GN88 ESa)88 C-3 CL^S^j^t Abundance of Trace and Minor Elements in Organic and Mineral Fractions of Coal J.K. Kuhn, F.L. Fiene, R.A. Cahill, H.J. Gluskoter, and N.F. Shimp Illinois Institute of Natural Resources STATE GEOLOGICAL SURVEY DIVISION, URBANA Jack A. Simon, Chief ENVIRONMENTAL GEOLOGY NOTES 88 August 1980 URBANA Cover figure: Comparisons of concentrations of organically associated elements independently derived from mineral-matter-free (acid-treated) coal and float/sink gravity fractions of coal. (Left) Illinois No. 6 seam; (Right) Pittsburgh No. 8 seam. Kuhn,J. K. Abundance of trace and minor elements in organic and mineral fractions of coal /J. K. Kuhn ... et.al. -- Urbana, III. : State Geological Survey Division, August 1980. 67 p. ; 28 cm. -- (Environmental geology notes ; 88) Printed by authority of the State of Illinois/1980/2500 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 2658 Abundance of Trace and Minor Elements in Organic and Mineral Fractions of Coal J. K. Kuhn,* F. L. Fiene,* R. A. Cahill,* H. J. Gluskoter,* and N. F. Shimp t * Formerly at ISGS. Now at Institute for Mining and Minerals Research, P. 0. Box 13015, Lexington, KY 40583. ' Illinois State Geological Survey. ■r Formerly at ISGS. Now at Exxon Production Research Co., P. O. Box 2189, Houston, TX 77001 • Illinois Institute of Natural Resources STATE GEOLOGICAL SURVEY DIVISION, URBANA ENVIRONMENTAL GEOLOGY NOTES 88 Jack A. Simon, Chief August 1980 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/abundanceoftrace88kuhn CONTENTS Figures iii Tables . iv Abstract v Acknowledgments vi I. Introduction 1 II. Conclusions and recommendations 3 III. Methods 4 Sampling 4 Analytical 4 Chemical demineral ization 5 Physical demineral ization 8 Exchangeable ions 10 Displaying washability data 10 Calculating the organic affinity index 12 Mineralogic methods 17 IV. Results 18 Whole coal and demineral ized coal 18 Concentrations of organically associated elements 18 Exchangeable and soluble ions 43 Mineralogy 43 V. Discussion 50 Validity of organically associated elements 50 Variability of organically associated elements 53 Comparative data 54 Importance of mineral matter 58 Coal cleaning application 58 VI. References 64 FIGURES Number Page 1 Germanium in specific gravity fractions (Davis Coal) 11 2 Gallium in specific gravity fractions (Blue Creek Coal, AL) 11 3 Washability curve of sulfur in specific gravity fractions (Herrin [No. 6] Coal). ... 12 4 Washability curve for chromium in specific gravity fractions (Herrin [No. 6] Coal) . . 13 5 Adjusted washability curve for chromium in specific gravity fractions (Herrin [No. 6] Coal) 14 6 Washability curves for lead in specific gravity fractions (Herrin [No. 6] seam). ... 16 7 Washability curves for boron in specific gravity fractions (Pittsburgh [No. 8] seam, WV) 16 8 Organic affinity index for total sulfur and ratio of organic to total sulfur in 9 washed coals 17 9 Mineral distributions in a single sample (Herrin [No. 6] Coal) 46 10 Comparison of independently determined concentrations of organic sulfur in 9 coals . . 51 11 Comparison of independently determined concentrations of organically associated trace elements (Davis Coal) 51 12 Comparison of independently determined concentrations of organically associated trace elements (Pittsburgh [No. 8] seam, WV) 51 13 Comparison of independently determined concentrations of organically associated trace elements (Rosebud Coal, MT) 51 14 Comparison of independently determined concentrations of organically associated trace elements (Herrin [No. 6] seam) 52 15 Elemental concentrations of calcium in ammonium acetate (ion-exchanged) samples. ... 52 iii TABLES Number Page 1 Whole coal selections 5 2 Analytical methods used in this study 6 3 Effect of physical and chemical treatment on elemental concentrations (Illinois No. 6 Coal) 7 4 LAH extraction versus HNOt extraction 9 5 Chromium in specific gravity fractions (Herrin [No. 6] Coal) 13 6 Comparison of concentrations of trace and minor elements in raw and demineralized (MMF) Coal 19-30 7 Mean concentrations in mineral-matter- free and raw coals 31 8 Identification of coal samples and gravity separations 32-33 9 Concentrations and organic affinities of elements (Herrin [No. 6] Coal) 34 10 Concentrations and organic affinities of elements (Davis Coal) 35 11 Concentrations and organic affinities of elements (Herrin [No. 6] Coal) 36 12 Concentrations and organic affinities of elements (Pittsburgh [No. 8] seam, WV) . . . 37 13 Concentrations and organic affinities of elements (Pittsburgh [No. 8] seam, WV) . . . 38 14 Concentrations and organic affinities of elements (Pocahontas [No. 4] seam, WV) . . . 39 15 Concentrations and organic affinities of elements (Blue Creek seam, AL) 40 16 Concentrations and organic affinities of elements (Rosebud seam, MT) 41 17 Concentrations and organic affinities of elements (Black Mesa Field, AZ) 42 18 Comparison of concentrations of minor and trace elements in coal and NH.AC extracted residue 44 19 Results of qualitative mineral analysis of low- temperature ashes 45 20 Results of mineralogical analysis 47-48 21 Results of clay mineral analysis (<2ym fraction of LTA) of 2 coals 49 22 Prediction of mean elemental concentrations in mineral -matter-free coal for 3 basins. 55 23 Total retention percentages of elements and concentration summations for demineralized coal and ash or mineral -matter content for whole coal 56 24 Mean MMF values for coal compared to plant material and crustal abundance (ppm) ... 57 25 Elements commonly associated with the principal minerals found in coals 59 26 Organic association of trace elements in coal: Illinois coals 60-62 IV ABSTRACT New data on the abundance and mode of occurrence of trace and minor elements in coal are presented in this report. A summary of related studies previously conducted at the Illinois State Geological Survey is also included. Twenty-seven coals, fifteen from Illinois, three from West Virginia, three from Alabama, two from Montana, and one each from Pennsylvania, Arizona, North Dakota, and Wyoming, were selected for study in the new phases of this work. Each coal sample underwent acid treatment, and selected coals underwent float/sink and ion exchange treatments. From these treated samples, coal fractions were obtained and analyzed by various methods. An enriched organic-matter fraction, virtually free of mineral matter, was prepared by extracting coal under prescribed conditions with dilute nitric, hydrofluoric, and hydrochloric acids. Excluding organic sulfur, the resulting demineralized product contained no detectable coal minerals and only 250 to 600 ppm of ash-forming elements. These elements, and certain of the more volatile ones, are securely bound within the organic coal matrix; consequently, they were termed organically associated. The concept of an organic affinity index was used to measure the tendency of an element to associate with the organic matter in coal. Of the elements studied, B, Be, Br, Ge, and Sb were consistently classified organic; sul fide-forming elements, Zn, As, Cd, and Fe, were classified inorganic; and others, such as Al , Ca, Ga, Ni , P, Si, and Ti , were intermediate or variable in their association. Generally, concentrations of organically associated trace elements were low, the lowest of which occurred in western coals. Conversely, western coals contained the greatest number of elements associated with organic matter. Three general observations were made: (1) the total concentration of an element in coal is not indicative of its concentration in the organic phase; (2) because concentrations vary widely, accurate appraisals of trace and minor element associations by the methods used require that each coal be evaluated separately; and (3) the highest concentrations of trace and minor ele- ments in coal are associated with mineral matter. The validity (accuracy) of results for elements associated with the organic phase of coal was supported by the unexpectedly good agreement between two independent sets of values. One set was obtained by direct analysis of the acid-treated coal; a second set of values was derived from extrapolation of adjusted washability curves to zero percent recovery. Initially, these curves were used for calculating the organic affinity index. The values obtained by extrapola- tion represent the theoretical concentration of an element in a coal when no mineral matter is present. Further evidence for valid results stems from the fact that acid treatment did not alter organic sulfur concentrations and, therefore, probably did not significantly alter the coal structure itself. In some coals, variations existed between values obtained from the two independent pro- cedures for estimating organically associated elements; however, these differences can be explained by exchangeable ions on coal surfaces and by the solubility of some minerals. Acid treatment of coal removed exchangeable and soluble ions, but float/sink procedures did not. Failure to remove these elements from the coal organic fraction inflated the organic affinity index. Differences were apparent for Na, Ca, Mg, Ba, and B in western low-rank coals where, for example, more than 70 percent of the total Ca and Mg occurred in soluble or exchangeable forms. When allowance for such differences is made, the values for organically associated elements obtained by the two methods are in good agreement; they are thought to be reasonable estimates of concentrations in coal organic matter. Despite evidence that many elements exhibit some degree of organic association, most of the trace and minor elements in these coals were in a mineral form. Thus many elements could be significantly reduced by physical cleaning procedures. The degree of reduction depends on the mineral, its size, and its distribution. Detailed mineralogic and microscopic analyses of low- temperature ash residues were made of gravity separations from nine of the coals. The same mineral data were obtained for 26 of the 27 whole coals studied. Western coals had distinctly different mineral suites than Illinois and eastern coals; kaolinite predominated over other clay minerals, and significant amounts of bassanite were formed during the low temperature ashing process. Western coals also contained minor quantities of calcite, quartz, and pyrite. Gen- eral associations were compiled for trace elements with minerals. This report was submitted in partial fulfillment of Contract No. 68-02-2130 by the Illinois State Geological Survey and the University of Illinois, under partial sponsorship of the U.S. Environmental Protection Agency, Industrial Environmental Research Laboratory, Fuel Process Branch, Research Triangle Park, NC. ACKNOWLEDGMENTS This publication is based on data which were obtained with partial support from U.S. EPA Contract No. 68-02-2130 and U.S. EPA Grant R804403 and R806654. This financial support is gratefully acknowledged as is the cooperation of the University of Illinois, which administered the contracts. The coal companies in Illinois and other states contributed greatly to the success of this project by allowing the collection of samples in their mines. An expression of gratitude is extended to S. D. Hampton, L. R. Henderson, E. Fruth, L. R. Camp, M. Siefrid, R. A. Keogh, L. B. Kohlenberger, R. D. Harvey, S. M. Rimmer, J. A. Schleicher, R. J. Helfinstine, J. Thomas, Jr., and others at the Illinois State Geological Survey for their efforts on the project. Special thanks are due E. S. Gladney, Los Alamos Scientific Laboratories, NM, who performed the boron determinations, and to C. W. Kruse for helpful comments on the manuscript. VI SECTION I INTRODUCTION Although coal is the most abundant fossil fuel resource in the United States, environmental restraints are preventing its optimum use. A primary cause of these restraints is the occurrence of accessory elements and minerals in association with the coal. Their abundance and especially their type of association or combination can have a significant effect on the ease with which these elements and minerals are removed before the coal is used. For example, organic sulfur, which is not removed from coal by physical cleaning methods, appears in process streams and effluents as an undesirable constituent and must be removed later. Adverse characteris- tics may be identified in other organically associated elements in coal. An element's form does affect the extent to which it can be removed or recovered. Little direct evidence for the kinds and concentrations of elements in the organic fractions of coal is available. That some elements in coal have either a high organic or inorganic affinity was considered more than 40 years ago by V. M. Goldschmidt, who pioneered modern investigations of trace elements in coals. He identified trace elements in inorganic (mineral) combination in coals. He also postulated the occurrence of metal- organic complexes in coal; the observed concentrations of vanadium, molyb- denum, and nickel were attributed to the presence of such complexes (Goldschmidt, 1935). Nicholls (1968) plotted the concentration of an element in coal or in coal ash against the ash content of the coal. Diagrams depicting a number