2irgonne national caboratorg/67531/metadc870539/...during adsorption measurements of the platinum...
TRANSCRIPT
ANL-6811 ANL-6811
\m. 2irgonne National Caboratorg
ANION EXCHANGE CHARACTERIiTICS OF THE Ei|MENTS IN NITRIC ACID AND
NITRATE SOLUTIONS AND APPLICATION IN TRACEELEMENT ANALYSIS
by
J. P. Faris and Robert F. Buchanan
LEGAL NOTICE
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ANL-6811 Chemis t ry ( T I D - 4 5 0 0 , 32nd Ed.) AEC R e s e a r c h and Development Repor t
ARGONNE NATIONAL LABORATORY 9700 South Cass Avenue Argonne, Illinois 60440
ANION EXCHANGE CHARACTERISTICS OF THE ELEMENTS IN NITRIC ACID AND NITRATE SOLUTIONS
AND APPLICATION IN TRACE ELEMENT ANALYSIS
by
J. P . F a r i s and Robert F . Buchanan
Chemis t ry Division
July 1964
Operated by The Universi ty of Chicago under
Contract W-3 1-109-eng-38 with the
U. S. Atomic Energy Commiss ion
T A B L E O F C O N T E N T S
No. T i t l e P a g e
A B S T R A C T 5
I. NITRIC ACID 6
I n t r o d u c t i o n 6
E x p e r i m e n t a l 6
R e s u l t s and D i s c u s s i o n 7
A p p l i c a t i o n 10
II. N I T R A T E MEDIA 12
III. A N A L Y T I C A L A P P L I C A T I O N S 17
P l u t o n i u m 17
T h o r i u m 19
N e p t u n i u m 20
R a r e E a r t h s (Light) 20
R a r e E a r t h s (Heavy) 21
A C K N O W L E D G M E N T 21
R E F E R E N C E S 22
LIST O F F I G U R E S
No. T i t l e P a g e
1. R e m o v a l f r o m Solut ion of E l e m e n t s in 0.1 to 14M N i t r i c Acid wi th S t r o n g l y B a s i c Anion E x c h a n g e R e s i n 8
2. Anion A d s o r p t i o n of U(Vl) and Bi ( l l l ) in NH4NO3-HNO3 M i x t u r e s . . 13
3 . V a r i a t i o n of D i s t r i b u t i o n Coeff ic ient wi th Ac id M o l a r i t y in M i x t u r e s of 10% N i t r i c A c i d - 9 0 % M e t h a n o l . . . . . . . . . . . . . . 14
4. V a r i a t i o n of D i s t r i b u t i o n Coeff ic ien t wi th P r o p o r t i o n of 7M N i t r i c Acid 14
5. A p p r o x i m a t e D i s t r i b u t i o n Coef f i c i en t s of A lka l ine E a r t h s a s a F u n c t i o n of Ac id M o l a r i t y in M i x t u r e s of 10% N i t r i c A c i d - 9 0 % M e t h a n o l . 15
6. D i s t r i b u t i o n Coef f i c i en t s of A c t i n i d e s a s a F u n c t i o n of Ac id i ty in 10% N i t r i c A c i d - 9 0 % M e t h a n o l . . . . . . . . . . . . . . . 15
7. E l u t i o n C u r v e s for the S e p a r a t i o n of A m e r i c i u m and C u r i u m f r o m O t h e r C o m m o n A c t i n i d e s in a 10% N i t r i c A c i d - 9 0 % M e t h a n o l M i x t u r e 15
8. E l u t i o n C u r v e for the S e p a r a t i o n of C a l i f o r n i u m f r o m A m e r i c i u m and C u r i u m in a 10% N i t r i c A c i d - 9 0 % M e t h a n o l M i x t u r e 16
ANION EXCHANGE CHARACTERISTICS OF THE ELEMENTS IN NITRIC ACID AND NITRATE SOLUTIONS
AND APPLICATION IN TRACE ELEMENT ANALYSIS
by
J. P. Faris and Robert F. Buchanan
ABSTRACT
I. Nitr ic Acid
The adsorpt ion of most naetal ions onto a strongly basic anion exchange r e s in from ni t r ic acid solution has been determined. Distr ibution coefficients a r e given for some 70 e lements in acid concentrat ions ranging from O.IM to 14M. A comprehensive l is t of r e fe rences to s imi la r studies and to some typical uses of anion exchange separa t ion in a n i t r ic acid medium is included.
II. Ni t ra te Media
The increased absorpt ion of some e lements from ni t ra te solutions of low acidity offer additional poss ibi l i t ies for analyt ical separa t ions by anion exchange r e s i n s . Pas t work in inorganic n i t ra te solutions and in wa te r -mi sc ib l e organic solvent mix tu res is reviewed briefly from the standpoint of possible use in t r ace element ana lys i s .
IIL Analytical Applications
Some analyt ical p rocedures a r e outlined whereby t r a c e impur i t i es were concentrated by anion exchange in a n i t ra te medium and then de termined by an emiss ion spectro-graphic technique. Methods developed for the analysis of thorium, plutonium, and neptunium have uti l ized the la rge separa t ion factors from mos t other ions in a n i t r ic acid m e dium; differences in adsorpt ion from methanol -n i t r i c acid mix tu res have been applied to the analys is of the r a r e ea r th s . Limits of detection by the copper spark method a r e given for m o r e than 50 e lements .
I. NITRIC ACID
I n t r o d u c t i o n
Anion exchange a d s o r p t i o n f r o m a n i t r i c ac id m e d i u m h a s m a n y s p e cific u s e s and m u c h h a s b e e n pub l i shed about the c h a r a c t e r i s t i c b e h a v i o r of v a r i o u s m e t a l l i c ions in s u c h m e d i a . To ga in m o r e c o m p l e t e i n f o r m a t i o n and to g a t h e r da t a n e c e s s a r y for a n a l y t i c a l a p p l i c a t i o n , the A n a l y t i c a l G r o u p of the C h e m i s t r y D i v i s i o n at A r g o n n e m a d e a s e r i e s of s t u d i e s in wh ich the a d s o r p t i o n of m o s t m e t a l ions f r o m n i t r i c ac id so lu t i ons of c o n c e n t r a t i o n r a n g i n g f r o m 1 to 14M h a s b e e n determined.^•'•3> 14) T h i s w o r k h a s now b e e n ex tended to inc lude the b e h a v i o r of s o m e 70 e l e m e n t s in ac id c o n c e n t r a t i o n s r a n g i n g down to O.IM. Both c o l u m n e lu t ion and b a t c h w i s e t e c h n i q u e s w e r e u s e d in the e x p e r i m e n t s , a s w e l l a s r a d i o c h e m i c a l , c h e m i c a l , and o p t i c a l e m i s s i o n s p e c t r o g r a p h i c m e t h o d s of a n a l y s i s .
E x p e r i m e n t a l
A n a l y t i c a l g r a d e Dowex 1 x 10, 200-400 m e s h s t r o n g - b a s e a n i o n -e x c h a n g e r e s i n w a s o v e n - d r i e d for s e v e r a l h o u r s a t a p p r o x i m a t e l y 100°C, we ighed in the c h l o r i d e f o r m , and t h e n c o n v e r t e d to the n i t r a t e f o r m by w a s h i n g t h o r o u g h l y wi th n i t r i c ac id and w a t e r . The r a t e d c a p a c i t y w a s 3 m e q / g , and the a p p r o x i m a t e d e n s i t y , d e t e r m i n e d f r o m d i s p l a c e m e n t of b e n z e n e by the d r y r e s i n , w a s 1.67 g / c m ' ' . A l l w o r k w a s at r o o m t e m p e r a t u r e (about 25°C).
