Environ. Sci. Technol. 1994, 28, 99-106
Leachate Characteristics and Composition of Cyanide-Bearing Wastes from Manufactured Gas Plants Thomas L. Thels,’ Thomas C. Young, Mohul Huang, and Kenneth C. Knutsen W. J. Rowley Laboratories, Department of Civil and Environmental Engineering, Clarkson University, Potsdam, New York 13699-5715
Past activities associated with the manufacture of gas from hydrocarbon feedstocks resulted in the generation of substantial quantities of cyanide-bearing wastes produced as a result of product gas cleanup for the removal of hydrogen sulfide and hydrogen cyanide. Large quantities of these wastes have been found a t several manufactured gas plant sites. I t was the purpose of this study to address questions relating to the availability of cyanide to the environment and to determine the chemical forms of cyanide in the waste. This information is necessary in order to assess the toxicity and possible methods of treatment and disposal of the material. Results using two samples of purifier waste indicate that cyanide exists entirely in complex forms, iron complexes being the dominant species with smaller quantities of Cu- and NiCN complexes. Other contaminants of concern include sulfur species (S04z-, S Z O ~ ~SCN-), -, ammonia, and trace metals. Studies for both samples indicate that major cations and anions (NH4+,Ca2+,Na+, K+,Sod2-, C1-, Nos-) are readily leached from the material; however, cyanide species are the least soluble at low pH, the rate of release increasing substantially as the pH rises above neutrality. These results have implications for the toxicity and the treatment and disposal methodologies for these wastes.
Introduction The manufactured gas industry produced gas for lighting and heating and produced feedstocks for the chemical industry from coal, coke, and oil in the United States from the mid-1800s to the 1950s. Many localities had their own manufactured gas plant (MGP),and larger cities often supported several such operations. There are over 1100 documented MGP sites in the United States (3). The construction of long-distance pipelines from natural sources has largely supplanted local production facilities, thus virtually all of these sites are now inactive. The manufacturing processes involved the thermal cracking and the distillation of organic feeds, producing a variety of residuals including tars, lampblack, tar/water emulsions, hydrocarbon sludges, ash, ammonia, and spent oxide scrubber wastes. Certain of these residuals, such as tar and lampblack, were recovered or reused; however others were disposed of, usually by landfilling or deposition on site ( I ) . One process in particular, coal carbonization, involved the heating of coal in a retort; the volatilization of hydrogen sulfide; and the generation of significant quantities of hydrogen cyanide, between 500-1000 ppm by volume (2). These gaseswere removed from the product gas stream through scrubbing with iron oxide particles. The resulting wastes, commonly referred to as purifier or oxide box wastes, were generated at the rate of 8-21 kgl 1000 m3 of gas produced. Although an exhaustive inven-
* To whom correspondence should be addressed. 0013-938X194/0928-0099$04.50/0
0 1993 Amerlcan Chemical Society
tory of these wastes at MGP sites has not been conducted, they have been noted at virtually all sites and are likely to be present in large quantities at several (3). The purpose of this study was to characterize these purifier wastes, in terms of both elemental composition and, to the extent possible, individual species distributions with particular emphasis on their cyanide content, and to assess their dissolution characteristics. Such information could be important for the proper handling, treatment, ultimate disposal, and performance of risk assessment for these materials.
