27 Carbamoylmethylphosphoryl Derivatives as Actinide Extractants Their Significance in the Processing and Recovery of Plutonium and Other Actinides
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E . P H I L I P H O R W I T Z , H E R B E R T D I A M O N D , and DALE G .
KALINA
Argonne National Laboratory, Chemistry Division, Argonne, I L 60439
Three classes of carbamoylmethylphosphoryl extractants were studied for their ability to extract selected t r i - , tetra-, and hexavalent actinides from nitric acid. The three extractants are dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP), hexyl hexyl-N,N-diethylcarbamoylmethylphosphinate (HHDECMP), and octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxideOФD[IB]CMPO.The above three extractrants were compared on the basis of nitric acid and extractant dependencies for Am(III), solubility of complexes on loading with Nd(III) and U(VI), and selectivity of actinide(III) over fission products. The influence of temperature on D from LiNO (10 M HNO ) and from 3 M HNO using dilute solutions of DHDECMP, HHDECMP,OФD[IB]CMPOin o-xylene showed that the increase in D in the series phosphone-phosphinate-phosphine oxide was due primarily to an increase in the enthalpy of extraction. -2
Am
3
3
3
Am
The above i n f o r m a t i o n was used t o d e v e l o p c o n c e p t u a l flowsheets f o r the extraction o f a l l o f the actinides (U, Np, P u , Am, a n d Cm) f r o m h i g h - l e v e l l i q u i d w a s t e f r o m PUREX p r o c e s s i n g u s i n g 0.4 M 097% p u r e . (See Table I f o r an e x p l a n a t i o n o f a b b r e v i a t i o n s . ) E x t r a c t a n t s o l u t i o n s were p r e p a r e d u s i n g d i s t i l l e d - i n - g l a s s grade o - x y l e n e ( B u r d i c k and J a c k s o n L a b o r a t o r i e s ) a n d d i e t h y l b e n z e n e (DEB) ( m i x t u r e o f i s o m e r s , A l d r i c h C h e m i c a l C o . ) . Hydroxylammonium f o r m a t e a n d h y d r a z i u m f o r m a t e w e r e p r e p a r e d b y m i x i n g h y d r o x y l a m i n e (Chem. S e r v i c e , I n c . ) o r h y d r a z i n e m o n o h y d r a t e ( J . T. B a k e r C h e m i c a l Co., I n c . ) w i t h a n e q u a l m o l a r amount o f f o r m i c a c i d . Synthetic h i g h - l e v e l l i q u i d w a s t e (HLLW) was p r e p a r e d u s i n g t h e p r o c e d u r e o f Bond a n d L e u z e ( 1 2 ) . O t h e r aqueous s o l u t i o n s w e r e p r e p a r e d u s i n g materials described previously (7). E x t r a c t i o n s t u d i e s w e r e p e r f o r m e d u s i n g 2 3 0 τ η , 2 3 3 u , 237Np, 2 3 9 N , 2 3 9 p , 2 4 2 p , 24lAm, a n d 243cm. Standard r a d i o m e t r i c a s s a y and c o u n t i n g p r o c e d u r e s w e r e u s e d t h r o u g h o u t . Distribution r a t i o s w e r e d e t e r m i n e d a t 25°C a n d a s a f u n c t i o n o f t e m p e r a t u r e u s i n g t h e p r o c e d u r e s d e s c r i b e d p r e v i o u s l y ( 7 , 1 3 ) . F o r N p ( I V ) and P u ( I V ) D s , e x t r a c t i o n s w e r e p e r f o r m e d f r o m 3 M HNO3 c o n t a i n i n g 0.1 M s u f l a m i c a c i d - 0 . 0 5 M f e r r o u s s u l f a m a t e , a n d 0.05 M s o d i u m n i t r i t e , respectively. M u l t i p l e s c r u b s ( u s u a l l y 2 t o 3) o f t h e l o a d e d o r g a n i c p h a s e s w e r e p e r f o r m e d u n t i l two s u c c e s s i v e e q u i l i b r a t i o n s gave t h e same d i s t r i b u t i o n r a t i o s . The d i s t r i b u t i o n r a t i o f o r Np(V) was m e a s u r e d u s i n g a m i x t u r e o f 237,239^p t h a t was s e p a r a t e d f r o m N p ( I V ) a n d N p ( V I ) b y c a t i o n i o n exchange f r o m 1 M HNO3. d i s t r i b u t i o n r a t i o s o f f i s s i o n p r o d u c t s w e r e measured p
u
u
f
T
n
e