In c o l u m n e x p e r i m e n t s the e l e m e n t s w e r e added in m i c r o g r a m q u a n t i t i e s to a s e r i e s of e q u i l i b r a t e d c o l u m n s and t h e n e lu t ed wi th n i t r i c ac id of a p p r o p r i a t e m o l a r i t y . The eff luents w e r e c o l l e c t e d in f r a c t i o n s tha t r a n g e d f r o m 2 m l for a 3 . 5 - m m - I D c o l u m n c o n t a i n i n g 0.4 g of r e s i n to 10 m l for a 6 - m m - I D c o l u m n con ta in ing 2 g of r e s i n . F l o w r a t e s w e r e f r o m 2 to 10 m l / h r .
W h e n e v e r a r a d i o a c t i v e t r a c e r w a s added to a c o l u m n , the eff luent w a s a n a l y z e d by coun t ing the a lpha , be t a , or g a m m a ac t i v i t y , depend ing on the d e c a y c h a r a c t e r i s t i c s of t h e e l e m e n t b e i n g d e t e r m i n e d . The a l p h a and b e t a a c t i v i t i e s w e r e s t i pp l ed on to s t a i n l e s s s t e e l p l a n c h e t s and coun ted in a 27T flow p r o p o r t i o n a l c o u n t e r u s i n g a 90% a r g o n and 10% m e t h a n e g a s m i x t u r e . T h e coun t ing e f f ic iency for a l p h a s w a s 50.5%; tha t for b e t a w a s about 70%. The g a m m a s w e r e coun ted in so lu t ion on a w e l l - t y p e s c i n t i l l a t i o n c o u n t e r wi th a Na l (T l ) c r y s t a l .
F o r m o s t e l e m e n t s the e lu t ion w a s d e t e r m i n e d by e m i s s i o n s p e c t r o g r a p h i c e x a m i n a t i o n of eff luent f r a c t i o n s by the c o p p e r s p a r k m e t h o d . ^•^"''*^' T h i s p r o c e d u r e w a s r a p i d and c o n v e n i e n t b e c a u s e it p e r m i t t e d a m i x t u r e of e l e m e n t s to be added to a c o l u m n and kep t the n u m b e r of t r a c e r p r e p a r a t i o n s o r t i m e - c o n s u m i n g c h e m i c a l a n a l y s e s to a m i n i m u m . S ince ionic s p e c i e s
w e r e p r e s e n t a t only t r a c e c o n c e n t r a t i o n s , d i s t r i b u t i o n coe f f i c i en t s ( K ^ ) could be d e r i v e d f r o m K^̂ = V / M , U 0 8 ) w h e r e V i s the n u m b e r of m l r e q u i r e d to r e a c h the e lu t ion c u r v e m a x i m u m ( l e s s the f i r s t - c o l u m n v o l u m e of d i s p l a c e d l iquid) and M is the weigh t of r e s i n in g r a m s .
In the b a t c h m e t h o d , a known a m o u n t of an e l e m e n t w a s e q u i l i b r a t e d wi th we ighed a m o u n t s of r e s i n and a c i d . D i s t r i b u t i o n coe f f i c i en t s w e r e d e r i v e d f r o m a n a l y s i s of the a q u e o u s p h a s e by the r e l a t i o n s h i p
_ c o n c e n t r a t i o n p e r g r a m d r y r e s i n " c o n c e n t r a t i o n p e r m l so lu t ion
R e s u l t s and D i s c u s s i o n
D i s t r i b u t i o n coe f f i c i en t s ob t a ined f r o m t h e c o l u m n e lu t ion and b a t c h -w i s e e x p e r i m e n t s a r e p r e s e n t e d in F i g . 1 a s a funct ion of n i t r i c a c i d m o l a r i ty. E l e m e n t s p l a c e d in the "no a d s o r p t i o n " c a t e g o r y w e r e t h o s e s p e c t r o g r a p h i c a l l y e s t i m a t e d to be q u a n t i t a t i v e l y e lu t ed in the f i r s t eff luent f r a c t i o n and not d e t e c t e d in s u b s e q u e n t f r a c t i o n s , a s w e l l a s t h o s e found to have v a l u e s of K^ of l e s s t han about one o r two a s d e t e r m i n e d by u s e of a r a d i o a c t i v e t r a c e r in c o l u m n or b a t c h w i s e e x p e r i m e n t s . A n e g l i g i b l e p e r c e n t a g e of an e l e m e n t a p p e a r i n g in a s e c o n d eff luent f r a c t i o n f r o m a c o l u m n w a s i n d i c a t e d by " s l i g h t a d s o r p t i o n . "
In s o m e c a s e s a v a l e n c e c h a n g e m a y have t a k e n p l a c e on the r e s i n ; a s a r u l e , the add i t i on of e x c e s s ox idan t or r e d u c t a n t to an e lu t ing so lu t i on or to a b a t c h w a s avo ided . An e x c e p t i o n w a s in the c a s e of n e p t u n i u m , for wh ich the t e t r a v a l e n t s t a t e w a s m a i n t a i n e d wi th O.IM f e r r o u s s u l f a m a t e . R u t h e n i u m m a y e x i s t in n i t r i c ac id a s n e u t r a l , a n i o n i c , o r c a t i o n i c s p e c i e s . ^ °^ ' ' A l though R U ( I V ) c a n be adsorbed , ' • ' • ^ ' ^ ' ' • ' • ^^ ' we found tha t wi thout a ho ld ing ox idan t m o s t of the r u t h e n i u m added to a c o l u m n b r o k e t h r o u g h e a r l y . F o r T l ( l l l ) , bo th c o l u m n and b a t c h w i s e e x p e r i m e n t s su f fe red f r o m l a c k of r e p r o d u c i b i l i t y , and the a d s o r p t i o n funct ion h a s not b e e n de f in i t e ly e s t a b l i s h e d . A l s o , Ce( lV) , for wh ich e x c e l l e n t a d s o r p t i o n h a s b e e n r e p o r t e d , v25, 72 ,94 ,95 j -was e l u t e d to about the s a m e ex ten t a s Ce( l l l ) , owing to a r e d u c t i o n by the r e s i n in the c o l u m n s .
P a r t i c u l a r c a r e w a s t a k e n to e x c l u d e the p r e s e n c e of c h l o r i d e ions d u r i n g a d s o r p t i o n m e a s u r e m e n t s of the p l a t i n u m m e t a l s and Au( l l l ) , b e c a u s e t h e s e e l e m e n t s a r e s t r o n g l y a d s o r b e d a s the c h l o r o c o m p l e x e s . ( 7 2 ) P l a t i n u m h a s not b e e n inc luded in F i g . 1 b e c a u s e the d i s t r i b u t i o n m e a s u r e m e n t s by the b a t c h w i s e m e t h o d did not a g r e e wi th t h o s e m a d e by the c o l u m n e lu t ion t e c h n ique . The r e a s o n for t h i s d i f f e r e n c e h a s not b e e n fully r e s o l v e d ; p r o b a b l y the h i g h e r b a t c h w i s e v a l u e s could be a t t r i b u t e d to s o m e ex ten t to the diff i cu l ty of r e m o v i n g c o m p l e t e l y a l l t r a c e s of c h l o r i d e . On the o t h e r hand, the a d s o r p t i o n of Pd ( l l ) w a s found to i n c r e a s e only s l i gh t l y when an e q u i v a l e n t
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9
a m o u n t of c h l o r i d e was d e l i b e r a t e l y added to a b a t c h . When t en t i m e s the e q u i v a l e n c e of c h l o r i d e was added , d i s t r i b u t i o n coef f ic ien t s at IM and at 2M n i t r i c ac id w e r e h ighe r by a fac tor of two to four .