Background The immediate cause for concern with regard to purifier wastes is their cyanide, sulfur, and trace metal contents. Previous studies have found total cyanide to range from 1to >2 % by weight (4,5). The natural pH of the wastes is acidic, with pH values in the range of 2-5, although management practices may bring about more neutral values. Previous analyses for Cd, Cr, Cu, Ni, Pb, and Zn found concentrations in the range of 20-80 mg/kg (6).The total sulfur content of these wastes is reported to be in excess of 40% by weight ( I ) . Perhaps the most visible sign of the presence of cyanide in some purifier wastes is the characteristic blue color associated with iron cyanide solids. This color is usually taken as evidence for ferric ferrocyanide, Fe4(Fe(CN)6)3, known as Prussian Blue, a common pigment. In aqueous solution this compound will dissociate, yielding the hexacyanoferrate(I1) ion (Fe(CN)&) and iron hydroxide solids. Meeussen et al. (7) have recently reviewed the thermodynamic data base for Fe(CN)& and have reported a solubility product for ferric ferrocyanide of pKso= -66.2 according to the reaction Fe,(Fe(CN),),(,, = 4Fe3++ 3Fe(CN)6” (1) The hexacyanoferrate(I1) ion can exist as the dibasic, tribasic, or tetrabasic ion depending on pH (pK, = 2.6, pKQ = 4.3). One consequence of this, and the hydrolysis of Fe3+,is that the solubility of ferric ferrocyanide increases markedly with pH from a minimum at about pH = 2. Cyanide ion is a weak base in aqueous solution (pKb = 4.81, but forms a variety of complexes with numerous transition metals in addition to iron. Table 1 contains data on the stability of several cyano-metal complexes, Standard testing methods draw an operational distinction between cyanide forms which dissociate under neutral or mildly acidic conditions (“weak”acid dissociable)and those which require extreme acidity for dissociation (“strong” acid dissociable). Referring to Table 1, complexes with H+, Cd2+,Cu+, Ni2+, and Zn2+are usually considered to fall within the former classification while Co2+, Fez+, and Fe3+complexes require very low pH conditions for rapid decay. The acute toxicity of complex cyanide species is related principally to the relative ease with which free cyanide Envlron. Sci. Technol., Vol. 28, No. 1, 1994 99
Table 1. Formation Constants for MetalCyanide Complexes (8, 9) reaction
log K (I= 0)a
reaction
H+ + CN- = HCN Cd2+ + CN- = CdCN+ Cd2+ + 2CN- Cd(CN)gO Cd2+ + 3CN- = Cd(CN)sCdZ++ 4CN- = Cd(CN)rZCut + 2CN- = Cu(CN)zCU++ 3CN- = Cu(CN)sZCU++ 4CN- = CU(CN)~'
9.2 5.6 11.0 15.0 18.9 18.8 23.5 30.3
COS++ 6CN- = Co(CN)a' Fez+ + 6CN- = Fe(CN)& Feat + 6CN- = Fe(CN)e" Ni2+ + 4CN- = Ni(CN)hZZn2+ + CN- = ZnCN+ Zn2+ + 2CN- = Zn(CN)20 Zn2+ + 3CN- = Zn(CN)&Znz+ + 4CN- = Zn(CN)dZ-
moisture contents. The total cyanide contents of these wastes have been reported previously to be 14.3 0.99 and 24.8 + 2.36 mg/gof dry weight (4). The total elemental composition of each sample was found using neutron activation analysis (Nuclear Engineering Laboratory, University of Illinois) with the exception of total sulfur, which was determined by X-ray fluorescence (Department of Geology, McMaster University). The rate of dissolution of the cyanide compounds contained in the wastes was measured using stirred batch reactors a t various pH and temperature conditions; the pH being controlled through the use of a microcomputercontrolled titrator which added necessary amounts of NaOH and "03 (Brinkman Model 6). These experiments were conducted in a controlled environmental room in which the temperature was maintained at the desired value (15, 22.5, 25, and 30 "C) . Samples were collected over the course of each experiment, filtered (0.45-pm membrane), and analyzed for total, and in some cases weak acid dissociable, cyanide according to Standard Methods (13) using a cyanide-selective ion electrode (Orion Research) for final quantitation. The duration of the experiments varied between 24 and 187 h. Individual distributions among species containing the CN entity, total trace metals, and other inorganicions were also determined in batch extracts at pH values of 3,7,9, and 11. In these cases, the total equilibration period was 48 h. Filtered extracts collected at pH = 12 over this same period of time were considered to represent the concentration of total cyanide, as distributed among various complex forms. Analysis for total soluble trace metals was carried out by atomic absorption spectroscopy(Perkin-Elmer Zeemanl 5000) according to the manufacturer's specifications. All other ionic constituents were determined by ion chromatography (Dionex 4000i/4270). Table 2 summarizes the various columns, regenerants, eluants, and detection methods for each class of ions analyzed. Positive identification of the presumed cyano-metal complexes was achieved by standard additions of the complexes (Fe, Cu, Ni, and Co) and by determining the metal content of the chromatograph eluant. The former was done to assure a match between peaks of added standards and the presumed complexes in the leachates; the latter to check for amatch between peaks in metal concentration in the eluant and retention time of presumed complexes.
