Energy & Fuels 1990,4, 755-766
755
Combustion and Leaching Behavior of Elements in the Argonne Premium Coal Samples? R. B. Finkelman,* C. A. Palmer, M. R. Krasnow, P. J. Aruscavage, G . A. Sellers, and F. T. Dulong U.S. Geological Survey, Mail Stop 956, Reston, Virginia 22092 Received April 2, 1990. Revised Manuscript Received August 16, 1990
Eight Argonne Premium Coal samples and two other coal samples were used to observe the effects of combustion and leaching on 30 elements. The results were used to infer the modes of occurrence of these elements. Instrumental neutron activation analysis indicates that the effects of combustion and leaching on many elements varied markedly among the samples. As much as 90% of the selenium and bromine is volatilized from the bituminous coal samples, but substantially less is volatilized from the low-rank coals. We interpret the combustion and leaching behavior of these elements to indicate that they are associated with the organic fraction. Sodium, although nonvolatile, is ion-exchangeable in most samples, particularly in the low-rank coal samples where it is likely to be associated with the organic constituents. Potassium is primarily in an ion-exchangeable form in the Wyodak coal but is in HF-soluble phases (probably silicates) in most other samples. Cesium is in an unidentified HN03-soluble phase in most samples. Virtually all the strontium and barium in the low-rank coal samples is removed by NH40Ac followed by HCl, indicating that these elements probably occur in both organic and inorganic phases. Most tungsten and tantalum are in insoluble phases, perhaps as oxides or in organic association. Hafnium is generally insoluble, but as much as 65% is HF soluble, perhaps due to the presence of very fine grained or metamict zircon. We interpret the leaching behavior of uranium to indicate its occurrence in chelates and its association with silicates and with zircon. Most of the rare-earth elements (REE) and thorium appear to be associated with phosphates. Differences in textural relationships may account for some of the differences in leaching behavior of the REE among samples. Zinc occurs predominantly in sphalerite. Either the remaining elements occur in several different modes of occurrence (scandium, iron), or the leaching data are equivocal (arsenic, antimony, chromium, cobalt, and nickel). The results of these combustion and leaching experiments indicate that some previously held assumptions concerning modes of occurrence of elements in coal should be reconsidered.
Introduction The mode of occurrence (chemical form) of an element in coal influences the element's environmental impact, technological behavior, and economic byproduct potential.' Dreher and Finkelman2 suggested that the mode of occurrence of selenium in Powder River Basin coal and overburden is the critical parameter in determining the amount of selenium in the backfill groundwater. Finkelman and others3 determined that the sodium in coal from the central and southern parts of the Wasatch Plateau in central Utah occurred primarily as analcime (NaA1Si206-H20).From this observation they were able to account for the moderate fouling behavior of Wasatch coal. They also speculated on the environmental and economic consequences of sodium occurring in this form. Finally, knowing the mode of occurrence of sodium allowed them to develop a model accounting for sodium distribution in the coal beds throughout the Wasatch P l a t e a ~ . ~ $ ~ The econimic significance of mode of occurrence information is discussed by Finkelman and Brown: who noted that knowledge of the mode of occurrence of an element is one of the critical factors in evaluating the potential for economic recovery of byproducts from coal and coal wastes. There are several ways to determine the mode of occurrence of an element in coal. Direct methods, such as scanning electron microscopy,6 electron microprobe analysis,' and X-ray diffractions are generally time inten+Paper from a symposium on the Argonne Premium Coal Sample Bank coals (see Energy Fuels 1990,4 ( 5 ) ) .