A d s o r p t i o n s of s e v e r a l e l e m e n t s i n v e s t i g a t e d by the s p e c t r o g r a p h i c p r o c e d u r e w e r e a l s o d e t e r m i n e d at the t r a c e r l e v e l wi th r a d i o m e t r i c m e t h o d s of a n a l y s i s or in m a c r o q u a n t i t i e s by the u s e of c h e m i c a l a n a l y s e s . R e s u l t s of s o m e s ing le b a t c h w i s e e q u i l i b r a t i o n m e a s u r e m e n t s of Th^^'* and U^^'' a d s o r p t i o n s and of Pd( l l ) and Hg(ll) a d s o r p t i o n s by s p e c t r o p h o t o m e t r i c a n a l y s e s a r e c o m p a r e d with s p e c t r o g r a p h i c a l l y d e t e r m i n e d a d s o r p t i o n s in T a b l e I. S i m i l a r a g r e e m e n t was found in c o l u m n e lu t ion e x p e r i m e n t s wi th U^'^'', Ce''*'*, and Mo t r a c e r s . It wi l l be noted tha t the v a r i a t i o n of r e s u l t s b e t w e e n the d i f fe ren t p r o c e d u r e s w a s l e s s than t h a t ob ta ined for Hg(l l ) when r e s i n f r o m d i f fe ren t lo ts w a s u s e d .
Table I
EXPERIMENTAL DISTRIBUTION COEFFICIENTS BY SPECTROGRAPHIC METHOD COMPARED WITH OTHER PROCEDURES AT VARIOUS NITRIC ACID CONCENTRATIONs(l3)
Th""
Th
U233
U233
U
P d
P d
Hg
Hg
Hg
Method
Batch
Column
Batch
Column
Column
Batch
Column
Batch^
Batch
Column
Anal
R. C >
Spec.
R. C.
R. C.
Spec.
Chem.
Spec.
Chem.
Chem.
Spec.
1
1.0
1.0
1.3
3.8
<2
45
50
11
3.5
2
6.0
3.3
3.3
3.8
3.0
57
52
23
7.8
8.0
4
51
47
6.7
9.2
7.2
41
54
20
6-9
M HNO3
6
216
13
17
12
29
38
18.4
8.6
5.0
8
303
323
15
16
12
12
18-25
5.7
3.5
10
227
9.7
13
7.2
6
10-18
2.5
3.0
12
130
93
7.2
12
5.6
14
8.0
2.0
1.5
14
67
51
6.2
7.3
5.4
4.0
4 - 7
<2
<1.5
'^ 'Resin
(b)R. C.
from different lot.
= radiochemical; Spec. = spectrographic; Chem. = chemical.
F o r the m o s t p a r t the a d s o r p t i o n s in F i g . 1 w e r e in s a t i s f a c t o r y a g r e e m e n t wi th t hose which have b e e n r e p o r t e d in the l i t e r a t u r e r e f e r r e d to be low, a l though m a n y of the c o m p a r i s o n s can only be q u a l i t a t i v e b e c a u s e of v a r i a t i o n s in p h y s i c a l p r o p e r t i e s or type of r e s i n u s e d . Af ter the e a r l y r e p o r t s f r o m Cha lk R i v e r , w'"> ^"'' the s t r o n g a d s o r p t i o n of p lu ton ium w a s m u c h i n v e s t i g a t e d , and a de t a i l ed s tudy of the exchange k i n e t i c s was m a d e by Ryan and Whee lwr igh t . (101) The a d s o r p t i o n of t h o r i u m h a s a l s o b e e n s tud ied e x t e n s i v e l y . ' 1 ^ ' ^ 0 , 2 1 , 24 ,25,72j The p r e s e n t v a l u e s found for the a d s o r p t i o n of Pb( l l ) and Bi( l l ) a r e in good a g r e e m e n t wi th t hose r e p o r t e d by N e l s o n and Kraus,(°-^^ and those found for R e ( v i l ) and Tc(VIl) a g r e e with the
u l t s of Huffman et al .^ •' The b a t c h w i s e m e a s u r e m e n t of P a ( v ) r e s
10
a d s o r p t i o n c o n f i r m e d the pub l i shed da ta . (15,47, 105, 122) The e lu t ion of Z r ( l V ) ( l 5 , 8 9 , 1 2 2 ) ^j^d of M o ( V l ) ( l 5 , 57) could be c o m p a r e d q u a l i t a t i v e l y . A g e n e r a l a g r e e m e n t of r e s u l t s w a s found wi th the K^j v a l u e s wh ich have b e e n r e p o r t e d in the l i t e r a t u r e for Zn( l l ) , (^ 1.72) u ( v i ) , ( l 5 , 2 1,72,88, 122) Np(lV), (46 ,92 ,95 ,107) Am( l l l ) , (15,95) Cm( l l l ) , (95) and the r a r e e a r t h s . 1^5, 56, 72, 74) A d s o r p t i o n s of n u m e r o u s e l e m e n t s f r o m n i t r i c ac id have b e e n s tud ied by K r a u s and N e l s o n , (72) a.nd in an e x t e n s i v e s u r v e y by I ch ikawa et a l . ' 5 ' ) a d s o r p t i o n s w e r e p r e s e n t e d for a l a r g e n u m b e r of r a d i o a c t i v e t r a c e r s . J a m e s ( 5 8 ) j-^^s r e p o r t e d d i s t r i b u t i o n coe f f i c i en t s for m a n y e l e m e n t s on Dowex 1 x 4 f r o m 7M n i t r i c ac id .
