Mendeleev
Communications
Mendeleev Commun., 2008, 18, 336–337
New systems based on 2,2'-dipyridyl-6,6'-dicarboxylic
acid diamides for Am–Eu separation
a
a
b
Mikhail Yu. Alyapyshev, Vasily A. Babain, Nataliya E. Borisova,
a
b
b
Rimma N. Kiseleva, Dmitry V. Safronov and Marina D. Reshetova*
a
b
V. G. Khlopin Radium Institute, 194021 St. Petersburg, Russian Federation. Fax: +7 812 297 5700;
e-mail: babain@atom.nw.ru
Department of Chemistry, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation.
DOI: 10.1016/j.mencom.2008.11.018
New synergistic extraction mixtures based on 2,2'-dipyridyl-6,6'-dicarboxylic acid diamides and chlorinated cobalt dicarbolide
were proposed as highly effective for americium–europium separation in acidic media.
The separation of minor actinides (particularly, americium and
curium) from rare earth elements is very important for reducing
actinide waste volume. There are many polynitrogen com-
pounds, which extract americium much more than europium from
solutions with pH 2–4. Note that compounds such as N,N,N',N'-
tetrakis(2-pyridylmethyl)ethylenediamine, tris(pyridyl)triazine,
bis(benzimidazolyl)pyridines, tripyridine and bis(triazinyl)-
pyridines have good separation factor for Am–Eu up to 1 M
OH
NR' R''
O
O
Br
N
N
N
N
N
N
N
i
ii
iii
O
O
1,2
nitric acid, but all of them are unstable in nitric acid. The main
goal of this investigation was to find the reagent that possesses
a high separation factor (SF) for actinides vs. lanthanides even
in acidic media.
OH
2, 92%
NR' R''
1
3a R' = Et, R'' = Ph, 74%
b R' = R'' = Bu, 80%
3
The reagents that possess high extraction ability together with
high hydrolytic stability were found among dicarboxylic acids
Scheme 1 Reagents and conditions: i, Raney Ni, toluene, 110 °C, 22 h,
1
0
then H O; ii, CrO , H SO , 70 °C, 1 h, 92%; iii, SOCl , Δ, 3 h, then
2
3
2
4
2
†
3
4–6
HNR'R'', Et N, THF, 50 °C, overnight.
(
malonic and dipicolinic ) amides. The latter type of amides
3
are the most promising agents for nuclear technology due to
their high stability toward acid hydrolysis and radiolysis. In
†
7
Synthesis of 2. To a solution of 5.76 g (31 mmol) of 1 in 64 ml of
concentrated sulfuric acid, 18.4 g of CrO was added in small portions at
3
1
994, Rais and Tachimori found during the study of extractive
7
0 °C. After the addition was complete, the reaction mixture was stirred
for 1 h at this temperature. The resulting green slurry was poured into
00 g of crushed ice. The white precipitate of 2 was filtered off, washed
properties of mixtures of chlorinated cobalt dicarbolide (CCD)
and phenanthroline that this mixture is suitable for separating Am
1
8
from Eu with separation factors up to 36 at pH 3.5. Mixtures of
1
2
with water and dried. H NMR ([ H ]DMSO) d: 8.16 (d, 1H), 7.99 (t,
6
tetraalkyl or dialkyldiaryl dipicolinic diamides (DPAs) with CCD
extract cesium, actinides and lanthanides from acidic solutions
1H), 7.89 (d, 1H).
Synthesis of 3a,b: 10 ml of SOCl , 2.0 g (8.2 mmol) of 2 and a drop of
DMF were refluxed for 3 h. Excess SOCl2 was removed under reduced
pressure, and the resulting solid was dried. Solid residue was dissolved
in dry THF (120 ml). This solution was added dropwise to a mixture
2
4–6
and strontium after addition of polyethylene glycol. However,
the SFAm/Eu lies in the range 2–5.4 for different DPAs–CCD
6
compositions. We propose 2,2'-dipyridyl-6,6'-dicarboxylic acid
of 2.22 ml (17.2 mmol) of HNR'R'', 8.3 ml (59 mmol) of NEt and THF
3
diamides as a substance of choice for Am/Eu separation. These
compounds have an additional pyridine ring comparing to DPA, so
they can coordinate metal ions as tetradentate ligands. Moreover,
an additional nitrogen coordination centre can increase the selec-
tivity of americium/lanthanides separation.9
(
20 ml) at 50 °C. The resulting mixture was stirred overnight at this
temperature, then poured into water (70 ml) and extracted with CHCl3
2×150 ml). Combined organic extracts were washed with water (2×120 ml)
and dried over Na SO . Rotary evaporation of organic solution yielded 3.
(
2
4
Compound 3a was additionally washed with small portion of EtOAc,
mp 182–184 °C. 1H NMR (CDCl ) d: 7.63 (d, 1H), 7.46 (t, 1H), 7.17 (d,
1H), 7.07 (m, 5H, Ph), 4.01 (q, 4H, CH ), 1.24 (t, 6H, Me). C NMR
(CDCl3) d: 153.57, 143.43, 136.88, 128.77, 127.55, 126.44, 124.21, 121.53,
The 2,2'-dipyridyl-6,6'-dicarboxylic acid diamides 3a and 3b
were prepared in high yields starting from 2-bromo-6-picoline
3
1
3
2
(
Scheme 1).†
–
1
4
5.51, 12.77. IR (KBr, n/cm ): 1639 (amide I). Found (%): C, 74.50;
The extraction behaviour of 2,2'-dipyridyl-6,6'-dicarboxylic
H, 5.90; N, 12.32. Calc. for C H N O (%): C, 74.65; H, 5.82; N, 12.44.
acid diamides is very similar to that of DPA. We studied the
28 26
4
2
extraction of americium and europium with 0.03 M 3a in F-3‡
Compound 3b was additionally dried at 80 °C at 0.1 Torr for 4 h.
1
H NMR (CDCl ) d: 8.42 (d, 1H), 7.89 (t, 1H), 7.60 (d, 2H), 3.54 (t, 2H,
3
from aqueous solutions with various concentrations of nitric
acid. The distribution ratios (D) of americium were 0.01, 0.33
and 0.76 for extraction from 0.2, 0.5 and 1.0 M nitric acid,
respectively. Thus, the extraction ability of pure diamide increases
with increasing nitric acid concentration, which is common for
cis-CH ), 3.36 (t, 2H, trans-CH ), 1.69 (m, 4H), 1.44 (q, 2H, cis-CH ),
2
2
2
1
.11 (q, 2H, trans-CH ), 1.00 (t, 3H, cis-Me), 0.74 (t, 3H, trans-Me).
2
13
C NMR (CDCl ) d: 168.68, 154.63, 153.92, 137.65, 123.45, 121.30,
3
4
8.69, 45.66, 31.11, 29.63, 20.29, 19.76, 13.90, 13.55. Found (%): C,
72.15; H, 9.18; N, 12.19. Calc. for C H N O (%): C, 72.07; H, 9.07;
2
8
42
4
2
DPAs, but the SF
for that of DPA.6
is much more for the diamide 3a than
N, 12.01.
Am/Eu
‡
meta-Nitrobenzotrifluoride (F-3) was used as a diluent.
©
2008 Mendeleev Communications. All rights reserved.
– 336 –