6 Elemental Distribution and Association with Inorganic and Organic Components in North Dakota Lignites F. R. Karner, H . H. Schobert, S. K . Falcone, and S. A. Benson
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Energy Research Center, University of North Dakota, University Station, Grand Forks, ND 58202
Elemental associations in Beulah-Zap and Kinneman Creek lignites have been evaluated by: 1) spatial patterns of vertical distribution of elements within seams; 2) behavior in chemical fractionation tests; 3) microprobe evidence of distribution in coal components; 4) inorganic and organic affinities determined by correlation with ash content; and 5) correlation with ionic potential data. Si, Sc, Ti, V, Cr, Co, Br, Y, Zr, Sb, Cs, La, Ce, Sm, Eu, Yb, Th and U are inorganically associated with mineral phases and are typified by concentration at the margins of coal seams, relative insolubility, and positive correlation with ash content. Na, Mg, Ca, Sr and Ba are organically associated with carbonaceous components and are typified by concentration within the central part of seams, high ion-exchangeability, and low correlation with ash content. Al, S, K, Mn, Fe, Cu, Zn, As and Se occur in significant amounts in both inorganic and organic components.
The a s s o c i a t i o n s o f m a j o r , m i n o r , and t r a c e e l e m e n t s i n l i g n i t e bearing s t r a t a o f t h e Fort Union Region present a c h a l l e n g e i n u n d e r s t a n d i n g t h e i r g e o c h e m i c a l r e l a t i o n s h i p s and h i s t o r y . In an e a r l i e r w o r k (_1), t h e s p a t i a l p a t t e r n s o f e l e m e n t a l distribution within a lignitic sedimentary sequence were examined and were r e l a t e d t o f a c t o r s o f a c c u m u l a t i o n o f p l a n t m a t e r i a l s and t o t h e d e p o s i t i o n a l and p o s t - d e p o s i t i o n a l i n f l u x o f i n o r g a n i c m a t t e r . In t h i s s t u d y , two b e d s , t h e Kinneman Creek and t h e B e u l a h - Z a p , which are part of the Sentinel Butte Formation (Paleocene) o f North Dakota, were compared t o determine elemental d i s t r i b u t i o n and a s s o c i a t i o n with s p e c i f i c coal components. The i n o r g a n i c e l e m e n t s i n l i g n i t e s a r e d i s t r i b u t e d as i o n s adsorbed on t h e o r g a n i c acid groups, as c o o r d i n a t e d species, and i n d e t r i t a l and a u t h i g e n i c 0097-6156/ 86/0301 -0070S06.00/0 © 1986 American Chemical Society
Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
6.
K A R N E R ET AL.
Elemental
Association
in North Dakota
Lignites
71
minerals. T h e d i s t r i b u t i o n o f e l e m e n t s i s d e t e r m i n e d by n a t u r a l p r o c e s s e s , a n d , t h e r e f o r e , i s e x p e c t e d t o be s y s t e m a t i c e v e n t h o u g h complex. The methods used to qualitatively identify the interrelationships of m a j o r , m i n o r , and t r a c e e l e m e n t s include examining the s p a t i a l patterns of d i s t r i b u t i o n of elements w i t h i n a s t r a t i g r a p h i e sequence ( 1 ) , c o n s i d e r a t i o n of r e s u l t s of chemical f r a c t i o n a t i o n p r o c e d u r e s ~~[2j, and d i r e c t s t u d y o f t h e d i s t r i b u t i o n of elements by m i c r o p r o b e techniques (_3). Evaluation of the o r g a n i c and i n o r g a n i c a f f i n i t i e s ( 4 - 5 ) o f t h e e l e m e n t s c o r r e l a t e d these methods with theoretical considerations based on ionic potentials and a l l o w e d broad c h a r a c t e r i z a t i o n of elements into i n o r g a n i c , o r g a n i c and c o m b i n e d i n o r g a n i c - o r g a n i c a s s o c i a t i o n s .
