Anionic Acetato Complexes of the Hexavalent Actinides - Advances in

25 Anionic Acetato Complexes of the Hexavalent Actinides A n i o n Exchange and Amine Extraction o f

Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch025

Hexavalent Actinide Acetates J. L. RYAN and W. E. KEDER Battelle-Northwest Laboratories, Richland, Wash. Spectrophotometric studies were used to identify the anionic hexavalent actinide acetate complexes present in aqueous and nonaqueous solutions, anion exchange resins, and amine extracts. The previously unreported tetraacetato complexes, MO (C H O ) 2-, were identified in all these systems. The formation constant for the reaction UO (C H O ) - + C H O -—>UO (C H O ) 2-in acetonitrile was found to be 2.0 ± 0.2. The ratio of tetraacetato to triacetato complex in anion exchange resins was found to be independent of aque ous acetate concentration but depended somewhat on aque ous acidity. The ratio of these species in amine extracts was almost independent of all variables except the ionizing power of the diluent used. The formation constant of the tetraacetato complex in the amine extract increases with decreasing dielectric constant of the diluent. 2

2

3

2

4

2

2

3

2

2

2

3

2

2

3

2

3

4

Τ Τ e x a v a l e n t actinides c a n b e extracted i n t o l o n g c h a i n amines ( J I ) a n d A

A

l o a d e d i n t o a n i o n exchange resins f r o m acetic a c i d solutions w i t h

r e s i n d i s t r i b u t i o n coefficients a p p r o a c h i n g 1 0 . Salts of t h e g e n e r a l for 3

mula M[U0 (C2H.302)3] 2

W

a r e w e l l k n o w n , a n d t h e existence of t h e t r i

acetato c o m p l e x i n aqueous solutions has b e e n s h o w n w i t h n o e v i d e n c e of h i g h e r complexes (1,3,5,22).

A f e w salts c o n t a i n i n g f o u r acetate ions

p e r u r a n y l i o n h a v e b e e n r e p o r t e d (4, 12).

T h e P b a n d M n salts w e r e

r e p o r t e d b y N i c h o l s a n d H o w e s w i t h o u t analysis (12) b a s e d o n t h e o l d w o r k ( about 1885 ) of R a m m e l s b e r g w h o a n a l y z e d a C d salt a n d assigned a s i m i l a r f o r m u l a to t h e P b a n d M n salts. N i c h o l s a n d H o w e s c o u l d n o t 335 Fields and Moeller; Lanthanide/Actinide Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

336

LANTHANIDE /ACTINIDE CHEMISTRY

p r e p a r e the C d salt (12)

a n d i n a later w o r k r e p o r t e d the P b a n d M n

salts as triacetates (13).

D i e k e a n d D u n c a n r e p o r t e d several u r a n y l salts

as tetraacetates w i t h no basis for this assignment except for a reference to Ref. 12 a b o v e i n the case of the P b salt. It w a s f o u n d i n the present w o r k that the P b salt is a triacetato salt, a n d it is p r o b a b l e t h a t a l l of these reports of tetraacetato u r a n y l salts are i n error. T h e triacetato u r a n y l c o m p l e x trinitrato uranyl complex

(6)

(24)

is s t r u c t u r a l l y s i m i l a r to

the

(three b i d e n t a t e l i g a n d s a r r a n g e d e q u a -

t o r i a l l y a r o u n d the u r a n y l Ο — U — Ο a x i s ) .

It was expected

that the

v i s i b l e , near u l t r a v i o l e t s p e c t r u m of the triacetato u r a n y l c o m p l e x w o u l d Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch025

be

similar

to

the

spectrum

U0 (S0 )3 ", U0 (C0 ) 2

4

4

2

8

3

4

of

U0 (N03) ~ 2

3

as

are

the

~ , a n d other u r a n y l complexes

e n t l y h a v e the same structure (17).

spectra

of

which appar

T h e a b s o r p t i o n s p e c t r u m of u r a n y l

acetate extracted i n t o t r i - n - o c t y l a m i n e i n x y l e n e f r o m d i l u t e acetic a c i d is different f r o m the t r i n i t r a t o u r a n y l s p e c t r u m .

T h i s indicates that the

triacetato u r a n y l c o m p l e x is p r o b a b l y not the species i n v o l v e d . B y a n a l o g y to the u r a n y l n i t r a t e system (14), p l e x m i g h t be expected.

f o r m a t i o n of a tetraacetato u r a n y l c o m

T h e p u r p o s e of this w o r k is to d e t e r m i n e the

n a t u r e of the a n i o n i c h e x a v a l e n t a c t i n i d e acetate complexes a n d to i d e n t i f y the species i n v o l v e d i n the a m i n e e x t r a c t i o n a n d a n i o n exchange

of

the h e x a v a l e n t actinides f r o m acetate systems.

Experimental Reagents. C o m m o n l y a v a i l a b l e reagents w e r e a l l reagent grade. C e s i u m acetate a n d l i t h i u m acetate w e r e p r e p a r e d b y n e u t r a l i z i n g the c o r r e s p o n d i n g C . P . h y d r o x i d e s w i t h acetic a c i d , f o l l o w e d b y e v a p o r a t i n g a n d d r y i n g at 1 1 0 ° C . at 200 m m . pressure. T e t r a e t h y l a m m o n i u m acetate was prepared b y neutralizing E a s t m a n 1 0 % tetraethylammonium hydrox i d e w i t h acetic a c i d , e v a p o r a t i n g o n a hot p l a t e u n t i l b o i l i n g ceased, a n d d r y i n g at 110 ° C . at 200 m m . pressure for a b o u t 5 hours. P r o l o n g e d d r y i n g u n d e r these c o n d i t i o n s causes g r a d u a l d e c o m p o s i t i o n a n d d i s c o l o r a t i o n . T h e r e s u l t i n g m a t e r i a l was a n almost colorless o i l y l i q u i d w h e n c o o l e d to r o o m t e m p e r a t u r e , w h i c h c r y s t a l l i z e d u p o n a b s o r p t i o n of a t m o s p h e r i c m o i s t u r e . T h e c o m p o u n d appears to b e the same as that r e p o r t e d b y S t e i g m a n a n d H a m m e t t (20) as the m o n o h y d r a t e . It c r y s t a l l i z e d w h e n c o o l e d to — 8 0 ° C . a n d d i d not r e m e l t w h e n w a r m e d to 2 5 ° C . W h e n a nonaqueous s o l u t i o n of t e t r a e t h y l a m m o n i u m acetate of k n o w n c o n c e n t r a t i o n w a s d e s i r e d , the salt w a s p r e p a r e d as a b o v e w i t h a m e a s u r e d v o l u m e of s t a n d a r d i z e d t e t r a e t h y l a m m o n i u m h y d r o x i d e , a n d the entire p r e p a r a t i o n w a s d i s s o l v e d to v o l u m e i n the n o n a q u e o u s solvent. Preparation of Cesium and Quaternary Ammonium Actinide ( V I ) Acetate Salts. T e t r a e t h y l a m m o n i u m u r a n y l acetate w a s p r e p a r e d b y e v a p o r a t i n g to dryness a s o l u t i o n of u r a n y l acetate c o n t a i n i n g t e t r a e t h y l a m m o n i u m acetate i n slight excess. T h e r e s i d u e w a s d i s s o l v e d i n b o i l i n g absolute e t h a n o l , a n d the p r o d u c t w a s p r e c i p i t a t e d b y c o o l i n g i n a d r y ice b a t h . T h e p r o d u c t w a s filtered a n d r e c r y s t a l l i z e d a g a i n f r o m e t h a n o l .