sive and are applicable to a limited number of elements. Inferring the mode of occurrence from indirect methods, such as volatility, leaching behavior? analysis of density separates,'O and statistical correlations," is less time intensive, but these indirect methods are prone to misinterpretation.12 By combining the results from combustion and leaching experiments of the coal, we reduced the potential for misinterpreting the results from these indirect methods. By observing the behavior of an element during the com(1)Finkelman, R. B. In Mineral Matter and Ash Deposition from Coal; Bryers, R. W., Vorres, K. S., Eds.; Engineering Foundation: New York, 1990;pp 1-12. (2)Dreher, G. B.; Finkelman, R. B. Factors Affecting Ground Water Quality in the Caballo Mine: Final Report; Report on file with Wyoming Department of Environmental Quality, Cheyenne, WY, 1986;135 pages. (3) Finkelman, R. B.; Yeakel, J. D.; Harrison, W. J. Geol. SOC.Am., Abstr. Program 1987,19 (7), 663. (4)Finkelman, R. B. In USGS Research on Energy; Carter, M. H., Ed.: USGS Circ. 1988. 1025. 16-17. ( 5 ) Finkelman, R. B.; Brown, R. D. In USGS Research on Energy; Schindler, K. S., Ed. USGS Circ. 1989,1035,18-19. (6) Finkelman, R. B. Scanning Electron Microsc. SEM/1978 1978,I , 763-768. ._
(7) Minkin, J. A.; Chao, E. C. T.; Thompson, C. L. P r e p . Pap.-Am. Chem. SOC.Diu. Fuel Chem. 1979,24(l),242-249. ( 8 ) Rao, C. P.; Gluskoter, H. J. Ill. State Geol. Suru. Circ. 1973,476, 56 pages.
(9)Kuhn, J. K.;Fiene, F. L.; Cahill, R. A.; Gluskoter, H. J.; Shimp, N. F. Ill. State Geol. Suru. Enuiron. Geol. Notes 1980,88, 67 pages. (10)Palmer, C. A.;Filby, R. H. Fuel 1984,63,318-328. (11)Roscoe, B. A.; Hopke, P. K. In Atomic and Nuclear Methods in Fossil Energy Research; Filby, R. H., Ed.; Plenum: New York, 1982;pp 163-174. (12)Finkelman, R. B. USGS Open-File Rep. 1981,81-99,322pages.
This article not subject to U.S.Copyright. Published 1990 by the American Chemical Society
Finkelman et al.
756 Energy & Fuels, Vol. 4 , No. 6, 1990
bed" Wilcox Beulah-Zap Wyodak Blind Canyon Illinois No. 6 Stockton Pittsburgh Upper Freeport Lower Bakerstown Pocahontas No. 3
Table I. Samde Information ash, % state rank 13.3 TX lignite 10.7 ND lignite 9.2 WY subbituminous high-vol bit. 5.1 UT high-vol bit. 16.3 IL high-vol vit. 19.8 WV high-vol bit. 9.4 PA 13.6 PA med-vol bit. 6.7 PA med-vol bit. low-vol bit.
5.6
VA
age Paleocene Paleocene Paleocene Cretaceous Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian Pennsylvanian
'Samples are identified by the name of the bed from which they were collected. The analytical results presented refer only to the sample and not the bed.
bustion and leaching experiments, we gained insights into its mode or modes of occurrence in the coal. Perhaps this approach would also lead to a rapid and reliable method for determining the modes of occurrence. We are aware of the limitations of leaching coal. Solvents may not contact minerals encased in organic matter or in other minerals. Alternatively, the fine-grained nature of most minerals in coal may enhance their reactivity. Nevertheless, the value of simple but accurate procedures for determining the modes of occurrence of elements in coal requires a careful evaluation of these procedures. In this paper we report the results of a series of combustion and leaching experiments conducted on the eight Argonne Premium Coal samples as well as two additional coal samples: a Texas (Wilcox) lignite and an Appalachian bituminous coal (Lower Bakerstown) (Table I).