Downloaded by FUDAN UNIV on November 18, 2016 | http://pubs.acs.org Publication Date: April 2, 1986 | doi: 10.1021/bk-1986-0301.ch006
Methods and
Procedures
The s a m p l e s were c o l l e c t e d f r o m f r e s h l y e x p o s e d f a c e s w i t h i n open pit mines. The l i g n i t e , l i g n i t e o v e r b u r d e n , a n d u n d e r c l a y w e r e c o l l e c t e d from two p i t s a t t h e B e u l a h Mine where l i g n i t e i s mined f r o m t h e B e u l a h - Z a p bed and f r o m t h e Kinneman C r e e k bed i n t h e Center mine. The s a m p l e c o l l e c t i o n p r o c e d u r e s have been s u m m a r i z e d b y K a r n e r {6) and Benson {]_). The l i g n i t e s a m p l e s c o l l e c t e d a t v a r i o u s i n t e r v a l s w i t h i n t h e s t r a t i g r a p h i e sequence were s u b j e c t e d t o t h e f o l l o w i n g analyses: p r o x i m a t e , u l t i m a t e , h e a t i n g v a l u e , a s h a n a l y s i s , and t r a c e e l e m e n t analysis by neutron activation analysis (NAA) (_8) and x-ray f l u o r e s c e n c e (XRF) ( £ ) . M i n e r a l s i n t h e c o a l and t h e a s s o c i a t e d s e d i m e n t s were d e t e r m i n e d by x - r a y d i f f r a c t i o n and by scanning e l e c t r o n m i c r o s c o p y and e l e c t r o n m i c r o p r o b e a n a l y s i s . A s p l i t from a b u l k s a m p l e was e x a m i n e d b y c h e m i c a l f r a c t i o n a t i o n t o s e l e c t i v e l y extract inorganic constituents based on t h e i r bonding in the coal. The c h e m i c a l f r a c t i o n a t i o n p r o c e d u r e i n v o l v e s e x t r a c t i n g t h e coal with 1M ammonium acetate to remove soluble and ionexchangeable inorganic components. The coal is subsequently e x t r a c t e d w i t h 1M h y d r o c h l o r i c a c i d t o r e m o v e e l e m e n t s p r e s e n t as carbonates, oxides, or coordinated species. The e x t r a c t s and r e s i d u e s f r o m t h e c h e m i c a l f r a c t i o n a t i o n p r o c e d u r e a r e a n a l y z e d by a c o m b i n a t i o n o f NAA, XRF, i n d u c t i v e l y c o u p l e d a r g o n p l a s m a ( I C A P ) , and a t o m i c a b s o r p t i o n s p e c t r o s c o p y ( A A ) . Direct determination of inorganic elements associated with m a c é r a i s and l i t h o t y p e s was b a s e d o n a n e l e c t r o n m i c r o p r o b e s t u d y o f c o a l m i c r o c o m p o n e n t s (3>) u s i n g e n e r g y d i s p e r s i v e x - r a y a n a l y s i s t o d e t e r m i n e t h e p r e s e n c e o f e l e m e n t s and t h e i r r a t i o s as w e l l a s v a r i a t i o n at t h r e e l o c a t i o n s i n t h e Beulah-Zap seam. Results Patterns of Elemental D i s t r i b u t i o n . T h e m a j o r , m i n o r , and t r a c e element abundances and t h e l i t h o l o g y o f t h e s t r a t i g r a p h i e sequence a r e summarized i n T a b l e s I and I I f o r t h e B e u l a h c o a l s . The d a t a f r o m t h e C e n t e r M i n e i s g i v e n i n K a r n e r a n d o t h e r s (_1) w h e r e t h e spatial d i s t r i b u t i o n of elements i n the seam was d e s c r i b e d as f i t t i n g into several patterns. In t h i s s t u d y t h e c l a s s i f i c a t i o n o f elemental d i s t r i b u t i o n patterns includes: 1) Concentration at
Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
Clay Lignite Lignite Lignite Lignite Clay CI a y Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Lignite Clay Silt Chert Sand CI a y
-0.3 0.0 0.1 0.5 0.9 1.0 1.6 1.7 2.1 2.6 2.9 3.3 3.4 3.6 4.2 4.8 5.1 6.3 7.3 7.5 7.8 8.9
--
—
—
10.80 7.20 7.60 7.10 7.40 5.60 15.28 6.40 12.0 9.10
—
17.0 8.47 7.30 22.20
+ +
% ^ Ash Mg
10364 722 678 642 1598 13741 12454 671 707 717 731 571 564 3386 472 1242 914 14031 14605 3800 9826 14771
Na
1964 7767 14348 3479 753 1821 2159 3991 7497 9482 6598 6988 6692 6583 5907 5631 5561 4385 3440 464 4084 1771
84699 8394 1935 2584 27082 113270 111945 9428 5192 4542 3431 3886 2664 7312 4308 9554 5937 88995 88403 13052 49621 81163
Al
321210 17290 3830 4190 22070 295900 307701 12670 4920 4950 2820 4260 1600 20170 4750 10490 5110 293117 288425 56211 250031 287669
Si*
289 683 332 271 420 0 0 305 467 362 572 345 352 346 580 348 425 0 134 0 0 196
p**
2992 11980 9790 6310 17820 7932 3343 8520 7770 8040 7910 9780 7660 5920 11440 87000 119104 1214 3019 9369 2931 4544
S*
10062 530