of such points for a single coal seam, or for a group of coal seams in a single geographic area, were interpreted for degree of inorqanic or organic affinity of the element. Nicholls described elements as (1) associated with the organic fraction, (2) generally associated with the inorganic fraction; and (3) elements that could be associated with either or both fractions. Horton and Aubrey (1950) handpicked pure vitrain samples from coals and separated the samples into five different specific gravity fractions. They then analyzed these fractions for minor elements. For the three vitrains that were studied, they concluded that beryllium, germanium, vana- dium, titanium, and boron were contributed almost entirely by the inherent (organically combined) mineral matter and that manganese, phosphorus, and tin were associated with the adventitious (inorganically combined) mineral matter. Results of investigations of the organic-inorganic affinities of trace elements in coals were published by Zubovic, Stadnichenko, and Sheffey (1960, 1961, 1964). In more recent articles Zubovic (1966, 1976) listed 15 elements in decreasing order of percentage of organic affinity. He suggested also (1976, p. 50) that the metals having high organic affinities in coal are present as chelates. Ruch, Gluskoter, and Shimp (1974) and Gluskoter (1975) published tables of organic affinities for 21 elements determined on four samples of Illinois coals, which had been separated into specific gravity fractions in the laboratory. They listed the elements in decreasing order of organic affinity, but numerical values were not given for the index. Since these results were published, Gluskoter et al . (1977) and Kuhn et al . (1978) reported washability data for up to 53 elements and 10 coal parameters from seven additional coals. They calculated an index of organic affinity from washability curves for the elements determined in the washed coals. Gluskoter et al . (1977) presented tables that listed the organic affinity index values for nine coals and ranked the elements as "organic," "intermediate-organic," "intermediate inorganic," and "inorganic." Each coal analyzed was ranked separately because an element that is "organic" in a sub-bituminous coal from Wyoming may be "inorganic" in an Appalachian coal. A study recently completed at the Illinois State Geological Survey and briefly reported by Kuhn et al . (1978) used chemical demineralization of coal as a totally independent approach. The study obtained results that were applied to the determination of organic affinities. Fiene, Kuhn, and Gluskoter (1978) reported on the mineral phases found in the same coal samples as those studied by Gluskoter et al . (1977), Kuhn et al . (1978), and Kuhn, Fiene, and Harvey (1978). The study determined minerals in both the low temperature ashes of the coals and their specific gravity fractions. Data from these studies are summarized in this report and are combined with results of our new research to provide a single source of information on the occurrence of organically associated trace elements in coal . The scope of this work includes nine coals, separated into specific gravity fractions, from the eastern, central, and western portions of the United States. To gain a wider distribution of sample types, another 18 coals were also subjected to chemical demineralization. Ion exchange determinations were performed on seven coals. Chemical and mineralogical analyses were made on all of these materials; however, in an effort to remain as concise as possible, only the values regarded as pertinent to conclusions for this study are presented. SECTION II CONCLUSIONS AND RECOMMENDATIONS The chemical form of an element influences its behavior during coal processing and pyrolysis. In this study, procedures for determining the forms in which minor and trace elements occur in coal were investigated. Two methods— chemical and physical— were used to prepare highly enriched organic fractions of coal. Comparison of results from analyses of these fractions enabled reasonable estimates to be made of the concen- trations of up to 45 minor and trace elements associated with coal organic matter. These values, all of which were low in comparison to total amounts, are believed to represent the theoretical lower limit attainable for an element in cleaned coal. The concept of an organic affinity index to measure the tendency of an element to remain with the coal organic matrix is reviewed and expanded. Forms of elements other than organically associated ones were also investigated; significant concentrations of exchangeable and acid soluble elements, e.g., Ca and Mg, are more abundant in western coals than in eastern or Illinois Basin coals. Unless these elements were first removed or taken into account, estimates of the organically associated elements were inflated for the low rank coals. In addition, the western coals con- tained different mineral suites. General mineral associations were compiled for trace and minor elements. Chemical form is believed to be only one of the factors controlling element behavior. Preliminary evidence from our current research indicates that the occurrence and distribution of certain elements in the products of pyrolysis is also influenced by the conditions under which coal is pyrolyzed. Thus, an element with a high organic affinity— or two different elements with equally high affinities— may report to very different coal fractions when pyrolyzed under different conditions. A knowledge of process conditions and organic affinities needs to be considered if accurate estimates are to be made of distributions of elements in process streams. Organic affinity indexes, if made sufficiently accurate for a range of coals, could be used in conjunction with total concentrations for deter- mining, in addition to sulfur, the chemical forms of many elements, for estimating the theoretical percentage of an element that can be removed by coal cleaning, and for predicting material balances in the coal products and wastes. Before this is feasible, however, additional evidence for the validity of the organic affinity concept is needed. SECTION III METHODS SAMPLING Twenty-five of the 27 coals used in this study were face-channel or com- posite face-channel samples collected in coal mines by Illinois State Geolo- gical Survey personnel. The two exceptions were obtained from a Federal agency. The 25 samples were hand cut and represent the full face of the coal seam excluding mineral bands, nodules, and partings greater than 1 cm thick, following an established procedure described by Holmes (1911). All were air dried and riffled according to standard procedures of the American Society for Testing and Materials (1978a). Representative portions of the raw coal were stage ground to -60 mesh (250 urn) for chemical analysis and low- temperature ashing and to -100 mesh (149 urn) in a Pitchford uniform-particle- size grinder for trace element determinations. Subsamples used for acid demineralization were comminuted to less than -325 (44 urn) mesh in a ball mill. Table 1 lists the whole coal samples used in these projects; each material is assigned an analysis number ("C" number), which is used for identification throughout this report. ANALYTICAL Analytical methods used for the analysis of samples are given in table 2. Details of these methods were reported by Gluskoter et al . (1977), except for the energy dispersive X-ray fluorescence method, which is contained in Ruch et al . (1979). Although the methods are the same, the elements determined by each method are not entirely comparable with those described by Gluskoter et al . Methods requiring ashing procedures, e.g., atomic absorption and optical emission, could not be used because of the extremely low level of ash in the acid demineralized coal (MMF). Except in the case of Be, attempts to analyze whole coal samples by optical emission failed because the necessary sensitivity could not be achieved. In most cases, for any particular element, a single method was used to analyze an entire set of samples. However, for the nine float/sink sets, different methods were used for some elements and could bias results, espe- cially at very low concentrations. This study uses three different approaches to the investigation of the mode of occurrence of trace elements in coals. The first approach is based on differences in specific gravity or "coal washing" and seldom, if ever, results in a complete separation of mineral matter from the coal. Rather, a fractionation results in which the parts are enriched in either mineral or organic matter. A second approach, which is basically a chemical demineral- ization of the coal, was used in an attempt to achieve a more complete sepa- ration of the organic and mineral fractions of coal than is possible by gravity separations. Extraction of exchangeable ions with a neutral, buffered solution was the third approach used. TABLE 1. Whole coal selections Number Coal seam State C-18126 t C-16543 C-16993 C-17001 * C-18304 C-18560* C- 18704 C-18816 C- 18820* C-18841 *t C-18848*t C-18857 C-19000*t C-18571 C- 18844 C-19824 *+ C-19854 *t C- 18824 C-18440t C-18748 C-18320 C-18368 C-18445 C-18457 C-14684 C-15999 C-16173* Herrin (No. 6) Herrin (No. 6) Herrin (No. 6) Davis De Koven Herrin (No. 6) Herrin (No. 6) Mammoth Pocahontas (No. 4) Pittsburgh (No. 8) Blue Creek Herrin (No. 6) Black Mesa Field Herrin (No. 6) Pittsburgh (No. 8) Pittsburgh (No. 8) Rosebud Johnson Noonan Abbott Fm. Herrin (No. 6) Herrin (No. 6) Rosebud Hanna 24 Herrin (No. 6) Herrin (No. 6) Herrin (No. 6) Ill- no is Ill- no is 111- nois 111- no is Illl nois nil nois 111 inois Montana West Virginia West Virginia Alabama 111 inois Arizona 11 1 inois Pennsylvania West Virginia Montana Alabama North Dakota 111 inois Illinois Illinois Montana Wyoming Illinois 111 inois 11 1 inois *Samples for which gravity separations were made. rSamples for which ion exchange determinations were made. CHEMICAL DEMORALIZATION The method used to chemically remove minerals from the organic fraction of the coal is a variation of the procedure for the determination of forms of sulfur in coal (American Society for Testing and Materials, 1978b), in which HC1 and HN0 3 are used under prescribed conditions to extract sulfate and pyritic sulfur. In this study, HF is also used to dissolve the silicate minerals in a manner similar to that described by Bishop and Ward (1958) and by the International Organization for Standardization (1974). The coal was first floated at 1.40 specific gravity in perchloroethylene and naphtha to reduce the mineral phases, especially pyrite. Dissolution of TABLE 2. Analytical methods used in this study Instrumental neutron activation: Fe, Na, K, Mn, Sc, Cr, Co, Ni , Zn, Ga, As, Se, Ba, Rb, Sr, Mo, Sb, Cs, Ba, La, Ce, Sm, Eu, Tb, Dy, Yb, Lu, Hf, Ta, W, Th, U, I,* Ag,* Au* X-ray fluorescence— Wavelength dispersive: Si, Al, Fe, Ca, Mg, Ti , P, Mn, V, Cu, Pb Direct reading optical emission: Be Prompt gamma ray/neutron activation:"^ B X-ray fluorescence — Energy dispersive: Ba, Cd, I,* In,* Sn,* Te* *Elements not reported. Most values were below detection limits. +Work performed by E. S. Gladney, Los Alamos Scientific Laboratories, NM. the minerals in the demineralizing solutions could add to the concentration of elements associated with the organic matter, and it was deemed desirable to reduce elemental concentrations in the solutions as much as possible. We have assumed, as others have in the past, that the coal organic material is unaltered by this process, although little evidence is available to support or disprove the assumption. The float fraction was then comminuted to less than -325 (44 ym) mesh, and 10-gram samples were placed in a flask containing a cold finger condenser and 50 mL of 10 percent HN0 3 and refluxed for 1, 2, or 3 hours. The materi- als were quantitatively removed from the flask and were filtered, washed, and dried at room temperature overnight. The samples were then placed in poly- ethylene flasks, covered, and allowed to digest in 49 percent HF at 70°C for periods of 1, 2, or 3 hours. The material was again quantitatively removed from the flasks, filtered in plastic funnels, washed, and dried. Finally the materials were placed in a flask and, utilizing a cold finger condenser, were refluxed for 1 hour with 25 percent HC1 at approximately 100°C. After refluxing, the materials were quantitatively removed from the flasks, fil- tered, washed, and dried. (Yields of coal organic material from this pro- cedure were not measured.) The samples were subsequently analyzed by the analytical methods in table 2. A number of coals were processed by this procedure to ascertain the conditions for use with subsequent samples. An example of the results is shown in table 3. It was concluded from these tests that no significant advantage was gained from refluxing the materials for 3 hours. Because the intent was to cause as little change in the nature of the coal as possible, TABLE 3. Effect of physical and c hemical treatments on the concentrations of some e lements in a Herri n (No . 