Experimental Procedure The Lower Bakerstown and Wilcox lignite samples were ground to -100 mesh, which is the same mesh size as the eight coal samples provided by the Argonne National Laboratory. Each sample was subjected to the procedure depicted in Figure 1. Splits of each coal sample were analyzed by instrumental neutron activation analysis (INAA) for 30 elements (Table 11). Details of the analytical procedure are given in Appendix Table A1 and is described by Palmer and others.13 The splits were ashed in a low temperature (LT) ashing unit following the method of Miller.14 The maximum temperature attained during the LT ashing is believed to be less than 200 "C. Other splits from each coal sample were ashed a t 550 O C , which is the temperature generally using by the U S . Geological Survey for ashing coal samples.ls Several coal samples were also ashed a t 750 O C , which is the temperature recommended by the ASTM,16and a t lo00 "C. The ash residues were analyzed by INAA, and the analytical results were calculated to a coal basis and compared to the analytical data from the coal. All analytical results presented in this paper are on an as-received basis. A 10-g split of each coal sample was subjected to sequential leaching first with 50 mL of 1 N ammonium acetate (NH,OAc) followed by 50 mL of 1:3 hydrochoric acid (HCI), then with 50 mL of 48% hydrofluoric acid (HF), and finally with 50 mL of 10% nitric acid (HN03). Each sample was agitated a t rooin temperature in each of the solvents for 1&24 h. After leaching with each (13) Palmer, C. A.; Baedecker, P. A. In Methods /or Sampling and Inorganic Analysis of Coal; Golightly, D. W., Simon, F. O., Eds.; USGS Bull. 1989, 1823, 27-34. (14) Miller, R. N. In Interlaboratory Comparison of Mineral Constituents in a Sample from the Herrin (No. 6 ) Coal Bed From Illinois; Finkelman, R. B., Fiene, F. L., Miller, R. N., Simon, F. O., Eds.; USGS Circ. 1984, 932, 9-15. (15) Walthall, F. G.; Fleming, S. L., I1 In Methods for Sampling and Inorganic Analysis o/ Coal; Golightly, D. W., Simon, F. O., Eds.; USGS Bull. 1989, 1823, 15-19. (16) American Society for Testing and Materials, Annual Book of ASTM Standards; Vol. 05.05 Gaseous Fuels; Coal and Coke; 1989, 459 pages.
A I
Figure 1. Schematic diagram of analytical procedure. Solid lines indicate procedures used on all 10 samples. Dashed lines indicate procedures used on selected samples. solvent, the residue was rinsed two to three times with distilled water, air-dried, and weighed. Splits were then removed for INAA. Other tests, such as water leaching, leaching with single solvents, and leaching the low-temperature ash, were performed on selected samples. Selected leachates were analyzed by atomic absorption spectroscopy and by ion chromatography.
Results from Combustion Experiments The purpose of the combustion experiments was to determine the degree of volatility of the elements at various temperatures. Our criteria for establishing volatility were that at least 10% of the element had to be lost upon heating and that this loss had to be exhibited by at least half of the samples for which we had data. The analytical error for most elements was less than 10% of the amount detected in the coal samples (Table 11) and in the ash samples. Low-Temperature Ashing. Only bromine (Br), selenium (Se), and mercury (Hg) exhibited