+
log K (I = 0)'
64.0 35.4 43.6 31.8 5.3 11.1
16.0 19.6
At 25 OC.
can be dissociated from the complex, with comparatively weaker complexes being more toxic than stronger complexes (10). However, soluble iron cyanide complexeshave been observed to undergo rather rapid photolysis in the presence of sunlight, yielding free hydrogen cyanide under conditions representative of natural waters (11). Meeussen et al. (12) have also demonstrated that iron cyanide complexes can dissociate in the absence of light under selected conditions of pt and pH; the reaction possessing half-times on the order of years above pH = 4.
Materials and Methods Two samples of purifier waste (approximately 30 kg) were obtained from different MGP sites in New York. The first was a relatively unweathered material, brownorange in color, containing a mixture of fine granular solids and larger wood shavings and flakes. A subset of this material (approximately 500 g) was ground by mortar and pestle before additional testing. The pH of a 200 g/L slurry in distilled-deionized water was measured to be 3.99, the moisture content as received was 21.1 % , and the mean ignitable matter content (five replicates) was 44.8%. The second sample was a blue-black granular material and was used without further pretreatment. The pH of a 200 g/L slurry was 2.11, its moisture content was 58.0%,and the ignitable matter was 92.8%. Particle size distributions for both samples, as determined by laser ensemble light scattering (Malvern Mastersizer Model E),gave d50 values of 3.2 and 0.9 pm, Because of the low pH of the samples and the consequent potential for volatilization losses of any HCN that may form or be present, both samples were stored in enclosed opaque containers at 4 OC. For similar reasons, it was deemed inappropriate to perform any cyanide analyses on oven-dried subsamples; consequently, all values obtained and reported were corrected for
Results Rate of Cyanide Release. Figures 1and 2 show total constituent analysis for samples 1and 2, respectively, as
Table 2. Methods and Conditions for Determinations by Ion Chromatography (14) guard columna
separation column
suppressor column andregenerant
anion
4G4A
4S4A
cation
CGlO
CSlO
SCN-
AG5
AS5
AMMS-I* 25 mM HzS04 CMMS-11' 100 mM TBAOHd AMMS-I 25 mM HzS04
AG5
AS5
analyte class
SZO? cyano-metal complexes
detector conductivity conductivity conductivity
UV-visible
All columns are Ion Pac. b Anion micro membrane suppressor. c Cation micro membrane suppressor. d Tetrabutyl ammonium hydroxide. ~~-2,3-Diaminopropionic acid. @
e
none
eluant 1.8 mM NazCOa 1.7 mM NaHCO3 (isocratic) 60 mM HCl 6 mM DAP HCl" (isocratic) 2.0 mM NaOH, 4.5 mM NazC09 2.0 mM NaOH 0.8 mM 4-cyanophenol 2 % acetonitrile (isocratic) 30-135 mM NaC104 20 mM NaOH 15 mM NaCN (gradient)
100 Envlron. Scl. Technol.. Vol. 28, No. 1, 1904
S
Fe
AI Ti CN Ca Na SCN Mn Cr
v
Ni cu Ce La sc Nd Cn
Eu Ta Tb Br se Lu In CI
I
1
1 o-2
IO0
d 0''
1 1 1 , 1 1
I
1
I l l l l l l
io3
IO2
IO'
1
I 1 1 1 1 1 1
1
,
1 1 l I L
1o s
1 0 4
1o s
Analyte Content, mg/kg (dry basis) Figure 1. Total concentration analysis for sample 1. I
I
I I I I I I
I
'
! l l ! l l
I
1 1 1 1 1 1 1
I
I
I11111
I
I
I IIIII
I
I
I I I I I
1111I
I
I
l l l l l l l
1
1
I I I I I
rrn
S CN Fe SCN AI ...
cu Mn Ti Ni CI Zn co
v
A8 Sb Se Rb
Br
sc
1
Ca Ta Yb Sm Tb Eu In
Lu
Ce
I
1 o'2
10''
IO0
IO'
IO2
1o 3
1 0 4
I
1
I I I , ,
I
I
1 0 5
I i l l L
1o s
Analyte Content, mg/kg (dry basis) Flgure 2. Total concentration analysis for sample 2.