6) Coal sample 1-hr 2-hr 3- ■hr Raw coal 1.40 (%) float (ppm) treatmen (%) t* (ppm) treatment (%) ( * ppm) treatment * Element (*) (ppm) (%) (ppm) Al 1 .40 1 .08 124 35 31 Si 3 .20 2 .15 250 41 42 Ca .51 .094 33 25 23 K .13 .11 1 1 1 Na .04 .027 7 5 6 CI .05 S 6 .45 3 .59 2.64 2.52 2.54 Fe 2 .60 .90 170 66 65 Ti .06 .08 25 11 14 Organic S 2 55 2 .66 2.64 2.52 P 50 13 9.7 <1.0 <1.0 As 3.4 2.8 .1 .1 .1 Pb <.l <.l <.l <.l <.l Br 3.5 3.4 2.4 2.9 2.5 Cu 13 13 3.4 2.1 2.2 Ni 24 7.5 2.5 <1 1 Zn 43 20.5 8.8 4.4 4.0 V 36 28 6.1 3.5 3.3 Rb 23 10 <1 <1 <1 Cs 2.0 .7 <.l <.01 <.01 Ba 54 42 21 3.6 2.8 Sr 28 10.3 1.8 1.3 1.1 Sc 4.1 2.8 .9 .5 .5 Cr 21 16.8 8.8 6.2 6.1 Co 5.5 3.7 .4 .4 .4 Ga 2.4 2.8 .9 .6 .6 Se 4.3 1.4 .2 .3 .2 Sb .4 .2 .1 .1 .1 Hf 1.1 .5 .1 .1 .1 W .5 .3 .1 La 6.1 3.4 .9 .6 .6 Ce 25 7.3 1.8 1.5 1.5 Sn .8 .8 .4 .35 .3 Eu .2 .2 .1 .1 .1 Dy 1.2 .6 .5 .4 .5 Lu <.02 .02 Yb .8 .5 .2 .20 .2 Tb .4 .1 .1 .09 .1 Th 3.6 1.9 .9 .88 .9 U 1.9 .5 .2 .09 .1 Mo 18 3.5 .5 .44 .4 Hg .23 .1 Mn 60 10.3 .4 .3 .2 NOTE: All values normalized to raw coal ♦Includes HN0 3 and HF but not HC1 . the 2-hour refluxing and digestion procedure was adopted. This procedure was selected although it is recognized that in some instances, such as, in peat or materials with high silicon content, total elimination of the mineral -matter content in coal may not result. Further tests were made to determine the extent to which the coals were demineralized. The acid-extracted coal product was subjected to low tempera- ture ashing, a process which destroys organic matter but leaves minerals relatively unaltered. Ash percentages ranged from 0.32 percent to 1.69 percent, and x-ray diffraction analysis of the residues failed to detect any of the minerals originally present in the whole coals. Only traces of chlo- ride and fluoride were detected, and these probably originated in the acid treatment. The absence of detectable minerals from the whole coal supported the belief that the samples were now virtually free of mineral matter. It is known that HN0 3 oxidizes organic materials; consequently, a second procedure was investigated using the reducing agent lithium aluminum hydride (LAH), instead of HN0 3 , for removal of pyrite and other sulfides. Previous work has shown the procedure to be an acceptable and, in some instances, a preferable substitute for the HN0 3 digestion (Lawlor, Fester, and Robinson, 1963; Kuhn, Kohlenberger, and Shimp, 1973). Table 4 compares the results of the two procedures, and although a few minor differences exist (e.g., Fe and Mn), the two sets of values compare quite favorably. While the procedure using LAH yields approximately the same values as the nitric acid method, the latter was selected because it requires less time and is less hazardous. Another aspect which was considered during development of the deminer- alization procedure is the common occurrence of minute, widely disseminated mineral grains, which may be occluded within organic coal particles. For this reason, the coals extracted for this study were pulverized to a very fine size (approximately -325 mesh) after the 1.40 gravity separation was performed. Because some mineral particles occur as submicron crystallites, the data determined may well represent the limits to which the coal can be cleaned by practical methods. The terms "organic association" and "organic affinity" rather than "organic combination" are, therefore, preferred for elemental concentrations in "mineral -matter-free" coal. PHYSICAL DEMORALIZATION About half of the coals produced in the United States are "washed" or "cleaned" prior to delivery to the consumer. Cleaning involves reducing the content of ash and sulfur of the coal by removing a portion of the mineral matter associated with the coal. Because specific gravities of the minerals in coal are from two to four times greater than that of the organics (macer- als) in the coal, conventional coal-cleaning techniques involve specific gravity separations. Nine coal samples were separated into specific gravity fractions and were analyzed for major, minor, and trace elements. Gravity separations were made on a 3/8-inch by 28-mesh fraction, obtained by stage grinding and screening the coal. The sized coal was separated into five or six speci- fic gravity fractions ranging from 1.28 float to 1.60 sink in mixtures of per- ch! oroethylene and naphtha. Chlorine values in the washed coals are unreli- able because relatively large and variable amounts of this element may have TABLE 4. LAH extraction versus HN0 3 extraction IL No. 6 Subbituminous IL No. 6 IL No. 6 C- 14684 C- 18457 C-15999 C-18560 LAH HN0 3 LAH HNO3 LAH HNO3 LAH HNO3 Element (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) Al 45 82 115 78 282 77 400 35 Si 65 98 83 69 122 81 95 41 Ca 10 19 21 16 74 41 80 25 K <10 <10 <10 <10 <2 <1.1 <5 1 Na <4 1 21 11 4 6 18 6 Fe 700 93 800 56 900 64 700 66 Ti 58 58 43 30 60 56 100 90 P 2 5 <1 <1 7 5 6 <1 V 4 6 2.0 2.1 4 7 5 3.5 Cu 2.2 2.2 2.1 2.4 1.6 1.4 2 2.1 Rb <1.0 <1.0 <.l 1.2 <1 <1 <1 <1 Cs .1 .06 <.l <.l <.l .1 Ba 1.60 Specific gravity fraction ISGS 1980 Percentage of recovery Figure 2. Gallium in specific gravity fractions of a sample from the Blue Creek coal from Alabama. Left: Washability curve. Right: Distribution of gallium in individual fractions. 11 Sulfur is present in coals in both organic and inorganic combinations; standard analyses report the varieties of sulfur as sulfate sulfur, pyritic sulfur, and organic sulfur. In a sample from the Herri n (No. 6) Coal in Illinois, the washability curve for total sulfur shows the contribution from both organic and inorganic sulfur (fig. 3). The sulfur content decreases rather rapidly in the washed coal as that part that is concentrated in the heavier mineral - matter-rich portion (inorganic sulfur) is removed. Then the curve flattens because the lighter coal fractions also contain appreciable amounts of sulfur (organic sulfur) . 3 100 20 40 60 80 Percentage of recovery ISGS 1980 Figure 3. Washability curve of sulfur in specific gravity fractions of a sample from the Herrin (No. 6) Coal Member. METHOD OF CALCULATING THE ORGANIC AFFINITY INDEX OF AN ELEMENT Washability curves and histograms of washability data are effective means of depicting the mode of combination of elements in coal— they indicate whether the elements are associated with the organic or inorganic fractions of the coal. However, a much easier means of comparing results for different elements or coals was needed. Therefore, an attempt has been made to quan- tify the information presented on the curves by producing an "organic affinity" index. The present report expands upon the work of Gluskoter et al . (1977) and clarifies both the rationale and the techniques used to obtain a value for an index of organic affinity. This is both appropriate and necessary because certain values obtained during the derivation of the index are germane to the verification of the elemental concentrations determined in demineralized coal, The decision to name the index "organic affinity" rather than "inorganic affinity" was arbitrary; one is the inverse of the other. The shape of the washability curve is dependent upon the mode of occur- rence of the element, the analyses of which are plotted on the curve. There- fore, the area under the curve is also dependent upon the mode of occurrence of the element. The value for the organic affinity index for a specific element is obtained by calculating the area beneath the washability curve. This calculation is done on a curve that has been drawn to a predetermined and constant scale (normalized) and on a curve that has been adjusted for that part of the mineral matter that is inseparable from the lightest coal fraction. An example of the calculations necessary to obtain the organic affinity index follows using the data for chromium in table 5. A normal washability curve can be constructed with cumulative concentration values generated from the following equation: rAiDDMm [CALPPM(I-I) • SUMPCT(I-l)] + [RECPCT(I) - ANLPPM(I)] LALPm(lj SUMPCT(I) " where, 12 TABLE 5. Chromium in specific gravity fractions of a washed sample of Herrin (No. 6) Coal in Illinois (normal and adjusted cumulative concentrations) Percentage Cumulative Cumulative Cumulative Specific of raw Chromium Low percentage of chromium Adjusted adjusted Analyses gravity coal (ppm) temperature raw coal (ppm) chromium chromium (ppm} number fraction (RECPCT) (ANLPPM) ash (%) (SUMPCT) (CALPPM) (ppm) (CALPPM) C18123 C18124 C18125 C18126 C18127 C18128 1.25F 1.29FS 1.33FS 1.40FS 1.60FS 1.60S 36.1 17.4 14.7 9.3 6.9 15.6 8.0 12 16 25 33 71 3.84 88.4 36.1 8.0 4.9 4.9 53.5 9.3 8.9 6.2 68.2 10.7 12.9 7.7 77.5 12.5 21.9 9.4 84.4 14.1 29.9 11.1 100 23.0 67.9 19.9 CALPPM = the cumulative elemental concentration, SUMPCT = the cumulative coal recovery percentage, RECPCT = the coal recovery percentage in the fraction being calculated, and ANLPPM = the analytical concentration of the element in the fraction being calculated. This curve (fig. 4) graphs the cumulative concentrations (column 7) versus the cumulative percentage of recovery (column 6) in table 5. For ease of handling the data and for making additional calculations, the washability curve is plotted in a square format in which the lengths of the abscissa and ordinate at 100 percent recovery are equal. In this case, the washability curve (fig. 4) suggests chromium is princi- pally in the inorganic form; but even the cleanest fraction tested has 8 ppm chromium, and if the curve were extrapolated to the vertical axis, it would intersect well above the origin. The separation of mineral matter from or- ganic matter in specific gravity fractions of coal is not absolute; mineral matter is present in the cleanest (lightest) gravity fraction that could pos- sibly be obtained. Some of the chromium may be present as part of this insep- arable mineral matter; therefore, ad- justment of the curve for this possi- ble contribution must be made before calculating the area under the curve. The amount of inseparable mineral matter is assumed to be equal to the percentage of low temperature ash in the lightest gravity fraction. The low tem- perature ash is determined by radio-frequency ashing at a tem- perature below 150°C. The other necessary assumption is that the con- centration of chromium in the mineral matter (LTA) of the 1.25 float frac- tion (lightest fraction in this case) 23.0 100 ISGS 1980 Percentage of recovery Herrin (No. 6) Coal Figure 4. Washability curve for chromium in specific gravity fractions of a sample of the Herrin (No. 6) Coal. 13 is the same as the concentration of chromium in the mineral matter of the 1.60 sink fraction. This assumption is certainly not as accurate as one would wish because it tends to overestimate the amount of an element contributed by insep- arable mineral matter, and there- fore, conclusions concerning the amount of organically associated elements (in this case, chromium) are conservative. An adjusted cumulative curve is constructed after a value (F) for chromium in the inseparable mineral matter is subtracted from each of the concentrations that were determined on the various speci- fic gravity fractions by using the following example of calcu- lations for F: E a 3. E E o U 19.9n 15.9- 11 11.9- 8.0- a n 20 1 40 60 80 101 Percentage of recovery Herrin (No. 6) Coal ISGS 1980 Figure 5. Adjusted washability curve for chromium in specific gravity fractions of a sample of Herrin (No. 6) Coal. F (inseparable Cr) = 71 ppm x 3.84 = 3.1 ppm 88.4 3.84 is the percentage of low temperature ash in the lightest (1.25 float) fraction. 88.4 is the percentage of low temperature ash in the heaviest (1.60 sink) fraction. 