2 Recovery of Plutonium Traces from Nitric A c i d -Fluorhydric A c i d Solutions by Sorption onto Alumina J. A D R O A L D O D E A R A Ú J O and A L C Í D I O A B R Ã O Chemical Engineering Center, Energetic and Nuclear Research Center, Cx Postal 11049, Pinheiros, S.P., Brazil
Sorption of plutonium traces onto alumina from uranyl nitrate solutions has been investigated. Several methods have been previously proposed for the recovery of plutonium traces from reprocessing solutions. Those methods include ion exchange (1,2), solvent extraction (3,4) and, extraction chromatography (5,6). Several hydrous oxides, such as those of aluminum, silicon and, iron have been used to extract traces ions. Nevertheless, the sorption mechanism is not definitively established. Those oxides probably exhibit some ion exchange capacity among their properties and they can act as anionic or cationic exchangers and sometimes both. The separation of plutonium traces in the presence of HF by sorption onto an alumina column is based on its chemical similarities with thorium and lantanide elements reported by Abrão (7). In this case only thorium and rare earths are sorbed onto alumina from nitric acid-fluoride solutions while uranium remains in the effluent. The redox methods are well known for the purification and concentration of plutonium from the Purex process solutions. This paper deals with three different oxidation states of plutonium Pu(III), Pu(IV), and Pu(VI) in HNO -HF systems. The c h r o m a 3
t o g r a p h i c c o l u m n method u s i n g a l u m i n a h a s b e e n a p p l i e d s u c c e s s f u l y t o t h e s e p a r a t i o n o f p l u t o n i u m when u r a n y l n i t r a t e s o l u t i o n c o n t a i n i n g 0 . 1 - 0 . 3 M HF was p e r c o l a t e d t h r o u g h t h e c o l u m n . EXPERIMENTAL A l l 239pu s o l u t i o n s u s e d d u r i n g t h e r u n s w e r e p r e p a r e d f r o m a s t a n d a r d s o l u t i o n ( A m e r s h a m / S e a r l e ) , o f 1 u C i / m l (160 y g / m l ) s p e c i f i c a c t i v i t y . The u r a n i u m s o l u t i o n s were o b t a i n e d by d i s s o l u t i o n o f n u c l e a r g r a d e u r a n i u m o x i d e s . One m l o f AI2O3 c h r o m a t o g r a p h i c g r a d e was c o n d i t i o n e d a c c o r d i n g BROCKMANN (8) w i t h 0 . 8 M HNO3 i n g l a s s c o l u m n s 0 . 6 c m i n d i a m e t e r and 20cm l o n g . The e x p e r i m e n t s were f o l l o w e d b y a l p h a s p e c t r o m e t r y a f t e r t h e p l u t o nium was e x t r a c t e d w i t h 0 . 5 M T T A / X Y L O L . The s a m p l e s f o r q u a n t i * ' t a t i v e d e t e r m i n a t i o n were p r e p a r e d b y e l e t r o p l a t i n g a c c o r d i n g t o WENZEL and HERZ (90 . The a l p h a e n e r g y m e a s u f e m e n t was made b y a
0-8412-0527-2/80/47-117-009$05.00/0 © 1980 A m e r i c a n C h e m i c a l Society
10
ACTINIDE SEPARATIONS
