Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide [BenzoDODA] - First selective extractant for plutonium(IV) recovery (SEPUR) from acidic media

Article abstract of DOI:10.1016/j.tetlet.2012.07.124

A novel extractant, namely, Benzodioxodiamide (BenzoDODA) has been synthesized and evaluated for its extraction behaviour towards plutonium and other elements present in the spent nuclear fuel. High separation factors for plutonium over other elements were observed, indicating the high selectivity of the extractant for plutonium. The extractant is quite promising for the selective separation of plutonium from dissolver solution and various acidic waste streams.

Full text of DOI:10.1016/j.tetlet.2012.07.124

Tetrahedron Letters 53 (2012) 5434–5436
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Tetrahedron Letters
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Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide
[BenzoDODA]—first selective extractant for plutonium(IV) recovery (SEPUR)
from acidic media
R. Ruhela a, , S. Panja b, B. S. Tomar c, M. A. Mahajan c, R. M. Sawant c, S. C. Tripathi b, A. K. Singh a,
⇑
P. M. Gandhi b, R. C. Hubli a, A. K. Suri a
a Material Processing Division, Bhabha Atomic Research Centre, Mumbai 400085, India
b Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400085, India
c Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel extractant, namely, Benzodioxodiamide (BenzoDODA) has been synthesized and evaluated for its
extraction behaviour towards plutonium and other elements present in the spent nuclear fuel. High sep-
aration factors for plutonium over other elements were observed, indicating the high selectivity of the
extractant for plutonium. The extractant is quite promising for the selective separation of plutonium from
dissolver solution and various acidic waste streams.
Received 16 June 2012
Revised 27 July 2012
Accepted 28 July 2012
Available online 3 August 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
BenzoDODA
Pu(IV)
Liquid–liquid extraction
HLW
Plutonium is the only artificial element which has been pro-
duced in thousands of metric tons during the last 60 years owing
to its strategic importance as well as its use in fast reactors for elec-
tricity production. Every ton of uranium fuel, upon burning in the
reactor, results in the production of about 1–3 kg of Pu in the spent
fuel. The dissolver solution, obtained by dissolution of the spent
fuel, is processed to recover Pu and the remaining U for use in
the next generation of nuclear reactors. Further, the high level li-
quid waste (HLW) generated during the reprocessing of spent fuel
contains a few mg of Pu per litre of waste volume. Therefore, there
is a need for selective separation of Pu from the dissolver solution
as well as HLW and other waste streams.1
During the last five decades various ligands have been proposed
for the recovery of plutonium from reprocessing waste streams of
diverse nature. O’Boyle et al. and Gorden et al. have reviewed, in
detail, the various ligands/methods available for the separation of
Pu from various waste streams.2,3 To date, the only commercial
scale process used for the separation and purification of plutonium
from spent nuclear fuel is the well known PUREX process which in-
volves the bulk extraction of uranium along with plutonium in the
organic phase comprising of tributyl phosphate and aliphatic dilu-
ents.4 The extracted metal ions are later separated by reducing the
oxidation state of plutonium and stripping it into aqueous phase
thereby retaining uranium in the organic phase. This process,
though simple to use, offers several disadvantages, namely, (i)
the use of organophosphorous extractants which are non-inciner-
able, (ii) the use of various reducing agents which tend to increase
the waste volume and (iii) the co-extraction of other fission prod-
ucts, such as, Zr, Tc, Ru, etc. either with the extractant or with the
degradation products formed after radiolysis of the extractant.
Likewise several other extractants which include tertiary and qua-
ternary amines,5 sulphoxide,6 alkylated monoamides,7 carbamoyl
methylene phosphine oxides,8 catecholamides,9 terepthalimides,9
pyrolidones,10 etc. have been explored in various laboratories.
The use of these extractants is mainly hampered by co-extraction
of other actinides and fission products in appreciable fractions.
So far there is no reagent available which can selectively extract
Pu from various acidic waste streams.
With this in view we have focused on the designing of ligands
based on (1) incorporation of only C, H, N and O in the extractant
to maintain its incinerability, (2) incorporation of appreciable
number of hard donor oxygen atoms appropriately placed in the
extractant to provide better chelation and (3) incorporation of ami-
dic functionality which serves the dual purpose of providing effec-
tive chelation as well as solubility of the metal extractant complex
in paraffinic diluents. In this Letter we report the synthesis and
evaluation of Pu selective extractant, namely, bis-(2-ethylhexyl)
⇑
Corresponding author. Tel.: +91 2225592605.
E-mail address: riteshr@barc.gov.in (R. Ruhela).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.07.124