71 ppm is the chromium content of the 1.60 sink fraction. CALPPM(I) = [(CALPPM(I-l) - SUMPCT (1-1)] + [(RECPCT(I) - (ANLPPM(I)- F)] SUMPCT (I) ~~ Table 5 lists the normal and adjusted data and the calculated cumulative values from which an adjusted washability curve can be constructed (fig. 5). The washability curves shown in figures 4 and 5 are \/ery similar. The adjusted curve for Cr (fig. 5) has been "lowered" and the extrapolated inter- cept of the vertical (zero mineral matter) axis has a lower value. (A con- stant value for the inseparable mineral matter (3.1 ppm) was subtracted from the concentration in each fraction. However, a more accurate correction may be obtained by subtracting variable amounts based on the percentage of low temperature ash in each gravity fraction.) The total area of the square on which the adjusted washability curve is drawn is defined to have the value of 1.00 at 100 percent recovery. The percentage of that area that lies beneath the curve, expressed as a number with two figures to the right of the decimal is the index of organic affinity. (The significance of a second decimal place has not been determined.) The area under the curve can be determined by constructing a polynomial curve to fit the datum points and 14 deriving the value mathematically; or, more simply, a line can be drawn through the points and the area planimetered by hand or by computer methods (digitizer). The digitizer method produced the most reliable results and was used exclusively in this study. An element that is removed, to any degree, from the clean coal fraction by washing the coal has a value of less than 1.00; for example, see Pb in figure 6. The organic affinity of lead in that sample is 0.08, an extremely low value, indicating that the element is present almost entirely in the mineral -matter fraction. An element may have an organic affinity greater than 1.00, as in the case for boron in a sample of the Pittsburgh (No. 8) seam from West Virginia (fig. 7). Both standard and adjusted washability curves for B are shown in figure 7. The lighter specific gravity fractions of the coal contain larger amounts of B than the heavier fractions that are rich in mineral matter. Boron is an element that often has a high organic affinity index— in this case, 1.14. Standard and adjusted curves are nearly identical, inasmuch as there is only a minor contribution from the inseparable mineral matter to the total boron content. The organic affinity index is an open-ended scale. The upper limit is dependent only upon the difference between the concentra- tion of the element in the clean coal at the extrapolated Y intercept and the concentration of the element in the coal prior to washing (adjusted end point). A number of metals have washability curves intermediate between those elements that are generally concentrated in the inorganic fraction (such as zinc) and those that are concentrated in the organic fraction (such as bromine) . Chromium in the Herrin (No. 6) Coal (table 5, figs. 4 and 5) is an example. The adjusted curve intersects the ordinate at a lower value than does the standard curve. But even with the removal of a hypothetical amount of chromium contained in the inseparable mineral matter, there is still an appreciable amount of chromium left in the cleanest, organic-rich coal fractions. The calculated organic affinity of chromium in this sample is 0.37, Precision and Accuracy of Organic Affinity There are many potential sources of errors in the analyses and calcu- lations leading to an index of organic affinity. The washability data (percentage of total coal in each specific gravity fraction), the chemical analyses for the element or other constituent, and the amount of low tem- perature ash in the various fractions are all used in making the calculation; any error in their determinations affects the organic affinity values. One set of values exists with which the results can be tested. Varie- ties of sulfur (pyritic sulfur, organic sulfur, and sulfate sulfur) as well as total sulfur had been determined on fractions of washed coal samples. The percentage of sulfate sulfur is very low and generally does not make a significant contribution to the total sulfur content of a fresh coal sample. If analyses for varieties of sulfur were precise and accurate, if measure- ments of the amount of coal in each washability fraction were accurate, and if measurements of the amount of low-temperature ash were accurate, a perfect correlation should result between organic affinity of total sulfur and per- centage of organic sulfur in the total sulfur. This relationship is shown for the nine coals in figure 8. The agree- ment is generally good and well within analytical error for determining those 15 101.4 81.1 - 60.8- a a 40.6 20.3- 0.0 69.5 55.6 27.8 0.0 -> 1 1 1 1 1 1 1 1 — 20 40 60 80 100 Percentage of recovery Herrin (No. 6) seam, northwestern Illinois i 1 — *—i <— • — r 20 40 60 Percentage of recovery (adjusted) Herrin (No. 6) seam , northwestern Illinois "l 1 80 100 ISGS 1980 Figure 6. Washability curves for lead in specific gravity fractions of a sample from the Herrin (No. 6) seam. Left: Standard wash- ability curve. Right: Adjusted washability curve. 100 Percentage of recovery (adjusted) Pittsburgh (No. 8) seam. West Virginia Percentage of recovery Pittsburgh (No. 8) seam, West Virginia ISGS 1980 Figure 7. Washability curves for boron in specific gravity fractions of a sample from the Pittsburgh (No. 8) seam from West Virginia. Left: Standard washability curve. Right: Adjusted washability curve. 16 factors mentioned above for eight of the nine coals analyzed. One point representing a sub-bituminous coal from Montana is anomalous. It arises from the unusual washability characteristics of this coal with regard to total sulfur. Virtually all of the pyritic sulfur in the raw coal sample was removed in the 1.60 sink fraction and there was no detectable pyritic sulfur present in the lighter fractions. Therefore, the assumption, made during the calculation of the organic affinity, that the concentration of sulfur in the inseparable mineral matter of the heaviest and lightest frac- tions were the same, was invalid. In this case the organic affinity calcu- lated on the unadjusted washability curve is more nearly correct The know- ledge that such anomalies exist contributes to better interpretation of such data and the organic affinity index. MINERALOGIC METHODS Qualitative mineralogic analyses of 26 of the 27 raw coals and detailed mineralogic studies of single samples of nine raw coals (see table 1) and their various specific gravity fractions were conducted in conjunction with chemical analyses. The samples were characterized by x-ray diffraction analyses and microscopic examination of low-temperature-ash (LTA) residues prepared from the coal. The original minerals contained in the coal were retained by this radio-frequency plasma ashing technique. Because tempera- tures are sufficiently low (<150°C), the mineral phases are not significantly altered by oxidation, dehydration, or decomposition (Gluskoter, 1965). Semi- quantitative mineralogic analyses of the major nonclay minerals using an internal standard and prepared calibration curves were carried out by methods adapted from Ward (1977) and Russell and Rimmer (1979). Mineral phases in the LTA in quantities of <1 percent were generally not detectable above background intensities. The total clay percentage was obtained by sub- traction. Clay mineral analysis of the <2 um fraction was conducted using the preparation and analytical methods of Stepusin (1978). Organic sulfur x 100 Total sulfur 100 SGS 1980 Figure 8. Organic affinity index for total sulfur and the ratio of organic to total sulfur in nine washed coal samples. 17 SECTION IV RESULTS WHOLE COAL AND DEMORALIZED COAL Twenty-seven samples of coal, collected from three geographical areas of the United States, were prepared, demineral ized, and analyzed as previously described. Of these samples, six were from the eastern region, six from the western region and fifteen from the Illinois Basin. Whole coal, 1.40 float material, nitric acid digested material, and the demineral ized product from the 1.40 gravity separation were all analyzed for major and minor ash-forming elements and for trace elements. Of the analytical results, those for whole coal and "mineral -matter-free" coal are most significant to this study. These are presented in table 6. The whole coal values were calculated to the moisture-free basis. The organic portion of the 1.40 gravity separation is assumed to be equivalent to the organic portion of the whole coal, i.e., only the mineral matter content is affected by the separation. Percentage reten- tion of the elements was calculated, and it is also presented in table 6. When the concentration of the element retained was below the detection limit, no percentage was calculated. If the detection limit is approached for both the whole coal and the mineral -matter-free product, the resulting retention percentage may be subject to considerable error, e.g., ± 100 percent. Table 7 presents the mean elemental concentrations for the whole coals and the demineral ized material from the different geographical regions repre- sented. For the purpose of simplicity the coals were divided into three regions; however, an inspection of the standard deviation of the values will indicate that for some elements the variation between samples from the same region is greater than the variation between regions. The implications of this fact will be discussed later. CONCENTRATIONS OF ORGANICALLY ASSOCIATED ELEMENTS Table 8 identifies the coals and lists the specific gravity fractions that were obtained from the nine coals used in this portion of the project. Data from these float-sink sets have been used to calculate the relative organic affinities and the elemental concentrations for the whole coals when the adjusted washability curves are extrapolated to percent recovery (tables 9-17). The analytical data for the individual gravity fractions in table 8 are not given because data are so extensive and have been reported in Gluskoter et al . (1977), p. 90-104, except for set 4 from sample 18841 and set 8 from sample CI 9854. 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CO i— * CM «3" CM lO ^•roio^ co C O O i— o O O O LO o LT) IX) co lx> to oo cm id r~- r- cd *a- lo cm -■ CD co co OOOOO Or— CO 2-- g CD r-^ cd o o r^ co co cm ^f CM LT) IX) LO CD NfOCMrvCM i — ix) r-^ 00 «=T r— «XJ i— cm o uo o cd CM CM CO >— LT) r-. o oo CO CO r— CO CNJ cm ^a- ix) LX IX) ^ttNOii — O CO i — CO tx> CM CO ID IX) IX) CM «3" r-~ IX) CD ID co co i — «d- C\HtO)00 i— IX) CD O CO 00 *X> >-D r-^ CO I I I uuouo ID 00 o cm co o r~~ CM «3" r— CM r— O «3- Id O i — ID O i — CM «3- IX) r~~ 00 00 00 00 CO 00 CO 00 <_>(_> o o o •5J- r- r- Or- IX) CM «d" <— "* <* r- r— *d- r*» i — co id ID CO CO 00 «^" 1X> r— i — CO CO CM >J^ l-> U> <-) CO CM CO IX) •* "sj- r-- id o u c o o ro S- o ro o u s ro S- ro s_ +J c CD u c o u >) X5 cu T3 ro o u T3 ro s~ CD c E o> T3 OJ T3 5- cu 4J ro s- 0) c QJ QJ c c o o «* CO «5f ■f— •<— r — CM I — -!-> +J ro ro s- S. 4-> +j c c 5^- CD CO cu QJ COO)tv o (J Tj- LD CD r^ CO CO CM i — O CM CO CM i — r^ CO CM LD i — LD CM CM i — «d" CO l>>. CM |-*» CTl CM i — i — CO CM <3" I — O CM i— LD >* r>. CTi CTl CO LD LD i — CO r— O O CO i — CM CM CM CO LD CM CM CM r-. r>. ^f cr> cm V LO i — LO LO ^- CM «* «d" CM Pv LO wo- LD CO CO LD CO LD CO LO ■vf "3" CO CM CM *3" LD CO CM OO CM CO ■=}- «d" "3" CO r-~ OO LD CM LD CM CM CO CO LD OO «3" CM CO CM CO r». «3" LD LD LD CO LD r-^ CM O LO CM "=J- i — «— O V i— O LD CO i— «* V i — i — i — i — , — i — OLDLD vvvv vvvvv oo o r— r-^ r~- LO O ^J" CM CM lo r-- CM LD LD CO CO r— «rj" CM «vf CT. O CD i — ld o co CO LD LD (-- 00 r-»i — ro cm ■* cMOoor^LD LDOOl — r — r — LD I — i — O «rj- LD O i— LD O . — CM "3" ld r--. 00 CO CO 00 CO CO CO CO MNOr-tJ ^LOON* CO CO O LD CO co co cri co oo r— CD «3" CM LD VVVVV O «3- O «=J" LD i — CM V CM ■*^-*oco CM LD CM «3" "=J- oo co co >* r-. en ai co co co LD CM CM LD VVVV O LD LO «CT LD I — CM o oo ld r-- CM LD r— ^3" LD LD I I I I I LD <_> CD CD CD I I I I I LD CD LD CD LD I I I LD CD LD CD LD l I I l CD CD CD CD LD I 1 I I I (0 o o c CD T- .c +-> E O 4- -r- O 4-> (0 C 4_ O 4-> ■i- c +-> cu o o CO c i- o 4- CJ +-> (V (O -C o +-> «H >> o «*■ -a • O) r— TD cu > ^: ■!- -t-> -a o (O o O) o "O •r- (O r- E res i S_ r— CU (0 c i- •>- ai E c QJ .r- -o E CD CD +-> ■(-> c: c o o CO (O s- s- +j +-> c c CD CD o u cz c: o o CD CD * +- CD CD CD CD 24 CD a: a. a. 5 r- E (O eO O. oi o Q- +- c o +J ■ c CD- -t-J cu Cx' o CXI O r— V o r-COO oi in ■ — CVI .— r— ^" r— V CO Mr-O O . . . (X) . ID i— r— r— V V cnj *d- o V v evi r~- cnj i — v i— v S- 1/1 "a g s o Co CO < cx 3 f- E fO n3 Q. Oi O O- CD X3 Q. q. 2 .- E (T3 "3 Q. 0£ O Q- O +- c o cu E a. Q. Sr-E ig ig a ac o Q- o — en r-~ r-~ O ro ^ i— evi o oo in crv co r«. i->- in i — evi cm i — V V V co oo ro oo «d- co m in in co i— r~~ evi en «d- evi co r~ «=J- «3" CVI i— 7v VV VVVVV VVVVV VV V *v v v v v v i-- in in evi evi evi co CVI in co co . •- £. ^; ro r- r- in r^ O — .— CVI CV] CVICO 1— r— 1— CVI r— r— «sT f— >.Xj V cr> in 1 — o 10 co «3- CTi o «=t co «3- r-~ . — CVI ix> co r~- co id S^fONCO CTi IX) O ID CO CO CVI CO CO o ID CO IX) o o cu id co co 1 — «d- CVI «3- CXi CD O CL 1 — in en co E O 00 id 10 P-- CO n3 C i— r— r— r— r— O <_> O o o CVI in en id evi in o evi 00 COSOi — «=r ■cf in o r-^ «d- co 00 o in 00 00 00 en 00 co ouuuu ix) co in evi «3- *3- co *d- .— evi IONO r— CTI CO ^t ^i- >a- oco evi ix) evi «3- «* co 00 co "3- r-~ en en 00 00 00 co o in 00 evi id m evi o 1— 00 1— 00 in evi OCOWN evi «3- in co co «tf- «d- 00 00 00 00 1 1 1 1 1 (_><_><_> O (_) O C_) (_) o o ■— r-. •3- r^ evi o evi CTi ID 1— CO CO r— CVI «3" CJ1 CO CO CTi r- Cn 1— <3- in id I I I 000 RS o o 2 fO S- CU +J o o (J T- CU c 14- a> o o c c o o o o x: s_ 4- >> X3 +-> (O "O o ai 1— -o If- -r- > O T- ^- -o l/l cu S- -a ai cu u c o ■X o u QJ CU s_ 4- I S- 4-> 25 to c o +J • c CU ■ +-> OJ at * E Li_ Q. s: o. 2 r- E 10 io a Di O Q- O QJ 3 K +i e o to CQ * E U- CL 2: a. - 4-> OJ OC -O oo 2 ■— E (0 (O D. or o cl ■+- c o +J. CU- TS C_3 a; a: -x E 2: cl 2 >— E io iq a a: o a cu CL O E «= rO 1/0 i— CO «* CM CM CM CO CO V OOMiDr- CO LO ^- CO "=* CM i — LO CO O V CO i — "vT O O O CM inOlDODN LO «vf i — CM V i — •— o o lo o r-~ co id id cti oo CM CM r-- o lo co cm CM «3" r— V o co o o lo co o co o CTi r— CO •— LO COW ID CM LO LO CM ID CM LO O "3" CTl CTi LO ■3- ^d- O O co i— CM CM LO CO *d- -=3- i— O CO CO ■*CMID i — CO "51- o o o CM CO i— O CM o LO LO i— i — o r— o o o r-. co co lo o •— lo CTi CM ^t LO <=f CO r— LO i — CO CO IDWOlOO co cr> i — co CM «v)- LO i— o LO en CM CO CM O *d- co co lo r— i — SfOlDi — CO N i — LD CM ID «3" ID LO LO CM LO CO MiriN ID CO >=t CO ^f LO 4- cu fO S- c cu o c o <_) >) f0 "O O OJ >— X3 H- -r- > O •■- «3- -a LD LO CM CM CO r^ CO LO LO LO LD LO LD CM CM Or— LO <_> o o CONOr-3- lo o r^ «d- co co o LO oo co 00 CTi co co -*'*'*OC0 CM LO CM ^f" ^j" C0CO 00"*t^ CTi CTi 00 CO CO OCO^N CM LO <3" LO co co >=a- *3- CO 00 CO CO «d- en co oo CTi r-^ LD CTl r— <3" LO LO I I I <_><_> CJ> l_> O I I I I I I I <_> O C_> O O o ooo I I I CD T3 CU S- ■o cu N ra S- c CD U o C_> * cu cu S- I s_ cu +-> ■t-> cu +-> S- +-> c cu c o C_) +- 26 c CD ■ CD 2-— E ro ro Q- cc: o Q- o CU ■ +J CD LD ID CO CO «=f ro co «3- ld ld o o o o o CM i — CNI «3" LD ld ld cm o o cm i— r-innr-co CM CM CO CNI ID LD LD 00 LD o o o ■— NNinr^ o CNJ C\J r— CM I — LD "3" CTi CO CTi o o o o o in " ,— i— **■ co cm ^i- LD o «3- r— >^- co »^- ^3- cm «3- a~> ld LD CO In CT LD LD , — CM i — in *3- •— *t cm CM i— CM I — CTi I — LD CO .