determined by neutron activation, X-ray fluorescence, ion chromatography (SCN-), and total cyanide analysis. As expected, sulfur and iron comprise the major fraction of the materials with significant quantities of cyanide, aluminum, titanium, and thiocyanate present. There is some suggestion of the effects of exposure (sample 2) since
the alkaline earth cations sodium and calcium,which would be expected to have been solubilized and lost over time at the naturally low pH values, are beneath the limit of detection for the site 2 sample. Other concentrations, with the exception of iron, sulfur, and cyanide, also tend to be lower in sample 2, probably due to the greater amount of Envlron. Sci. Technol., Vol. 28, No. 1, 1994 101
Table 3. Fractional Cyanide Release in Batch Systems8 expt no.
sample
PHb
1
1
7.0
2
1
9.0
3
1
11.0
4
1
11.0
5
2
7.0
6
2
9.0
7
2
11.0
8
2
11.0
time (h) 18.0 45.5 75.5 96.0 123.5 142.0 168.0 187.0 17.5 28.0 42.0 66.0 77.0 89.0 101.0 114.0 0.33 0.67 1.0 2.5 5.5 8.0 11.75 17.33 24.0 0.5 1.0 2.5 5.0 8.0 12.0 15.25 24.0 18.0 45.5 75.5 96.0 123.5 142.0 168.0 187.0 18.0 29.0 43.0 67.0 78.0 90.0 102.0 114.0 0.42 0.75 1.08 2.83 5.67 8.67 13.75 23.67 1.0 2.0 3.0 4.0 7.25 10.0
CN~OLKNT~ 0.0029 0.0039 0.0043 0.0050 0.0057 0.0064 0.007 0.0057 0.030 0.043 0.054 0.074 0.076 0.082 0.095 0.109 0.038 0.056 0.042 0.143 0.280 0.286 0.390 0.560 0.706 0.024 0.034 0.098 0.210 0.310 0.402 0.450 0.640 0.029 0.038 0.045 0.050 0.052 0.058 0.062 0.096 0.124 0.158 0.199 0.213 0.230 0.240 0.253 0.260 0.226 0.242 0.347 0.404 0.500 0.590 0.637 0.887 0.266 0.282 0.298 0.327 0.375 0.415
0 W aste concentration equal to 10 g/L. * Studies at pH = 3 were beneath the detection limit of 0.5 mg/L of CN. @NT= 14.3 and 24.8 mg/g for samples 1and 2, respectively.
organic matter and volatile sulfur it contains. Because neither carbon nor sulfur are determined by NAA, their presence serves to dilute the mass-normalized concentration of other elements. Additional elements not able to be activated are Si, Pb, Cd, 0, and N. Table 3 presents data for both samples on the release of total cyanide over time as pH is varied. Multiple linear regression for each sample using the logarithm of fraction 102 Envlron. Scl. Technol., Vol. 28, No. 1, 1994
m . - -
-h
.
.Load
' Zinc
6
10
10
-,
12
10
1
10
Flgure 3. Forty-eight hour batch release of total cyanlde, ammonia, iron, and selected trace metals as a function of pH: (a) sample 1, (b) Sam& 2.
released as the dependent variable yielded significant correlations with pH, as would be expected, and showed the overall greatest correlation with the square root of time (r2= 0.85 and 0.95 for samples 1and 2, respectively). This latter result suggests the possibility that diffusive mass transport is a factor in the release of material from the waste particles, at least under the reactor conditions used in the experiments. Consistent with these results, a general expression relating the fraction of total cyanide released into aqueous solution between the pH values of 7 and 11 is given by [CNISOL/CNT= k[OH-l" tl/' (2) Nonlinear regression of data sets for each sample using eq 2 gave values of kl = 5.85 + 1.80, x1 = 0.56 + 0.04 (r2 = 0.95) and kz = 3.15 + 0.53, x2 = 0.41 + 0.02 (r2= 0.90) for samples 1and 2, respectively. Such consistency for waste samples that had been handled in substantially different ways indicates the probable existence of a common mechanism for the solubilization reaction. The results of release studies conducted on sample 2 at various temperatures and pH = 11 yielded an activation energy of 44.7 kJ/mol using the standard Arrhenius analysis. Analysis of Leachates. Figure 3 shows results of 48-h batch extractions of each waste sample at pH values of 3, 7,9, and 11for total cyanide, ammonia, and trace metals. Following the findings of Meeussen et al. (12)only the results at pH 11 can be considered to be at or near equilibrium; however, the trends among cyanide, iron, copper, nickel, and cobalt suggest possible associations in the form of complex species. The presence of NH4+3"( in the pH 11leachate) may signify a potential role in metal mobilization in the waste, because it is a relatively strong
Na
a \
0 2.0
a
Cations
E
Anions
m
v) +
c a c
NH4
1.5 I
K SO4
0 1.0
1
0
0
I c1 Cations
Anions
a, 0.5
NO3 NO2
+ a E
Pe(CN)6
0
g 0.0
SCN
J
S203
Sample I Figure 4.