Fields and Moeller; Lanthanide/Actinide Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

25.

R Y A N

A N D

Hexavalent

K E D E R

337

Actinides

T h e salt was d r i e d at 1 2 0 ° C . at 200 m m . pressure. A n a l y s i s : c a l c u l a t e d for ( C H 5 ) 4 N U 0 ( C H 0 ) : U , 41.23; f o u n d : U , 41.29. C e s i u m u r a n y l triacetate was p r e c i p i t a t e d b y a d d i n g a s o l u t i o n of c e s i u m acetate c o n t a i n i n g a s m a l l a m o u n t of acetic a c i d to a s o l u t i o n of u r a n y l acetate i n w a t e r . T h i s p r e v i o u s l y r e p o r t e d c o m p o u n d w a s not analyzed. C e s i u m n e p t u n y l acetate was p r e p a r e d as follows. N e p t u n i u m ( V I ) nitrate w a s p r e p a r e d b y h e a t i n g anion-exchange p u r i f i e d (15) n e p t u n i u m ( I V ) a n d ( V ) nitrate i n 0 . 5 M H N 0 to 1 0 0 ° C . for one h o u r . T h e N p ( V I ) was p r e c i p i t a t e d w i t h C s O H . T h e p r e c i p i t a t e w a s separated, w a s h e d w i t h w a t e r , a n d r e d i s s o l v e d i n a m i n i m u m of c o n c e n t r a t e d acetic a c i d . T h i s s o l u t i o n was d i l u t e d t e n f o l d w i t h w a t e r , a n d the p r e c i p i t a t i o n , w a s h i n g , a n d d i s s o l u t i o n i n c o n c e n t r a t e d acetic a c i d w e r e repeated. E x c e s s c e s i u m acetate was a d d e d , a n d the green p r o d u c t was filtered, w a s h e d w i t h e t h a n o l a n d t h e n acetone, a n d d r i e d over M g ( C 1 0 ) . A n a l y s i s : c a l c u l a t e d for C s N p O > ( C H 0 ) : C s , 23.0; N p , 40.9. F o u n d : C s , 23.2; N p , 39.7. C e s i u m p l u t o n y l triacetate ( p i n k ) w a s p r e p a r e d i n the same m a n n e r as t h e n e p t u n y l a n a l o g except the anion-exchange p u r i f i e d (18) P u ( I V ) nitrate w a s o x i d i z e d to P u ( V I ) nitrate b y ozone at about 8 0 ° C . A n a l y s i s : c a l c u l a t e d for C s P u 0 ( C H 0 ) : C s , 22.9; P u , 41.2. F o u n d : C s , 23.6; P u , 41.3. C e s i u m a n d l i t h i u m analyses w e r e b y flame p h o t o m e t r y . U r a n i u m ( 2 ) , n e p t u n i u m ( 2 1 ) , a n d p l u t o n i u m ( 1 9 ) analyses w e r e b y c o n t r o l l e d potential coulometric titration. Solvents. A c e t o n i t r i l e a n d n i t r o m e t h a n e w e r e E a s t m a n spectro grade. S u c c i n o n i t r i l e was E a s t m a n w h i t e l a b e l . Amine Extraction. T r i - n - o c t y l a m i n e was p r e p a r e d b y r e p e a t e d w a s h i n g of t r i - n - o c t y l a m m o n i u m c h l o r i d e w i t h I N N H O H f o l l o w e d b y w a s h i n g w i t h w a t e r . U r a n i u m extraction experiments w e r e p e r f o r m e d w i t h U - 2 3 3 tracer w h i c h c o n t a i n e d a s m a l l a m o u n t of h y d r o c h l o r i c a c i d . Successive b a c k w a s h i n g of extracts w i t h acetic a c i d was u s e d to e l i m i n a t e the c h l o r i d e . N p - 2 3 7 a n d P u - 2 3 9 w e r e o x i d i z e d w i t h o z o n e a n d b a c k w a s h e d t w o or three times to e l i m i n a t e l o w e r o x i d a t i o n states. Spectrophotometric Measurements. Spectrophotometric measure ments w e r e m a d e w i t h a C a r y M o d e l 14 r e c o r d i n g spectrophotometer. A b s o r p t i o n spectra of solutions w e r e o b t a i n e d i n silica cells. A b s o r p t i o n spectra of the c r y s t a l l i n e salts w e r e o b t a i n e d u s i n g m i x t u r e s of the m a t e rials w i t h p e t r o l a t u m b e t w e e n glass or s i l i c a plates u s i n g the C a r y M o d e l 1417200 source. B l a n k s for the s o l i d spectra w e r e C a C 0 m u l l s i n p e t r o l a t u m p l u s aqueous starch s o l u t i o n i f necessary to p r o d u c e a flat base l i n e . T h e reference was adjusted so the base l i n e was flat i n the 520 to 600 τημ r e g i o n w h e r e the U ( V I ) acetate complexes d o not absorb. Slit w i d t h s for spectra of solids w e r e t y p i c a l l y < 0.1 m m . 2

2

2

3

2

3


3

4

2

2

2

3

2

3

2

2

3

3

4

3

Results and Discussion Identification of Species. F i g u r e 1 shows the a b s o r p t i o n spectra of s o l i d C s U 0 ( C H 0 ) a n d ( C H ) N U 0 ( C H 0 ) i n a c e t o n i t r i l e so l u t i o n . O t h e r s o l i d triacetato salts p r o d u c e essentially the same s p e c t r u m , 2

2

3

2

3

2

5

4

2

2

3

2

3


338

LANTHANIDE/ACTINIDE

CHEMISTRY

w h i c h is also o b t a i n e d w h e n the t e t r a a l k y l a m m o n i u m salt is d i s s o l v e d i n n i t r o m e t h a n e , acetone, acetic a n h y d r i d e , a n d s u c c i n o n i t r i l e . T h i s d i s t i n c t i v e s p e c t r u m is s i m i l a r to those of U 0 ( N 0 ) ~ 2

(17),

U0 (C0 ) 2

3

3

4

3

" , a n d U 0 ( C 1 0 ) " (23), 2

4

3

(7, 14),

3

U0 (S0 ) 2

4

3

4

""

a n d i t appears that this spec

t r u m is p e c u l i a r to u r a n y l ( V I ) , w h i c h is b o n d e d t h r o u g h o x y g e n to three

Ο—U—Ο

b i d e n t a t e l i g a n d s l y i n g i n a p l a n e p e r p e n d i c u l a r to the T r i n i t r a t o (6)

a n d triacetato (24)

axis.

u r a n y l ions h a v e this geometry, w h i l e

no ions w h i c h c o u l d not fit this p a t t e r n are k n o w n to h a v e a s i m i l a r


spectrum.