— CNJ **• CO cm «d- rN cm «3- CM CO CO i— LD CM LD O O CM CO «* «*■ o cn o co cm LT) CM CO i — i — in ld CTi ^tMCOO"* CO CTi CO ^" 00 CTl ON IN LD CO lT) co in in CM CO r— CNI ID CM CO LD i — r— ID «^- LD LD *T co «d- O CM i— LD 1 T3 CD -a ro o U OCOLf)- CM i — i — IN O O CM CO LD LD ID tN CO fN O r— ^" ?tLf)ON* CO CO O LD 00 00 00 CTi 00 00 I I I I I oouuo u o oo u I I I I o ooo o LD LD i— |n 00 ■3" CM i — iono>jo CM i — CM CM ID LD 00 LD LD i— CM 5t* <_> o o I — LD i — CO r- f— CO CM CO o 00 i — CM CO LD IN «3" «d" O CO LD IN CM LD «* LD CO CO **- «3" 00 00 CO CO I I I I L_> o o o LD ID CM CO LD IN LD CTl fN CM CM «d" CTl CO 00 CTl IN LD CTi r— ^- LD LD CD -a 00 CD S- T3 CD N QJ ■a CD CD S_ M- i s_ CD 4-> ro i. CD c # c o •r— +J ro i. +-> c CD o c o 27 e QJ ■ +J CU cc ro ro CI. Qi O Q. O +- e o +->■ c QJ ' QJ OS S >— E ro ro ex a: o o. <_> — - S o to co +- c o QJ DC Q * E U. Q. 3 r- E ro ro Q. o; o Q- cu — - +-> a) * E s: a. 10 10 a oc o Q- u ai Q. . E o rO c CO o lo <3- lo CM CO i — i — C\J CM r— r— CO O O O O O mrois cm ro cm i — CM CO ID LO o o o o o O O r-. ro O O O O lo o o CM LO «=t" CM CO O o o — LfJ o CO O CO CM «3" CO i— i— o o o o LO CM CO i — CM >d- CO O O O CO r-«. -o lo «d- O O CM CO CO CM LO CM LO <— •— o o LOr-CO O i— o O CO CO O CM (V CON O O O CM CM n Wi — id o i — n lo en co CM CM CM CM «d" CO CO "3" i — LO CO CTi CO LO CO Sf LO «3" i — CM lo ro lo ro CM CM i — CM oo en r>» ro CM CM CO O CO o o CM i— i— CM CM inor-in CM i — i — i — CM ro en cno cm co lo lo lo i — r^ i — i — *3" O CM CM i— O O i — CMO en ro r-- lo lo lo en ^fini — LT> CO "=3- lo r^ lo ON ^trvCTi CO CM CM LO CM OwniflN ro ro co lo co >3- r»» r>. lo CO I — CO CM en cm lo ro r^ cm IT) O . — CO LO en ro r— ID CO CM =3- LO LO ro CO CO CO «tf- ro «* CM CO LO ^f LD CM LO ro ro ro LO ro CO o r— r-. ro cj co lo o CM "3" i— ro en ro ro o o CO LO o o i— LO ro 00 LO CO O r— O O O i— i— CO ro ro «sf LO CM O O CM r— I— LO CM CO i — cm r-» 4- Ll_ en r--. co lo co en cm O ^1 1 — (_> (_) I I I ouuu u I I I O C_> (_> <_> I I o o o f0 o u 3 CO s_ QJ S- +J c cu o c o CJ X) CD CU ro S- +J c cu o c: o r_> C o +-> ro S- +-> c (D U c o CJ 28 CD a: -O 3 -— E a: o d. o — c o 4->. c CD- -!-> 'a 3 CO 3 ■— E ig ig a Qi O Q. O-— ' +- o c a»- +j OS * E U_ Q. S Q. 3 ■— E 10 m a a o a o — c o -1-1 • c — v v v v v CM CM ro C 4- V O L> c C O u 4- >. XJ +-> O -f— <* T3 1 , n3 CD O -C O CM 00 O CO 1 — O CO CO in «3- 1— • — in en in o o «3- in cOMOroo OCMIVOHJ- O CO (— CM 3- «3- in o r^ «3- 00 00 o in 00 co co en 00 00 cm in cm >^- ^j- CO 00 co ■=*• r>. en cr* co co co o co in r^. cm in ^3- in co co ^ «d- co co co 00 1 1 1 o o o <_> o I I I I ouuuu I I I c_> <_> o o o i C_> (_> (_> O O I I I *3- CTi CO 00 CTv r^ IO CTi f— *j- in O -0 CD ■1 — CD l/l S- CD 4- i. 1 S- -a QJ CD ■M fsl 4-> • i — n3 1 — E BJ 1 S- r— ai (O cz 5- •1— CD r- C CD •p— -a b oj CD -C -C 4-> -M ■•-> +-> i. S- -•-> +-> c c CO C1J o o c c o o o o * +- 29 5- > o o O CU i— CU CU 'Xi 3 £ £ CO 2 >— E (D IB Q Di O Q- O CU 2 -— E rO n3 Q- q; o q. o- — CU 'o. o E c f0 oo 00 CTi O CO CD CTi -vt- Ln o CM CO CNJ in CTi noii — rs CT> O COCD is is is is oo oo i — is is oo co oo en CO CO CO IS LO CO is oo SNC0 00 CO CM Is LO CO CO i — «3- CO CM i — i — O CO CM CTi O O CO r— CM CM CM CM CO LT) LT> co Ln i— i — i — CM co en Ldrswocn CO is r— CM CO co is o •— r— CO CO CTi CO CM CM CM CM r— CTi CNJ is o m o cm o Ln co Ln o co i — i — CM Ln co co Ln i— CM CM CO cr> is co i — co OMfioON co i — Mi — i — is r— ■ — CTi CO is <3" coLnoiocM — CM i— i— i— i— i— s" O O i— CM O Ln O CTi i — CM CNJ CM CM i— CO O CO CO i— CM CM CO r— CM CTi CO 00 Is CM >* i — CO CM i— 00 CM CO in CO CM CM CNJ CO CO 00 CO CM CO CM O LO CO CM CO in Ln «* co cm O^Or-CO «3- CM O CO CO CM CM CM CNJ i — CO CO CO i — «3" w^-oioo i — in cti o co co co co is co CO CM CTi CO CM CO CO CM O <^- CO O i— CO O i — CM "3" LONCOCOCO CO CO CO 00 00 en «3- co cm cti is o <* «* «3- CO «d- LOi — i — i — CM CONOi-t <*U10N<* oo oo o in oo oo co en oo oo i — IS loud, — i — in ^a- is en CM CM in CM CO CM Ln CM "3" «3" CO OOoCtN CTi CTi 00 CO CO m oo r— IS «3" i— CTi CO o oo en is cm co «3- in CO CO «3- «3" 00 CO CO CO 00 00 o r— CM i— *3- CTi CO 00 CTi IS CO CT. i— «d- in co I I I I O CO C_> CO CO I CO CO CO CO CO I I I I uuuuo CO CO CO CO CO I I I I ouuu (T3 o o 2 ra s- CU ■l-J o o o •<- -t-> cu re -E s- +-> +J c <4_ ai o o c c o o u (O +-> S- M- >, o ai i— "O M- -r- > O ■!- s- -a cu i_ ■o cu N E QJ c o •r— ■•-> +-> IT3 E cu +-> c o s- +J c cu u c o CO 30 TABLE 7. Mean concentration s and mean retention percentages in mineral -matter-free coals* IL Herrin (No. 6) Eastern Western Element Si Al Fe Ca Na Mg K Ti P Mn S Organic S Be B Sc V Cr Co Ni Cu Zn Ga As Se Br Rb Sr Mo Cd Sb Cs Ba La Ce Sm Eu Tb Dy Yb Lu Hf Ta W Pb Th U ISAt Raw Coal Retention MMF Percentage 2.60±.6% 1.28±.3% 1.96±.9% 0.96+.8% 592 ±472 0.06±.03% 0.16 ±.05% 0.07±O.02% 52 ±30 88 ±75 3.9±1.4% 1.7±.57o 1.5 ±.8 148 ±81 29±.8 37+17 28±13 5.3±3 21±8 20 ±9 832±1700 3.2±1 6.8±8 2.6±.9 8.9±7 16.8+7 31+11 6.8±4 1.1 ±1 1.3±.7 237+445 6.8±2 14.7±8 1.1+.4 0.30±.l 0.26+.1 1.0 + .4 0.58±.2 0.09: 0.70: 0.17±.07 0.68±.4 29±27 2.1±0.8 2.3±2 197 ,02 ,3 56±19 61±14 96±53 38±22 5.8±4 26+10 9.3±14 30±14 4.1+3 0.72±1 1.7±.5% 1.7+.5* 0.04±.03 8.1+2 0.4±.3 6.5±4 5.7 + 3 0.4±.2 6.0±5 5.0±3 0.60±.l <1 0.34±.2 6.0+4 <1 4.U3 0.90±0.6 0.4±.3 0.04±.03 3.3±1.5 0.7±.2 1.1±.4 0.30±.01 0.06±.03 0.26+.1 0.13±.06 0.03±.01 0.09±.04 0.52±.2 0.22±.l 0.2 0.5 0.5 0.4 1 4 0.6 4 8 0.8 44 98 3 5 1 18 20 8 28 25 19 13 67 13 13 30 3 1 3 36 0.30±.l 2 26 22 33 13 25 ID Raw Retention Coal MMF Percentage Raw Coal Retention MMF Percentage 2.41±.4% 1.94±.6% 1.0±.5% 0.62±.5% 481+248 0.06±.05% 0.19+.09X 0.10±.04% 85±57 20±10 2. Oil. 756 1.0i.74% 0.70±.2 53±42 4.9±2 48±22 20±7 6.8±6 12±3 22±8 29±45 4.7±2 10±8 3.1+2 11±9 14±4 121+53 6±5 2.3+2 1.4±.6 146+61 13±6 21±8 2.2+. 8 0.4+.2 0.02±.09 1.7±0.7 0.58±.2 0.13±.08 1.3±.4 0.37+.3 0.57±.4 8.9±9 4.1+2 1.2+1 60±12 144±100 107±75 71±72 10 + 11 25±22 1.8±1 76+68 2.3±2 2.4±3 1.0±.7% l+.7% 0.05+.03 14±7 1.2±0.9 9.3+13 7.3±4 3.5±4 2.8±2 3.8+2 <1 1.2±0.6 <1 0.58±.2 6.7+6 29±19 0.40+.3 0.08±.08 20±9 2.8+1.2 3.2+. 7 0.54±.3 0.12±.05 0.19i.04 0.06+.03 0.29±.2 0.09±.01 0.26±.3 1 . 0± . 4 0.27±.2 0.2 0.7 1 1 2 4 0.1 8 3 12 50 100 7 26 24 19 36 51 23 17 26 19 61 24 17 6 13 22 15 24 30 33 46 22 24 46 23 22 1.39+.7% 1.06i.4% 0.4+0. IX 1.66+1.2% 960±1410 0.20+0.1% 0.03+.03% 0.05+.02% 96+47 55±38 0.73±.2% 0.45±.1% 0.40±.l 59±33 1.4±.4 17+12 2.7±3 1.3±0.8 4.2±2 14+8 10±9 2.7±2 1.8±2 1.4±.4 1.1+.4 1.8+.9 185±66 3.7+3 1.1+1 0.19+.2 498±175 5.7±2 9.7+3 0.69±0.2 0.17±.07 0.15+.04 0.60±0.2 0.39±.2 0.07±.02 0.99+.2 0.13±.05 0.80±.3 4.1+1 2.0+.9 0.98±0.2 56±20 76±58 71±77 61±69 7.8+6 17±5 31 + 16 1.8+2 0.42+. 1% 0.42±.1% 0.03+.03 7.3±6 0.29+.2 2.3±2 l.li.3 0.5±0.5 3.6±3 0.73±.8 0.5+.3 0.39+.2 1.8±2 0.38±.2 13+14 1 . 3+ . 7 1.7+1 0.21+.1 0.05+.02 0.11+.04 0.02±.01 0.26+.1 0.80±.2 0.13+.1 0.4 0.7 2 0.4 0.8 0.9 3 58 93 8 12 21 14 14 38 26 27 28 28 163 34 3 23 18 30 29 28 28 26 40 13 *A11 values in ppm unless noted. Less than values were not included in calculation of means, tlnternal surface area by C0 2 method (values in m 2 /g). 31 TABLE 8. Identification of coal samples and gravity separations 1 Analysis Specific Percentage of number State Coal seam Float-sink set No gravity fraction . 1 raw coal C18560 RAW C18562 111 inois Herri n (No. 6) 28M x C18563 1.29F 34.3 C18564 1.33FS 25.9 C18565 1.40FS 18.6 C18566 1.60FS 12.5 C18567 Float-sink set No. 1.6S 2 8.7 C17001 RAW C18090 111 inois Davis 3/8 x 28M C18094 1.28F 25.9 C18095 1.30FS 19.5 C18096 1.32FS 19.7 C18097 1.40FS 19.3 CI 8098 1.60FS 7.2 C18099 1.60S 8.5 Float-sink set No. 3 CI 6137 RAW C18121 Illinois Herri n (No. 6) 3/8 x 28M C18122 28M x C18123 1.25F 36.1 C18124 1.29FS 17.4 C18125 1.33FS 14.7 C18126 1.40FS 9.3 C18127 1.60FS 6.9 C18128 Float-sink set No. 1.60S 4 15.6 CI 8841 RAW C18892 West Virginia Pittsburgh No. 8 3/8 x 28M C18893 1.28F 33.8 C18894 1.30FS 20.9 C18895 1.40FS 25.7 C18896 1.60FS 13.5 C18897 Float-sink set No. 1.60S 5 6.1 CI 9824 West Virginia Pittsburgh No. 8 RAW CI 9827 1.28F 27.8 CI 9828 1.29FS 26.5 CI 9829 1.32FS 19.7 CI 9830 1.40FS 13.3 C19831 1.60FS 5.5 C19832 1.60S 7.2 32 TABLE 8. {Continued) Analysis number CI 8820 CI 8890 C18891 CI 8883 CI 8884 CI 8885 CI 8886 CI 8887 CI 8848 C18889 C18878 C18879 CI 8880 CI 8881 CI 8882 CI 9854 CI 9848 CI 9849 CI 9850 C19851 C19852 CI 9853 CI 9000 C19014 CI 9009 C19010 C19011 C19012 C19013 State West Virginia Coal seam Float-sink set No. 6 Pocohontas No. 4 Alabama Float-sink set No. 7 Blue Creek Montana Float-sink set No. 8 Rosebud Arizona Float-sink set No. 9 Black Mesa Field Specific Percentage of gravity fraction raw coal RAW 3/8 x 28M 28M x 1.30F 24.7 1.33FS 25.3 1.40FS 25.0 1.59FS 14.1 1.59S 10.9 RAW 28M x 1.30F 25.3 1.32FS 20.5 1.40FS 36.0 1.60FS 11.8 1.60S 6.4 RAW 1 .301 F 36.8 1.32FS 24.4 1.32FS 13.1 1.40FS 12.3 1.60FS 10.4 1.60S 3.0 RAW 28M x 1.28 25.0 1.30FS 26.3 1.40FS 40.8 1.60FS 6.9 1.60S 1.0 *For analytical results of concentrations of major, minor, and trace elements in the coal fractions, see Gluskoter et al . , 1977, p. 90-104, and Kuhn et al . , 1978, p. 5-8. 33 TABLE 9. Concentrations and organic affinities of elements for sample C18560 from Herrin (No. 6) Coal Member in Illinois Organic affinity .30 Raw coal Organic fractions F/S ext* MMFf Element 1.40 (ppm) (%) (ppm) [%) (ppm) Al 0.10 41 Ca .06 0.51 25 Fe .06 2.60 66 K .56 0.13 0.04 <1 Mg .27 0.06 0.003 21 Na .64 0.04 0.01 6 Ti .29 0.06 0.13 20 Si .45 3.20 0.017 41 Organic S 1.11 1.87 2.33 1.81 Total S .45 6.45 1.1 1.81 As .04 3.4 <.7 B .77 200 57 6.6 Ba .15 54 2 <2 Be .87 1.4 0.6 0.03 Br .92 13.4 12 3.3 Cd .07 <0.1 <0.1 Ce .07 25 1.7 Co .74 7.2 1.7 .4 Cr .77 21 20 7 Cs .44 2.0 0.2 0.1 Cu .66 13 3.3 2.1 Dy .89 1.2 0.8 0.4 Eu .67 .3 0.1 0.1 Ga .15 2.4 0.3 .7 Hf .48 1.1 0.1 0.1 La .04 6.1 0.7 Lu .59 0.1 0.03 <.01 Mn .06 60 0.3 Ni .75 24 5.9 <1 P .03 50 <1 Pb .32 <1.0 0.3 <1 Rb .45 23 0.3 <1 Sb .90 0.5 0.4 .1 Sc .57 4.1 0.8 0.6 Se .28 4.3 .3 Sm .39 0.9 0.2 0.4 Sr .07 33 0.8 1.5 Ta .44 0.2 0.05 0.1 Th .55 3.6 0.8 1.0 U 1.29 1.9 2.7 0.1 V .97 36 35 3.5 U — 0.6 — 0.1 Yb .52 0.8 0.2 0.2 Zn .04 57 1 ^Extrapolation of float-sink data. ■(-Concentration in the acid demineral ized residue of the 1.40 float fraction of the coal . 34 Element Al Ca Fe K Mg Na Si Ti Organic Total S As B Be Cd Co Cr Cu Ga Mn Ni P Pb Sb Se V Zn TABLE 10. Concentrations and organic affinities of elements for sample CI 7001 from Davis Coal Member in Illinois Organic affinity .58 .63 .04 .63 .41 .76 .50 .76 1.09 .10 .05 1.05 1.03 .07 .65 .69 .56 .67 .35 .82 .75 .04 .68 .69 .60 .02 Raw coal (*) 0.86 0.82 2.76 0.14 0.02 0.048 2.08 0.06 1.51 4.14 (ppm) 9.4 37 1.6 1.3 8.0 30 8.0 2.0 22 17 48 56 2.5 3.3 62 170 (%) Org anic fractions F/S ext* (ppm) (%) .32 .16 .05 .01 .009 .54 .03 1.2 0.1 30 2. 7 1. 3 5. 5 2. 7 1. 3. 9 5. .3 11 .2 1 .3 11 .8 *Extrapolation of float-sink data. tConcentration in the acid demineralized residue of the 1.40 float fraction of the coal . MM Ft 1.57 1.57 (ppm) 125 67 64 31 95 25 197 19 <5 6.1 0.1 <0.1 <1 <5 1.8 0.9 0.7 <4 2 • 1 < 1 ■ 1 35 TABLE 11. Concentrations and organic affinities of elements for sample CI 61 37 from Herri n (No. 6) Coal Member in Illinois Organic affinity Raw coal Organic fractions F/S ext* MM Ft Element (%) (ppm) (%) (ppm) (%) (ppm) Al .10 1.12 60 Ca .04 0.73 13 Fe .16 1.70 0.12 55 K .13 0.18 0.004 1.3 Mg .32 0.05 17 43 Na 43 0.02 140 6.6 Si .09 2.48 36 Ti .16 0.07 0.005 20 Organic S 1.15 1.95 1.58 1.12 Total S .54 3.25 1.56 1.12 As .05 27 <.5 B .94 100 86 6.6 Be .88 2.8 2.0 0.03 Cd .04 — 0.1 Co .35 8.0 1.1 0.2 Cr .37 28 4.3 5.2 Cu .26 20 2.1 4.1 Ga .41 4.2 1.1 0.7 Mo .52 9.0 .4 <1 Mn .04 71 .3 Ni .36 30 5.2 <3 P .16 21 1.4 Pb .05 72 <1 Sb .67 4.2 1.0 0.6 Se .39 2.4 0.7 0.4 V .58 32 13 8.5 Zn .04 2700 3 *Extrapolation of float-sink data. tConcentration in the acid demineral ized residue of the 1.40 float fraction of the coal . 36 TABLE 12. Concentrations and organic affinities of elements for sample C18841 from Pittsburgh (No. 8) seam in West Virginia Element Al Ca Fe K Mg Na Si Ti Organic Total S As B Ba Be Br Cd Ce Co Cr Cs Cu Dy Eu Ga Hf La Lu Mn Ni P Pb Rb Sb Sc Se Sm Sr Ta Tb Th U V Yb Zn Organic affinity .34 .50 .30 .12 .49 .54 .12 .05 1.07 .71 .25 .81 .72 .53 1.00 .66 .41 .53 .40 .09 .47 .65 .54 .53 .30 .45 .26 .43 .44 .71 .62 .20 .41 .40 .36 .44 1.03 .24 .33 .23 .79 .48 .32 .42 Raw coal (%) 1.20 0.53 1.70 0.19 0.04 0.060 2.30 0.06 2.51 5.02 (ppm] 3.2 120 72 0.7 10 <.l 15 3.3 15 1.0 5.1 1.5 0.3 4.3 0.7 8.7 .1 20 6.3 59 3.0 13 0.2 2.6 1.1 1.5 110 0.8 0.1 2.9 0.7 26 0.4 14 Organic fractions F/S exf (%) 14 10 .011 .016 (ppm) 35 0. 