volatility during LT ashing (Table 111). A t least 90% of the Br was voltailized from the seven bituminous coal samples. The three low-rank coal samples exhibited increases of Br of from 10 to more than 1000% (see discussion below). From 25 to 80% of the Hg was volatilized from four of the eight samples for which we had data. From 10 to 30% of the Se was volatilized from five samples. In stark contrast to these samples, the Beulah-Zap lignite exhibited a 50% increase in Se (see discussion below). No other element exhibited volatilization in more than two samples. 550 OC Ashing. At 550 "C eight elements exhibited volatility (Table IV). No other element exhibited volatility in more than one sample. About 90% of the Se and Br was volatilized from the seven bituminous coal samples. However, there were substantial increases for Br in the three low-rank coal samples and for Se in the Beulah-Zap lignite (Table V). There was no apparent rank-related volatility for Hg, nickel (Ni), strontium (Sr), antimony (Sb),and uranium (U).The behavior of tungsten (W) is discussed below. 750 and 1000 "C Ashing. Separate splits of four samples (Lower Bakerstown, Wilcox lignite, Illinois No. 6, and Blind Canyon) were ashed overnight in a muffle furnace a t 750 and 1000 "C. Compared to the 550 "C ash, there was no indication of additional volatilization of any ele-
Leaching of Elements in Argonne Premium Coal Samples
eleBeulahmentsa Wilcox Zap Ne 0.038 f 0.524 f 370b 3% K 0.021 f 38 >38 ? ? ? Stockton 0 ? 0 0 0 Pittsburgh >42 >42 ? ? ? Upper Freeport 36 16 0 9 11 Lower Bakerstown 19 67 22 45 0 0 Pocahontas No. 3
"- = no data; ? = poor data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases. Antimony. Antimony (Sb) was one of the eight elements that exhibited volatility at 550 "C (Table IV). However, there was no correlation between volatility and leachability. None of the samples that exhibited volatility had more than 10% NH,OAc-leachable plus HC1-leachable Sb, except for the Pocahontas No. 3 sample from which 25% of the Sb was leached by NH,OAc (Table XVII). There was as much as 41% HC1-leachable Sb in those coal samples in which this element was not volatile. H F was not an effective solvent for Sb. Thirty and 40% of the Sb was leached by HNOBfrom the two lignites.
Finkelman et al.
764 Energy & Fuels, Vol. 4, No. 6, 1990 Table A6. Percent Leachable Barium" H 2 0 NH,OAc HCl H F HN03 0 22 >46 ? ? Wilcox lignite 23 73 ? ? Beulah-Zip lignite 18 74 0 >4 Wyodak 40 10 0 0 Blind Canyon 11 25 9 8 Illinois No. 6 46 0 13 0 Stockton 36 >6 ? ? Pittsburgh ? ? ? ? Upper Freeport 23 ? ? ? Lower Bakerstown 36 34 0 12 Pocahontas No. 3
total >68 96 >96 50 53 59 >42 ? >23 82
Table A10. Percent Leachable Cerium' H,O NHIOAc HCl HF HNO, total 39 0 20 59 0 0 Wilcox lignite 14 70 0 7 91 Beulah-Zap lignite 70 0 12 89 7 Wyodak 0 21 0 16 37 Blind Canyon 8 38 0 24 70 Illinois No. 6 0 0 28 28 0 Stockton 0 25 0 14 39 Pittsburgh 33 0 13 46 0 Upper Freeport 3 0 22 25 0 Lower Bakerstown 11 0 18 0 21 39 Pocahontas No. 3
"- = no data; ? = poor data; 0 = change not statistically significant, The unit digit may not be statistically significant in all cases.
- = no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table A7. Percent Leachable Uranium" H,O NH,OAc HC1 H F HNO, total 49 26 7 82 Wilcox lignite 60 27 0 87 Beulah-Zap lignite 51 26 6 83 Wyodak 0 54 18 10 Blind Canyon 0 0 16 16 Illinois No. 6 12 19 5 36 Stockton 0 28 8 36 Pittsburgh 14 0 19 5 Upper Freeport 9 31 0 22 Lower Bakerstown 0 0 0 0 Pocahontas No. 3