1.4 ι — ι

1

1

1

1

Wavelength, πιμ Figure 1. Absorption spectra of the U0 (C H 0 ) ~ i° compared with that of a tri-n-octylamine extract of U(VI) from I M HC H 0 ; (1) 0.022M U(VI) in 5% tri-noctylamine in xylene (1 cm. cell), (2) 0.024M (C H ) NU0 (C H 0 ) in acetonitrile (1 cm. cell), and (3) solid CsU0 (C H 0 ) 2

2

2

2

3

5 a

3

n

2 3

2

2

2

3

2 3

2

2

3

2 3


25.

R Y A N

Hexavalent

A N D K E D E R

339

Actinides

It w a s o b s e r v e d i n p r e l i m i n a r y w o r k (9, 10)

t h a t t h e s p e c t r u m of

u r a n y l ( V I ) e x t r a c t e d i n t o T O A - x y l e n e f r o m acetic a c i d is d e f i n i t e l y n o t that of the triacetato a n i o n ( F i g u r e 1 ). T h e g e n e r a l l a c k of strong v i b r a t i o n a l features i n b o t h this s p e c t r u m a n d t h a t of U 0 ( N 0 ) 2

3

4

2

~ , combined

w i t h t h e r e l a t i v e l y h i g h e r m o l a r a b s o r p t i v i t y of b o t h of these r e l a t i v e to those of the c o r r e s p o n d i n g t r i s u b s t i t u t e d complexes, s t r o n g l y i n d i c a t e t h e presence of the tetraacetato u r a n y l i o n i n the T O A - x y l e n e extract. T o i d e n t i f y this u n k n o w n species,

I n the u r a n y l n i t r a t e system the

[(C H ) N] U0 (N0 )

c o u l d be p r e p a r e d

2

5

4

2

2

m o l a r m i x t u r e of


a n a t t e m p t w a s m a d e to

p a r e a tetraacetato salt.

NU0 (C H 0 ) 2

2

3

2

3

4

by fusing an equi-

(13)

( C H ) N U 0 ( N 0 ) 3 and ( C H ) N N 0 . 2

5

4

2

2

3

pre

compound

5

4

3

(C H ) 2

5

4

does not m e l t w i t h o u t d e c o m p o s i t i o n , so a n a q u e o u s

3

solution was prepared containing equimolar ( C H ) N U 0 ( C H 0 ) 3 2

and

(C H ) NC H 0 2

5

4

2

3

2

5

4

2

2

3

2

w i t h a s m a l l excess of acetic a c i d . T h i s w a s d r i e d

at 1 1 0 ° C . at 200 m m . pressure. T h e p r o d u c t w a s a viscous o i l w h i c h d i d not c r y s t a l l i z e at 25 ° C . T h e a b s o r p t i o n s p e c t r u m of t h i s m a t e r i a l b e t w e e n f u s e d - q u a r t z plates w a s f o u n d to b e i d e n t i c a l to t h a t of u r a n y l e x t r a c t e d f r o m 1 M acetic a c i d i n t o t r i - n - o c t y l a m i n e i n x y l e n e . A series of solutions was

prepared

w h i c h contained

(C H ) NC H 0 2

5

4

2

3

2

to

(C H ) NU0 2

5

4

2

( C H 0 ) 3 ratios f r o m 0 to 2 a n d a s m a l l excess of acetic a c i d . 2

3

These

2

w e r e d r i e d at 1 0 0 ° C . at 200 m m . , a n d the a b s o r p t i o n s p e c t r a w e r e

ob

t a i n e d . T h e s a m p l e w i t h no excess t e t r a e t h y l a m m o n i u m acetate p r o d u c e d c r y s t a l l i n e ( C H ) N U 0 ( C H 0 ) 3 , a n d its s p e c t r u m w a s o b t a i n e d i n 2

petrolatum.

5

4

2

2

3

2

T h e samples c o n t a i n i n g b e t w e e n 3 a n d 4 moles of

acetate

p e r m o l e of u r a n i u m w e r e m i x t u r e s of c r y s t a l l i n e m a t e r i a l a n d a viscous l i q u i d , a n d the spectra w e r e r u n b e t w e e n q u a r t z plates w i t h o u t m i x i n g w i t h p e t r o l a t u m . T h e r a t i o of the a b s o r b a n c e at 460 πΐμ, w h e r e the t r i acetato c o m p l e x has a s t r o n g peak, to t h a t at 453 τημ, w h e r e i t has a m i n i m u m , is p l o t t e d against acetate to u r a n i u m r a t i o i n F i g u r e 2.

It is

a p p a r e n t f r o m this p l o t that a tetraacetato u r a n y l c o m p l e x forms.

The

samples h a v i n g a n acetate to U r a t i o of 4.0 a n d 4.1 a p p e a r e d to d i s p r o p o r t i o n a t e s l i g h t l y a n d h a d a f e w s m a l l crystals of (C H 0 2

3

2

(C H ) NU0 2

5

4

2

) present. T h e i r spectra are not the p u r e tetraacetato s p e c t r u m . 3

A t h i g h e r acetate to U ratios n o crystals w e r e present, a n d no f u r t h e r c h a n g e i n s p e c t r u m o c c u r r e d w i t h i n c r e a s e d acetate ( u p to a n acetate to u r a n i u m r a t i o of 100) i n d i c a t i n g l a c k of h i g h e r complexes.

T h e spectrum

of samples h a v i n g a n acetate to U r a t i o of 4.5 or greater is t h a t of t h e p u r e tetraacetato u r a n y l c o m p l e x . When (C H 0 ) 2

3

2

(C H ) NC H 0 2

3

5

4

2

3

2

is a d d e d to a s o l u t i o n of

(C H ) NU0 2

5

4

2

i n a r e l a t i v e l y n o n c o m p l e x i n g solvent, s u c h as a c e t o n i t r i l e or

n i t r o m e t h a n e , t h e s t r o n g v i b r a t i o n a l peaks of the t r i a c e t a t o c o m p l e x

de

crease i n i n t e n s i t y , a n d the o v e r - a l l a b s o r b a n c e increases. A t h i g h acetate concentrations the s p e c t r u m a p p r o a c h e s

t h a t of the p u r e

tetraacetato


LANTHANIDE/ACTINIDE CHEMISTRY

340

c o m p l e x o b t a i n e d a b o v e b u t s t i l l contains a s m a l l a m o u n t of triacetato complex. such

I f a h i g h d i e l e c t r i c - c o n s t a n t solvent of l o w c o m p l e x i n g p o w e r

as 8 5 %

(C H 0 ) 2

3

2

succinonitrile-15% acetonitrile

is s o l u b l e .