2 6. 8 1 1. 2 0. 6 3. 2 1. 3 0. 5 0. 1 1. 0. 1 1. 7 5. 6 1 .4 28 1 .5 .8 .02 .3 .04 .21 66 .02 .04 .4 5 .0 .01 1 .5 ♦Extrapolation of float-sink data. tConcentration in the acid demineralized residue of the 1.40 float fraction of the coal. MM Ft (%) 2.28 2.28 (ppm) 280 210 240 0.7 7 6 64 94 <.5 24 10 .01 3.8 <0.1 3.3 0.8 8.6 0.03 <0.3 .1 1.7 .1 2.4 0.05 3.7 3 2 <1 <1 0.1 1.3 0.4 0.6 01 07 6 1 4 0.2 1.0 37 TABLE 13. Concentrations and organic affinities of elements for sample CI 9824 from Pittsburgh (No. 8) seam in West Virginia Organic affinity Raw coa 1 Organic fractions F/S ext* MMFt Element (%) (ppm) {%) (ppm) (%) (ppm) Al .62 1.02 0.43 41 Ca .04 1.61 30 Fe .17 1.12 80 K .10 0.102 2.5 Mg .04 0.16 <20 Na .71 0.068 0.036 8.8 Si .39 1.95 0.33 40 Ti .58 0.06 0.023 11 Organic S 1.15 1.10 1.67 1.18 Total S .81 2.23 1.65 1.18 As .11 3.9 .3 B 1.14 82 86 — Ba .90 130 100 27 Be .77 0.4 0.3 0.1 Br 1.02 12 12 12 Cd .09 0.2 <.l Ce .68 16 6.2 2.5 Co .79 2.2 1.5 0.2 Cr .58 14 5.0 2.0 Cs .28 0.8 0.1 0.03 Cu .49 8.6 2.1 1.5 Dy .67 0.8 0.4 0.5 Eu .67 0.2 0.1 0.1 Ga .79 2.6 2.1 1.4 Hf .40 1.0 0.2 0.6 La .68 5.7 3.0 2.6 Lu .62 .1 0.03 0.02 Mn .06 35 0.7 Mo .04 1.7 <0.2 Ni .62 9.0 2.6 2 P .68 103 42 <5 Pb .04 25 <1 Rb .18 9.5 <1 Sb .37 1.6 0.2 0.8 Sc .67 2.3 1.1 0.1 Se .53 1.6 0.7 0.5 Sm .72 0.9 0.5 0.5 Sr .94 143 0.1 24 Ta .51 .2 0.04 0.1 Tb .90 0.1 0.1 0.04 Th .62 2.1 0.7 1.1 U .74 0.6 0.7 0.1 V .57 17 6.6 2.7 w .67 0.3 0.2 <0.9 Yb .74 0.3 0.2 0.1 Zn .31 10.3 0.8 1 *Extrapolation of float-sink data. -{-Concentration in the acid-demineralized residue of the 1.40 float fraction of the coal . 38 TABLE 14. Concentrations and organic affinities of elements for sample C18820 from Pocahontas (No. 4) seam in West Virginia Element Al Ca Fe K Mg Na Si Ti Organic Total S As B Ba Be Br Cd Ce Co Cr Cs Cu Dy Eu Ga Hf La Lu Mn Ni P Pb Rb Sb Sc Se Sm Sr Ta Tb Th U V w Yb Zn Organic affinity .25 .53 .67 .12 .37 .50 .11 .29 1.18 .82 .07 .47 .77 .87 1.07 .63 .50 1.16 .38 .14 .55 .60 .57 .49 .24 .41 .52 .40 .99 .65 .38 .12 .55 .48 .46 .46 .89 .28 .54 .29 .40 .56 .80 .60 .52 Raw coal (%) 1.40 0.56 0.90 0.21 0.06 0.070 2.50 0.12 0.51 0.80 (ppm) 1 15 8 220 22 0.1 33 7.0 17 1.9 20 2 4 1 20 0.1 14 12 26 1.6 16 4.6 3.0 5.8 2.7 120 0.1 0.3 5.9 1.1 22 0.5 0.7 11 Organic fractions F/S ext* MMF 1 (%) 0.15 0.15 0.43 0.011 0.012 0.021 0.58 0.56 (ppm) 1 2. 120 0.9 28 0.1 9.4 6.7 3.2 8.3 0.9 0.2 1.5 0.1 4.9 0.04 3.8 11 16 1 0. 0. 1 0. 78 0.03 0.1 0.5 0.3 15 0.5 0.3 2.2 (%) 0.47 0.47 (ppm) 169 74 72 <10 18 0.5 56 19 <0.5 9.7 33 0.1 16 -0 4 5 6 1 5 4 3 0.2 6.5 0.9 0.2 0.7 0.2 5.0 0.05 0.5 <5 0.1 <1 <1 .6 2.0 1 0.9 50 0.1 <1 1.1 0.2 1.5 0.1 .2 <1 *Extrapolation of float-sink data. tConcentration in the acid demineralized residue of the 1.40 float fraction of the coal. 39 TABLE 15. Concentrations and o rga nic affini ties of e lements for san iple CI 8848 from Blue Creek seam in Alabama Organic Raw coa l Organic fractions F/S ext* MMF+ Element affinity (%) (ppm) (%) (ppm) (%) (ppm) Al .40 1.90 0.25 240 Ca .34 0.35 0.037 48 Fe .44 0.70 0.14 54 K .12 0.28 2.3 Mg .07 0.05 <20 Na .20 0.030 <3 Si .17 2.80 64 Ti .54 0.15 0.04 28 Organic S 1.08 0.50 0.53 0.33 Total S 1.08 0.55 0.56 0.36 As .05 1.8 <0.5 B .37 15 0.8 5.1 Ba .62 230 76 20 Be .76 0.7 0.4 0.05 Br 1.20 2.5 2.5 1.7 Cd .45 <0.1 0.05 <0.1 Ce .64 30 14 3.5 Co 1.08 9.4 7.9 10 Cr .60 21 7.1 14 Cs .10 2.3 0.05 Cu .78 12 8.0 4.1 Dy .78 2.1 1.5 .7 Eu .78 0.4 0.2 0.1 Ga .64 6.3 2.6 1.7 Hf .44 1.2 0.3 0.3 La .74 18 9.6 2.8 Lu .69 0.1 0.04 0.1 Mn .05 13 <1 Ni 1.01 11 9.9 1 P .60 190 90 <4 Pb .68 12 1.9 <1 Rb .10 18 <1 Sb .64 0.8 0.2 0.7 Sc .53 4.3 1.2 2.5 Se .58 3.0 0.9 .4 Sm .66 2.8 1.0 0.1 Sr .80 130 54 13 Ta .34 1.1 0.04 <0.1 Tb .66 0.2 0.2 <.l Th .43 5.4 0.6 5 U .71 0.9 0.8 0.3 V .75 54 29 <5 w .70 0.4 0.3 0.1 Yb .56 0.9 0.2 .2 Zn .21 2.0 <1 *Extrapolation of float-sink data. tConcentration in the acid demineralized residue of the 1.40 float fraction of the coal. 40 TABLE 16. Concentrations and organic affinities of elements for sample C19854 from Rosebud seam in Montana Element Al Ca Fe K Mg Na Ti Si Organic S Total S As B Ba Be Br Cd Ce Co Cr Cs Cu Dy Eu Ga Hf La Lu Mn Mo Ni P Pb Rb Sb Sc Se Sm Sr Ta Tb Th U V W Yb Zn Organic affinity* 18 .82 .02 .02 .97 .88 .15 .06 1.10 .74 .03 1.24 .02 .73 .99 .06 .89 .80 .09 .03 .44 .77 .89 .76 .39 .90 .68 .04 .83 .64 1.02 .04 .03 .95 .78 .05 .73 .98 .61 .79 .56 .58 .60 1.15 .74 .02 Raw Coal (%) (ppm) 1.15 0.97 0.47 0.079 0.44 0.019 0.05 2.41 0.62 .90 0.7 100 808 0.5 1.6 0.2 10.3 1.2 6.2 0.4 8.8 0.6 3.3 1.2 5. 0. 85 7. 3. 121 4. 3. 1.6 0.9 0.9 103 0.1 0.1 2.5 1.5 10.6 0.7 0.2 4.3 Organic fractions F/S Ext 1 MMFT- (%) 0.43 0.32 0.009 0.53 0.59 (1W) 115 0.1 5.0 5.3 0.6 1.2 0.3 0.1 1.7 0.2 3.1 0.02 2.6 0.8 95 0.5 0.7 0.3 94 0.5 0.5 0.6 0.2 2.3 .7 .1 (%) (ppm) 0.56 0.46 20 20 35 <5 <20 15 4 30 <.3 40 0.03 4.5 <0.1 3.3 1.5 0.6 <0.04 1.8 0.2 0.04 2.2 0.2 1.3 0.03 1.5 1.4 <2 <5 "1 <1 0.7 0.6 0.3 0.2 4.4 .1 0.05 .8 0.2 1.2 <.l 0.2 <0.3 *0rganic affinity calculated on unadjusted washability curve. "^Extrapolation of float-sink data. ^Concentration in the acid demineralized residue of the 1.40 float fraction of the coal. 41 TABLE 17. Concentrations and organic affinities of elements for sample C19000 from Black Mesa Field in Arizona. Element Organic affinity Raw coal (%) (ppm) Organic fractions F/S Ext* MMF+ (%) (ppm) (%) (ppm) 0.12 187 0.65 200 0.28 225 0.007 <10 0.064 <20 0.153 1.4 0.007 54 53 0.41 0.32 0.32 0.32 0.2 37 5.3 220 15 0.4 0.03 1.3 1.0 0.1 <0.1 4.6 1.2 0.6 0.5 1.3 1.4 <0.05 2.4 <3 0.5 — 0.05 0.05 0.4 0.2 0.3 0.2 2.1 1.3 0.04 0.03 1.1 0.4 1.2 <1.5 96 <4 <1 0.3 <1 0.1 .2 0.7 0.4 0.7 0.6 0.2 .3 130 — 0.03 — 0.05 <.05 0.4 0.6 0.4 0.05 8.7 <5 0.1 <.3 0.2 .1 2.3 <0.5 Al Ca Fe K Mg Na Ti Si Organic S Total S As B Ba Be Br Cd Ce Co Cr Cs Cu Dy Eu Ga Hf La Lu Mn Ni P Pb Rb Sb Sc Se Sm Sr Ta Tb Th U V w Yb Zn .39 .82 .89 .53 .95 1.00 .33 .10 .95 .88 .11 1.09 .92 .79 .83 .99 .64 .83 .54 .03 .74 .82 .57 .38 .47 .58 .72 .53 .88 .94 .06 .40 .66 .64 .61 .47 .84 .39 .54 .38 .50 .74 .52 .75 2.2 1.40 0.46 0.40 0.02 0.07 0.150 0.06 0.71 0.52 0.72 1. 37 270 0. 0, <0. 6.0 0.8 3.5 6.0 1 1 120 < 1 1 1 0.8 200 1 <0 7 1.2 0.2 7.0 *Extrapolation of float-sink data. t Concentration in the acid demineralized residue of the 1.40 float fraction of the coal. 42 The extrapolated values are thought to represent the theoretical con- centration of an element in a coal when no mineral matter is present or, in other words, the quantity of an element that is intimately associated with the organic matrix. EXCHANGEABLE AND SOLUBLE IONS Results of analyses of raw coals and their residues, which have been leached with ammonium acetate, are given in table 18. Comparison of the two values (raw coal minus residue) is a good indicator of the potential for removal of exchangeable ions and soluble elements from coal. However, the data may be subject to some error when comparisons are made for inter- pretive purposes with data in tables 9-17 because different samples of the same coals were used in the two studies. The desirability of making this comparison is discussed in the section on "Validity of Organically Associated Elements," page 50. MINERALOGY The results of qualitative mineral analyses for 26 whole coals in this study are presented in table 19. Certain mineral phases, such as kaolinite, illite, expandable clays, calcite, pyrite, and quartz, are ubiquitous in these coals. However, some regional differences in mineralogy related to deposi- tional and geochemical environments can be observed and are in agreement with the findings of previous workers (Rao and Gluskoter, 1973; O'Gorman and Walker, 1972; Miller and Given, 1978). As a group, the western United States coals in this study have dis- tinctively different mineral assemblages from the other two regions. Bassa- nite composes a major mineral phase in the low temperature ash of western lignites and subbituminous coals; it forms during the low temperature ashing process both by the dehydration of the mineral gypsum, when it is present, and by the fixation of exchangeable calcium cations, which are common in low rank coal containing organic sulfur (Miller and Given, 1978). The exception in the group is a high volatile bituminous coal from Arizona in which the level of exchangeable cations is quite low. Another major dif- ference between western United States coals and the other two groups studied is the predominance of \/ery high intensity, well -crystal i zed kaolinite over other clay minerals in the LTA. There are traces of barite, chlorite, and aragonite in these coals. Eastern United States and Illinois Basin coals are somewhat similar mineralogically, although a higher frequency of iron carbonate minerals is evident in the eastern coals studied. Pyrite content is likely to be highly variable throughout both regions. The presence of the iron sulfates, szomol- nokite and coquimbite, in these samples is primarily due to the oxidation of pyrite during storage, although it is possible that limited quantities of these sulfates can be produced in the low temperature asher. Detectable amounts of epigenetic sphalerite are characteristic of northwestern Illinois coals. Nine of the 27 coals (see table 8) were studied in greater detail to evaluate the distribution of the major mineral phases in the various specific gravity fractions of each coal. Quantitative x-ray diffraction determinations 43 T_ OJ OJ 3 x TJ u •H rt cn OJ OJ d X TJ u •H rt W CN o o CO o o o I O CN o CN m o CNI i o o rH CO CO r-{ SO m rH 00 CO CO O SO rH oo ON r~~ o r-. rH rH CO in co rH CM rH 00 sr OJ rH m CN CM CO o sD CO CM ON O in o O CNJ O CO rH r-~ rH O O in O rH 00 rH CO lO OMO In lO N O CN O in r-. rH r^ CO st 00 N IN O O sO rH O O so rH O CM in co o r» so CO rH O st- CM CO r-i o CM m st CM rH o CO CM O O CO CM CO CM o 00 m m m CM in sO ON o CO CO CN o 00 CM CM CO r-i CN IN rH CM rH CN O o CO ON O sDOO incOrHONOOsO O CN O CM cn H st iH O SO in st O CM O CM IN r-i IN |N St CN r-i O 00 H rH SO St H H CO CM in o m CM CM O ON ON CM &•« 6-8 e-5 Sn? O.S-S 6 £ ^"N S~\ 04 P-l /— N *~\ e e s b e b a a a a a a a a a a a a B 6 B B B B a a a a a a a a a a a a B B B B B B O. Q. 0-. D-. 0- O- o. p, 0-, a, o-, a, BBBBBBE6EBES B b&aaaaaaaaaa o- q.p-p-p-p-&o-o,0.o,p-q, ex •H H OJ H) (d M -H 3 r-i 10 n) QJ |j OJ O hOI3rN3H 3>'N r< 44 TABLE 19. Results of qualitative mineral analysis of low-temperature ashes. +-> c o n 4-J Expandable clays o QJ > o o 1/1 3 o ra CD i o o Q QJ +-> si CD z QJ _*: c CD ■!-> o CT: >> QJ +-> o i- QJ -M s~ QJ « Q- OJ ■!-> -^ o ' — o E o M QJ +-> E 3 cr o o QJ +-> V. CO E 1/1 Q. >l o OJ +J c CC1 M i- o- OJ on u o en QJ 1/1 10 IJ o -M (- o QJ T3 CL Illinois Basin C-14684 X X X X X X X X C-15999 X X X X X X X C-16543 X X X X A X X X X C-16993 X X X ■ A X C-17001* X X X X X X X C-18126* X X X X X X X C-18304 X X X X X X X C-18320 X X X X X X X X X X C-18368 X X X X X X X X C-18560* X X X X X X X X X X C-18571 X X X A X X X X X C-18704 X X X X X X X X X C-18748 X X X X X X C-18857 X X X X X X X X Eastern U nited States C-18820* X X X X X X X C-18824 X X X C-18841* X X X X X X C- 18844 X X X X X X X X C- 18848* X X X X X X X X C-19824* X X X X X X X X X Western U nited States C-18440 X X X X X X X X X C-18445 X X X X X X C- 18457 X X X X X X X C-18816 X X X X X C-19000* X X X C-19854* X X X X X X X X X *Quantitative mineral analysis of washed fractions of these coals are presented in subsequent tables. 