental Mercury from Wastewaters Using Polysulfides David M. Findlay and Ronald A. N. McLean* Research Centre, Damtar Inc., Senneville, Quebec H9X 3L7
Following the discovery in the late 1960s in Sweden that inorganic forms of mercury released in effluents from industrial plants could be converted to methylmercury in the natural environment ( I ) , a number of measures were taken to prevent the release of mercury. In North America the chloralkali industry effected a rapid reduction in its losses to the environment in the early 1970s. In the treatment of wastewater, the most common methodology involved treatment with sodium sulfide or hydrosulfide to convert the mercury 1388
Environmental Science & Technology
to mercury(I1) sulfide which could be precipitated ( 2 , 3 ) .In some plants, ion-exchange resins and activated carbon were used as polishing steps after sulfide precipitation to reduce mercury concentrations in effluents even further. In our studies (4-7) on the control of mercury losses from a chlor-alkali plant, the form of mercury in the various effluents and solid wastes was studied. I t was discovered that a considerable proportion of the mercury in the wastewaters and solids was elemental mercury (6) and that the traditional
0013-936X/81/0915-1388$01.25/0
@ 1981 American Chemical Society