3

is u s e d ,

(16)

T h e same effect c a n b e

observed

CsU0 2

by

adding

C s C H 0 , a l t h o u g h the r e a c t i o n c a n n o t b e c a r r i e d as far t o w a r d t h e 2

3

2

tetraacetato c o m p l e x because of the s o l u b i l i t y l i m i t of C s C H 0 . 3

2


2

A series of a c e t o n i t r i l e solutions w a s p r e p a r e d w h i c h c o n t a i n e d k n o w n concentrations acetate.

of

(C H ) NU0 (C H 0 ) 2

5

4

2

2

3

2

3

and

tetraethylammonium

T h e s p e c t r u m of a s o l u t i o n c o n t a i n i n g n o t e t r a e t h y l a m m o n i u m

acetate w a s t a k e n to b e that of p u r e U 0 ( C H 0 ) " , a n d the s p e c t r u m 2

2

3

2

3

i n l i q u i d t e t r a e t h y l a m m o n i u m acetate [ p r o b a b l y the m o n o h y d r a t e

(20)]

w i t h a n acetate to U r a t i o of a b o u t 100 w a s t a k e n to be t h a t of p u r e U0 (C H 0 ) 2

2

3

2

4

2

~.

T h e a b s o r p t i o n spectra of the p u r e triacetato c o m p l e x ,

the p u r e tetraacetato c o m p l e x , a n d one m i x t u r e are c o m p a r e d i n F i g u r e 3. W i t h the m o l a r a b s o r p t i v i t i e s of the p u r e complexes o b t a i n e d i n this


25.

R Y A N

A N D K E D E R

Hexavalent

341

Actinides

m a n n e r , t h e f r a c t i o n of e a c h c o m p l e x present i n a l l t h e a c e t o n i t r i l e s o l u tions c a n b e c a l c u l a t e d at a n y w a v e l e n g t h w h e r e there is a n a p p r e c i a b l e difference i n t h e m o l a r a b s o r p t i v i t y of t h e t w o complexes.

This was done

at 494 m ^ w h e r e t h e tetraacetato c o m p l e x has a n a b s o r p t i o n m a x i m u m a n d t h e triacetato c o m p l e x has almost n o a b s o r p t i o n .

This wavelength

w a s chosen because i t w a s one of t h e f e w w a v e l e n g t h s w h e r e t h e a b s o r p w a s e x t r e m e l y steep

thus


t i o n s p e c t r u m of n e i t h e r of t h e complexes

Wavelength, ηιμ Figure 3. Absorption spectra of 0.0240M (C H )jJS!O0 (C H 0 ) in (1) pure liquid (0 Η ) Ν0 Η 0 · H 0, and in acetonitrile solutions containing (2) 0.225M and (3) 0.000M (C H ) NC H 0 2

2

3

2 3

2

5 Α

B

s k

2

3

9

2

s

5

2

2

2

m i n i m i z i n g errors c a u s e d b y s m a l l errors i n w a v e l e n g t h .

( T h i s is also

true at 420 τημ, b u t here d i s c o l o r a t i o n of t h e t e t r a e t h y l a m m o n i u m acetate p r o d u c e s a b s o r p t i o n , a n d there w a s some p r o b l e m i n e n s u r i n g this w a s c o r r e c t l y b l a n k e d o u t at t h e h i g h e s t t e t r a e t h y l a m m o n i u m acetate c o n c e n trations. ) C h e c k s w e r e m a d e at several w a v e l e n g t h s other t h a n 494 τημ,


342

LANTHANIDE/ACTINIDE

CHEMISTRY

a n d the results agreed w i t h i n e x p e r i m e n t a l a c c u r a c y w i t h those o b t a i n e d at 494m/x. T h e f o r m a t i o n constant, [ υ θ 2 ( 0

Κ -

2

Η

3

θ 2 ) 4

2

- ]

[U0 (C H 0 ) -] [C H 0 2

2

3

2

3

2

3

]

2

w a s c a l c u l a t e d for e a c h acetate c o n c e n t r a t i o n e x a m i n e d ( T a b l e I ). Table I .

Initial Molarity (C H ),NC H 0 0.000 0.045 0.090 0.225 0.450 0.900 2.25 2


Formation of Tetraacetato U r a n y l Complex in Acetonitrile

5

2

3

2

%

U0 (C H 0 ) ~ 100.0 92.9 83.3 66.7 56.0 35.7 17.9 2

2

3

2 3

%

Κ

U0 (C H 0 )r 0.0 7.1 16.7 33.3 44.0 64.3 82.1 2

2

3

2

1.77 2.34 2.25 1.79 2.00 2.04 Av. = 2.0:±O2

Aqueous Solutions. A h r l a n d ( 1 ) has c o n c l u d e d t h a t U 0 ( C H 0 ) ~ 2

2

3

2

3

is the highest u r a n y l acetate c o m p l e x present i n aqueous solutions a n d that this species constitutes >

9 5 % of the t o t a l u r a n y l species at 0 . 3 M

a n d h i g h e r acetate. T h e triacetato u r a n y l c o m p l e x does not c o n t a i n w a t e r a n d the tetraacetato c o m p l e x u n d o u b t e d l y does not. B e c a u s e of this, the f o r m a t i o n constant of the tetraacetato c o m p l e x f r o m the triacetato c o m p l e x m i g h t b e e x p e c t e d to b e of a b o u t the same o r d e r of m a g n i t u d e i n w a t e r as i n a c e t o n i t r i l e . A l s o the tetraacetato c o m p l e x m i g h t b e e x p e c t e d to f o r m to a n a p p r e c i a b l e extent at h i g h aqueous acetate concentrations. A n y difference b e t w e e n a c e t o n i t r i l e a n d w a t e r s h o u l d b e c a u s e d b y the effects o n the f o r m a t i o n constant c a u s e d b y a difference i n i o n i z i n g p o w e r of the solvent as affected b y d i e l e c t r i c constant, solvent structure, etc., since w a t e r is not d i r e c t l y i n v o l v e d i n the e q u i l i b r i u m . A q u e o u s l i t h i u m acetate-acetic a c i d solutions of U ( V I ) w e r e e x a m i n e d s p e c t r o p h o t o m e t r i c a l l y for e v i d e n c e of the tetraacetato u r a n y l c o m p l e x . A c e t i c a c i d c o n c e n t r a t i o n w a s k e p t at least t w i c e the l i t h i u m acetate c o n c e n t r a t i o n , except for the highest l i t h i u m acetate c o n c e n t r a t i o n e x a m i n e d , to p r e v e n t h y d r o l ysis ( 1 ). S o l u t i o n s r a n g i n g i n acetate c o n c e n t r a t i o n f r o m U 0 ( C H 0 ) 2

i n acetic a c i d to 5 . 4 M L i C H 0 2

3

2

2

3

2

2

w e r e e x a m i n e d at 0 . 0 4 0 M u r a n i u m i n a l l

cases. Some of the spectra are s h o w n i n F i g u r e 4, a n d it is a p p a r e n t t h a t at least three u r a n y l species are present i n this c o n c e n t r a t i o n range. A t l o w acetate c o n c e n t r a t i o n ( u r a n y l acetate i n acetic a c i d ) l i t t l e if a n y triacetato c o m p l e x is present as seen b y the absence of the f o u r strong v i b r a t i o n a l peaks at a b o u t 420, 432, 445, a n d 460 τημ. A s the acetate l e v e l is i n c r e a s e d , these strong triacetato peaks b u i l d i n t o the


R Y A N


25.