45 of pyrite, calcite, quartz, and other major minerals present in the washed fractions are given in table 20. The relative percentages of pyrite, calcite, quartz, and most of the minor minerals in the LTA generally increase in the heavier washed fractions as the relative percentage of total clays in each fraction decreases. These trends are especially evident in coals having numerous mineralized bands and partings or in coals having heavy epigenetic mineralization in cleats and fractures. Minerals such as these are easily removed during normal coal cleaning operations. In sets of washed coals having an inverse mineral distribution in the LTA, for example, siderite and ankerite in set 6 and bassanite in set 8, the data indicate that these min- erals are finely disseminated in the coal and that they are intimately associ- ated with the macerals rather than being in cleat fillings. Examples of washability curves prepared from the mineral data in table 20 are shown in figure 9 for the Herrin (No. 6) Coal. These curves demonstrate that a large portion of the pyrite and calcite in this coal can be concentrated and removed through physical cleaning methods; removal of quartz and clay min- erals is less efficient than removal of heavier minerals. Mineral washability curves for the remaining washed coals display similar results. Yancey and Geer (1962) suggest that the retention of clay minerals in the lighter frac- tions is due to the buoyant effect of imbedded coal in shale particles. The aggregation of quartz and clay minerals in detrital mineral bands found in the coal typically produces similar washing characteristics for the two groups of minerals. Results of clay mineral analysis of the <2 ym fraction of the low temper- ature ash for 2 sets of washed coals are given in table 21. Because of the inherent problems involved with clay mineral preparation and analysis, these data are given to indicate general trends and are not absolute. Both coals were found to contain higher propor- tions of kaolinite in the lighter frac- tions and increased amounts of illite and expandable clays in the 1.60 frac- tion. These data show that a dual pop- ulation of clay minerals may be present in the coal. Shale particles having a specific gravity approximating 2.3— derived from partings, joint fillings, and other rock materials mined with the coal— are concentrated in the heaviest fraction. This shale component con- tains an increased amount of expandable clays and lesser amounts of kaolinite. The clay minerals associated with the coal macerals in the lighter washed fractions may be principally composed of authi genie kaolinite and moderate amounts of illite and other clays. The apparent distribution of all the clay minerals present in the washed fractions may also be affected by the disintegra- tion of shale particles and their suspen- sion in the washing medium; subsequently, lighter gravity fractions may be 20 40 60 80 100 Percentage of recovery I i i i l I I i 20 40 60 80 100 Percentage of recovery % i'iii' — r 20 40 60 80 100 Percentage of recovery 8.1 6.8 5.4' 4.1- 2.7- 1.4 0.0 TOTAL CLAYS i » i i l I I 20 40 60 80 100 Percentage of recovery HERRIN (No. 6) COAL SEAM, ILLINOIS Figure 9. Mineral distributions in a single sample of the Herrin (No. 6) Coal Member, Illinois. (C18560) 46 03 OJ o. E 00 0J <_> 4-1 r— (T> Is O o n3 I. v c 3 I/) OJ o CM 0Q 01 co ^? co Vj ^v 1 1 1 1 1 1 1 OJ B-5 1 1 1 1 1 1 1 -* w N 4-1 ^> l-c fr-S C3 ^ P c ►J ^ >> U OJ > ^ o e^s o ^ c ui m ^ n I I i i I I I CM CO CO CM I — i— I \0 * 00 O in nO ON r-~ vO I-- CM CM i-H CM l-~ CO ON nO m l-~ vo m in m s oo rg sj m m no o m I— I I— I i— I CM VO I < H rJ >n M > • o ; o ■ 0) OS u cfl fa o S3 ex E cd CO vt H N »o m oo r- r- no -* i— i !— lr- I cn cn cn oo cn r^ oococooooor-r--NO in cm o oo co O oo oo oo on oo oo oo m I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ■JOOOvO HON ^O vO N iO vO * C cncoriNNNN-j Cn rH rH rH rH rH 00 V V V V V CN oo on rH no rH m cn 00 o / Ce» / Co« / / Mo. •La A j v 'Sb/«Sc / Sr(x10)« *y H\S / Dy • y 1 r • T f,.M 1 0.1 0.2 0.4 0.6 1 2 4 6 10 Extrapolated float/sink data (ppm) | SGS 1980 Figure 12. Comparison of independently determined concen- trations of organically associated trace elements in the Pittsburgh No. 8 seam, West Virginia (C19824). Figure 13. Comparison of independently determined concen- trations of organically associated elements in the Rose- bud Coal, Montana (C19854). 51 float-sink extrapolated and mineral - matter-free material values. (Stron- tium in figure 13 is probably another such example.) In the case of B (figs. 11 and 14), high concentra- tions from extrapolated float/sink data relative to the mineral -matter- free values, could be due to loss of B as BF 3 from the latter during acid digestion. The ion exchange data on some elements, such as Ca in three differ- ent coals shown in figure 15, help explain most of the differences ob- served between extrapolated values (zero percent recovery) derived from washability data and mineral -matter- free values (acid extracted). Like- wise magnesium is either soluble or undergoes exchange reactions. This is especially apparent in the west- ern and low rank coals where more than 70 percent of the total con- centrations of both Ca and Mg were removed. Sodium values indicate 10 i- E 0.6 0.4 0.2 0.1 Cu» / / Cr / 7 / / /Ga / / / Sb» / B» / / 5e9 / - / / / Co* " £ T- 1 1 1 1 1 1 — ! T " ~1 T 1 1 T" 1 ! T'T 0.1 0.2 0.4 0.6 1 2 4 6 10 Extrapolated float/sink data (ppm) isgs 1980 Figure 14. Comparison of independently determined concen- trations of organically associated trace elements in the Herrin (No. 6) seam coal, Illinois (C16137). o 1.4- Whole coal 1.21 ' ' \:i- me Y/A Residue 1.0- 0.8- 0.6- 0.4- 0.2- nn- i .10 mi .97 .5 .28 I Extract 3 .09 .06 Pittsburgh No. 8 seam. Rosebud seam, Blue Creek seam. West Virginia Montana Alabama ISGS 1980 Figure 1 5. Elemental concentration of calcium in ammonium acetate (ion-exchanged) samples. 52 nearly total exchange or solubility in all cases but one. The exception is coal C-19824, which is unique in that 95 percent of the internal surface area consists of relatively small micropores less than 5 microns in size. It is suspected that pore size is a contributing factor in exchange or solubility reactions for both Na and CI and probably for other elements as well . The data in table 18 show that no significant quantity of Al , Si, P, S, K, Fe, V, Ti, Ni, Cu, Zn, As, Br, or Pb are attached to the coals in an exchangeable form or occur as a mineral that is soluble in the exchange medium used (ammonium acetate). Thus exchangeable ions, which are not removed during float-sink procedures, remain with the coal organic fraction and tend to increase organic affinities of these elements. The acid extrac- tion procedure, however, removes the exchangeable and/or soluble ions attached to surfaces of the polymerized coal. This evidence suggests that exchangeable ions may be contained in associated ground water after initial polymerization has taken place— perhaps even being a result of present-day conditions. The amount of surface area made available to exchange reactions through grinding of coal is a wery small percentage of the actual surface area that would be present if the material were totally depolymerized. These data indicate that virtually all of the exchangeable elements can be removed by the acid treatment. It seems likely that adsorption occurs on the surfaces of the coal particles and pores. The same logic applies to elements that may be chelated with organic material. If major portions of such elements can be removed, they probably come from the available surface area, and chelation probably occurred after the initial polymerization had taken place, and the coal structure had become at least partially fixed. While some disagreement exists in the values derived from the two inde- pendent procedures for investigating elemental occurrence in coal, an account- ing of these differences can be logically made. Moreover, agreement of trace element concentrations, determined in acid-extracted mineral -free coal and the concentrations calculated from adjusted washability curves, is suf- ficiently good to permit their use as estimates of absolute quantities of elements associated with coal organic material. These concentrations, for the most part, are relatively low. VARIABILITY OF ORGANICALLY ASSOCIATED ELEMENTS Table 6, which compares elemental concentrations of the raw coal and the the mineral -matter-free material, illustrates the large amount of variability among coals. For example, in two high-rank eastern coals, the retained cobalt is 72 percent in sample C-18820 but only 10 percent in C-19824. A different effect can be shown for titanium; a retention of about 200 ppm results in a percentage of 16.6 percent in C-18820, while a retention of only 39 ppm in C-18440 results in a slightly higher 19.5 percent of titanium remaining in the demineralized material. Therefore, knowledge of only the total concentration of an element in a coal without knowledge of its organic affinity is of little use in estimating the percentage associated with organic matter. Table 7 gives the mean retention percentages of each organ- ically associated trace element for each of the geographical regions studied. 53 The degree to which coals in this study are representative members of their respective regions is illustrated in table 22. Predicted concentrations of an element in mineral -matter-free (demineralized) material were calculated by multiplying the mean values for each element in whole coal (given in Gluskoter et al . [1977], tables 8 through 10) by their respective mean retention factors found in this study (table 7). Agreement between the mean of predicted values and mean of determined values for the limited number of samples included (24) is generally very good. Poor agreement occurs particularly for elements where the uncertainty for retention values is greatest, i.e., at low concentrations. Table 7 summarizes the mean elemental concentrations in coals for the three geographical regions. The table presents evidence that for some ele- ments greater variations in concentrations occur within a geographical area than between such areas. Especially for whole coal, the standard deviations within a single seam can exceed the mean concentrations in some instances (see also Gluskoter et al . , 1977, p. 121). For example, in the Herrin (No. 6) coal seam (see tables 1 and 6), both the inorganic and the organic components vary widely. Such differences demonstrate the need for each coal to be considered on an individual basis. Perhaps a better overall perception of the variability of organically associated elements can be gained from the data in table 23. The total mean retention percentages for all elements are combined, and the summation of all element concentrations have been calculated for each demineralized coal (values do not include sulfur). No relationship was observed between data concerning ash content of the whole coals and other data in table 23. Despite the apparent consistency in total mean retention percentages, large standard deviations indicate wide concentration variations of the organically associated elements within regions. Further, correlations made between all pair combinations of organic affinities for Illinois No. 6 coal indicate that knowledge of the organic association of one element is of little value in predicting the organic association of other elements. There is also an apparent lack of correlation between the residual trace element concentration and the internal surface area of coal (table 23, last column). If this characteristic of coal organic matter had significantly affected results of the demineralization procedure, i .e., influenced extraction of certain elements, correlation between surface area and the percentage of trace elements removed should have been observed. This evidence indicates that most organically associated elements are actually contained within the polymerized structure of the coal. Minerals and exchangeable ions or, per- haps, chelated elements on the surfaces of the coal particles are the mat- erials thought to be removed by acid leaching. COMPARATIVE DATA Table 24 shows some of the relationships between the organically associ- ated elements in coal and concentrations of the same elements in plant material. This table presents the overall mean concentrations of the organi- cally associated elements from this study, mean plant values compiled by Siegel (1974), the mean crustal abundance of elements compiled by Mason (1958), and certified values for the orchard leaves samples of the National Bureau of Standards (SRM 1571). For the latter, additional values determined at the Illinois State Geological Survey have been added. A few mean values 54 TABLE 22. Prediction of mean el emental concentrations in mineral -matter-free coal for three basins. All values ppm unl ess noted Illinois Eastern Western Predicted Actual Predicted Actual Predicted Actual mean* mean^ mean mean mean mean Element (114) (15)(w) (23) (6)(N) (28) (6)(w) Si 72 65 56 60 85 56 Al 72 74 170 144 100 7^ Fe 100 76 150 106 106 71 Ca 67 50 70.5 71 170 61 Na 10 7.9(13) 16 10(5) 28 7.8 Mg 45 47(12) 42 25(3) 14 17(3) K 17 11(9) 2.5 1.8(3) 3 < Ti 24 31 72 76 45 31 P 5.8 4.3(14) 6 2.8(4) 3.9 2.5(2) Mn 1.06 1 1.8 2.4(5) 1.96 1.8 S 1.6% 1.6% 1.2% 1% 0.4 5% .42% Organic S 1.6% 1.6% 0.86% .98% 0.53% .42% Be 0.05 .05 0.09 .06 0.05 .03(5) B 17 8 17 14 9 7 Sc .49 .53 1.3 1.3 0.4 .3 V 4.5 5.5(13) 7 9.3 3 2.3(5) Cr 4.5 6(14) 7 7 1.6 1 Co .80 .45(14) 4 3.5 0.6 .5 Ni 6.1 5.1(7) 4 2.8(5) < ■ Cu 3 4(12) 3 4 2 4 Zn 15 2.7(3) < < < < Ga 1.9 0.6(14) 1.7 1.1 0.9 0.7 As 0.7 0.2(2) 1.7 .3(1) 0.9 .5(4) Se 0.3 0.4(14) 0.9 0.6 0.4 0.4 Br 8.5 7.7 9 9.7 3.6 1.7 Rb 1.1 3(1) < < • < Sr 5.6 5.7(9) 21 29(3) 8 4(2) Mo .65 .87(4) < < 0.4 1.4(1) Cd .37 •67(4) < < < < Sb .44 .38(12) 0.4 .4 0. ', .38 Cs .08 .06(8) 0.1 .08(4) 0.07 .01(1) Ba 6 3.3(11) 28 20 15 13 La 0.9 0.9 3.7 2.7 1.1 1.3 Ce 1.4 1.5 4.2 3.2 1.9 1.7 Sm .4 .3 .73 .54 0.2 .21 Eu .05 .06 .19 .12 0.06 .05 Tb .06 .09(6) .10 .04(1) 0.08 .05(2) Dy .34 .28(10) .94 .66(3) 0.22 •19(2) Yb 0.14 0.14 0.36 0.23 0.11 0.1 Lu .02 .03(12) .08 .06(5) 0.02 .02(5) Hf .08 .11(13) 0.29 .29 0.21 .26 Ta .04 •05(5) 0.10 .09(3) 0.08 .09(2) W .21 .38(7) 0.20 •26(4) 0.16 .22(2) Pb < < < Th .52 .55 1.2 2.6 0.76 • 8(5) U .28 .22(10) 0.3 .27(4) 0.20 .13(5) *Mean percentage retention (table 7) times mean elemental concentration (Gluskoter et al u Mean elemental concentration determined (table 7). 