s u r f a c e b a r r i e r d e t e c t o r a s s o c i a t e d w i t h a ORTFC m u l t i c h a n n e l a n a l y s e r . The p l u t o n i u m o x i d a t i o n s t a t e s were d e t e r m i n e d b y a p h o t o m e t r i c method u s i n g ARSFNAZO I I I . The d e t e r m i n a t i o n s were carried o u t w i t h a d o u b l e beam PFPFIN-FLMF ? s p e c t r o p h o t o m e t e r vising q u a r t z 11
microcells. The f i r s t e x p e r i m e n t s were c a r r i e d o u t t o u n d e r s t a n d t h e p e r f o r m a n c e o f p l u t o n i u m in^an. A 1 0 - TîNO^ m e d i u m . T h i s was done by 0
p e r c o l a t i o n o f 25 m l o f 23 ^ p s o l u t i o n i n 0 . 8 M HNO^ w i t h a l p h a a c t i v i t y o f 55,000 -f 235 (counts/2000 s e c / m l ) , through a glass c h r o m a t o g r a p h i c c o l u m n ( i . d . 6mm) c o n t a i n i n g 1 ml o f A 1 0 ^ . n
9
A l l r u n s were made w i t h 0 . 8 M * N0~ s o l u t i o n s w i t h a Pu a l p h a a c t i v i t y of 10,000 316 ( c o u n t s / 2 0 0 0 s e c / m l ) a n d , F F c o n c e n t r a t i o n r a n g i n g from 0.1 to . 3 M . T
n
The f e e d s o l u t i o n f o r t h e A 1 0 ~ c o l u m n h a s t h e f o l l o w i n g comp o s i t i o n : 1,5 χ 1 0 " M P u ; a l p h a a c t i v i t y = 2 3 0 , 0 0 0 + 480 (coun0
S
2
3
9
ts/2000/sec/20ml); 0 . 8 M F.N0 ; 6.1 - n . 3 M F F ; u r a n y l n i t r a t e 47.6 g U / l ; 0 . 0 0 5 M FeSO^ and 0 . 0 4 M N a N 0 . P u ( I V ) was o b t a i n e d i n t h i s solution by p r e v i o u s r e d u c t i o n o f ^ t o t a l p l u t o n i u m to P u ( I I I ) w i t h F e ( I I ) f o l l o w e d b y o x i d a t i o n w i t h n i t r i t e . No i n t e r f e r e n c e o f u r a n i u m was o b s e r v e d i n t h e p r o c e s s . To a v o i d t h e interference 3
9
of 234j^ ( u r a n i u m d a u g h t e r ) on t h e measurements o f p l u t o n i u m , i t was p r e v i o u s l y removed b y p e r c o l a t i n g t h e s o l u t i o n i n t o a n o t h e r a l u m i n a column b e f o r e the a d d i t i o n o f 2 3 9 p a
u #
RESULTS AND_PISCUSSI0N The retained
results by t h e
t o n i u m must typical Table
I.
(Table
I)
show t h a t
alumina from 0 . 8
likely
be
complexed
plutonium breakthrough Plutonium Retention
Fxp.
M
o n l y 17
nitric
to
be
curve
of
acid
sorbed.
the
plutonium
is
and t h e r e f o r e
plu
Figure
a
.1 shows
from 0.8H n i t r i c
f r o m 0 . 0 8 M ΤΙΝ0- o n t o
acid.
A1 0« 9
23° Pu.retained
1 2
(%) 1.8 1.0
3
0.8
4
0.9
5
1.1
T a b l e I I shows t h a t t h e p l u t o n i u m s o r p t i o n o n t o Alo^3 * 87% and i t was d e m o n s t r a t e d t h a t w i t h t h e a i d o f f l u o r i d e t h e r e c o v e r y o f p l u t o n i u m t r a c e s f r o m w a s t e s o l u t i o n s was possible. s
a
r
^ ions
o
u
n
ADROALDO D E ARAUJO A N D ABRAO
Sorption
Al O
ΟΠ
2
s
Figure 1. Breakthrough curve of Pu onto Al 0 column; feed: 25 ml Pu-O.8M HN0 ; ^Pu activity = 55,000 ± 235 counts/2000 sec/ml; column = 1 ml Al 0 ; flow rate = 0.8 ml/min/cm . 2
239
3
3
2
2
3
12
ACTINIDE SEPARATIONS
Table
II.