Sample II
Maw Ionic constituents found In purlfler waste leachates, pH = 11.
complexing agent with several transition metals, most notably copper. Moreover, the AAS and NAA analyses noted significant amounts of Cu in the leachate, and chemical equilibrium calculations also suggested that copper in the leachates exists partly as amine complexes, thus offering a possible explanation for the noted elevated Cu concentrations. Analyses of the purifier waste leachates collected at pH 11 by ion chromatography (IC) provided two kinds of information. First, the analytical results provided data on the primary ionizable constituents of the leachable material. Second,by couplingthe procedure withancillary studies to confirm and verify unknown substances, the procedure provided a means to identify the ionic CNcontaining species. The previouslynoted elementalcomposition differences between the two purifier waste samples, thought possibly to be partly attributable to differences in environmental exposure and weathering during storage, became much more apparent when the samples were compared on the basis of their leachable constituents. As indicated by the bar chart representing such constituents in the pH 11 leachate (Figure 4), it is clear that all major constituents were present at substantially greater concentrations in sample 1,the relatively unweathered sample, as compared with sample 2, which had been exposed and allowed to weather for decades. It should be noted that the data in Figure 4 exclude some components known to be present in the chromatograms due to the nature of the eluant or the chemical conditions during leaching. Among the excluded species were the anionic species OH-, COS2-, HCOs- and dissolved organic carbon; also excluded was the cationic fraction of Na+ associated with these anions.
As will be discussed subsequently, both samples of purifier waste leachate contained significant quantities of Fe(CN)& (Figure 4);in pH 11 leachate from sample 2, this complex was the dominant anionic species. Excluding the metal cyanide complexes, other anions determined by IC included sulfate in relatively high concentrations and thiosulfate and thiocyanate in lesser amounts. The presence of various sulfur-containingspecies is, of course, expected because sulfur removal wasaprimary motivation for using the purifier. For similar reasons, the scrubber wastes were expected to contain significant amounts of cyanide-bearing compounds. The forms of sulfur and cyanide in the purifier wastes would be influenced by their original chemical forms in the product gas and also by subsequent reactions between these chemicals and the oxide scrubber materials. On the other hand, while the cyanide and sulfur compounds were initially present in chemically reduced forms and were complexed with the metals present in the gas or in the solid purifier reactants, the passage of time plus exposure may have allowed oxidation and biological action to cause changes in the composition of these process wastes. It appears, for example, that sulfur may have been converted to sulfates and thiosulfates while sulfur and cyanide compounds may have reacted to form thiocyanates (1). Peaks on pH 11 leachate chromatograms from each sample were identified by comparison to standard chromatograms and confrmed by standard addition techniques. Figure 5 shows the presence of Fe(CN)$e, Cu(CN)s&,and Ni(CN)2-, although the nickel-cyanide. complex is present only at trace levels. Also present in each sample are two unidentified peaks, which appeared at retention times of about 5 and 10 min, respectively. Envkm. Sd. Techxi.. Vol. 28. No. 1. 1094 101)
3
c
4
5
6
T
B
9
PH
B
Figure 6. pH dependency of CN-containing species, 4841 batch leachates.
0
5
10
15 Elution Time (mid
SAMPLE 1
pH1 1
0
6
.
I
10
f 6 Elution Time (mid
SAMPLE 2 Figure5. Ion chromatogramsfor pH 11leachates analyzedaccording to the conditions given in Table 2: (a) sample 1, (b) sample 2.