Hexavalent

A N D K E D E R

343

Actinides

400

450 Wavelength,

500 ιτιμ

Figure 4. Absorption spectra of 0.040M aqueous Ό(VI) acetate solution in 1 cm. cells: (1) 5.4M LiC H 0 —3.5M HC H,0 (2) 3.0M LiC H 0 — 6.0M HC H 0 , (3) 0.165M LiC H O —0.6M HC H 0 , and (4) 0.6M HC H 0 2

3

2

2

2

3

2

spectra.

2>

g

2

3

2

2

2

3

3

3

9

2

2

T h e a b s o r b a n c e at 420 ni/x decreases s o m e w h a t , goes t h r o u g h

a m i n i m u m at a b o u t 0 . 1 - 0 . 3 M acetate, a n d increases m a r k e d l y at h i g h e r acetate concentrations. T h i s increase i n a b s o r b a n c e appears to b e c a u s e d b y the f o r m a t i o n of the tetraacetato u r a n y l c o m p l e x .

T h e triacetato

c o m p l e x appears to b e d e c r e a s i n g at the h i g h e s t l i t h i u m acetate

con

centrations, a n d a l a r g e f r a c t i o n of the t o t a l u r a n i u m is present as t h e tetraacetato c o m p l e x . A q u a n t i t a t i v e i n t e r p r e t a t i o n of these spectra is not feasible for t w o reasons. F i r s t , there are at least three species present i n c l u d i n g at least


344

LANTHANIDE /ACTINIDE CHEMISTRY

one c o m p l e x w h i c h contains less t h a n three acetates, a n d the s p e c t r u m of this c o m p l e x ( or complexes ) is not k n o w n . S e c o n d , a n y c h a n g e i n the triacetato or tetraacetato spectra f r o m those m e a s u r e d as d e s c r i b e d p r e viously w o u l d further complicate a quantitative interpretation.

There

does a p p e a r to be a n energy shift a m o u n t i n g to a b o u t 2 m/x i n the t e t r a acetato s p e c t r u m i n g o i n g f r o m a c e t o n i t r i l e to w a t e r .

E v e n a slight

b r o a d e n i n g of the sharp triacetato v i b r a t i o n a l peaks w o u l d also

cause

l a r g e errors. A s e m i q u a n t i t a t i v e i n t e r p r e t a t i o n i n d i c a t e s that the t e t r a acetato, triacetato, a n d at least one l o w e r c o m p l e x coexist i n a p p r e c i a b l e amounts i n the same solutions w i t h the a m o u n t of triacetato Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch025

a p p a r e n t l y i n c r e a s i n g u p to about 1 M acetate.

complex

T h e a m o u n t of t h e t r i

acetato u r a n y l c o m p l e x never appears to exceed a b o u t 5 0 - 6 0 %

of the

t o t a l u r a n i u m unless the acetic a c i d to l i t h i u m acetate ratio is i n c r e a s e d to w e l l a b o v e 2. A t h i g h acetate concentrations, a large a m o u n t of the U0 (C H 0 ) 2

2

3

2

4

2

" c o m p l e x is present. A t 5 . 4 M L i C H 0 - 3 . 5 M 2

the U 0 ( C H 0 ) 2

2

3

2

4

2

3

2

HC H 0 , 2

3

2

~ appears to constitute about 5 0 % or m o r e of the t o t a l

uranium, and in 3 M L i C H 0 - 6 M H C H 0 2

3

2

2

3

a b o u t 2 0 % as d e t e r m i n e d

2

b y the i n c r e a s e d absorbance at 420 τημ a n d at 494 τημ. I n c r e a s i n g the acetic a c i d c o n c e n t r a t i o n at a constant l i t h i u m acetate increases the a m o u n t of triacetato c o m p l e x .

concentration

T h i s occurs at the expense

of l o w e r complexes b y d e c r e a s i n g w a t e r a c t i v i t y since w a t e r is n o d o u b t present i n the l o w e r acetate complexes.

T h i s m a y also decrease acetate

a c t i v i t y b y h y d r o g e n b o n d i n g to the acetic a c i d a n d s i m u l t a n e o u s l y f a v o r the triacetato c o m p l e x

over the tetraacetato c o m p l e x .

The formation

constant for the tetraacetato c o m p l e x f r o m the triacetato c o m p l e x appears s o m e w h a t s m a l l e r i n w a t e r t h a n i n a c e t o n i t r i l e b u t a p p a r e n t l y not

by

m o r e t h a n a factor of 10. Anion Exchange Resin Studies. F i g u r e 5 shows the a b s o r p t i o n spectra of U ( V I ) l o a d e d i n t o D o w e x 1, X - 4 ( 5 0 to 100 m e s h ) a n i o n exchange r e s i n f r o m several acetate solutions. B o t h the triacetato a n d tetraacetato u r a n y l complexes are a b s o r b e d b y the a n i o n exchange resin. A n increase i n t h e f r a c t i o n of triacetato c o m p l e x occurs w i t h a n increase i n the acetic a c i d c o n c e n t r a t i o n of the solutions.

T h e f r a c t i o n of e a c h c o m p l e x c a n

be a p p r o x i m a t e d b y m e a s u r i n g the r a t i o of the absorbances at 460 τημ a n d 454 m/x a n d c o m p a r i n g w i t h the values o b t a i n e d i n a c e t o n i t r i l e . T h i s c a l c u l a t i o n is not exact because the spectra of the t w o p u r e species i n the r e s i n m a y be different f r o m those i n a c e t o n i t r i l e . I n contact 1 7 . 5 M acetic a c i d the r e s i n contains a b o u t 9 %

with

tetraacetato c o m p l e x , i n

1 0 M acetic a c i d a b o u t 1 3 % , a n d i n 1 M acetic a c i d a b o u t 2 5 % .

This

increase is also o b s e r v e d b y the b u i l d - i n of the tetraacetato p e a k at 494 τημ w h e r e the triacetato c o m p l e x does not absorb.

I n solutions h a v i n g a

l i t h i u m acetate to acetic a c i d r a t i o of 1/2, the U ( V I ) i n the r e s i n w a s about 3 0 %

i n the tetraacetato f o r m f r o m 0 . 1 6 - 3 . 0 M l i t h i u m


acetate.