1977' 55 TABLE 23. Total retention percentages of elements and concentration summations for demineralized coal and ash or mineral -matter content for whole coal Sum. of Total mean Number of elements High-temp. Low- temp. Surface area retention* elements determined ash ash CO, Coal sampl e (%) for meant (ppm) (%) (%) (m 2 /g) EASTERN C 18820 22±21 33 735 11.5 12.9 327 C 18841 17±15 29 980 10.2 14.5 53 C 18848 20±20 26 514 11.6 12.7 98 C 18844 22±19 26 510 8.3 10.4 56 C 19824 26±31 33 296 11.0 14.5 68 C 18824 20±16 30 418 12.5 14.7 112 Mean 575.5±245 10.8±1.4 13.3±1.7 WESTERN C 18816 16 ±20 28 273 9.0 10.6 277 C 19000 21 ±17 24 756 7.0 8.7 240 C 19854 30±36 30 191 11.6 13.1 236 C 18440 19±19 28 305 9.8 14.7 147 C 18445 19±21 26 272 7.5 10.2 232 C 18457 21 ±19 29 294 6.3 8.2 219 Mean 348.5±204 8.5±2 10.9±2.5 ILLINOIS C 14684 17±15 33 448 9.9 12.3 163 C 15999 17±15 34 415 12.4 15.1 155 C 16543 12±14 34 332 11.9 16.2 254 C 16993 14±20 31 415 16.0 20.6 87 C 17001 21 ±24 28 681 11.8 16.0 97 C 18126 11 ±11 33 277 209 C 16317 18±18 29 340 215 C 18304 14±12 31 719 10.9 14.5 85 C 18320 17±17 31 309 13.8 16.8 79 C 18368 15±21 31 265 13.2 16.4 80 C 18560 14±20 31 253 16.5 20.4 79 C 18571 14±15 25 377 16.9 23.4 241 C 18704 12±13 31 423 17.1 21.7 218 C 18748 16±17 33 287 35 C 18857 14+12 26 264 13.9 17.4 227 Mean 387±143 13.7+2.4 17.6±3.3 *Except sulfur. +Number of elements used to determine the mean. "Less than" values not included. for peat taken from Casagrande (1976) are included to illustrate concentra- tions of certain elements in a modern coal -forming type of environment. The only elements in coal that show concentrations significantly in excess of crustal abundance (dark values) are S and Se (Gluskoter et al . , 1977). This is expected because the chemistry of these elements is wery similar. They occur at concentrations of 50 to 20 times the clarke value. Most of the elements that are found in relatively high concentrations in plants (Fe, Ca, K, Mg, Na, P) and certain of the other known nutrients such as Mn, B, and Zn are less concentrated in the organic fraction of coal than in plant material. Perhaps these elements are in soluble or mobile forms that are readily leached from the material during epigenesis before polymeri- zation takes place. Conceivably, some may also have been leached from the coal by the acid extraction, as in the case of the exchangeable ions studied 56 TABLE 24. Mean MMF values fo " coal con pared to plant material and ( :rustal abundance (ppm) NBS + Crustall Element Mean MMF Mean (plant)* (orcha rd leaves) abu ndance Peat** Si 59 200- 5,000 480 277 ,200 Al 63 5- i.OOO 400 81 ,300 Fe 60 140 290 50 ,000 339 (25-2,100) Ca 39 18 ,000 20 ,900 16 ,300 5,396 Na 3.1 1 ,200 78 28 ,000 3,580 (77-20,700) Mg 16 3 ,200 ft ,000 2 ,000 965 (200-4,750) K 3.9 14 ,000 14 ,000 25 ,900 6,525 (4-35,000) Ti 34 1 0.06 4 ,400 P 3.1 2 ,100 2 ,300 1 ,050 Mn 1.0 630 0.91 950 121 (7-701) S 12,200 3 ,400 1 ,900 260 Be 0.05 <.l 0.03 2.8 B 10 50 33 10 Sc 0.7 0.008 22 V 4.8 1.6 0.7 135 Cr 5.9 0.23 2.3 100 Co 1.2 0.5 0.2 25 Ni 3.4 0.3 1.3 75 Cu 2.5 14 12 55 Zn 0.7 100 2 r > 70 Ga 0.6 0.06 0.08 15 As 0.15 0.2 10 1.8 Se 0.4 0.2 0.08 0.05 Br 4.4 15 10 2.5 Rb 0.25 20 12 90 Sr 5.9 26 37 3.75 Mo 0.3 0.9 0.3 1.5 Cd 0.1 0.6 0.11 0.2 Sb 0.3 0.06 3.0 0.2 Cs 0.06 0.2 0.04 3 Ba 6.5 14 51 425 La 1.4 0.09 30 Ce 1.3 1 60 Sra 0.3 0.006 6.0 Eu 0.08 0.03 0.3 1.2 Tb 0.09 0.002 0.9 Dy 0.6 0.02 3.0 Yb 0.18 <0.02 3.3 3.4 Lu 0.05 0.5 Hf 0.17 0.01 3 Ta 0.04 2 W 0.18 0.07 <2 1.5 Pb 0.2 2.7 45 13 Th 0.5 65 7.2 U 0.2 0.04 0.03 1.8 *Siegel, 1974. Values on dry weight basis. tVarious literature sources. Values on dry weight basis. {Mason, 1958. **Casagrande, 1976. Values on dry weight basis. 57 From the coal washability and demineral ization data it seems probable that the largest portion of trace and minor elements are not associated with the organic fraction of the coal. IMPORTANCE OF MINERAL MATTER Although many elements exhibit some organic association, the total elemental content of acid-demineralized coals in tables 9 through 17 generally is low, ranging only from 250 to 600 ppm (excluding organic sulfur). Addition of exchangeable, soluble, and chelated elements still results in the con- clusion that most of the trace and minor elements in coal are in a mineral form and are subject to significant reduction by physical cleaning procedures. Sulfides, sulfates, carbonates, quartz, and clay minerals, together with small amounts of many other minerals, form a multi -component system in the coal with complex origins and variable chemical compositions. The chemical elements present in the mineral matter occur not only as major components of minerals but also, to a limited extent, as isomorphic replacements in solution or as exchangeable cations on clays. These types of sites in the mineral matter are presumably the position of many of the trace elements found in coals. Table 25 gives the principal minerals commonly found in coals and some of the trace elements associated with them. These associations have been compiled from the results of trace element investigations of coal (Gluskoter et al., 1977; O'Gorman and Walker, 1972; Miller and Given, 1978) and from reviews of basic geochemical and mineral research (Deere et al . , 1966; Weaver and Pollard, 1973; and Grim, 1968). Kaolinite, illite, and expandable clays commonly make up a major portion of the mineral matter of most coals. Cation adsorption and exchange are important properties of these minerals. The minor and trace alkali and alkaline earth elements are favored for the exchangeable sites in clays. Because of inherent higher cation-exchange capacities, illites, montmorillo- nites, and mixed-layered clays tend to adsorb a greater variety of ions than kaolinite. A number of elements are also known to substitute for Al , Si, and other major constituents bound into the crystal lattice. Determinations of trace elements in partings and shale strata associated with coal seams indicate higher concentrations of many minor and trace elements in these com- ponents, but because of the complex combinations of clays and other incor- porated minerals, specific mineral -trace element associations are inconclusive COAL CLEANING APPLICATION Knowledge of the distribution and form of elements within a coal will allow better predictions of the cleaning potential for coal than are now possible. Table 26 shows the wide differences in the organic association of trace elements in coals; broadly speaking these differences may be classified within each of the three major coal -producing areas. For the Illinois coals used in this study, Br, Ge, Be, Sb, B, and organic sulfur consistently fall in the organic phase. The sulfide-forming elements, Zn, As, Cd, Fe, and pyritic sulfur, are consistently found in the most inor- ganic fraction and can, therefore, usually be materially reduced by gravity 58 TABLE 25. Elements commonly associated with the principal minerals found in coals* Mineral phases Major cons tituents Trace constituents Sulfides Pyrite, marcasite Fe, S ( As, Cd, Hg, Ag, Pb, Sphalerite Zn, s Fe, Zn , Cu , Co , Sn , Galena Pb, s ( Ni, Mo, Se, Ga Sulfates Barite Ba, s Sr, Pb, Ca Gypsum Ca, s Carbonates Calcite Ca ( Ba, Sr, Pb, Mn, Ca Siderite Fe ) Fe, Mg Ankerite Ca, Fe 1 Dolomite Ca, Mg Phosphates Apatite Ca, P, F Rare earths, U, Ce, Mn, CI, Mg Silicates Quartz Si Zircon Si, Zr Hf, Th, P Tourmaline Ca, Mg, Fe, B, Al, Si Li, F Plagioclase feldspar Ca, Na, Al, Si Ba, Sr, Mn, Ti, Fe, Mg Apali feldspar K, M, Si Rb, Ba, Sr, Fe, Mg, Ti, Li Muscovite K, . Al, Si F, Rb, Cs, Ba, Mg, Fe Clay minerals Kaolinite Al, Si Ti, Mg, Fe, and others Illite Al, Si, K ( Fe, Mg, Ca, Na, K, Ti, Montmorillonite Al, Si, Mg, Fe J Li, V, B, Mn, Cr, Cu, Ni, Mixed layer clays Al, Si, K, Mg, Fo / Rb, Cs, Ga, Be, Zn, Se, F, Chlorite Al, Si, Fe, Mn, , Mg V La, Ba, Sr, Co, and others *This partial listing does not preclude the probability of additional mineral-trace element associations. separation procedures. A number of other elements, Zr, Hg, Pb, Hf, and Mn, also are highly inorganic in association and can be removed rather easily. The other elements determined— Al , Si, Ti , Mo, K, P, Ga, Ca, Cr, Co, Ni , Cu, Mg, Se— are either intermediate in their association or highly variable. Br, Ge, Sr, and organic sulfur have some of the highest organic affinities and As, Rb, K, and pyritic sulfur are among the highest inorganic affinities in the eastern United States coals. Other elements that show relatively high organic associations are B, Ba, Be, Br, and Co. The remaining elements are variable or intermediate in their association. The western coals contain a larger number of elements with high organic affinities (B, Mg, Br, Sr, Be, P, Na, and Ca) than coals studied from either of the other regions. Elements such as Si, As, Cs, Hg, Pb, and pyritic sulfur are highly inorganic; the other elements are variable in their associa- tions. In a physical cleaning process the elements that have high organic affinities are difficult to remove; conversely the inorganic elements are 59 TABLE 26. Organic association of trace elements in coal: Illinois coals C18560 C17001 C18126 Herrin (No. 6) Coal Member Illinois Davis Coal Member Illinois Herrin (No. 6) Coal Member Illinois Float-sink set No. 1 Ge 1.76 U ORS Hg V Br Sb Dy Be .87 Float-sink set No. 2 Ge ORS B Be Ni Na, Ti P Cr, Se Sb Ga 1.28 .66 Float-sink set No. 3 Ge 1.29 ORS B Be Sb .67 B, Cr Ni Co Eu Cu Na Lu Sc K Th Ag Yb Zr Hf TOS, Rb, Ti Cs, Ta Sm Pb Al Si Se Mg 77 .52 .49 27 Co Ca, K V Al Cu Si Mg Mn 65 56 50 35 sus V TOS Mo Na Ga Se Cr Ni Co Hg Cu 62 40 39 25 SUS Sn, HTA, LTA Ba, Ga Cd, Ce, Sr Mn, Ca, Fe PYS As, La, Zn P 17 03 Zr HTA LTA TOS As, Hg Mo, Pb, Fe Cd, PYS Zn, SUS 23 P, Fe, Ti .16 Zr, K LTA, PYS Al, HTA Si As, Pb Cd, Mn, Zn, Ca .04 .02 60 TABLE 26. Continued. Eastern coa Is C18841 C19824 C18820 C18848 Pittsburgh No. 8 Seam Pittsburgh No. 8 Seam P Dcohontas No . Blue Creek West Virginia West Virginia West Virgin ia Alabama Float-sink set No. 4 Float-sink set No. 5 Float-sink set No 6 Float-sink set No. 7 ORS 1.07 ORS 1.15 ORS 1 18 Br 1.20 Sr B Co Ge Br Br Sn Co B Sr Br ORS , TOS U Ba Ni SUS Ba TOS Sr Hg P, TOS Co, Ga Be Ni 1.01 Ge .69 Be U, Yb Sm Na .71 N Ba Ge Fe .67 Cd .66 Ce, La, P .68 P 65 Sr .80 Dy Dy, Eu, I, Sc, W Dy, Yb Cu, Dy Pb Li Eu Be Eu, Na Lu, Ni, Th, Al V V Be, Co, Ga .53 Cr, Ti V Se Cu, Tb Ca Sb La Ag U Ta .51 Ag, Lu, Zn 52 W Lu Pb, Sm, Eu, PYS Ba Cr, Se Yb Sn Tb Ga, Sb, Ce P, Zr Ti .S_c_ ,5J_ Ca .50 Cu ~.~ Na ~50~ Cd .45 Mg Hg Ga Hf, Fe V Hf B Th Cu Si Se, Sm Al Hg Sb La B La Zn Mn, I! Ta, Ca .34 Ni, Sm Mn Zn Ce, Sb Cr, Sc Se Sn Al Tb Yb _Zr_,_ F_e_, _Hf _ Lu As, PYS Ta Th Rb LTA SUS HTA K, Si Cs Ti Cs Zr 27 28 J0_ 26 05 Rb, PYS .18 Hf Fe Zr HTA Cs LTA Rb, K SUS Si As PYS K As Cd Sn Mn, TI Mo, Pb, Ca , Mg .04 24 07 Zn Na LTA HTA, Si K Cs, Rb Mg As, Mn 21 05 61 TABLE 26. Continued. Western coals C19854 C19000 Rosebud Seam Montana Black Mesa Field Arizona B W ORS P Br Sr Mg Sb La Ce, Eu Na Mo Ca Co Tb Sc Dy F, Ga Ge, Yb Be, Sm Float-sink set No. 8 1.24 73_ .68 Float-sink set No. 9 Zn 2.2 B Na Cd Mg, ORS P Ba Fe Ni, TOS Sr Br, Co Dy, Ca Ag Be .79 Lu Al Ni Ta V U Th 56 Yb V, Cu Lu Sb Ce, Sc Se La Eu 75 _5_7_ 54 Cu Hf Ag Ti Li LTA Tl Cr HTA Cd, Se Mn, As, PYS, ,44 33 15 Si Pb, Sn, Zr Cs, Hg, Rb Ba, I, Zn, Fe, K, SUS, Tos Cr, Tb Mn, K W U Hf, Sm Zr Rb Ta, Al Ga, Th Ti Sn HTA Hg LTA PYS As Si Pb Cs, Ge 21. 22 .03 02 62 more easily removed. Depending on the coal, the elements that are intermed- iate or variable in their association will exhibit a limited potential for reduction or a large variation in procedures for removal. The low-rank western coals contained the largest number of elements not readily removed by standard washing methods (table 26), in many cases, these elements have rather low concentrations and would not be expected to present a problem. The potential for reduction of elements and minerals in coal, however, is dependent on characteristics other than just their organic-inorganic associations. The particle size of the minerals plays a significant role in the reduction potential. For example, 95 percent of the pyrite occurring in coal C-19824 has an average particle size of only 8 microns, and 15 percent of the pyrite is encapsulated within the coal particles; this makes its removal extremely difficult. (Kuhn et al . , 1978). (For all practical purposes, such particles are "organically associated.") Furthermore, if an element such as Mn is associated with calcite, its removal is easier than if associated only with clay minerals. Clays tend to concentrate in the lighter fractions of the coal, and they are often finely dispersed within the macerals. Compositional trends of the two coals selected for clay analysis (table 21) show higher proportions of kaolinite in the lighter fractions and increased amounts of illite and mixed-layer clays in the 1.60 S fractions. Such variations have a practical importance for utilization. The com- position of the clay and other minerals in coals affects the fusion tempera- ture of the resulting ash. White and O'Brien (1964) have indicated that increased concentrations of illite, especially in conjunction with higher amounts of carbonate, will lower the melting point and viscosity and change the glass-forming characteristics of the ash. (See also Kent and Champion, 1964) If a portion of the clays is removed during cleaning, the resultant clay composition may substantially change; trace element contents and adsorp- tion properties are altered as well as fusion and sintering characteristics of the ash. 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