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Kansas Geological Survey, Bulletin 204, pt. 1, originally published in 1972

Brine Leaching of the Heebner Shale (Upper Pennsylvanian) of Kansas

by Lawrence R. Hathaway, O. Karmie Galle, and Tamara Evans

Originally published in 1972 as part of Kansas Geological Survey Bulletin 204, pt. 1, p. 15-18. This is, in general, the original text as published. The information has not been updated. An Acrobat PDF version of the complete bulletin (15 MB) is also available.


Leaching studies on samples of the Heebner Shale indicate the mobilization of trace elements such as Ni, Co, Mn, and Zn in the presence of chloride brines. The length of time the brines were in contact with the shale as well as the effect of increased temperature was studied. Increased temperature and the presence of SO4-2 improved leaching ability for the chloride brines. Tabulated results show that when some Kansas oil field brines were left in contact with the Heebner Shale for 3 days at a temperature of 80°C, as much as 2.94 ppm Mn, 2.26 ppm Fe, 0.20 ppm Co, 0.53 ppm Ni, 0.10 ppm Cu, and 8.98 ppm Zn was extracted.


Black shales represent large volumes of potential sources of a variety of trace elements. The geochemical mobility of trace elements associated with black shales is determined by the extent to which these elements are fixed in the shales compared to the ability of reacting fluids to produce soluble species of these elements. Many of the trace elements associated with black shales have the ability to form chloride complexes which are soluble in aqueous solutions. This study represents an effort to determine the solubility behavior, and thus mobility, in chloride brines of some of the trace elements (Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb) which are associated with the black shale of the Heebner. A suitable method for the determination of trace elements in chloride brines has been described by Galle (1971) and this method has been employed here to determine the trace element concentrations in the brine leach solutions.

Experimental Method

Samples of the Heebner Shale Member of the Oread Limestone used in this study were taken from a road cut at the SE corner of Lone Star Lake (NE NW sec. 23, T 14 S, R 18 E), Douglas County, Kansas. Large pieces of apparently unweathered shale were rinsed with distilled water, dried at 110°C, pulverized in a titanium carbide shatter box and mixed together. Solutions used consisted of three synthetic chloride brines, distilled water, and three oil field brines--R. Hays # 1 (upper "Squirrel sandstone"), R. Hays #2 (upper "Squirrel sandstone"), and Kerr-Magee ("Cherokee sand").

In the leaching studies 20 g of shale per 100 ml of brine solution were placed in stoppered flasks and allowed to stand, with occasional shaking, for periods of 1-9 days. The flasks were maintained at either room temperature (24°C) or 80°C during the leaching period. After an appropriate length of time, the samples were centrifuged and then filtered through a 0.45µ, filter. The pH of the filtrates was adjusted to 4.5 and separation of the trace elements in 100-ml aliquots of the filtrates was achieved using columns of Dowex A-1 chelating resin adjusted to a pH of 4.5. Elemental analyses were achieved by atomic absorption.

A 1-g sample of shale for the determination of total trace element concentration in the shale was treated three times with 5 ml of 48 percent HF and 5 drops H2SO4, and taken to dryness after each treatment. Next, 150 ml of 10 percent H2O2 was added, stirred, and left overnight. The solution was treated with 20 ml of concentrated HCl, warmed, and filtered. The filtrate volume was reduced to 100 ml, using a flash rotary evaporator, and analyzed directly by atomic absorption.

One 20-g sample of shale was treated with four 100-ml portions of brine to determine effect of successive leachings upon a single sample. Each time the brine and shale were in contact for 24 hours.

The compositions of the synthetic brines are given in Table 1. Brine A corresponds to a synthetic sea water. The oil field brines were found to be low in SO4-2 and had Cl- concentrations of 50,000-70,000 ppm.

Results and Discussion

The concentrations of trace elements found in the leach solutions under varying conditions are given in Tables 2-4. For comparison, the concentrations of trace elements solubilized by HF-H2O2-HCl treatment are listed in Table 5. Coefficients of variation for the various elements determined in the leach solutions are given in Table 6.

Table 1--Ionic composition of synthetic brines.

Brine Ion Total
A 10,900 1,300 410 390 19,600 2,700 70 33.58
B 19,900 40 260   30,700 710   52.06
C 23,400 466 990   33,100 8,400   69.46

Table 2--Leaching data for synthetic brines.