The data in Figure 5 demonstrate that hexacyanoferrate(11) is the dominant cyanide species in each sample of purifier leachate. The release of CN-containing components from the purifier solids was clearly a function of pH, as suggested in Figure 3 and confirmed in Figure 6.In general, the trend in pH dependence of leachability was direct: the higher the pH, the higher the concentration of CN complexes in the leachate. This was especially true for hexancyanoferrate(I1). 104 Environ. Sci. Technoi., Vol. 28, No. 1, 1994
Metal-Cyanide Complex Verification. As noted previously, the MGP purifier waste samples were quite heterogeneous and highly contaminated with a variety of organic as well as inorganic substances. These waste samples showed such variability because of numerous factors including differences in formation conditions, source materials, and storage conditions. It was recognized that these differences,together with the uncontrolled levels of auxiliary contamination, could lead to matrix interferences, which in turn had the potential to confound the identification of metal-cyanide complexes. Accordingly, to verify the metal-cyanide complexes identified and confirmed by standard addition and to identify the elemental constituents and stoichiometry of the unknown peaks that appeared in the leachate chromatograms, an analysis was conducted for total metal concentrations on sequentially collected volume fractions of the chromatographic eluent. The results of these analyses are shown in Figure 7 for iron, copper, and nickel. The times at which the respective standards appeared in the eluant also are reported on these figures. The two peaks in the eluant Fe concentration (Figure 7a) show very good confirming evidence that both purifier waste samples contained Fe(CN)&. The results also show, however, the presence of a second peak containing iron. Because of the coincidence of this peak with one of the “unknowns” observed during the UV analysis of the leachates, it was suspected as possibly a second cyanidecomplexing iron species. In order to estimate the cyanide content and, thereby, permit partial evaluation of the stoichiometry of this unknown, the sequential eluant volume collection was repeated on the purifier leachate. This was done to accumulate a quantity of the eluant volume fraction containing the unknown iron complex that was sufficient for total cyanide analysis. The analyses for total cyanide and iron on the eluant fraction yielded an CN:Fe molar ratio of approximately 4:l. This suggests that the molecular formula of the “unknown” Fe-containing peak is approximately Fe(CN)4, but does not preclude the possibility that other sulfur-, oxygen-,or nitrogen-containing ligands may also be present in the complex. The copper concentration data from the sequentially collected eluant volumes (Figure 7b) also verified the presence of Cu(CN)a2- in the leachates. In addition, however, the data give indication of the presence of an additional, but unidentified, copper complex. Because of the nature of the IC method employed, the complexes are
E
?
I,
0.6 1
5 0.4 $60 . 3
Appearance of Fe(CN),-' in standard
(a)
I
Ni(CN)42-; an iron-cyanide complex with CN:Fe ratio of approximately 41, but of uncertain composition; plus a copper-containing complexthat is probably Cu(CN)z-.The most important cyanide complexes, in terms of quantity, were those involving Fe, which comprised over 97 % of the total CN in the two MGP purifier waste samples.
I
Conclusions I 0.0
2
0
4
6
8
10
12
14
16
18
20
Time of fraction collection, min
Appearance of 0
1
in standard
2
0
1.8 1,6
I
4
8
10
12
14
16
18
I
).,(
Appearance of Ni(CN)," in standard
$14 0
6
20
Time of fraction collection, min
I
h
,I,,
'
1
l
)
This research has demonstrated that, although major cations and anions are readily leached from purifier wastes under natural conditions, the cyanide species, which are dominated by hexacyanoferrate(II), are quite insoluble under acidic conditions. It is not clear if the acidity of the wastes is a result of the manner in which they were generated or was produced subsequently through biological or chemical reactions. Free cyanide, if it was ever present in the wastes, would be expected to have been lost through volatilization; no evidence for HCN or CN- was found in this research. Cyanide, in complex form, is solubilized increasingly as the pH rises, with reaction times of minutes to weeks depending on pH and temperature. This behavior has practical consequences for treatment and disposal methods, should this be deemed necessary. For example, soil washing may be a viable treatment step under alkaline conditions, however disposal of the waste without treatment should avoid chemical neutralization. Thermal methods for the removal of CN from the waste may be possible, although acid gas controls for S02, NO, and HCN (if not destroyed) may be required. It would be expected that the removal of CN and NH3 will affect the subsequent behavior of trace metals, although further study is required.
