Plutonium Chemistry - American Chemical Society

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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