25.

R Y A N

A N D

Hexavalent

K E D E R

345

Actinides


Τ

Wavelength, ηιμ Figure 5. Absorption spectra of Ό(VI) absorbed in Dow ex 1, X-4 (50-100 mesh) from acetate solu tions: (1) 4.0M LiC H O —2.0M HC H 0 , (2) 0.6M HC H 0 , and (3) J 7 M HC H 0 . U(VI) concentrations in resin phase are approximately equal 2

2

3

3

9

2

2

2

3

3

2

2

W i t h 5 M l i t h i u m acetate a n d < 4 M acetic a c i d , the U ( V I ) i n t h e r e s i n was a b o u t 4 0 % i n t h e tetraacetato f o r m . The

decrease i n tetraacetato c o m p l e x i n t h e r e s i n phase w i t h i n

creased acetic a c i d c o n c e n t r a t i o n is p r o b a b l y a t t r i b u t e d to l o w e r e d acetate a c t i v i t y i n t h e resin phase c a u s e d b y h y d r o g e n b o n d i n g of i n v a d i n g acetic a c i d to the r e s i n acetate.

A similar but more pronounced

effect

occurs i n t h e u r a n y l sulfate system o w i n g to c o n v e r s i o n of r e s i n sulfate to b i s u l f a t e (17).

T h e o n l y clear c u t effect of a w i d e v a r i a n c e i n the

l i t h i u m acetate c o n c e n t r a t i o n seems to b e a decrease of t h e acetic a c i d effect.

T h i s is p r o b a b l y c a u s e d b y t y i n g u p of acetic a c i d b y h y d r o g e n


346


b o n d i n g to acetate f r o m l i t h i u m acetate t h e r e b y decreasing its effect o n resin acetate.

A s i m i l a r m a r k e d l a c k of d e p e n d e n c e of the u r a n y l sulfate

species i n r e s i n o n t o t a l aqueous

sulfate occurs

(17).

It appears t h a t

the r a t i o of c o m p l e x species i n a n i o n exchange resins ( w h e r e m o r e t h a n one species is a b s o r b e d ) is d e t e r m i n e d b y r e s i n l i g a n d a c t i v i t y , a n d this is not m u c h affected b y aqueous l i g a n d c o n c e n t r a t i o n b u t m a y b e m a r k e d l y affected b y other factors s u c h as aqueous a c i d c o n c e n t r a t i o n . T h e u r a n y l n i t r a t o a n d acetato a n i o n i c complexes are s i m i l a r . l o w a c i d 5 M m e t a l n i t r a t e (14) U0 (N0 ) 2

3

4

2

to U 0 ( N 0 ) " a n d U 0 ( C H 0 ) 2

8

From

or acetate solutions the r e l a t i v e ratios of

3

2

2

3

2

4

2

to U 0 ( C H 0 ) " 2

2

3

2

3


i n the r e s i n phase closely reflect the difference i n f o r m a t i o n constants of the tetra complexes f r o m the t r i complexes.

T h i s is despite the fact that

the f o r m a t i o n constants of the triacetato c o m p l e x a n d the t r i n i t r a t o c o m p l e x f r o m the respective l o w e r complexes are o b v i o u s l y different a n d the aqueous phase contains m a i n l y a n i o n i c species i n the acetate case b u t essentially n o a n i o n i c species i n the n i t r a t e case

(14).

A m i n e E x t r a c t i o n . E x t r a c t i o n of u r a n i u m ( V I ) a n d p l u t o n i u m ( V I ) f r o m acetic a c i d w i t h t r i - i s o - o c t y l a m i n e i n x y l e n e has b e e n s t u d i e d p r e v i o u s l y b y M o o r e (11),

w h o suggests that the extracted species is the t r i -

acetato i o n . T h e spectra i n F i g u r e 1 s h o w this is not the p r e d o m i n a t e species e x t r a c t e d i n t o T O A - x y l e n e solutions ( 9 ) .

C o m p a r i n g the spec-

t r u m of this extracted u r a n i u m w i t h the spectra of p u r e tetraacetato a n d triacetato complexes i n F i g u r e 3 shows that the T O A - x y l e n e extracts a m i x t u r e of these ions that is l a r g e l y tetraacetato u r a n y l c o m p l e x . W e n o t e d earlier t h a t the p r i n c i p l e u r a n y l ( V I ) f r o m acetic a c i d b y T O A - c h l o r o f o r m (10).

T O A - x y l e n e is different f r o m

species

extracted

that e x t r a c t e d

by

T o explore the effect of the solvent f u r t h e r w e

h a v e n o w m e a s u r e d the spectra of u r a n i u m ( V I ) e x t r a c t e d w i t h solutions of T O A i n different solvents. I n these experiments a 0 . 1 0 M u r a n y l acetate s o l u t i o n i n I N acetic a c i d w a s extracted w i t h a n e q u a l v o l u m e of 0 . 1 0 M T O A i n e a c h of the several solvents, a n d the spectra of b o t h phases w e r e measured.

I n most cases the extracted u r a n i u m w a s f o u n d to b e a m i x -

ture of t r i - a n d tetraacetato complexes.

S o m e examples of these spectra

are s h o w n i n F i g u r e 6. U s i n g the t e c h n i q u e e m p l o y e d e a r l i e r i n this p a p e r w e h a v e c a l c u l a t e d the f r a c t i o n of the extracted U w h i c h is i n the tetraacetato f o r m . T h e s e results are s h o w n i n T a b l e I I . T h e values are not precise since s m a l l s o l v e n t - d e p e n d e n t f r e q u e n c y shifts o c c u r r e l a t i v e to the spectra of the p u r e species w h i c h w e r e o b t a i n e d i n n i t r i l e solutions. If the d a t a i n the table are p l o t t e d , a s m o o t h c u r v e c a n be d r a w n t h r o u g h a l l of the p o i n t s , w i t h i n the e s t i m a t e d p r e c i s i o n , except those f r o m the h a l o f o r m solutions. T h e f r a c t i o n of the tetraacetato c o m p l e x decreases u n i f o r m l y


R Y A N

A N D


25.

Hexavalent

K E D E R

347

Actinides

Wavelength, πιμ Figure 6. Absorption spectra of U(VI) extracted from 1M HC H O —0.10M U(VI) into 5% tri-n octylamine in: (1) xylene, (2) isopropl ether, (3) chloroform, and (4) hexone 2

s

2

w i t h increase of d i e l e c t r i c constant of the solvent w i t h no a p p a r e n t r e l a tionships to the m o l e c u l a r f o r m of the solvent, except for C H C 1

3

and

C H B r . Since o n l y a n i o n i c complexes c a n be present i n the o r g a n i c phase, a

w h a t w e observe is s i m p l y a decrease of the f o r m a t i o n constant of the r e a c t i o n U 0 ( acetate ) ~ + 2

3

acetate" —* U 0 ( acetate ) ~ w i t h i n c r e a s i n g

i o n i z i n g p o w e r of the solvent.