Distilled Water
Concentration in solution, ppm
3 days
6 days
9 days
3 days
Cr   N.D.* N.D. N.D. N.D.
Mn   0.14 0.18 0.25 1.42
Fe   0.14 0.19 0.27 0.38
Co   N.D. N.D. N.D. 0.06
Ni   0.10 0.11 0.26 0.33
Cu   0.03 0.03 0.09 0.09
Zn   0.18 0.59 0.98 2.96
Pb   N.D. N.D. N.D. N.D.
Brine A
Cr N.D. N.D. N.D. N.D. N.D.
Mn 0.02 2.38 2.61 3.79 5.29
Fe 0.11 0.18 0.12 0.22 2.99
Co N.D. 0.13 0.08 0.18 0.25
Ni 0.07 0.45 0.44 0.65 0.80
Cu 0.04 0.05 0.04 0.13 0.10
Zn 0.43 13.0 6.86 4.09 9.72
Pb N.D. N.D. N.D. N.D. N.D.
Brine B
Cr N.D. N.D. N.D. N.D.  
Mn 0.02 2.04 2.06 3.42  
Fe 0.10 0.18 0.14 0.14  
Co N.D. 0.08 0.11 0.18  
Ni 0.06 0.38 0.36 0.65  
Cu 0.06 0.04 0.10 0.10  
Zn 0.17 4.20 3.40 3.71  
Pb N.D. N.D. N.D. N.D.  
Brine C
Cr N.D. N.D. N.D. N.D. N.D.
Mn 0.01 2.52 2.79 4.21 5.70
Fe 0.11 0.14 0.16 0.18 3.90
Co N.D. 0.11 0.10 0.26 0.27
Ni 0.07 0.50 0.56 0.91 0.82
Cu 0.04 0.05 N.D. 0.10 0.11
Zn 0.20 6.46 8.57 6.36 12.80
Pb N.D. N.D. N.D. N.D. N.D.
* Not detected.

Table 3--Leaching data for oil field brines.

R. Hays #1 Brine
Concentration in solution, ppm
3 days
3 days
Cr N.D.* N.D. N.D.
Mn 0.18 3.02 4.94
Fe 0.11 0.12 2.26
Co N.D. 0.13 0.20
Ni 0.07 0.43 0.53
Cu N.D. N.D. 0.10
Zn 0.19 8.58 8.98
Pb N.D. N.D. N.D.
R. Hays #2 Brine
Cr N.D. N.D. N.D.
Mn 0.02 2.82 4.89
Fe 0.09 0.14 2.02
Co N.D. 0.14 0.19
Ni 0.07 0.50 0.69
Cu 0.03 0.02 0.12
Zn 0.19 4.07 7.99
Pb N.D. N.D. 0.48
Kerr-Magee Brine
Cr N.D. N.D. N.D.
Mn 0.03 2.30 4.12
Fe 0.12 0.14 0.71
Co N.D. 0.11 0.17
Ni 0.08 0.30 0.47
Cu 0.05 0.02 0.09
Zn 0.16 2.23 2.95
Pb N.D. N.D. N.D.
* Not detected.

Table 4--Effect of successive leaching on a single shale sample at 24°C.

R. Hays #2 Brine
Successive leachings, concentration, ppm
1st 2nd 3rd 4th
Cr N.D.* N.D. N.D. N.D.
Mn 1.25 1.22 0.77 0.48
Fe 0.20 0.14 0.08 0.09
Co 0.10 0.11 0.07 0.06
Ni 0.45 0.38 0.35 0.33
Cu 0.17 0.12 0.09 0.08
Zn 2.13 1.87 1.93 1.79
Pb N.D. N.D. N.D. N.D.
* Not detected.

Table 5--Trace element concentrations from HF-H2O2-HCl-treated shale sample.

133 35.0 8080 3.92 39.0 18.1 226 18.7
* Equivalent to 20 g shale dissolved in 100 ml brine.

Table 6--Coefficients of variation.