Effect
o f HF o n Pu R e t e n t i o n
23Q
FF
'Pu
(M)
0.1 0.1 0.1 0.2 0.2 0.3 0.3
As
was
D.F.
ret. (%)
C 'Pu) J
7.0 6.9 7.2 6.4 6.5 9.5 9.5
85.7 85.5 86.1 84.4 84.8 89.6 89.4
observed
i n the
on A1„0,
first
experiments,
p l u t o n i u m was
not
c o m p l e t e l y s o r b e d o n t o a l u m i n a f r o m 0 . 1 t o 0.3>f F F . So t h e n e x t s t e p was t o examine t h e p o s s i b i l i t i e s o f a d d i n g r e d o x a g e n t s t o m a i n t a i n a s i n g l e o x i d a t i o n s t a t e . A c o n c e n t r a t i o n o f 0 . 1 M HF was c h o s e n b e c a u s e t h i s i s enough F F t o c o m p l e x a l l t h e p l u t o n i u m (Pu - 10~^M) £ h f e e d s o l u t i o n and w i l l n o t c a u s e s i g n i f i c a n t c o r n
t
G
r o s i o n e f f e c t s o n t h e g l a s s c o l u m n . Some o f t h e r e d o x a g e n t s u s e d and t h e a v e r a g e y i e l d s o f p l u t o n i u m r e c o v e r y a r e g i v e n i n T a b l e I I I . T e t r a v a l e n t p l u t o n i u m i s b e t t e r s o r b e d t h a n Pu ( I I I ) o r Pu ( V I ) . The t h r e e o x i d a t i o n s t a t e s o f p l u t o n i u m were d e t e r 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 by c o m p l e x i n g Pu w i t h ARSFNAZO I I I ( 1 ° ) i n n i t r i c a c i d medium b y a d a p t i n g b o r a t o r s (11,12) . Table
III.
Fffect tion:
the
o f Pu o x i d a t i o n 2
3
9
Pu
method
states
~ 1 0 0 , 0 0 0 + 316
0 . 8 M HN0- ~ 0 . 1 M HF c o l u m n :
Pu Valence III VI
Redox
agent
i n the
load
cone.
-0.2M
NH .0H.HC1 9
0.01M N a N 0
IV
0 . 0 3 M NaNCC
IV
0.1M ΝΗ .ΝΠ 9
i.d.
65.0 87.2 89.0 90.9
9
-O.01M NaN0
(NO )
0.002M Fe
IV
N H H . F C l - 0.02M N a N 0 0.ΠΟ5Μ F e S O , - 0 . 0 4 M N a N 0 4 I n
-
?
IV
9
on s o r p t i o n ,
counts/2000
69.7
PC10*
IV
NEMODRUCK and
6mn;
Pu ret. (?) CO
solution 0 . 2 M NF .NH
of
Feed
sec/10
vol.
colla
solu ml;
1 ml
A1 0 ?
D.F. (
Pu)
2.8 3.6
7.8
9.0 11.0
0.W 0
o
°2.3
13.0
07.8
47.2
A s e t o f l a b o r a t o r y e x p e r i m e n t s n r o v e d t h a t t h e most e f f e c t i v e and c o n s i s t e n t method t o e l u t e p l u t o n i u m f r o m t h e a l u m i n a was by r e d u c i n g p l u t o n i u m t o t r i v a l e n t s t a t e i n n i t r i c a c i d . The c o l l e c t e d d a t a ( T a b l e IV) p r e s e n t good r e s u l t s when 3M HNO - 0 , 0 0 5 ! ' F e S 0 , s o l u t i o n was u s e d as « l u t r i e n t . ApA
2.
ADROALDO D E ARAUJO AND ABRAO
proximately re
Sorption
on
2
95% o f t h e p l u t o n i u m was r e c o v e r e d
( 2 5 ° C ) . To d e t e r m i n e
Table
a s h a r p e r peak w h i l e
I V . Plutonium e l u t i o n
from A l 0 o
Elutrient (M)
HN0
s
a t room
i f the temperature could
t o n i u m d e s o r p t i o n , t h e e l u t i o n was done w i t h a t 25 and 5 0 ° C . F i g u r e 2 , shows t h e s e c u r v e s elution presents some t a i l .
temperatu
improve
the
plu
t h e same e l u t r i e n t a n d , a t 500C, t h e
the curve
o
13
Al O
column
Pu e l u t e d
at
at
25°C
exibits
25°C.