2

4

2

A s i m p l e electrostatic a r g u m e n t w o u l d

p r e d i c t this result. T h e same b e h a v i o r appears to h o l d for the

aceto

n i t r i l e a n d aqueous solutions d i s c u s s e d above, a l t h o u g h c o n d i t i o n s there are different a n d a strict c o m p a r i s o n is difficult. T h e o c c u r r e n c e of extra l o w fractions of the tetraacetato c o m p l e x i n the h a l o f o r m solutions m i g h t be expected f r o m the fact that h y d r o g e n b o n d i n g b e t w e e n acetate ions


348


a n d h a l o f o r m m o l e c u l e s lowers the acetate a c t i v i t y b e l o w w h a t i t w o u l d o t h e r w i s e be. O n e w o u l d expect the o r g a n i c phase of other a m i n e e x t r a c t i o n systems i n w h i c h m o r e t h a n one m e t a l a n i o n c a n b e f o r m e d to e x h i b i t s i m i l a r equilibria.

It is f o r t u n a t e that i n this system not o n l y is the solvent not

present i n the c o o r d i n a t i o n sphere of either c o m p l e x b u t also the e q u i l i b r i u m constant b e t w e e n the t w o is of a n order of m a g n i t u d e w h i c h a l l o w s c o n c e n t r a t i o n of b o t h to be m e a s u r e d r e a d i l y b y m e t r i c methods.

spectrophoto-

T h i s a l l o w s the effect of the d i e l e c t r i c constant of the

solvent o n the r a t i o of the species to b e s t u d i e d easily w i t h o u t the p e r Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1967 | doi: 10.1021/ba-1967-0071.ch025

t u r b i n g effect of specific interactions c a u s e d b y differences i n the t e n d e n c y of the solvents to enter the c o o r d i n a t i o n sphere. Table I I . U r a n y l ( V I ) Species Extracted from 1ÎV Acetic A c i d into 0.22V* Tri-w-Octylammonium Acetate Solutions Solvent Pentane Carbon tetrachloride Tetrachloroethylene Toluene o-Xylene Trichloroethylene Isopropyl ether Bromoform Chloroform Chlorobenzene a-Chlorotoluene 1,2-Dichloroethane M e t h y l isobutyl ketone Cyclopentanone a

h

Dielectric Constant

Fraction of U as Tetraacetato Complex

1.84 2.24 2.30 2.38 2.57 3.42 3.88 4.39 4.81 5.6 7.0 10.6 13.1 16.3

0 . 9 1 0.11* .73 .70 .62 .63 .35 .42 .14 .08 .26 .08 .0 .0 .05 a

Pentane phase. T h i r d phase containing most of the T O A a n d u r a n i u m .

I n the present w o r k w e h a v e m e a s u r e d the d i s t r i b u t i o n ratios

(D)

b y tracer t e c h n i q u e s for e x t r a c t i o n of U ( V I ) , N p ( V I ) , a n d P u ( V I ) f r o m 1 or 2 N acetic a c i d i n t o T O A - x y l e n e over a c o n c e n t r a t i o n r a n g e 0 . 2 0 M T O A a n d for e x t r a c t i o n of U ( V I ) i n t o T O A - C H C l c o n c e n t r a t i o n range.

P l o t s of l o g D

3

0.002-

over the same

vs. l o g T O A c o n c e n t r a t i o n gave

straight lines w i t h slopes b e t w e e n 1.3 a n d 1.6. T h e n a t u r e of the e x t r a c t e d c o m p l e x is not c l e a r l y s h o w n b y these slopes; therefore, this d a t a is not shown.

N o n - i n t e g r a l slopes w e r e not u n e x p e c t e d since p r e v i o u s e x p e r i -

ence has s h o w n t h a t the slopes of s u c h curves often d o not i n d i c a t e the p r o p e r i d e n t i t y of the e x t r a c t e d species

(8).

T h i s has u s u a l l y b e e n


25.

R Y A N

A N D

K E D E R

Hexavalent

349

Actinides

a t t r i b u t e d to a difference i n the state of a g g r e g a t i o n of the T O A c o n t a i n i n g species before a n d after m e t a l extraction. I n the present case, extraction of a m i x t u r e of a n i o n i c species is a c o m p l i c a t i n g factor, b u t c h a n g e of species extracted is not reflected b y a large c h a n g e i n c o n c e n t r a t i o n d e p e n d e n c e of D.


D i s t r i b u t i o n r a t i o values for extraction of the three h e x a v a l e n t metals f r o m I N acetic a c i d b y 0 . 1 M T O A - x y l e n e w e r e a l l about 1, i n d i c a t i n g little separation a m o n g the metals. F o r e x t r a c t i o n of U ( V I ) b y 0 . 1 M T O A - C H C I 3 , D was n e a r l y 10. M o o r e has s h o w n that thet e x t r a c t a b i l i t y of U ( V I ) b y 5 % tri-isoo c t y l a m i n e i n xylene passes t h r o u g h a m a x i m u m at about 0 . 5 N aqueous acetic a c i d , a n d it continues to decrease to 1 4 N a c i d . O u r s p e c t r a l measurements s h o w that the species extracted b y T O A i n either x y l e n e or c h l o r o f o r m are n e a r l y i n d e p e n d e n t of aqueous a c i d c o n c e n t r a t i o n , a l t h o u g h the triacetato c o m p l e x seems to be s l i g h t l y f a v o r e d b y increase of a c i d to I O N . T h e r e is also a s m a l l increase i n the percentage of the triacetato i o n extracted w h e n u r a n i u m to a m i n e ratio is increased. W h e n e x t r a c t i o n is b y T O A i n l o w d i e l e c t r i c constant solvents—e.g., p e n t a n e — a t h i r d phase is f o r m e d , l e a v i n g o n l y a d i l u t e major o r g a n i c phase. I n this case the spectra s h o w that the U ( V I ) species i n the t w o o r g a n i c phases are different, w i t h m a i n l y tetraacetato i n the d i l u t e o r g a n i c phase a n d m a i n l y triacetato i n the h e a v y , viscous t h i r d phase. C e s i u m triacetato n e p t u n y l ( V I ) a n d p l u t o n y l ( V I ) w e r e p r e p a r e d , a n d spectra w e r e m e a s u r e d i n 8 5 % s u c c i n o n i t r i l e - 1 5 % a c e t o n i t r i l e s o l u tions. B o t h metals w e r e extracted f r o m I N acetic a c i d into C C 1 a n d CHCI3 solutions of T O A , a n d the spectra of these solutions w e r e also m e a s u r e d . T h e n e p t u n i u m spectra are not d i s t i n c t i v e a n d h e n c e are o m i t t e d . T h e spectra of t r i - n - o c t y l a m m o n i u m p l u t o n y l acetate i n C C 1 a n d i n C H C 1 are c o m p a r e d w i t h that of P u 0 ( C H 0 ) " i o n i n F i g u r e 7. T h e p r e d o m i n a t e species that extracts i n t o C H C 1 s o l u t i o n is c l e a r l y the triacetato c o m p l e x . T h e p r i n c i p a l species that extracts i n t o C C 1 is a different one, w h i c h b y analogy w i t h the u r a n y l case a n d b y c o m p a r i s o n w i t h the spectra of 8 5 % s u c c i n o n i t r i l e - 1 5 % acetonitrile solutions of C s P u 0 ( C H 0 ) 3 c o n t a i n i n g excess c e s i u m or t e t r a e t h y l a m m o n i u m a c e tates w o u l d be the tetraacetato i o n . T h e o u t s t a n d i n g difference i n these spectra is the s h a r p intense peak at 840 τημ i n the latter (e — 2 2 0 ) . T h e r e l a t i v e l y h i g h a b s o r p t i v i t y of this p e a k makes i t easy to measure s m a l l amounts of the tetraacetato species i n the presence of the other. S m a l l amounts of triacetato i n the presence of the tetraacetato c o m p l e x w o u l d best be m e a s u r e d b y difference u s i n g the 840 τημ peak. W e h a v e not m e a s u r e d the a b s o r p t i v i t y of this p e a k p r e c i s e l y e n o u g h ; therefore, w e h a v e e s t i m a t e d the r e l a t i v e amounts of p l u t o n y l acetate species i n t h e C C 1 solutions f r o m the s p e c t r u m of the triacetato c o m p l e x present. It 4