Table A l l . Percent Leachable Samarium' NH,OAc H F HN03 total HCl 10 Wilcox lignite 0 65 0 75 7 88 0 0 Beulah-Zap lignite 81 77 8 0 0 69 Wyodak 6 14 0 10 30 Blind Canyon 44 13 57 0 0 Illinois No. 6 0 17 0 15 32 Stockton 28 9 37 Pittsburgh 0 0 3 0 0 36 39 Upper Freeport 0 9 0 17 26 Lower Bakerstown 16 16 32 0 0 Pocahontas No. 3
"- = no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
= no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table AS. Percent Leachable Hafnium" HIO NH,OAc HCl H F HNOs total 0 0 0 19 16 Wilcox lignite 35 0 0 55 0 55 Beulah-Zap lignite 0 0 65 0 65 Wyodak 0 0 0 0 0 Blind Canyon 0 8 23 9 32 Illinois No. 6 0 0 22 4 26 Stockton 0 0 15 0 15 Pittsburgh 25 10 4 39 0 Upper Freeport 0 0 0 21 7 28 Lower Bakerstown 41 0 0 16 25 Pocahontas No. 3
Table A12. Percent Leachable Europium" H,O NHdOAc HCl HF HNOI total 60 0 9 69 Wilcox lignite 79 0 8 77 Beulah-Zap lignite 0 7 75 68 Wyodak 0 10 26 16 Blind Canyon 0 7 47 40 Illinois No. 6 7 0 11 18 Stockton 17 0 12 29 Pittsburgh ? ? >33 33 Upper Freeport 14 7 16 37 Lower Bakerstown 9 0 15 24 Pocahontas No. 3
0 - E no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table A9. Percent Leachable Bromine" H,O NH,OAc HC1 H F HN03 0 16 ? ? ? Wilcox lignite 0 ? ? ? Beulah-Zap lignite 54 ? ? ? Wyodak ? ? ? Blind Canyon 34 53 ? ? ? Illinois No. 6 19 0 0 0 Stockton 26 0 16 0 Pittsburgh Upper Freeport 17 23 0 0 0 0 19 15 0 Lower Bakerstown 9 17 0 Pocahontas No. 3 30
total >16 ? >54 >34 >53 19 42 40 34 56
a - = no data; ? = uncertain data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
The low totals (all but one less than 50%) for Sb leachability can be explained in three ways: (1) Sb is largely organically complexed and would be unaffected by mineral acids, (2) Sb is generally associated with pyrite and was not effectively leached by the procedure used, and/or (3) Sb is primarily associated with fine-grained accessory sulfides that were not exposed to the solvents. Further work is needed to determine the mode of occurrence of this element. Zinc. It is widely accepted that most of the zinc (Zn) in coal occurs as ~ p h a l e r i t e . ' ~ ,The ~ ~ high proportion of
O= no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table A13. Percent Leachable Terbium" H20 NH,OAc HCl HF HN03 total 0 0 58 0 13 71 Wilcox lignite 84 0 3 87 Beulah-Zap lignite 0 9 76 67 Wyodak 0 4 17 13 Blind Canyon 0 12 40 28 Illinois No. 6 0 0 0 0 Stockton 16 0 7 23 Pittsburgh 37 ? ? >37 Upper Freeport 15 0 16 31 Lower Bakerstown 0 13 22 9 Pocahontas No. 3 0= no data; ? = poor data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
HC1-leachable Zn (21-76% in six of the seven samples for which we have data; Appendix Table A16) appear to be consistent with this belief. The low totals of several samples may be explained by the fine-grained nature of many sphalerite grains.lg These grains are commonly encased in the organic matter and were shielded from the solvents. One curious feature of the data is that 64% of the Zn in the Pocahontas No. 3 was leached by NH,OAc. The only HF-leachableZn was in the low-rank coal samples; perhaps (32) Gluskoter, H. J.; Lindahl, P. C. Science 1973,181 (4096), 264-266.