Some l i t e r a t u r e v a l u e s for an ion e x c h a n g e a d s o r p t i o n in n i t r i c ac id a r e a l s o inc luded in F i g . 1. F r o m the d a t a p u b l i s h e d for the a d s o r p t i o n of Np(V)(22,46, 107, 122) ^nd Np(Vl)(22,46, 57, 107) ^ m a x i m u m d i s t r i b u t i o n c o eff ic ient of about 15 can be e x p e c t e d . Neg l ig ib l e a d s o r p t i o n h a s b e e n r e -p o r t e d for N b ( v ) , (15 ,58 ,86 ,88) R ^ d l ) , (23) A C ( I I I ) , (23. 54) ^nd P u ( l l l ) . (95, 122)
P o l o n i u m a d s o r p t i o n in n i t r i c a c i d w a s s tud i ed by Danon and Z a m i t h , ( 2 ' / who r e p o r t e d d i s t r i b u t i o n coe f f i c i en t s for Po( lV) r a n g i n g f r o m 120 to 90 in n i t r i c ac id f r o m 0.8M to 5M. In the p r e s e n c e of an ef fec t ive r e d u c t a n t the a d s o r p t i o n d e c r e a s e d to g ive a c u r v e s i m i l a r to tha t of Bi ( l l l ) in n i t r i c ac id . I c h i k a w a et a l . (57 j l a t e r found Po( lV) to be only s l igh t ly a d s o r b e d . S t a r i k and A m p l e l o g o v a ( 104) s tud ied the s o r p t i o n of po lon ium ions f r o m n i t r i c ac id . In 7M ac id , I r ( lV) w a s a d s o r b e d , w h e r e a s Se(lV) and T a ( v ) w e r e no t . (5o j F o r Ge(lV), bo th n e g l i g i b l e a d s o r p t i o n ( 5 8 , 7 2 ) and s t r o n g a d -s o r p t i o n ( 5 7 j have b e e n r e p o r t e d . It h a s b e e n i m p l i e d tha t f r a n c i u m and the t r a n s c u r i u m e l e m e n t s would not be a d s o r b e d on an ion e x c h a n g e r e s i n s f r o m n i t r i c ac id so lu t ion . \54, 55 ;
J a m e s ( 5 9 j h a s s tud ied the s y n e r g i s t i c effect of t h o r i u m on the d i s t r i b u t i o n coe f f i c i en t s of s e v e r a l e l e m e n t s . Ryan(98) h a s s tud ied the s p e c i e s invo lved in the an ion e x c h a n g e a d s o r p t i o n of q u a d r i v a l e n t a c t i n i d e n i t r a t e s . K a z a n t s e v ' 6 1) h a s c o m p a r e d the c h e m i c a l r e s i s t a n c e of s e v e r a l an ion e x c h a n g e r s in n i t r i c ac id s o l u t i o n s . F e r n a n d e z ( 3 9 j h a s r e p o r t e d on the r a t e of diffusion for a lpha e m i t t e r s in s o m e an ion e x c h a n g e r e s i n s .
A p p l i c a t i o n
The s t r o n g an ion ic a d s o r p t i o n of the t e t r a v a l e n t c o m p l e x h a s b e e n u s e d to a d v a n t a g e in fuel p r o c e s s i n g for p l u t o n i u m r e c o v e r y and s e p a r a t i o n f r o m f i s s i o n products . (2 , 6,17, 18 ,88 ,89 ,99 , 100, 10 1,107, 118, 120) in s i m i l a r p r o c e s s e s wh ich Lave b e e n d e s c r i b e d for the c o n c e n t r a t i o n and p u r i f i c a t i o n of n e p t u n i u m , ( 1 ° ' 1" '̂ °2 , 8 1 , 90, 97, 107) |-he t e t r a v a l e n t s t a t e w a s u s u a l l y m a i n t a i n e d wi th the add i t ion of r e d u c t a n t s such a s s e m i c a r b a z i d e , f e r r o u s s u l f a m a t e , o r h y d r a z i n e . P r o c e d u r e s for s e q u e n t i a l s e p a r a t i o n of the a c t i n i d e e l e m e n t s ( 9 5 , 121, 122) and t h e i r i s o l a t i o n f r o m f i s s i o n
products '14,82,86,92, 100, 120, 122j have incorporated anion exchange adso rp tion from ni t r ic acid. Similar use in analyt ical methods has been descr ibed for the quantitative recovery of plutonium(60,73) and of thorium, (43, 59 j for the chemical a s say of plutonium alloys, (8,41) and for the remova l of interfer ing ions in chemical or rad iochemica l analyses . (5 ,9 , 14,87, 121 j
II. NITRATE MEDIA
Anion exchange of the lanthanides and actinides from inorganic ni t ra te solutions have been studied in considerable detail . In slightly ac idified solutions of li thium ni t ra te Marcus and Nelson(78) found increas ing adsorpt ion with increas ing ni t ra te concentrat ion. The lighter r a r e ea r ths were more strongly adsorbed than the heavier and could be readily separated. Fu r the r work provided more data for the heavier lanthanides(75,76) and compared the effect of n i t ra te ion concentrat ion for severa l n i t ra te sa l t s . Distribution coefficients were highest for the l ighter lanthanides in n i t ra te solutions of l i thium, and dec reased in magnitude for solutions of aluminum, calcium, ammonium, and hydrogen. Adar et a l . , ( l ) and Marcus et al.,(77) have m e a s u r e d dis t r ibut ion coefficients for a number of the t r ivalent actinide ions in l i thium ni t ra te solutions and repor ted an efficient separat ion of a m e r i c i u m and cur ium. Danon(26) separa ted t r ace amounts of act inium from weighable quantities of lanthanum by elution with l i thium ni t ra te solution. Edge(31) found the adsorpt ion of thor ium var ied with the nature of the cation of supporting ni t ra te solution in the o rder alunninum y l i thium > calcium > hydrogen. He also developed a procedure for separa t ion and spect rographic determinat ion of t race r a r e earths.(32) The strong adsorpt ion of uran ium from a solution near ly sa tura ted with alunninum ni t ra te was used by Okenden and Foreman(o5) for an analyt ical separa t ion from la rge amounts of i ron. Vita et al.,(112) s imi la r ly s ep ara ted uranium from many e lements and compared dis t r ibut ion ra t ios for uranium in solutions of seve ra l n i t ra te sa l t s , including those of aluminum, sodium, nickel, and zinc. Higgins(48) recovered uran ium from calc ium ni t ra te solutions. F o r e m a n et al.,(40) found that the addition of inorganic n i t ra tes inc reased the uptake of uran ium onto an anion exchange r e s in in the o rder aluminuin > ca lc ium > l i thium > ammonium at constant n i t ra te molar i ty , Caracciolo( 1 9) adsorbed thor ium from ni t r ic ac id-sodium ni t ra te solutions on an agitated bed of anion exchanger. In a detailed study by Nelson and Kraus(°3) the strong adsorpt ion of bismuth permi t ted a ready separa t ion from lead in ammonium ni t ra te solutions of low acidity. Kraus and Nelson(72) a lso found a marked inc rease in the adsorpt ion of uranium and the r a r e ear ths in the same medium but not for thor ium. Korkisch_et al.(71) collected uran ium from a solution ha l f - sa tura ted with ammonium n i t ra te . The adsorpt ion of a number of e lements from ammonium ni t ra te solutions has been repor ted in studies naade at this Laboratory,^ including the effect of free acid on the adsorpt ion functions of uranium, b i s muth and the r a r e ear ths (see Fig. 2).
The elution of severa l rad ioe lements from ni t ra te - loaded columns containing a complexing agent were studied by Schonfeld et al .vl02; ^.t about pH 8, lead, y t t r ium, and bismuth were adsorbed, while s t ron t ium was eluted with a O.IM sodium n i t ra te , 0.0005M, 8-hydroxyquinoline sulfonate solution.
13
Ui o o of . (O
(T O
u™
••/
^
^-^ ^^"^
y
- o •
B F
. ^ ^
- - '
o
V 8 12 0 4 8
MOLARITY (NO3)
NH4N03(0.1M HNO3)
. — — - IM HNO3+ NH4NO3
o 2M HNO3+NH4NO3
4M HNO3+ NH4NO3
HNO3
12 14
Hal ide ions w e r e s e p a r a t e d by A t t e b e r r y and Boyd(lO) and by R i e m a n and L indenbaum, (91 ) who u s e d a s t r o n g l y b a s i c an ion exchange r e s i n in the n i t r a t e f o r m . E l u t i o n wi th a s o d i u m n i t r a t e so lu t ion f i r s t d i s p l a c e d f l uo r ide , then c h l o r i d e , b r o m i d e , and f inal ly iod ide . D e G e i s o , R i e m a n , and L indenbaum(28) l a t e r i m p r o v e d the p r o c e d u r e , e s p e c i a l l y for iodide e lu t ion .