(%)
3
1
62.9
2
65.3
3
78.9
4
70.6
5
22.6
6
15.7
(M) HNO
-
(M) F e S 0
A
1
0.005
2
0.005
30.8 81.3
3
0.005
94.7
To d e m o n s t r a t e t h e v a l i d i t y o f t h i s p r o c e d u r e f o r t h e r e c o v e r y o f t r a c e amount o f p l u t o n i u m f r o m d i l u t e s o l u t i o n s , 30 l i t e r s o f s o l u t i o n w i t h a s p e c i f i c a c t i v i t y o f 2 3 9 p 135 + 12 ( c o u n t s / 2 0 0 0 / s e c / m l ) was p e r c o l a t e d t h r o u g h a s m a l l c o l u m n c o n t a i n i n g 10 u
ml
of A l ^ O ^ .
About
97% o f p l u t o n i u m were s o r b e d
The e x p e r i m e n t s
have
shown t h a t
trace
onto
sorption
the
alumina.
of Pu(IV)
onto
A1 0 i s a l m o s t c o m p l e t e f r o m 0 . 8 M HNO^ - O . i y H F . T h e s t a b i l i z a t i o n o f £ u ( I V ) s t a t e was o b t a i n e d b y p r i o r r e d u c t i o n t o P u ( I T I ) and r e o x i d a t i o n t o P u ( I V ) u s i n g F e ( I I ) and n i t r i t e . 2
3
The ^lo^3 c o l u m n
loaded
with
p l u t o n i u m was s a t i s f a c t o r i l y
washed w i t h an 0 . 1 M HNO^ - 0 . 0 5 M TIF s o l u t i o n f o r t h e r e m o v a l of t h e l a s t t r a c e s o f u r a n i u m and o t h e r e l e m e n t s n o t s o r b e d . T h e e f f l u e n t s c o n t a i n e d l e s s t h a n 0.01% o f p l u t o n i u m . W a s h i n g t h e c o l u m n w i t h a n 0.8M HN0 - 0.05M HF s o l u t i o n r e s u l t e d i n 0.1% o f p l u t o n i u m a c t i v i t y i n t h e e f f l u e n t . T h i s i n d i c a t e s t h a t the. column 3
should b e washed w i t h more d i l u t e n i t r i c a c i d . The e f f e c t i v i n e s s o f ^ e l u t i o n w i t h FNO^ p l u s a r e d u c i n g a g e n t a t room t e m p e r a t u r e and 50 C was c o n f i r m e d i n b o t h c a s e s . As P u ( I ) i s more s o r b e d o n t o a l u m i n a t h a n t h e o t h e r p l u t o n i u m o x i d a t i o n s t a t e s , i t was r e d u c e d t o P u ( I I I ) t o i m p r o v e t h e e l u t i o n . On t h e o t h e r hand HNO^ i s t h e most c o n v e n i e n t medium f o r f u r t h e r u s e s o f n l u t o n i u m , so f o r t h a t r e a s o n n i t r i c a c i d (1-6M) was s e l e c t e d as e l u t r i e n t . P u r e 3M IWO^ at room t e m p e r a t u r e e l u t e d 79% o f p l u t o n i u m . A 3M ΗΝ0~ - 0f005M F e S O . s o l u t i o n was c h o s e n as e l u t i n g a g e n t a n d , t h e e l u t i o n y i e l d u
Figure 2. Elution curve of Pu from Al 0 column; Al 0 = 1 ml; flow rate = 1.4 ml/minicm , surface barrier detector: (Ο) 3 M HNO -0.005M Fe \ tempera ture ~ 25°C (A)3M HNO -0.005M Fe \ temperature ~ 50°C. 239
2
3
2
2
3
3
;
3
2
2
ADROALDO ED ARAUJO AND ABRAO
Sorption
on
Al O 2
s
WASTE SOLUTION Pu traces U-W g/l
FEED
ADJUSTMENT
0./-0.8M HN0 Q/-0.3M HF _ O0O5M F e S 0 PuUW Q.04M NaNOzt 3
J
M
4
WASHING
ELUTRIENT
O./M HN0 0.05M HF
3
3M HN0 0Ό05Μ FeS0 | 20-50°C 3
4
AI2O3
QQLUm
PuilV) PRODUCT 3M HN0 PuilV) HF traces I FeS04 traces I
EFFLUENT
3
waste
EFFLUENT waste Recycle PROCESS
CONTROL
Influent, effluent, product : A) Pu extraction: 0,5M TTA/xylol B) Pu
eletroplating
C) Pu alpha counting
Figure 3.