Leaching of Elements in Argonne Premium Coal Samples
Energy & Fuels, Vol. 4, No. 6,1990 765
Table A14. Percent Leachable Ytterbium" HzO NH,OAc HCl H F HN03 total 0 0 47 0 10 57 Wilcox lignite 0 72 0 7 79 Beulah-Zap lignite 0 50 0 18 68 Wyodak 0 0 0 0 0 Blind Canyon 0 0 18 0 18 Illinois No. 6 0 0 0 13 13 Stockton Pittsburgh 0 0 8 0 8 10 ? ? >10 0 Upper Freeport 20 ? ? 9 >29 Lower Bakerstown 11 0 0 0 0 0 Pocahontas No. 3
Table A18. Percent Leachable Cobalta HzO NH40Ac HC1 H F HN03 total Wilcox lignite 0 0 44 0 17 61 Beulah-Zap lignite 5 58 0 11 74 0 0 20 35 55 Wyodak 11 Blind Canyon 0 6 15 32 19 Illinois No. 6 39 0 13 61 0 7 Stockton 0 0 7 15 10 Pittsburgh 8 7 40 0 Upper Freeport 39 0 0 39 59 0 0 Lower Bakerstown 8 67 0 0 12 14 26 Pocahontas No. 3
"- = no data; ? = poor data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
" - = no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table A15. Percent Leachable Arsenic" H,O NH,OAc HCI H F HNOl total 0 0 0 0 0 0 Wilcox lignite 16 4 11 31 0 Beulah-Zap lignite 0 7 36 + 43 Wyodak 0 24 35 59 0 Blind Canyon 0 17 0 0 17 Illinois No. 6 6 15 Stockton 0 9 0 16 0 23 + 39 Pittsburgh 0 23 0 + 23 Upper Freeport 7 0 41 6 6 53 Lower Bakerstown 0 0 26 18 44 Pocahontas No. 3
" - = no data; + = increase; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases. Table A16. Percent Leachable Zinca H,O NH,OAc HCl H F HNOl total - Wilcox lignite Beulah-Zap lignite 0 76 16 0 92 16 0 76 42 18 Wyodak >5 43 ? 0 >48 Blind Canyon Illinois No. 6 6 0 0 34 40 Stockton 0 21 0 13 34 Pittsburgh 0 2 3 0 0 23 Upper Freeport 0 64 21 0 0 Lower Bakerstown 85 Pocahontas No. 3 a - = no data; ? = poor data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
Table A17. Percent Leachable Chromium" H 2 0 NH,OAc HCl HF HNO, total 0 0 0 11 11 22 Wilcox lignite 0 0 54 0 54 Beulah-Zap lignite 0 34 0 45 11 Wyodak 29 8 12 49 0 Blind Canyon 22 9 20 51 0 Illinois No. 6 0 0 27 27 0 Stockton 0 13 15 15 43 Pittsburgh 0 23 0 16 39 Upper Freeport 0 12 11 23 Lower Bakerstown 0 0 Pocahontas No. 3 0 17 12 9 38 = no data; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases.
some of the Zn in these coal samples had not yet been remobilizedmand was still associated with clays. Relatively little Zn was removed by HN03. Chromium. There was virtually no exchangeable chromium (Cr) in the coal samples (Appendix Table A17). In five of the seven high-rank coal samples, 13-29% of the Cr was HC1-leachable. As much as 54% of the Cr was (33)Finkelman, R. B.;Stanton, R. W.; Cecil, C. B.; Minkin, J. A. American Chemical Society-Chemical Congress Abstracts, 1979 paper 49.