Trace element %
Cr 5
Mn 5
Fe 11
Co 14
Ni 7
Cu 15
Zn 4
Pb 16

The elemental analyses for synthetic brines A, B, and C indicate low background concentrations of Mn, Fe, Ni, Cu, and Zn which are probably due to traces of these elements in the reagents used to achieve the ion-exchange separation of the trace elements from the leach solutions. This background was assumed to be relatively constant throughout the leaching studies, and increases in concentrations above these levels are assumed to be indicative of the effectiveness of the leaching process.

At both 24°C and 80°C, the synthetic and natural chloride brines were found to be more effective than distilled water in leaching trace metals from the Heebner Shale. As noted in Tables 2 and 3, Cr was not detected in leach solutions under any conditions, and Pb was observed in only one 80°C oil field brine extract. The concentration of Fe found in the 24°C extracts is fairly constant (range 0.09-0.27 ppm) and not greatly different from the background values obtained for the three synthetic brines (range 0.10-0.11 ppm). An increase in temperature appears to improve the effectiveness of the brines as well as that of distilled water in leaching Fe from the shale. Copper does not appear to be mobilized to any great extent by the brines at 24°C or 80°C and distilled water is observed to be about as effective as the chloride brines in removal of Cu under the conditions of temperature and shale-brine contact time used in this study.

Chloride brines appear to mobilize Mn, Co, Ni, and Zn, and are generally found to be much more effective than distilled water under similar conditions of temperature and shale-brine contact time. Increasing the temperature of the brine again is found to improve the effectiveness of the leaching process.

Maturation studies using distilled water and synthetic brines A, B, and C for periods of 3, 6, and 9 days of shale-brine contact at 24°C suggests an increase in the extent of leaching with time for Mn, Fe, Co, Ni, and Zn. The data for Fe and Co are not extensive enough to verify this trend. The data for Zn in the brines show no clear-cut trend, whereas a trend toward greater leaching with greater shalesolution contact time is noted for distilled water extracts. Factors such as non-uniform shaking of the shale-brine mixtures during the maturation studies and slight variations in the bulk of the mixed shale powder used could be responsible for some variation in the general trend established by the maturation studies.

The effect of repeated leaching upon a single shale sample is shown in Table 4. The concentrations of Mn, Fe, Co, and Cu in the fourth extract are about one-half or less of the concentration of those elements in the first extract. The value of Fe appears to reach the background level with the third leaching. The concentrations of Ni and Zn are found to remain relatively high even after four extractions.

A feeling for the general efficiency of the brines in the leaching studies can be obtained by comparing the data of Tables 2-4 with that of Table 5. Table 5 shows the concentrations of the various trace elements expected in 100 ml of brine leach solution if the entire trace element content was extracted from the 20 g of shale used in each experiment. Considering the 80°C runs of the chloride brines to be the most effective in removing the trace elements from the shale, the leaching yields range from about 0.05 percent for Fe to about 14 percent for Mn. It appears that Cr, Fe, and Pb are tightly fixed in the black shale and not easily removed. Increasing the temperature beyond 80°C would presumably increase the effectiveness of the leaching process for Pb and other less mobile elements.

The data for the synthetic brines A, B, and C also provide an indication of solubility trends as a function of brine composition and salinity. The salinity of brine B is nearly 70 percent greater than that of brine A, and the chlorinity of brine B is nearly 50 percent greater than that of brine A, yet, brine A and brine B show about the same effectiveness in leaching except for Mn and Zn where brine A appears to be somewhat more effective. Brine C also has a fairly high salinity and a chlorinity similar to that of brine B and about 4 times as much SO4-2 as brine A. Brine C appears to be somewhat more effective than brine A in leaching Mn, Ni, and Zn from the shale as compared to brine A.

It appears the most effective combination of chlorinity and salinity has been reached or exceeded in brine A. Compositional changes in the brine do appear to alter the geochemical behavior of chloride brines. This suggests the need to determine the leaching behavior of brines rich in ions such as SO4-2 and CO3-2. Studies at extended temperature ranges are also desirable in order to determine how firmly the trace elements are fixed in the black shales.


Galle, O. K., 1971, The determination of trace elements in brine by atomic absorption: Appl, Spectry., v. 25, no. 6, p. 664-667.

Kansas Geological Survey, Brine Leaching of the Heebner Shale (Upper Pennsylvanian) of Kansas
Placed on web March 24, 2016; originally published in March 1972.
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