Proposed flowsheet for recovery of Pu traces from reprocessing solu tions
ACTINIDE SEPARATIONS
16
being ence
improved to in
the
The of
about
95%.
descontamination
uranyl nitrate
easily
(N0 )
0. 8 .
U0
with
plutonium-239,
through
3
the
2
of
the
t e m p e r a t u r e has
plutonium traces
by s o r p t i o n
and s u c e s s f u l l y 2
Also
some
influ-
elution. of Pu(IV)
accomplished.
solution, the
from
3
macroquantities
an A l 0 ^
column
o
Percolation
0.8M i n HN0
Pu was
onto
of
vas
a
and 0 . 3 M i n HF t r a c e d
sorbed"while
uranium
passed
A ^ O ^ column.
CONCLUSION The alumina the
sucessful
p r o p o s e d method
solutions urse, are
experiments
for
f r o m HNO^-HF s o l u t i o n i n the
to
separate
presence
o n l y macroamounts
serious
interfering
thorium,
ions,
since
they
p l u t o n i u m , t h o r i u m and r a r e
for
Pu was
neptunium i n the HF s o l u t i o n s
around
95%.
Figure
the
of
uranium (IV)
of
from r e p r o c e s s i n g
waste
to
recomend
precipitate
earths.
(VI).
and r a r e
same s y s t e m
flowsheet
Of
co-
earths
iv'ith H F . The
s h o u l d be
The r e t e n t i o n
i n progress.
proposed
p l u t o n i u m onto
p l u t o n i u m from waste
The s o r p t i o n m e c h a n i s m
established. Pu t r a c e s
3 shows
is
of
confidence
uranium
milar yield
of
o f macroamounts
of
expected
n e p t u n i u m f r o m HNO^ -
retention
traces
behavior to
for
the
gave enough
The is for
si-
of
sorption not
well
recovery
solutions.
LITERATURE CITED 1. Aikin, A.M. Chem. Engng. Progr. 1957 53, 82. 2. Billiau, R., Lafontaine, I., Mostin, N., Zamorani, E. Proc. Symp. chimie des traitments des combustibles irradies par voie aqueuse, Bruxelles, 1963. 3. Howells, G.R., Hughes, T.G., Mekey, D.R., Saddington, K. ETR report 222, March, 1968. 4. Merril, E.T., Stevenson, R.L. HW report 38684, 1955. 5. Eschrich, H. Hundere, I. ETR report 222, March, 1968. 6. Siekiersk, S., Fidelis, I. J. Chromatog. 1960, 4, 60. 7. Abrão, A. IEA report 217, June, 1970. 8. " The Merck index ", 8 ed. Rahway, N.J. Merck & Co., 1968, 46. 9. Wenzel, V., Herz, D. KFA-Jülich, ICT Jahresbericht für den Zeitraum von 1 Juli 1972 bis 30 Juni 1973, 1973, 115. 10. Milynkova, M.S., Sawin, S.B. Russ J. Anal. Chem. 1967, 22,308 11. Nemodruck, Α.Α., Gluklova, L.P. Russ J . Anal. Chem. 1963, 18, 85. 12. Nemodruck, Α.Α., Kochetkova, N.F. Russ. J. Anal. Chem. 1962, 17, 333. RECEIVED May 25, 1979.
