J.Radioanal.Nucl.Chem.,Letters 201 (4) 325-331 (1995)
Join@ pnblished by Elsevier Science S. A., Lausanne and Akad~miai Kiad6. Budapest
SYNERGISTIC EXTRACTION OF URANIUM(VI) AND A M E R I C I U M ( I I I ) W I T H B I N A R Y M I X T U R E S O F A L I Q U A T 336 AND PC 88A - TOPO FROM NITRIC - SULFURIC ACID MEDIUM
S. Mishra, V. Chakravortty*, P.R. Vasudeva Rao**
Department of Chemistry, Utkal University, Vani Vihar, Bhubaneswar - 751 004, India **Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, India
Received 28 July 1995 Accepted 8 August 1995
Synergism is observed in the extraction of uranium(VI) by the binary mixture of Aliquat 336 and PC 88A (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) from 0.5-6M HNO 3 solution showing a maximum at 3M. In H2SO 4 medium, antagonism at lower acidity and slight synergism at higher acid concentrations have been observed. Synergism occurs in the extraction of Am(III) from nitrate solutions when a mixture of Aliquat 336 and TOPO is used.
The modified purex process
(Impurex process)
involves
the extraction of uranium(VI) from highly concentrated nitric acid solution I-3 . The leach liquor resulting from sulfuric acid leaching contains uranium. The highly active waste solution produced from reactor operation con-
*Author, to whom correspondence should be addressed. 023a-5731/OS/US $ 9.50 Copyright 9 199.9Akad:miai Kiad6, Budapest AI t . . ; ~ h t . . . . . . . . . . . . . i
325
MISHRA et al.: EXTRACTION OF U(VI) AND Am(III)
t a i n s americium(III).
In most of the cas~s studied,
quaternary ammonium compounds have been Ifound to have 4-6 better extracting ability than the tertiary amines The combinations of a m i n e
salts and a c i d i c compounds
or neutral: donors are assumed t o r e s u l t
in synergisti c
extraction 7. The extraction of uranium(VI) with a mixture of Aliquat 336 and P C 88A from aqueous HCI has already been investigated 8. There are reports on the extraction of americium(III)
using Aliquat 336 and TOPO
separately from hydrochloric a c i d
solutions 9.
The present study deals with the extraction of uranium(VI) by a mixture of Aliquat 336 ammonium chloride)
(tricapryl methyl
and PC 88A (2-ethylhexylphosphonic
acid mono-2-ethylhexyl ester)
from HNO 3 and H2SO 4 solu-
tions. The extraction of americium(III) with binary mixtures of Aliquat 336 and TOPO oxide)
(tri-n-octylphosphine
f r o m nitrate medium has also been reported.
EXPERIMENTAL Radiotracers 233U and 241Am were used for the extraction experiments. The commercial extractants, Aliquat 336
(Merck, 90% pure), PC 88A
tries, Japan,
95% pure)
(Daihachi Chemical Indus-
and TOPO
(Merck) were used
without further purification, p-Xylene
(BDH) was used as
organic phase diluent. All other chemicals were of A.R. grade. About 5% (v/v) solutions of Aliquat 336 PC 88A
(~0.15M) and their mixture
in p-xylene. The solution of TOPO tures with 5%
(~0.1M),
(1:1) were prepared (0.01M) and its mix-
(v/v) Aliquat 336 were also made in p-
xylene. The extractant solutions were pre-equilibrated with aqueous acid solutions of appropriate concentrations. Equal volumes
(2 ml) of extractant solution and 326
MISHRA et aL: EXTRACTION OF U(VI) AND Am(III)
aqueous
solution
containing
for I h in a constant
temperature
at 303 K. T h e n aliquots for r a d i o m e t r i c were measured a dioxane
ratios w e r e
336,
bath m a i n t a i n e d
from both phases w e r e w i t h d r a w n of 233U and 241Am
scintillation
scintillation
calculated
counting
cocktail.
from the ratios
and the aqueous
of uranium(VI)
extraction
5%
(v/v)
of the a c t i v i t i e s
phase.
from aqueous
of uranium(VI)
HNO 3
into 5%
PB 88A and their m i x t u r e
in Table
With
(v/v)
concentration
by A l i q u a t
since this e x t r a c t a n t the e x t r a c t i o n
increase
(1:1) was
changer
With
of HN03,
reaches
PC 88A behaves
whereas
formation
in e x t r a c t i o n
effect
at higher of A l i q u a t
is observed
tial e x t r a c t i o n "acid effect", the m i x t u r e
species
of acid lowers
at higher 327
at 3M
exability I0
acid con336 and
This e n h a n c e m e n t
(in this case HNO3)
of e x t r a c t a n t s
with
over the entire
in the System.
the e x t r a c t i o n
How-
as a cation
w i t h the m i x t u r e m a y be a t t r i b u t e d of adduct
increase,
a minimum
its c h e l a t i n g
0.5-6M of HNO 3 concentration.
extraction
the e x t r a c t i o n
shows a regular
the b i n a r y m i x t u r e
PC 88A a s y n e r g i s t i c range
336
increases.
the increase
centration.
are
w i t h PC 88A first d e c r e a s e s
at low acidity,
explains
ratios
carried
acts as an anion exchanger.
in HNO 3 c o n c e n t r a t i o n ,
and t h e r e a f t e r
Aliquat
I.