F i g . 2. Anion A d s o r p t i o n of U(VI) and Bi ( l I I ) inNH4N03-HN03 M i x t u r e s ( s ee Ref. 13)
The a d s o r p t i o n of s o m e e l e m e n t s by anion exchange r e s i n s can be m u c h g r e a t e r f r o m n i t r a t e s o l u t ions con ta in ing a h igh p r o p o r t i o n of a m i s c i b l e o r g a n i c so lven t than f r o m
aqueous n i t r i c ac id . At the A n a l y t i c a l Ins t i tu te of the U n i v e r s i t y of Vienna , K o r k i s c h and c o w o r k e r s have m a d e e x t e n s i v e s t u d i e s of the a d s o r p t i o n of ions f r o m m i x t u r e s of m i n e r a l a c i d s and a l i pha t i c a l c o h o l s o r o t h e r s o l v e n t s , such a s e t h e r s or k e t o n e s . Th i s w o r k h a s b e e n r e c e n t l y s u m m a r i z e d and the g e n e r a l t h e o r e t i c a l a s p e c t s d i s c u s s e d . ( " 8 ) in e a r l i e r w o r k ( 7 , 65,106) they u s e d to advan t age the s t r o n g a d s o r p t i o n of t h o r i u m in n i t r i c a c i d -e thano l m i x t u r e s for a r e a d y s e p a r a t i o n f r o m z i r c o n i u m and f r o m u r a n i u m , and l a t e r c o m p a r e d o t h e r a l coho l i c so lu t ions(70) for t h o r i u m - u r a n i u m s e p a r a t i o n s . T h e i r w o r k wi th n i t r i c a c i d - m e t h a n o l m i x t u r e s ( 6 9 ) d e m o n s t r a t e d tha t a n u m b e r of e l e m e n t s could be quan t i t a t ive ly s e p a r a t e d f r o m t h o r i u m and tha t the r a r e e a r t h s , b a r i u m , and l ead w e r e a d s o r b e d s t r o n g l y . Aka i sh i ( ' p r e p a r e d c a r r i e r - f r e e Th^^"* by an ion exchange f r o m m i x e d s o l ven t s and s tud ied t h o r i u m a d s o r p t i o n in the p r e s e n c e of phospha te . (4 ) Solvent m i x t u r e s of d ie thy l e t h e r o r d ioxane with n i t r i c ac id have b e e n e m ployed in a c o l u m n s e p a r a t i o n of u r a n i u m f r o m the m o r e s t r o n g l y a d s o r b e d ions of t h o r i u m , a l u m i n u m , and i r o n . ( l l O ) The a d s o r p t i o n of u r a n y l n i t r a t e f r o m s e v e r a l o r g a n i c so lven t s h a s b e e n r e p o r t e d . ( 11 > 111) T u c k and Welch(109) found a m a x i m u m a d s o r p t i o n for Pu(IV) a t about 0.4M n i t r i c ac id f r o m d ie thy lene g lyco l d ibutyl e t h e r .
E n h a n c e d a d s o r p t i o n of the r a r e e a r t h n i t r a t e s f r o m m i x e d so lven t s con ta in ing e thano l o r a c e t o n e was d e m o n s t r a t e d by M a r c u s and A b r a h a m e r . ( ' 6) Edge(-^^^ s e p a r a t e d y t t r i u m , n e o d y m i u m , and l a n t h a n u m by us ing e thano l a s the added so lven t . Work a t th is L a b o r a t o r y h a s shown tha t the r a r e e a r t h n i t r a t e s can be a d s o r b e d f r o m a n u m b e r of m i s c i b l e o r g a n i c so lven t s , (38 ) and d i s t r i b u t i o n coef f ic ien t s have b e e n p r e s e n t e d a s a funct ion of both the v o l u m e p e r c e n t a g e of m e t h a n o l and the ac id i ty ( s ee F i g . 3 and 4). Edge(33) s e p a r a t e d the l ight r a r e e a r t h g roup f r o m the heavy in a m e t h a n o l - n i t r i c ac id m i x t u r e . K o r k i s c h et a l . (67) gave d e t a i l e d da ta for the r a r e e a r t h s in s e v e r a l a l i p h a t i c a l coho l s and p r o p o s e d ind iv idua l s e p a r a t i o n t e c h n i q u e s tha t i nc luded s o m e o t h e r e l e m e n t s . As a g e n e r a l r u l e , the l ight r a r e e a r t h s .
14
l a n t h a n u m , and t h o r i u m could be quan t i t a t i ve ly i s o l a t e d in the above s y s t e m s , w h e r e a s the r a r e e a r t h s h e a v i e r than t e r b i u m w e r e e lu t ed f r o m a c o l u m n p r a c t i c a l l y a s a g r o u p .
1000
10,000
1000
o o
a: I-(n
100 -
o o
I-
(Q
a
100 -
0.01 0.05 0.1 0.5 1.0 1.5
MOLARITY HNO3
5 10 15 20 30 4 0
PERCENT OF 7M H N O ,
Fig. 3. Variation of Distribution Coefficient with Acid Molarity in Mixtures of 10% Nitric Acid-90<yo Methanol. Dowex 1 x 4 , 200-400 Mesh Resin (see Ref. 38).
Fig. 4. Variation of Distribution Coefficient with Proportion of 7M Nitric Acid. Dowex 1 x 4 , 200-400 Mesh Resin (see Ref. 38).
Within the a l k a l i n e e a r t h g r o u p , K o r k i s c h and T e r a ( 6 9 ) found ba r iuna to be s t r o n g l y a d s o r b e d f r o m a 90% m e t h a n o l - 1 0 % 5M n i t r i c ac id m i x t u r e and thus s e p a r a t e d f r o m s t r o n t i u m , c a l c i u m , and m a g n e s i u m . F r i t z and Waki(44) u s e d a s i m i l a r m i x t u r e wi th i s o p r o p y l a l coho l a s the added s o l vent for a quan t i t a t i ve s e p a r a t i o n of m a g n e s i u m and c a l c i u m , and a l s o d e m o n s t r a t e d a c a l c i u m - s t r o n t i u m - b a r i u m s e p a r a t i o n . C a l c i u m and s t r o n t i u m could be quan t i t a t i ve ly s e p a r a t e d in a m e t h a n o l - n i t r i c ac id mix ture . (45) Co lumn e lu t ion e x p e r i m e n t s have b e e n m a d e a t t h i s L a b o r a t o r y wi th m i c r o g r a m quan t i t i e s of a lka l i ne e a r t h s in so lu t ions of n i t r i c ac id wi th m e t h a n o l ( s e e F i g . 5) and s o m e o t h e r s o l v e n t s s i m i l a r to t hose t e s t e d for r a r e e a r t h s e p a r a t i o n s . ( 3 8 ) A d s o r p t i o n onto a s t r o n g b a s e an ion exchange r e s i n was in the o r d e r Be < Mg < Ca < Sr < Ba. R a d i u m would p r e s u m a b l y be a d s o r b e d to an even g r e a t e r d e g r e e .