\ I
Acknowledgments ; 0.8
5 0.6
0.0
--
'
0
--I
2
4
6
8
10
12
14
16
18
20
Time of fraction collection, min
Flgure 7. Comparlson of elution times tor complex cyanide species betweensamplesand with the CN standard: (a) Fe(CN)eC,(b) Cu(CNb2-, (c) NYCN),*-, (sample 1 = solid line, sample 2 = dashed line).
certain to be anionic. It was found that, when sodium cyanide was omitted from the chromatographiceluant (see Table 2), both of the copper-containing peaks in Figure 7b were absent. The purpose of cyanide in the eluant is to ensure the stability of cyanide complexes present, thus the disappearance of the Cu peaks is strong, although circumstantial, evidencethat the unknown copper complex contains cyanide. Its temporal position prior to the C U ( C N ) ~peak ~ - suggests a lower ionic charge; hence, it is likely that the peak contains the Cu(CN)2- anion. The data on nickel concentration in the chromatograph eluant provide very good verification of the presence of Ni(CN)2- in both purifier leachate samples, though at concentrations considerably lower than those observed for copper. Considering the results of the IC studies, including the verification work done by direct analysis of eluant volume fractions, it may be concluded that both MGP purifier waste samples contain SCN-; Fe(CN)$-; Cu(CN)s2-;
This research was supported in part by Grant 150W009D from the New York State Center for Hazardous Waste Management. Matching funds were made available by the Gas Research Institute. The authors gratefully acknowledgethe assistance provided by Mr. David G. Linz and Dr. Thomas D. Hayes of the Gas Research Institute, Dr. David V. Nakles of Remediation Technologies, Inc., and Mr. Dennis F. Unites of Atlantic Environmental Services, Inc.
Literature Cited (1) Gas Research 1nstitute.Management of Manufactured Gas
Plant Sites; Report No. 87/0260.1; Gas Research Institute: Chicago, 1987; Vol. I. (2) Middleton, A. C. Past Operations and Present-Day Site Management; Proceedings of the Technology Transfer Seminar, Management of Manufactured Gas Plant Sites; Gas Research Institute: Chicago, 1991. (3) Radian Corp. Survey of Town Gas and By-Product Production in the U.S.1800-1950; US.EPA Report 6001785-004; Government Printing Office: Washington, DC, 1987. (4) Young, T. C.; Theis, T. L. Environ. Technol. 1991,12,10631069. (5) Gould, J. E.; Theis, T. L.; Luthy, R. G. Cyanide in MGP Wastes;Report 89/0165; Gas Research Institute: Chicago, 1989. (6) Edison Electric Institute. Handbook of Manufactured Gas Plant Sites; E E I Washington, DC, 1984. (7) Meeussen, J. C. L.; Keizer, M. G.; vanRiemsdijk, W. H.; deHaan, F. A. M. Environ. Sci. Technol. 1992,26, 18321838. Environ. Sci. Technol.. Vol. 28, No. 1. 1004
10s
(8) Sillen, L. G.; Martell, A. E. Stability Constants of Metal Ion Complexes, Supplement No. 1; The Chemical Society: London, 1971. (9) Smith, R. M.; Martell, A. E. Critical Stability Constants ZV: Inorganic Complexes. 1976, Plenum, New York. (10) Doudoroff, P. Toxicity to Fish of Cyanides and Related Compounds; Report 600/3-76-038; U . S. Environmental Protection Agency: Duluth, MN, 1976. (11) Broderius, S. J.; Smith, L. C. Direct Photolysis of Hexacyanoferrate Complexes: Proposed Applications to the Aquatic Environment; Report 600/3-80-003,U.S. Environmental Protection Agency: Duluth, MN, 1980.
106
Envlron. Scl. Technol., Vol. 28, No. 1, 1994
(12) Meeussen, J. C. L.; Keizer, M. G.; dellaan, F. A. M. Environ. Sei. Technol. 1992, 26, 511-516. (13) Standard Methods for the Examination of Water and Wastewater, 17th ed.; American Public Health Assoc.: Washington, DC, 1989. (14) Determination of Metal Cyanides; Application Note AN 55, Dionex Corp.: Sunnyvale, CA, 1988. Received for review March 30, 1993. Revised manuscript received September 10, 1993. Accepted September 23, 1993." Abstract published in Advance ACS Abstracts, November 1, 1993.