Carnall and Choppin; Plutonium Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
Carnall and Choppin; Plutonium Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
0D[IB]CMPO
DHDECMPO
HHDECMP
DHDECMP
Abbreviations
0 )
2
0
C
2~ ~
N ( C
H
2
5
)
2 5 2
2
H
9
2
3
2
0 0 II II ^ P-CH -C-N[CH -CH(CH ) ]
2
0
« i 7
0
2
) P-CH -C-N(C H )
H
6 13°'
C H
0
P-CH -C-N(C H )
0
P
2 ~
0
Extractant
2
n-Octyl(phenyl)-Ν,Ν-diisobutylcarbamoylmethylphosphine oxide
oxide
hexyl-N,N-diethylcarbamoylmethylphosphinate
Dihexyl-N,N-diethylcarbamoylmethylphosphine
Hexyl
Dihexyl-N,N-diethylcarbamoylmethylphosphonate
Nomenclature
S t r u c t u r e s a n d N o m e n c l a t u r e o f CMP a n d CMPO E x t r a c t a n t s Employed i n t h i s Work
(C H
c
C
H
6 13
6"13 -
-
( C
TABLE I . A b b r e v i a t i o n s ,
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436
PLUTONIUM CHEMISTRY
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f r o m s y n t h e t i c HLLW u s i n g a n I n s t r u m e n t s SA, I n c . i n d u c t i v e l y coupled atomic e m i s s i o n spectrometer (argon plasma). S i n c e o n l y aqueous p h a s e s c o u l d be a n a l y z e d , t h e m e t a l i o n c o n s t i t u e n t s o f t h e o r g a n i c p h a s e s were q u a n t i t a t i v e l y b a c k - e x t r a c t e d by f i r s t d i l u t i n g t h e e q u i l i b r a t e d o r g a n i c phase w i t h 2 - e t h y l h e x a n o l ( 1 0 % by v o l u m e ) a n d t h e n e q u i l i b r a t i n g t h e r e s u l t a n t m i x t u r e t w i c e w i t h an e q u a l v o l u m e o f a n aqueous s o l u t i o n c o n t a i n i n g 0.01 M NaCN, 0.05 M d i e t h y l t r i a m i n e p e n t r a a c e t a t e (DTPA), a n d 0.50 M NH4OH. D i s t r i b u t i o n r a t i o s m e a s u r e d b y ICP/AES a n a l y s i s were e s t i m a t e d t o h a v e a s t a n d a r d d e v i a t i o n o f 20%. R e s u l t s and D i s c u s s i o n G e n e r a l C o m p a r i s o n o f t h e T h r e e C l a s s e s o f CMP E x t r a c t a n t s . T a b l e I I shows a g e n e r a l c o m p a r i s o n o f t h r e e e s s e n t i a l p r o p e r t i e s of a l i q u i d - l i q u i d e x t r a c t i o n system; namely, d i s t r i b u t i o n r a t i o , s e l e c t i v i t y , and s o l u b i l i t y o f loaded o r g a n i c phase, f o r h e x y l e t h y l a n a l o g s o f t h e t h r e e c l a s s e s o f CMP e x t r a c t a n t s and f o r 0(j>D[IB]CMP0. As d e s c r i b e d i n e a r l i e r p u b l i c a t i o n s ( 1 0 , 1 1 ) , t h e r e i s a p r o g r e s s i v e i n c r e a s e i n D^, b u t decrease i n s e l e c t i v i t y w i t h r e s p e c t t o i m p o r t a n t f i s s i o n products and i n l o a d i n g s o l u b i l i t y , as t h e d o n o r s t r e n g t h o f t h e p h o s p h o r y l group i n c r e a s e s . (The s e l e c t i v i t y o f A m ( I I I ) o v e r F e ( I I I ) i s a good i n d i c a t i o n o f s e l e c t i v i t y o f a c t i n i d e ( I I I ) i o n s o v e r a number o f f i s s i o n p r o d u c t s whose r e v e r s i b l e D s a r e more d i f f i c u l t t o m e a s u r e , e.g. > Z r . ) T h e r e f o r e DHDECMPO i s n o t a good c a n d i d a t e a s a p r o c e s s i n g e x t r a c t a n t i n s p i t e o f i t s h i g h D^m v a l u e . On t h e o t h e r hand, t h e p h o s p h o n a t e a n d p h o s p h i n a t e a n a l o g s h a v e good o v e r a l l e x t r a c t a n t p r o p e r t i e s e x c e p t f o r t h e l o w b u t u s a b l e D^m v a l u e f o r DHDECMP. The D ^ f o r DHDECMP c a n be i n c r e a s e d b y u s i n g 0.8 M c o n c e n t r a t i o n i n a diisopropylbenzenedecalin d i l u e n t (3). f
As T a b l e I I shows, t h e o c t y l ( p h e n y l ) - N , N - d i i s o b u t y l CMPO compensates, t o a l a r g e degree, f o r t h e u n f a v o r a b l e p r o p e r t i e s TABLE I I .