4

3

2

2

3

2

3

3

4

2

2

3

2

4


350


2.0

~To A =5.6

1.6


1.2

0.8

0.4

AJ^

400

1200

3 Wavelength, ιτιμ

1400

1600

Figure 7. Absorption spectra of Pu(VI) acetates: (1) Pu(Vl) extracted from I M HC H 0 into 10% tri-n-octylamine in carbon tetrachloride and into (2) 10%? tri-n-octylamine in chlo roform, and (3) CsPu0 (C H 0 ) in 85%) succinnonitrile15%) acetonitrile. Pu concentration is approximately 0.03M in each case (1 cm. cell) 2

2

3

2

2

3

2 3

appears that e a c h s o l u t i o n contains a b o u t 1 0 % of the m i n o r species, a n d the b e h a v i o r of p l u t o n y l ( V I )

is, therefore, not different f r o m that of

uranyl ( V I ) . T h e a c t i n i d e ( V I ) acetate system d i s c u s s e d here a n d the a c t i n i d e ( V I ) sulfate system to b e discussed later (17)

represent the o n l y cases k n o w n

to us i n w h i c h observable m i x t u r e s of l a b i l e a n i o n i c complexes of a g i v e n m e t a l are e x t r a c t e d f r o m a n a c i d s o l u t i o n b y s u s b t i t u t e d amines.

The

present system represents the o n l y one i n w h i c h the d i l u e n t is the o n l y m a j o r factor c o n t r o l l i n g the r a t i o of species i n the o r g a n i c phase. p r i n c i p l e m e c h a n i s m b y w h i c h the n a t u r e of the d i l u e n t appears

The to

d e t e r m i n e the r a t i o of species i n the o r g a n i c phase i n this system is b y


25.

R Y A N

A N D K E D E R

Hexavalent

Actinides

351

the effect of i o n i z i n g p o w e r of t h e d i l u e n t (as m e a s u r e d to a first a p p r o x i m a t i o n b y its d i e l e c t r i c c o n s t a n t ) o n t h e f o r m a t i o n constant of t h e tetraacetato c o m p l e x f r o m t h e triacetato c o m p l e x .


Literature Cited (1) Ahrland, S., Acta Chem. Scand. 5, 199 (1951). (2) Booman, G. L., Holbrook, W. B., Rein, J. E., Anal. Chem. 29, 219 (1957). (3) Brintzinger, H., Jahn, F., Z. Anorg. Allgem. Chem. 231, 342 (1937). (4) Dieke, G. H., Duncan, A. B. F., "Spectroscopic Properties of Uranium Compounds," pp. 133-136, McGraw-Hill, New York, 1949. (5) Golovnya, V. Α., Shubochkin, L. K., Russ. J. Inorg. Chem. (English Transl.) 8, 579 (1963). (6) Hoard, J. L., Stroupe, J. D., "Spectroscopic Properties of Uranium Com pounds," pp. 13-15, McGraw-Hill, New York, 1949. (7) Kaplan, L., Hildebrandt, R. Α., Ader, M., J. Inorg. Nucl. Chem. 2, 153 (1956). (8) Keder, W. E., Ryan, J. L., Wilson, A. S., J. Inorg.Nucl.Chem. 20, 131 (1961). (9) Keder, W. E., Wilson, A. S., Nucl. Sci. Eng. 17, 287 (1963). (10) Keder, W. E., Wilson, A. S., Burger, L. L., Symp. Aqueous Reprocessing Irradiated Fuels, Brussels, EuropeanNucl.Energy Agency (1963). (11) Moore, F. L.,Anal.Chem. 32, 1075 (1960). (12) Nichols, E. L., Howes, H. L., Carnegie Inst. Technol., Wash.,Publ.No. 298 (1919). (13) Nichols, E. L., Howes, H. L., Wick, F. G., Phys. Rev. 14, 201 (1919). (14) Ryan, J. L., J. Phys. Chem. 65, 1099 (1961). (15) Ryan, J. L., U. S. At. Energy Comm. Res. Develop. Rept. HW-59193 (1959). (16) Ryan, J. L., Jørgensen, C. K., J. Phys. Chem. 70, 2845 (1966). (17) Ryan, J. L., Keder, W. E. (to be published). (18) Ryan, J. L., Wheelwright, E. J., U. S. At. Energy Comm. Res. Develop. Rept. HW-55893 (1959). (19) Scott, F. Α., Peekema, R. M., Proc. Second Intern. Conf. Peaceful Uses At. Energy, Geneva 28, 573 (1958). (20) Steigman, J., Hammett, L. P., J. Am. Chem. Soc. 59, 2536 (1937). (21) Stromatt, R. W., U. S. At. Energy Comm. Res. Develop. Rept. HW-59447 (1959). (22) Tishkoff, G. H., "Pharmocology and Toxicity of Uranium Compounds," Part 1, Chapter 1, Appendix B, McGraw-Hill, New York, 1949. (23) Vdovenko, V. M., Skoblo, A. I., Suglobov, D. N., Radiochemistry (USSR) (English Transl.) 6, 658 (1964). (24) Zachariasen, W. H., Plettinger, Η. Α., Acta Cryst. 12, 526 (1959). RECEIVED September 12, 1966. Work was performed under Contract No. AT(45-1)-1830 for the U. S. Atomic Energy Commission.


CHEMISTRY


LANTHANIDE/ACTINIDE


Anionic Acetato Complexes of the Hexavalent Actinides - Advances in

Recommend Documents