100
0 0 5 01 MOLARITY HNO3
Fig. 5. Approximate Distribution Coefficients of Alkaline Earths as a Function of Acid Molarity in Mixtures of 10% Nitric Acid-SO'yo Methanol. Dowex 1 x 4 , 200-400 Mesh Resin
A n i o n e x c h a n g e s e p a r a t i o n of s o m e a c t i n i d e s i n a m e t h a n o l - n i t r i c a c i d m e d i u m h a s b e e n a c c o m p l i s h e d by H i n e s , W a h l g r e n a n d L a w l e s s ( 4 9 ) ( s e e F i g s . 6 a n d 7) . T h e s a m e g e n e r a l b e h a v i o r a s t h a t of t h e r a r e e a r t h s w a s o b s e r v e d . C a l i f o r n i u m w a s e l u t e d f r o m a c o l u m n b e f o r e c u r i u m , t h e n f o l l o w e d b y a m e r i c i u m ( s e e F i g . 8) . A s e p a r a t i o n f a c t o r f o r a m e r i c i u m a n d c u r i u m of 3 .25 w a s f o u n d in a 90% m e t h a n o l - 1 0 % n i t r i c a c i d m i x t u r e . E l e m e n t s h e a v i e r t h a n c a l i f o r n i u m w e r e n o t e x p e c t e d to f r a c t i o n a t e to a n y e x t e n t .
R e c e n t l y , K o r k i s c h a n d A r -r h e n i u s ( 6 6 ) f o u n d t h a t a n u m b e r of
i o n s , i n c l u d i n g t h e r a r e e a r t h s , b i s m u t h , l e a d , a n d c a d m i u m , w e r e s t r o n g l y r e t a i n e d by a n a n i o n e x
c h a n g e r e s i n f r o m a m i x t u r e of 90% a c e t i c a c i d a n d 10% 5M n i t r i c a c i d , a n d t h u s s e p a r a t e d f r o m m a n y n o n a d s o r b e d e l e m e n t s .
10'
DOWEX I x 10 2 0 0 - 4 0 0 MESH
04 06 08 01 0 2 MOLARITY HNO3
^4
32
3 0
28
26
24
2 2
2 0
18
16
14
12
10
8
6
4
2
- _ U - N p - P u
----_ --- 1 - ; - 1
- 1 - 1
- 1
- 1
— 1
//
>IO=c/m
,. .MIXED
1 l^f
\
,Vx
Am
/
DOWEX Ix lQ 2 0 0 - 4 0 0 MESH
2 Sml/cm^/min
Cm
!
/ \ / \ '
/ \ / / / \ / /
• Pm
1
'
l ^ / l 1 1 . ' 1 \ l 04 060810 20 30 40 50 60
VOLUME OF ELUENT 70 80
Fig. 6. Distribution Coefficients of Actinides as a Function of Acidity in 10% Nitric Acid-QO^ Methanol (from Hines, Wahlgren, and Lawless, Ref. 49)
Fig. 7. Elution Curves for the Separation of Americium and Curium from Other Common Actinides in a 10% Nitric Acid-90% Methanol Mixture (from Ref. 49)
DOWEX I X 10 2 0 0 - 4 0 0 MESH
2 5ml /cm^/min
10
F i g . 8
E l u t i o n C u r v e for the S e p a r a t i o n of C a l i f o r n i u m f r o m A m e r i c i u m and C u r i u m in a 10% N i t r i c A c i d - 9 0 % M e t h a n o l M i x t u r e ( f rom Ref. 49)
20 30 4 0 50 60 VOLUME OF ELUENT
Although an ion exchange in i n o r g a n i c n i t r a t e m e d i a c a n be of a d van tage in p u r i f i c a t i o n o r c o n c e n t r a t i o n p r o c e s s e s , in r a d i o c h e m i c a l s e p a r a t i o n s , and in the p r e s e n c e of high l e v e l s of r a d i a t i o n , a p p l i c a t i o n of thes s y s t e m s to a n a l y s i s for g e n e r a l t r a c e i m p u r i t i e s i s not s i m p l e . F u r t h e r s e p a r a t i o n o r c o n c e n t r a t i o n m a y be n e c e s s a r y to a t t a i n the n e c e s s a r y s e n s i t i v i t y o r a n a l y t i c a l p r e c i s i o n , and p r e p a r a t i o n of r e a g e n t s of a c cep t ab l e pu r i ty could be t i m e - c o n s u m i n g . On the o t h e r hand, the use of w a t e r - m i s c i b l e o r g a n i c so lven t s of fers a good advan tage in tha t m o s t s o l ven ts can be r e a d i l y pur i f i ed and s u b s e q u e n t l y v o l a t i l i z e d to c o n c e n t r a t e the s e p a r a t e d t r a c e i m p u r i t i e s .
III. ANALYTICAL APPLICATIONS
The cur ren t in te res t in high-puri ty m a t e r i a l s frequently r equ i r e s considerable analytical effort to provide good values for meta l l ic i m p u r i t ies p resen t in ext remely low concentrat ion. Among the methods used, var ious emiss ion spect rographic techniques a r e excellent for t r ace -e lement de terminat ions ; the re i s , how^ever, no un iversa l method. Norr i s (°4) has reviewed the spect rographic determinat ion of t r a c e e lements in me ta l s and has outlined separat ion methods as a means of extending the detection l imits for impur i t i e s . The advantages of using ion exchange for this p u r pose have been d iscussed . (^5; Spect rochemical methods using anion exchange in a n i t ra te medium a re par t icu la r ly effective for the analys is of plutonium, and p rocedures have been descr ibed for the de terminat ion of z i rconium,(°4j a m e r i c i u m , ( 1 1 " ' and most other impuri t ies .(°- ' ' l l -^~l ' Similar p rocedures have been used to separa te impur i t i e s from neptu-n ium(3 ' ,117; fQj. spec t rochemica l determinat ion. Mixed solvents have been used in the spect rographic analysis of the r a r e ea r ths .(33,96)
Anion exchange r e s in s a re routinely employed at Argonne to concent r a t e t r a c e e lements for determinat ion by the copper spark method of ana l ys is . (36; The method of Brody, F a r i s , and Buchanan(12) for the analys is of uran ium and plutonium has been modified by Huff(52) for the analysis of plutonium me ta l . This p rocedure , now in routine use at Argonne in the Fuels Technology Center analyt ical labora tory , is descr ibed below^ in de ta i l . Some other p rocedures in w^hich adsorpt ion from a n i t ra te medium has been par t i cu la r ly effective(37) have also been outlined.
Plutonium
All operat ions -were ca r r i ed out in a s e r i e s of enclosed chemical fume hoods equipped with glove por t s . Samples other than the me ta l were converted to a hydrochlor ic acid solution; plutonium oxide was dissolved by the sealed tube technique of Wichers , Schlecht, and Gordon.(119) Reagent solutions were p repa red and s tored in polyethylene conta iners as was p rac t i ca l .
a) Mate r i a l s
P u r e 13M HCl: P r e p a r e d by pass ing hydrogen chloride gas into chilled, deionized water .
P u r e 8M HNO3: P r e p a r e d by disti l l ing r eagen t -g rade n i t r ic acid from a quartz s t i l l .
Ion exchange res in : Analytical grade Dowex 1 x 8 , 100-200 m e s h (Bio-Rad L a b o r a t o r i e s , Berkeley, California) .
Ion e x c h a n g e c o l u m n s : 1 . 5 - c m - d i a m e t e r p o l y e t h y l e n e tub ing d r a w n to a t i p . The c o l u m n s w e r e 20 c m long , and the r e s e r v o i r s e a l e d to the top w a s 5 c m in d i a m e t e r and 5 c m h igh . P o l y p r o p y l e n e wool w a s m o d e r a t e l y p a c k e d at the t ip to s u p p o r t the r e s i n .