Table A19. Percent Leachable Nickel" H 2 0 NH,OAc HCl H F HN03 Wilcox lignite 0 Beulah-Zap lignite - 37* Wyodak Blind Canyon 35 0 Illinois No. 6 51 Stockton 17 0 Pittsburgh 0 0 Upper Freeport 55 0 0 Lower Bakerstown 25 Pocahontas No. 3
total
-
37
-
67 >51 17 >41 55 >25
"- no data; * = total of leachable Ni; 0 = change not statistically significant. The unit digit may not be statistically significant in all cases. HF-leachable, with the two highest percentages in the lower rank coal samples. As much as 27% of the Cr was leached by HN03. The leaching behavior of Cr does not give a clear picture of its mode of occurrence; some Cr may be associated with silicate minerals and some may be associated with sulfides. The absence of exchangeable Cr and HC1-leachable Cr in the low-rank coals argues against a substantial organic association. The low totals for leachable Cr (all less than 54%) may indicate that a significant amount of Cr is associated with acid-insoluble oxides such as chromite. Cobalt. There was little exchangeable cobalt (Co) (Appendix Table A18) except for the Lower Bakerstown coal in which 59% was removed by NH40Ac (55% was water soluble in this sample). From 7 to 58% of the Co was HC1-leachable. Virtually no Co was removed by HF while as much as 20% was removed by HNOP Some of the HC1-leachable Co may be due to the presence of soluble monosulfides, such as linnaeite-group minerals.'@ The HN03-leachable Co may be due to Co associated with pyrite. On the basis of the behavior of Co upon demineralizing (procedure not described) a German bituminous coal, PickhardP concluded that Co was predominantly organically bound. Chelation may account for some of the HC1-leachable Co. The ineffectiveness of HF leaching indicates that Co in coal is not associated with silicates. The water-soluble Co in the Lower Bakerstown sample is a mystery. Nickel. Relatively little data was obtained on the leaching behavior of nickel (Ni) (Appendix Table A19). A significant proportion of the Ni (as much as 55%) is exchangeable. The volatility of Ni may indicate some organic association. Probably, some of the exchangeable Ni is (34)Pickhardt, W.Int. J. Coal Geol. 1989,14, 137-153. (35)Hosterman, J. W.;Dulong, F. T. In CMS Workshop Lectures, u. I , Quantitatiue Mineral Analysis of Clays; Pevear, D. €2.; Mumpton, F., Eds.; The Clay Mineral Society: Evergreen, CO, 1989;pp 38-51.
766 Energy & Fuels, Vol. 4, No. 6, 1990
associated with organic functional groups, such as carbonyls. We obtained data for HCl leachability from only three samples, and two of the three had more than 32% leachable Ni. Although the data are sparse, there is no indication of substantial amounts of HF- or HN03-leachable Ni. There is insufficient information on the leachability of Ni from which to draw any other conclusions.
Conclusions Although useful information on modes of occurrence can be obtained from combustion and leaching experiments, care must be exercised in interpreting the results. For example, it is important to remove exchangeable cations from low-rank coals prior to heating. This removal prevents the formation of salts and the retention of elements such as Br and Se in the ash. Moreover, there does not appear to be any correlation between the volatility and the leachability of an element. Leaching experiments have a greater potential than combustion experiments for differentiating the modes of occurrence of the elements in coal. The wide variations in leaching behavior of different coals represent differences in chemical form as well as differences in textural relationships. Most elements are more readily leached from low-rank coals than from high-rank coals. Few elements are quantitatively removed
Book Reviews by a single solvent. Several elements (e.g., Cs and Hf) had leaching behaviors that would not have been anticipated from their geochemical characteristics. Additional studies are necessary if we are to generate quantitative information on the modes of occurrence of the elements in coal.
Acknowledgment. We thank Karl Vorres of the Argonne National Laboratory for providing samples used in this study. Thanks also to our US. Geological Survey colleagues Mike Pickering, who assisted with the INAA determinations, and Fred Simon and Blaine Cecil, who provided thoughtful reviews. Appendix Table A1 shows the elements analyzed for by INAA for each coal. Tables A2-Al9 detail the leaching data for Ta, W, Cs, Sr, Ba, U, Hf, Br, Ce, Sm, Eu, Tb, Yb, As, Zn, Cr, Co, and Ni, respectively. Registry No. Na, 7440-23-5; K, 7440-09-7; Sc, 7440-20-2; Cr, 7440-47-3; Fe, 7439-89-6; Co, 7440-48-4; Ni, 7440-02-0; Zn, 7440-66-6; As, 7440-38-2; Se, 7782-49-2; Br, 7726-95-6; Rb, 7440-17-7; Sr, 7440-24-6; Sb, 7440-36-0; Cs, 7440-46-2; La, 743991-0; Ce, 7440-45-1; Nd, 7440-00-8 Sm, 7440-19-9; Eu, 7440-53-1; Tb, 7440-27-9; Yb, 7440-64-4; Lu, 7439-94-3; Hf, 7440-58-6; Ta, 7440-25-7; W, 7440-33-7; Hg, 7439-97-6; T h , 7440-29-1; U, 144061-1.