R. Ruhela et al. / Tetrahedron Letters 53 (2012) 5434–5436
5435
Figure 1. Reaction scheme for the synthesis of BenzoDODA.
8
7
6
5
4
3
2
1
10
0.1 M BenzoDODA/n-dodecane
BenzoDODA/n-dodecane
Slope = 1.15 0.01
1
0
5
10
15
20
25
30
0.02
0.04
0.06
0.08
0.1
Time (Minutes)
Ligand (M)
Figure 2. Kinetics of extraction of Pu(IV) by 0.1 M BenzoDODA/n-dodecane from
Figure 4. Effect of ligand concentration (BenzoDODA) on extraction of Pu(IV) in
3.0 M HNO3 solution.
3.0 M HNO3.
12
With a view to optimise the conditions for extraction and strip-
ping, DPu(IV) was determined at varying nitric acid concentrations.
10
8
0.1 M BenzoDODA/n-dodecane
DPu(IV)was found to increase with the increase in acidity (Fig. 3).
This could be attributed to the salting out effect (of nitrate ions),
which facilitates the extraction reaction in forward direction.
The stoichiometry of metal to ligand in the extracted complex
was determined using slope analysis method. Figure 4 shows the
variation of DPu(IV) as a function of concentration of extractant at
fixed metal ion and acid concentration. The stoichiometry of pluto-
nium to ligand is determined to be 1:1.
6
4
Considering the neutral character of the ligand the
extraction
reaction
can
be
written
as,
2
Subsequently the ligand was evaluated for Pu separation from
dissolver solution obtained by dissolving neutron irradiated ura-
nium metal in 3.0 M HNO3. Figure 5 shows the extraction behav-
iour of different elements with 0.1 M BenzoDODA/n-dodecane.
From Figure 5 it is observed that among the elements studied only
Zr and Nb are extracted, albeit in very less amounts, along with
ꢀ85% of plutonium in a single contact.
0
0
1
2
3
4
5
6
HNO (M)
3
Figure 3. Effect of initial nitric acid concentration on Pu(IV) extraction by 0.1 M
BenzoDODA/n-dodecane.
carbamoyl methoxy phenoxy-bis-(2-ethylhexyl) acetamide, com-
monly named as Benzodioxodiamide (BenzoDODA) for the separa-
tion of Pu from different acidic solutions.
The extractant (Fig. 1) has been synthesized from commercially
available and tailor-made materials.11 All other chemicals used in
this study were of reagent grade.
The extraction studies of metal ions were carried out at
25 1 °C.12 Equilibration time was determined by contacting
0.1 M BenzoDODA/n-dodecane with aqueous solution containing
Pu(IV) (3.0 M HNO3) for different time periods. Figure 2 shows
the variation of DPu(IV) as a function of contact time. It is evident
that the minimum contact time required to reach the equilibrium
is less than 10 min, which is considered to be fast enough to be
used at a plant scale.
Table 1 shows the distribution ratio of Pu(IV) along with U(VI),
Am(III) and some of the fission products. The separation factors of
Pu(IV) over other elements are also shown in Table 1. The small,
but finite DM for some of the elements, namely, U, Zr, Te and Nb
can be taken care by scrubbing the organic phase with the aqueous
phase of similar acidity as that of the feed. Further, at higher load-
ing of plutonium, the co-extraction of these metal ions will be re-
duced, thereby, giving still higher separation factors (SF).
Studies on the recovery of plutonium from the loaded organic
phase were carried out with 0.2 M N2H4 + 0.6 M HNO3 and 0.1 M
oxalic acid. Table 2 shows the percentage back extraction of Pu
in a single contact. Pu can thus be effectively recovered from the
loaded organic phase in multiple stages thereby providing the op-
tion of recycling the solvent system.