Extractant DHDECMP
C o m p a r i s o n s o f 0.5 M S o l u t i o n o f CMP E x t r a c t a n t s i n DEB. 3 Μ HN0„, 25°C D. Am 1.8
HHDECMP
11
DHDECMPO 0c|)D[IB]CMP0
22 41
% Loading Nd(III)* U(VI)*
Am oc
Fe 3 χ 1 χ
io io
3
4 χ 10" 3 x 10
>75
z
1
>75 1
65-70 >75
100 80-85 30-35 40-45
^Percent l o a d i n g s a r e based on an e x t r a c t a n t - t o - m e t a l r a t i o o f 3 f o r N d ( I I I ) and 2 f o r U ( V I ) .
Carnall and Choppin; Plutonium Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
27.
HORWITZ ET AL.
Carbamoylmethylphosphoryl Derivatives
437
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o f t h e d i h e x y l - N , N - d i e t h y l CMPO, a l t h o u g h t h e U ( V I ) l o a d i n g o f 0D[IB]CMP0 o v e r DHDECMPO i n t h e e x t r a c t i o n o f Am(III) from n i t r i c a c i d media i s l a r g e l y an enthalpy e f f e c t , which i s c o n s i s t e n t w i t h the r a t i o n a l e f o r s u b s t i t u t i n g a p h e n y l group f o r a h e x y l . I n f a c t t h e i m p r o v e d e x t r a c t i o n o f Am ( I I I ) f r o m e i t h e r n i t r i c a c i d o r L1NO3 m e d i a i n t h e s e r i e s DHDECMP, HHDECMP, a n d 0(|>D[IB]CMP0 i s l a r g e l y a n e n t h a l p y e f f e c t . From a p r a c t i c a l s t a n d p o i n t , D^m d e c r e a s e s w i t h a n i n c r e a s e i n t e m p e r a t u r e f o r a l l e x t r a c t a n t s . However, a s a r e s u l t o f t h e d i f f e r e n c e s i n ΔΗ, t h e s u p e r i o r i t y o f 0c|)D[IB]CMP0 o v e r DHDECMP i s g r e a t e r a t lower than a t higher temperature although the d i f f e r e n c e i s n o t great. TABLE I I I . E q u a t i o n s a n d Thermodynamic P a r a m e t e r s f o r t h e E x t r a c t i o n o f A m ( I I I ) f r o m N i t r a t e M e d i a by C a r b a m o y l m e t h y l phosphoryl D e r i v a t i v e s
2 M LiN0
3
( 0 . 0 1 M H N 0 ) , 0.10 M E x t r a c t a n t i n o - x y l e n e 3
DHDECMP l n K
eq
HHDECMP
9.563
AG(kJ/mol)
-8.32
AH(kJ/mol)
-32.0
AS(j/mol-K)
-79.5
DHDECMPO
^ ψ - - 12.67
0φΡ[ΙΒ]0ΜΡ0
7.503
^ - 1 1 . 3 9
-17.5
-33.1
-28.9
-48.9
-51.7
-57.2
-62.4
-94.7
-105
3 Μ H N 0 , 0.25 M E x t r a c t a n t i n o - x y l e n e 3
DHDECMP lnK
35|9 _
e q
AG(kJ/mol)
1
Q
0
-4.559
HHDECMP 3
37|0 _ ^ -7.033
DHDECMPO 31|8 _
η
^
0(()D[IB]CMP0 Α ψ
-8.097
_
g
5
7
Q
-10.95
AHCkJ/mol)
-29.42
-31.43
-26.51
-34.67
AS(J/mol-K)
-83.38
-81.81
-61.74
-79.56
F i s s i o n P r o d u c t E x t r a c t i o n . T a b l e s I V and V l i s t t h e d i s t r i b u t i o n r a t i o s f o r most o f t h e f i s s i o n p r o d u c t s p r o d u c e d i n s p e n t fuel. A l s o i n c l u d e d a r e c o r r o s i o n p r o d u c t s C r , F e , and N i . Ex t r a c t a n t c o n c e n t r a t i o n s f o r DHDECMP, HHDECMP, a n d 0((>D[IB]CMP0 w e r e s e l e c t e d o n t h e b a s i s o f d a t a i n F i g u r e 2. The aqueous a c i d i t y
Carnall and Choppin; Plutonium Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
442
PLUTONIUM
TABLE I V .
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Element
CHEMISTRY
D i s t r i b u t i o n R a t i o s (Measured b y ICP/AES) f r o m S y n t h e t i c HLLW. 50°C
0.8 M DHDECMP i n DEB a
0.4 M 0D[IB]CMP0 i n DEB
0.8 M HHDECMP i n DEB^
C
*Rb Sr Y Zr Mo *Tc