Book Reviews Zeolite Synthesis. Edited by M. L. Occelli and R. E. Robson. ACS Symposium Series 398. American Chemical Society: Washington, DC, 1989. 650 pp. $139.95. This book consists of a compilation of 42 papers presented at a symposium sponsored by the Division of Colloid and Surface Chemistry at the 196th National Meeting of the American Chemical Society in Los Angeles, CA, September 25-30, 1988. The heavy emphasis in this volume on precrystallization studies, about a dozen papers, is evidence of a gradual maturation from empirical synthesis procedures to investigating and controlling the reactions occurring in gels and solutions prior to crystallization. Much of this work has been made possible by the introduction of new characterization methods. Most of the remaining papers are devoted t o synthesis of specific zeolites with emphasis of faujasite and ZSM-5, the two catalytically most successful zeolites, followed by framework-substituted silicates and aluminum phosphates. T h e opening paper by Milton presents interesting historical insights into the early zeolite research a t Union Carbide Corporation. In the subsequent paper, Barrer shares his broad experience in zeolite crystallization by guiding the reader, with a step-by-step discussion, through a zeolite crystallization from the initial solutions to reaction mixture, nucleation, crystal growth, and stabilization of the products by guest molecules. This excellent overview sets the stage for the next six papers, devoted largely to prenucleation reactions in solutions and gels monitored by NMR, light scattering, and Raman spectroscopy, followed by reports on the effect of gel aging and autocatalytic nucleation on zeolite crystallization. Hasegawa and Sakka found that quaternary ammonium ions form silicate anions with cagelike structures. Several papers report on systematic investigations into the structure-directing effect of quaternary and nonquaternary ammonium ions, polyamines, and even inorganic cations of various sizes. Especially noteworthy are the reports by Guth and coworkers on substituting fluoride for hydroxide ions, thus allowing
crystallization of zeolites from acidic reaction mixtures. This method, which usually leads to larger crystals with reduced structural defects, is stated to facilitate incorporation of heteroelements, e.g., Fe and Ti, in the zeolite framework and may open a new field of zeolite synthesis. Bibby et al. crystallized silicasodalite from nonaqueous reaction mixtures containing ethylene glycol as the solvent, but structures with larger pores were not obtained. Crystallization of Pentasil zeolites is the subject of several papers, including regulation of growth and morphology, crystallization with and without organic templates, and comparison of MFI products obtained with various organic templates. Another group of papers is concerned with synthesis of phosphate-containing framework structures. Synthesis of the 18-ring aluminum phosphate molecular sieve VPI-5 is reported by Davis and co-workers for the first time. T h e products are characterized by electron microscopy, X-ray diffraction, and adsorption measurements. Incorporation of silicon in the structure of aluminum phosphate molecular sieves generates catalytically active acid sites. Crystallization of such materials from biphasic systems is reported by Martens et al. A contribution by Wilson and Flanigen describes the synthesis and characterization of metal aluminum phosphate molecular sieves with Mg, Mn, Fe, Co, and Zn occupying framework positions. T h e parameters important for the crystallization of large crystals of ZSM-5 and A1P04-5 are explored by Muller et al. Five papers describe the synthesis of zeolites containing isomorphously substituted B in ZSM-5, mordenite, and zeolite Y, and Fe in faujasite. In an extension of earlier work, Skeels and Flanigen replace framework AI in zeolites with Fe or Ti by reaction with respective ammonium fluoride salts. Crystallization of a 10 Si02/A1203faujasite is still elusive. Robson, in a very thorough contribution, examines the crystallization of zeolite Y and points out conditions that may lead t o the synthesis of such high-silica Y. In the preparation, by steaming, of faujasite frameworks with SiO2/AI2O3near 10, A1 is removed from the framework to become octahedral and sub-