5436
R. Ruhela et al. / Tetrahedron Letters 53 (2012) 5434–5436
5 0 0 0 0
4 0 0 0 0
3 0 0 0 0
2 0 0 0 0
1 0 0 0 0
0
D iss o lv e r S o lu tio n
0 .1 M B e n zo D O D A /n -d o d e ca n e a fte r
co n ta ctin g w ith d iss o lv e r so lu tio n
140L a
140L a
0
2 0 0
4 0 0
6 0 0
8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0
E n e rg y (k e V )
Figure 5.
c Spectra of dissolver solution and 0.1 M BenzoDODA/n-dodecane after contacting with dissolver solution.
Table 1
Distribution ratio of Pu and other elements present in dissolver solution into 0.1 M BenzoDODA/n-dodecane
Element
Pu(IV)
U(VI)
241Am
147Nd
141Ce
140La
103Ru
140Ba
95Zr
95Nb
132Te
89Sr
DM
SF(DPu/DM
6.74
—
0.11
61.27
0.005
1348
0.002
3370
0.005
1348
0.019
354.7
0.011
612.7
0.0018
3744.4
0.151
44.64
0.124
54.34
0.116
58.10
0.021
320.9
)
Table 2
Back extraction of Pu from loaded organic phase in different stripping agents
9. Xu, J.; Gorden, Anne E. V.; Raymond, K. N. Eur. J. Org. Chem. 2004, 3244.
10. Veeck, A. C.; White, D. J.; Whisenhunt, D. W., Jr.; Xu, J.; Gorden, Anne E. V.;
Romanovski, V.; Hoffman; Darleane, C.; Raymond, K. N. Sol. Extr. Ion Exch. 2004,
22(6), 1037.
Extractant
0.2 M N2H4 + 0.6 M
HNO3
0.1 M Oxalic acid
11. General procedure for synthesis of extractant: To 50 ml of ethanol taken in a
round bottom flask fitted with air condenser was added 0.1 mol of KOH. To this
0.05 mol of catechol was added and stirred for a while. About 0.1 mol of N,N-
bis-(2-ethylhexyl)-2-chloroacetamide was added to the reaction mixture in
one lot and was continuously stirred for 6 h. The temperature of the reaction
mixture was raised to 50–60 °C and stirring was continued for 12 h. The
resulting solution was filtered and evacuated to remove the solvent. Hexane
was added to the residue and the resulting organic solution was washed
several times with 2.5 wt% Na2CO3 solution till the aqueous phase became
colorless. The organic phase was then treated successively with 0.5 M HCl and
water, and dried over anhydrous Na2SO4. This was then concentrated in
vacuum (0.01 mmHg) at 100–120 °C. The purity and yield of the product was
98.8% and 95% ‘respectively’. Elemental Anal. Calcd for C42H76O4N2: C, 75.0; H,
11.31; O, 9.52; N, 4.16%. Found: C, 74.78; H, 11.17; O, 9.94; N, 4.11%. 1H NMR
(CDCl3): 0.80–0.90 (m, 24H), 1.24 (m, 32H), 1.60–1.64 (m, 4H), 3.20–3.30 (m,
8H), 4.77 (s, 4H), 6.88 (s, 4H). GC–MS: 24.76 min, 1.24%, m/z 522 calculated for
0.1 M BenzoDODA/n-
dodecane
85% (1st Contact)
15% (1st
Contact)
In conclusion a novel extractant has been synthesized and eval-
uated for the selective separation of Pu from acidic media. It can be
effectively used for the separation of Pu from dissolver solution,
high level waste and other acidic waste streams. Detailed mixer
settler studies with dissolver solution are under progress to assess
the true potential of BenzoDODA/n-dodecane solvent system for
the separation and recovery of Pu from spent nuclear fuel.
References and notes
(C8H17)2NCH2CON(C8H17
)
and 40.92 min, 98.76%, m/z 671 calculated for
2
BenzoDODA(C8H17)2N–C(O)–CH2–O–(Ar)–O–CH2–C(O)–N(C8H17)2.
12. Solvent extraction experiments: Plutonium was stabilized as Pu(IV) using
NaNO2. Solvent extraction studies were carried out by equilbrating equal
volume of the organic and aqueous phases for 30 min followed by
1. (a) Lanham, W. G.; Runion, T. C. USAEC Report ORNL-479; ORNL: Oak Ridge TN,
1949; (b) David L. Clark. 2000, 26, Los Alamos Science.
2. O’Boyle, N. C.; Nicholson, G. P.; Piper, T. J.; Taylor, D. M.; Williams, D. R.;
Williams, G. Appl. Radiat. Isot. 1997, 48(2), 183.
centrifugation for phase separation. 100–500 ll of each phase was taken for
radiometric assay of Am(III) and fission products using High Purity Germanium
(HPGe) detector based gamma spectrometry system. The results were reported
as distribution ratio and are calculated as radioactivity of the corresponding
radionuclide in the organic phase divided by that in the aqueous phase. Each
experiment was done in duplicate and results agree within 5%. Independent
experiments with plutonium and uranium were also carried out. Plutonium
and uranium (233U) were assayed by alpha counting in a ZnS(Ag) based alpha
counter.
3. Gorden, Anne E. V.; Xu, J.; Raymond, K. N. Chem. Rev. 2003, 103, 4207.
4. (a) E. R. Iresh, W.H. Rheas, USAEC, Report 1953, TID-7534 (BK-1).; (b) Patil, S. K.;
Ramakrishna, V. V.; Prakas, B. H. Sep. Sci. Tech. 1980, 15(2), 131.
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6. Shukla, J. P.; Pai, S. A.; Subramanian, M. S. Sep. Sci. Tech. 1979, 14(10), 883.
7. US Patent, 1988, 4772, 429.
8. (a) Kolarik, Z. J.; Horwitz, E. P. Sol. Extr. Ion Exch. 1988, 6(2), 247; (b) Lambert, T.
N.; Jarvinen, G. D.; Gopalan, A. S. Tetrahedron Lett. 1999, 40, 1613.