B e a k e r s : Nag lene P R p o l y p r o p y l e n e ; Tef lon .
E l e c t r o d e s : " ^ - i n . - d i a m e t e r c o m m e r c i a l e l e c t r o l y t i c h a r d c o p p e r r o d s cut to 1-j-in. l e n g t h s .
Ap iezon so lu t ion : 1 g A p i e z o n - N g r e a s e d i s s o l v e d in 1 l i t e r of d i s t i l l e d l o w - b o i l i n g p e t r o l e u m e t h e r .
b) P r o c e d u r e
A s a m p l e of p l u t o n i u m m e t a l , g e n e r a l l y r e c e i v e d a s a so l id p i e c e , w a s c l e a n e d (by f i l ing and b r u s h i n g ) and we ighed in a n i t r o g e n a t m o s p h e r e g loved box d e s i g n e d for t h i s p u r p o s e . About 0.5 g w a s p l a c e d in a c l e a n v ia l and then s e a l e d in a p l a s t i c pouch for t r a n s p o r t to the a n a l y t i c a l hood t r a i n . Af ter t r a n s f e r to a p l a s t i c b e a k e r , the s a m p l e w a s d i s s o l v e d in about 0.5 m l of 8M n i t r i c - a c i d . The so lu t ion w a s h e a t e d gen t ly u n d e r i n f r a r e d h e a t l a m p s for a t l e a s t 10 m i n to effect a c o m p l e t e ox ida t ion to Pu ( lV) .
Ion e x c h a n g e c o l u m n s w e r e p r e p a r e d f r o m r e s i n w a s h e d a l t e r n a t e l y with w a t e r and d i lu te h y d r o c h l o r i c ac id and added a s a s l u r r y to an a p p r o x i m a t e he igh t of 15 c m . The r e s i n bed w a s cond i t i oned wi th 30 m l of 13M h y d r o c h l o r i c a c i d .
Af ter coo l ing , the s a m p l e so lu t ion w a s p o u r e d onto the c o l u m n and the p l u t o n i u m a l lowed to a d s o r b a s the c h l o r i d e c o m p l e x . The i m p u r i t i e s w e r e t hen e lu t ed wi th 120 m l of 8M n i t r i c a c i d . The w a s h so lu t ion w a s e v a p o r a t e d to d r y n e s s to r e m o v e the f r e e n i t r i c ac id and the r e s i d u e r e -d i s s o l v e d in 1 m l of 5M d i s t i l l e d h y d r o c h l o r i c a c i d . Th i s so lu t i on w a s s a v e d for the c o p p e r s p a r k a n a l y s i s . A c o l u m n could be cond i t i oned for r e u s e a f t e r s t r i p p i n g off the p l u t o n i u m wi th I M h y d r o c h l o r i c a c i d .
c) S p e c t r o g r a p h i c D e t e r m i n a t i o n
C o p p e r e l e c t r o d e s w e r e p r e p a r e d a s n e e d e d by m a c h i n i n g the end and s ide s u r f a c e s on a l a t h e to a s m o o t h , c l e a n f i n i sh . A d r o p of Ap iezor so lu t ion w^as d r i e d on the end of e a c h e l e c t r o d e . Then 0 . 1 - m l a l i -quots of the s a m p l e so lu t ion w e r e d iv ided e q u a l l y on e l e c t r o d e p a i r s and e v a p o r a t e d to d r y n e s s u n d e r i n f r a r e d hea t l a m p s . An add i t i ona l p a i r of g r a p h i t e e l e c t r o d e s w e r e u s e d for a d e t e r m i n a t i o n of c o p p e r . A l s o , a 1 to 10 d i lu t ion of the s a m p l e so lu t ion w a s u s u a l l y inc luded , p a r t i c u l a r l y for
t h o s e s a m p l e s known to have a h igh i m p u r i t y con ten t , to p r o v i d e s u b s e quent ly a b e t t e r eva lua t i on of m a t r i x ef fects on l i ne i n t e n s i t i e s and to give a b e t t e r e s t i m a t i o n of m a j o r i m p u r i t i e s .
The s a m p l e s w e r e s p a r k e d and t h e s p e c t r a p h o t o g r a p h e d u n d e r s t a n d a r d cond i t i ons . By v i s u a l c o m p a r i s o n wi th s t a n d a r d s p e c t r a the p r e s ence of a l m o s t 60 i m p u r i t y e l e m e n t s could be d e t e c t e d wi th the l i m i t s g iven m Tab le II. V a l u e s could u s u a l l y be e s t i m a t e d to wi th in a f a c t o r of two . S t a n d a r d p h o t o m e t r i c t e c h n i q u e s ( ^ 9 ) have b e e n app l i ed when a m o r e p r e c i s e d e t e r m i n a t i o n w a s d e s i r e d , cobal t o r s o m e o t h e r su i t ab l e e l e m e n t be ing added to s e r v e a s an i n t e r n a l s t a n d a r d . S i l icon w a s d e t e r m i n e d on a s e p a r a t e s a m p l e p o r t i o n by the m e t h o d of Hol t . ( '
T a b l e II
L I M I T S O F D E T E C T I O N ^ (ppm) F O R ION E X C H A N G E - C O P P E R S P A R K M E T H O D ( s e e Ref 36)
E l e m e n t
A m Ag Al B B a Be Ca Cd Ce Co C r C s Cu Dy E r Eu F e Ga Gd Hf Ho In I r K L a L i
Lu Mg
In T h , N p (HNO3)
0 5 2 0 5b 0 5 0 1 0 002 l b 0 4 0 3 0 2 0 2 5 1 0 2 0 1 0 02 1 0 1 0 2 0 5 0 2 0 5 1 0 5^ 0 02 0 001 0 01 0 5b
In U , N p , P u ( H C l )
0 5
0 5b 0 5 0 1 0 002 lb
0 3
0 2 5 1 0 2 0 1 0 02
0 2 0 5 0 2
0 5b 0 02 0 001 0 01 0 5b
Add'l 1 m
Pu(HN03)
2
0 4
0 2
1 0 1
1
E l e m e n t
Mn M o N a Nd N i P P b P r Rb R e Rh Ru Sc Sm Sr Tb Te Th T i
T l T m U V Y Y b Zn Z r
In T h . N p (HNO3)
0 05 0 05 l b 0 3 0 2
20 0 5 0 3 0 3 1 0 2 0 5 0 01 0 5 0 002 1 5
0 05 1 0 2 2 0 1 0 005 0 01 2 0 1
In U , N p , P u ( H C l )
0 05
l b
0 3 0 2
20 0 5 0 3 0 3
0 01 0 5 0 002 1
0 5 0 05
0 2
0 1 0 005 0 01
0 1
Add'l 1 m
Pu(HN03)
0 05
1 0 2 0 5
5
1
2
2
^ F o r a 0 1 -ml a l i q u o t of ef f luent fronn 1-g s a m p l e c o n c e n t r a t e d to 1 m l L i m i t e d by r e s i d u a l m b l a n k
T h o r i u m
A so lu t ion of a o n e - g r a m t h o r i u m s a m p l e m a p p r o x i m a t e l y 8M n i t r i c ac id w a s p a s s e d t h rough a p r e v i o u s l y condi t ioned c o l u m n conta in ing about
20 g of s t rong-base anion exchange res in . After washing w^ith about 50-70 ml of 8M ni t r ic acid, the effluent w^as evaporated to d ryness , taken up in hydrochloric acid, and the impur i t ies de termined by the copper spark method. Limi ts of detection and e lements de termined a re given in Table II. Dens i -tomet r i c p rocedures have been used for r a r e ear th determinat ions.(34j
Analysis for silicon and boron w^as made w^ith a separa te sample portion by the c a r r i e r dist i l lat ion method.(103)
Neptunium
A procedure s imi la r to that descr ibed for thor ium w^as applied to the analysis for neptunium. Samples of from 25 to 100 mg were reduced to Np(lV) by heating for at leas t an hour in an 8M ni t r ic acid, 0.2M hydra zine solution. After adding a sample to a conditioned column the impur i t i es were eluted w^ith a s imi lar mix tu re . Although the dark band of adsorbed neptunium was l a rge r than expected, nnore than 99% was retained by the res in . Fo r convenience, the l imi ts of detection in Table II a re given for a sample of one g ram, although sample w^eights have usually not exceeded 0.1 g.