increasing
of uranium(VI)
ever,
using
The d i s t r i b u t i o n
out from 0.5-6.0M HNO 3. The d i s t r i b u t i o n given
equilibrated
AND DISCUSSION
Extraction The
water
The a c t i v i t i e s
by e-liquid
in the o r g a n i c
RESULTS
assay.
based
the tracer w e r e
in
to the
The preferenknown as
of uranium(VI) a c i d i t y 11
with
MISHRA et al.: EXTRACTION OF U(VI) AND Am(III)
TABLE
I
Variation of distribution ratio with HNO 3 concentration for the extraction of U(VI) with 5% (v/v) Aliquat 336 (0.0125)* 5% (v/v) PC 88A (0.0193)* and their mixture [HN03 ], M
DI
D2
Dmi x
AD
0.5
0.145
2.0
S.C.
27.88
32.09
4.07
0.058
0.457
15.75
28'32
12.11
0.242
3.0
0.590
15.65
28.94
12.70
0.251
4.0
0.975
16.31
27.16
9.88
0.196
5.0
1.321
17.45
25.12
6.35
0.126
6.0
1.540
18.61
23.96
3.81
0.075
*Mole fraction in each Table. where D I , D 2 and Dmi x are the distribution ratios with Aliquat 336, PC 88A and their mixture, respectively and AD = Dmi x - (DI + D2), S.C. = ig ((Dmi x)/(D I + D2)) .
Extraction of U ( V I ) f r o m
aqueous H2SO 4
The distribution ratios obtained in the extraction of uranium(VI)
by Aliquat 336, PC 88A and their binary
mixtures from 0.01-2.0M H2SO 4 solution are given in Table 2. Extractions by Aliquat 336, PC 88A and their mixtures are found to decrease with increasing H2SO 4 concentration.
Both synergistic and antagonistic ef-
fects are observed with binary mixtures. The antagonism decreases with increasing acidity up to 0.3M. This effect at lower acid concentration is probably due to the interaction between Aliquat 336 and PC 88A.
(R3R'N)2SO4(org)
+ 2HA(org)~--a~ 328
2R3R'NA(org ) + H2SO4(aq )
MISHRA et al.: EXTRACTION OF U(VI) AND Am(III)
TABLE Extraction 5% (v/v) [H2SO4],
2
of U(VI) w i t h 5% (v/v) A l i q u a t 336 (0.0125)*, PC 88A (0.0193)* and their binary m i x t u r e DI
D2
Dmi x
AD
S.C.
0.01
16.55
32.85
33.52
-15.88
-0.168
0.05
15.44
35.29
36.11
-14.62
-0.148
0.10
8.37
32.36
29.02
-11 .71
-0.147
0.20
2.82
26.65
27.27
- 2.41
-0.036
0.30
1.19
19.38
20.05
- 0.52
-0.011
0.50
0.314
9.54
12.71
2.86
0.110
2.0
0.026
0.65
0.86
0.18
0..104
With
M
increasing
of q u a t e r n a r y tration nistic
of amine
are formed,
which
sulfate
species
lower the concen-
salt and in turn d e c r e a s e
the antago-
effect 12
Extraction
of americium(III)
Extraction Aliquat
336,
been m a d e
studies
from aqueous
of americium(III)
HNO 3
with
5%
0.01M TOPO and their binary m i x t u r e
from
Americium(III) salts
H2SO 4 concentration,
amine
0.001-0.05M
have
HNO 3 and 4M NaNO 3 solution.
is not e x t r a c t e d
in the absence
(v/v)
by q u a t e r n a r y
of s a l t i n g - o u t
agents,
earlier 13. With TOPO alone the e x t r a c t i o n
ammonium
as reported
decreases
at
moderately
high a c i d i t y due to the e x t r a c t i o n of 14 T O P O ' H N O 3 species There is an increase in e x t r a c t i o n (synergism)
with
a mixture
of A l i q u a t
336 and TOPO
(Table 3). This may be due to the solvation americium-Aliquat creases w i t h
336 species
increasing
by TOPO.
acid concentration.
329
of e x t r a c t e d
The AD value
de-
MISHRA et al:: EXTRACTION OF U(VI) AND Am(Ill)
TABLE 3 Extraction of Am(III) with 5% (v/v) Aliquat 3 3 6 (0.0125)*, 0.01M TOPO (0.125)* and their binary mixture in the p r e s e n c e of 4M NaNO 3 solution [HNO 3], M
DI
D2
Dmi x
AD
S.C.
0.001
0.595
1.081
7.50
5.82
0.65
0.003
0.515
0.710
6.86
5.64
0.75
0.005
0.490
0.626
6.65
5.53
0.77
0.01
0.475
0.495
5.37
4.40
0.74
0.05
0.340
0.080
2.11
1.69
0.70
where D1, D 2 and Dmix are t h e distribution ratios with A1iquat 336, TOPO and their mixture, respectively.
One of the authors
(S.M.) thanks the CSIR, New Delhi,
for the award of a Junior Research Fellowship. also thankful Division,
to Shri T.G.
Srinivasan,
She is
Fuel Chemistry
IGCAR for his kind help and suggestions
during
the course of work.
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MISHRA et al.: EXTRACTION OF U(VI) AND Am(Ill)
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