In some instances', par t icu lar ly for a determinat ion of thor ium impuri ty, adsorpt ion of neptunium from hydrochlor ic acid was des i rab le . Satisfactory separat ion of the nonadsorbed e lements^ ' 2j were made in 8 to lOM hydrochlor ic acid by a p rocedure s imi la r to that applied to the analysis of uranium.^ '
Rare Ea r ths (Light)
The strong adsorption of lanthanum, ce r ium, praseodymium, and neodymium from a n i t r ic ac id-methanol medium permi t ted their ready separa t ion from the heavier r a r e ear ths as well as from most other e l e men t s . Fo r analysis of a light r a r e ear th , a 0.5-g sample was dissolved in a few ml of strong n i t r ic acid and methanol added to give a solution of about 90-95% alcohol. The sample w^as then allowed to adsorb slowly on a "I-in.-ID re s in column containing about 20 g conditioned Dow^ex 1 x 4 . The weakly adsorbed impur i t i e s , including yt t r ium and the heavy r a r e ea r th s , could then be eluted with a mix ture of methanol (90-80%) and n i t r ic acid ( l -O. lM). Distr ibution coefficients var ied w^ith the acidity, and separat ion factors were influenced by the proport ion of alcohol.^ ' Recovery ex-perimentsv96} have demonst ra ted that the heavier r a r e ea r th s , including gadolinium, could be quantitatively separa ted . In the most difficult case , the recovery of s amar ium impuri ty from neodymium samples was consistently low, ranging from 40 to 75% for samples of about 0.5 g. A more quantitative separat ion could be made by use of smal le r samples , but with a c o r r e sponding loss in sensi t ivi ty. Similar detection l imits re la t ive to sample size as given in Table II could be achieved for the nonadsorbed metals.(69)
S e p a r a t i o n s could a l s o be m a d e wi th in the l ight g r o u p of r a r e e a r t h s tha t w e r e use fu l for ex tend ing the l i m i t s of d e t e c t i o n . S a m p l e w e i g h t s of fronn 10 m g to 50 m g w e r e a d s o r b e d on s m a l l e r c o l u m n s and c h r o m a t o -g r a p h i c a l l y e lu ted wi th a 75-80% a l coho l , d i lu te n i t r i c ac id m i x t u r e .
R a r e E a r t h s (Heavy)
F o r a g e n e r a l a n a l y s i s of an y t t r i u m o r a h e a v y r a r e e a r t h s a m p l e , about 100 m g w e r e d i s s o l v e d and a d s o r b e d a s d e s c r i b e d above f r o m a 95% m e t h a n o l - 5 % 7M to lOM n i t r i c ac id so lu t ion . C o l u m n s i z e s f r o m about 3 to 5 g of r e s i n h a v e b e e n u s e d . The n o n a d s o r b e d i m p u r i t i e s could r e a d i l y be s e p a r a t e d and w e r e r e c o v e r e d for a n a l y t i c a l d e t e r m i n a t i o n in the eff luent a f t e r a d s o r b i n g the s a m p l e . T h i s w a s v e r i f i e d in e x p e r i m e n t s in wh ich two n o n a d s o r b e d e l e m e n t s , g a l l i u m and coba l t , w e r e added to s a m p l e s of y t t r i u m oxide and l u t e t i u m o x i d e , and then r e c o v e r e d f r o m a c o l u m n b e f o r e an a p p r e c i a b l e b r e a k t h r o u g h of the m a t r i x . In add i t i on , the p r e s e n c e of s e v e r a l h e a v i e r r a r e e a r t h s could be d e t e c t e d in s a m p l e s of s a m a r i u m , e u r o p i u m , and g a d o l i n i u m f r o m an e x a m i n a t i o n of the c o m b i n e d effluent f r a c t i o n s c o l l e c t e d b e f o r e the m a t r i x b r o k e t h r o u g h .
To d e t e c t the p r e s e n c e of any l ight r a r e e a r t h o r t h o r i u m i m p u r i t y , t he a d s o r b e d s a m p l e -was r e m o v e d f r o m t h e c o l u m n wi th a 90% m e t h a n o l -10% 0.5M n i t r i c a c i d e luan t and d i s c a r d e d . T h e n d i lu te n i t r i c a c i d w a s added to the c o l u m n to e lu t e t h e r e m a i n i n g s t r o n g l y a d s o r b e d i m p u r i t i e s . D e t e r m i n a t i o n w a s m a d e by t h e c o p p e r s p a r k m e t h o d a f t e r e v a p o r a t i n g the eff luent . S i m i l a r d e t e c t i o n l i m i t s r e l a t i v e to s a m p l e s i z e a s g iven in T a b l e II could be a c h i e v e d for t h o r i u m , l a n t h a n u m , c e r i u m , p r a s e o d y m i u m , and n e o d y m i u m .
A C K N O W L E D G M E N T
The a u t h o r s w i s h to t hank t h o s e in the A r g o n n e C h e m i s t r y D i v i s i o n who h a v e o f fe red v a l u a b l e s u g g e s t i o n s and a d v i c e , and a r e i n d e b t e d to J . J . H i n e s , R. K r i s h n a m o o r t h y I y e r , M. A. E s s l i n g , J . W. W a r t o n , K. A. O r l a n d i n i , G. J e w e t t , and F . L a w l e s s for a n u m b e r of a n a l y t i c a l d e t e r m i n a t i o n s .
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Akaishi , J. , The P repa ra t i on of C a r r i e r - f r e e ^^^Th(UX^) by Anion Exchange from Nitr ic Acid-Alcohol Mixed Solution of Uranyl Ni t ra te , Bull. Chem. Soc. Japan 34, 1198 ( I96l ) .
Akaishi , J. , Adsorpt ion of Thor ium on the Anion Exchange Resin in Ni t r ic Acid-Alcohol Mixed Solution in the P r e s e n c e of Phosphate , Nippon Genshiryoku Gakkaishi 4, 154 (1962); Nucl. Sci. Abs . 1_6, 17606 (1962).
All ison, G. M., The Spectrophotometr ic Determinat ion of Plutonium as Pu(ll l) , Atomic Energy of Canada, Chalk River , Ontario, PDB-57 (1952); r e i s sued as AECL-1371 (1961).
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Antal, P . , Korkisch, J. , and Hecht, F . , Distr ibut ion of Thor ium, Z i r conium and Titanium in Inorganic-ac id Solutions Containing Alcohol, and the Strongly Basic Anion Exchanger Dowex-1 , J. Inorg. Nucl. Chem. 14, 251 (i960).
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