Extraction of U(VI) with N,N'-dimethyl-N,N'-dioctylmalonamide from nitrate media

Article abstract of DOI:10.1134/S0036023610030307

The extraction of uranyl nitrate with the novel extractant N,N '-dimethyl-N,N '-dioctylmalonamide (DMDOMA) from aqueous sodium nitrate (and nitric acid) was investigated. The extraction mechanism was established and the stoichiometry of the main extracted species confirms to UO₂(NO ₃)₂ · DMDOMA. The IR spectral study was also made of the extracted species. Methyl substituent improves the extraction ability of malonamide for U(VI) compared with that of N,N,N ', N '-tertrabutylmalonamide (TBMA). Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S0036023610030307

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 3, pp. 468–471. © Pleiades Publishing, Ltd., 2010.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Extraction of U(VI) with N,N'ꢀDimethylꢀN,N'ꢀDioctylmalonamide
1
from Nitrate Media
Yu Cui, Yufen Hu, Yanju Zhang, Shaohong Yin, and Guoxin Sun
School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, P.R. China
eꢀmail: sgx@ujn.edu.cn
Received September 15, 2009
Abstract—The extraction of uranyl nitrate with the novel extractant N,N'ꢀdimethylꢀN,N'ꢀdioctylmalonaꢀ
mide (DMDOMA) from aqueous sodium nitrate (and nitric acid) was investigated. The extraction mechaꢀ
nism was established and the stoichiometry of the main extracted species confirms to UO (NO ) ·
2
3 2
DMDOMA. The IR spectral study was also made of the extracted species. Methyl substituent improves the
extraction ability of malonamide for U(VI) compared with that of N,N,N',
N
'ꢀtertrabutylmalonamide
(TBMA).
DOI: 10.1134/S0036023610030307
1
INTRODUCTION
prepared by reduction of Nꢀmethyloctylamide using
NaBH4 as reducing agent and acetic acid as catalyzer
in THF. DMDOMA was purified by distillation under
vacuum. The final products were characterized by eleꢀ
mental analysis, IR and 1HNMR measurement.
The extraction and partition of lanthanides and
actinides are important in the hydrometallurgy,
nuclear reprocessing and so on [1, 2]. ', 'ꢀtetꢀ
N,N N,N
raalkyldiamides have been reported to be potential
extractants of actinides and also considered as an
alternate choice in place of TBP in the nuclear fuel
reprocessing [3–6]. It is now recognized that extracꢀ
tion behavior varies widely depending on the nature of
the alkyl groups on the diamide framework. For
Compound(N,N'ꢀdimethylꢀN,N'ꢀdioctylmalonaꢀ
mide): yield 72%, pale yellow oil, bp 205~208
°
C/2~4
ꢀ1
mm Hg; IR (KBr, cm ) 1660.1 (C=O);
δ
H
(300 MHz,
DMSO), 0.86 (6H, t, C–CH ), 1.245 (20H, s, –CH –),
3
2
1
.447 (4H, m, –CH –C–N–), 2.781, 2.889 (6H, t, N–
2
(
RR'NCO) CH2, if R is a small group (typically
2
CH ), 3.166–3.329 (4H, m, N
⎯
CH –), 3.449 (2H, d,
3
2
methyl) and R' a bigger one, the stereochimical
OC–CH –CO). Elem. Anal. Calcd. for C H N O2:
2
21 42
2
around the carbonyl oxygen atoms is kept to miniꢀ
mium and the lipophilic character of the ligands is
attained by the presence of a higher chainꢀalkyl or
arkyl groups at R'. Costa [7], Spjuth [8], Musikas [9]
and Nakamura [10] had reported the extractability of
some unsymmetrical diamides for U(VI) and Ln(III).
Our approach to investigating structureꢀfunction relaꢀ
tionships for binding diamides to fꢀbolck metals builds
upon the study of the extraction with various diamides
choosing different alkyl substituents. We had reported
the extraction of U(VI) with N,N'ꢀdimethylꢀN,N'ꢀ
dioctylsuccinylamide in our previous paper [11], here
presented the extraction of U(VI) from sodium nitrate
with DMDOMA, which shows good affinity for U(VI)
than that of TBMA.
C 71.14%, H 11.94%, N 7.90%. Found: C 70.45%, H
11.87%, N 7.71%.
Other agents employed in this work were all A.R.
grades.
Extraction and Analytical Procedures
Equal volumes of organic and aqueous phases were
agitated for 30 minutes (enough for equilibrium) at
25 C under the desired experimental conditions. The
°
two phases were then centrifuged and assayed by takꢀ
ing known aliquots (0.05–0.1 mL) from the aqueous
phases. The concentrations of U(VI) in the sample
were determined by ArsenazoꢀIII visible spectrophoꢀ
tometric analysis and that in organic phase obtained
by subtracting the aqueous concentrations from the
total initial aqueous concentration of U(VI). The disꢀ
EXPERIMENTAL
Reagents
The extractant DMDOMA was obtained by the
tribution ratio (
concentration of U(VI) in organic phase to that in
aqueous phase. If not stated otherwise, cU was 5.00
D) was calculated as the ratio of the
reaction of
onate. The unsymmetrical
Nꢀmethyloctylamine with diethyl malꢀ
Nꢀmethyloctylamine was
×
1
10–3 mol dm , camide 0.10 mol dm , cHNO3 0.01 mol dm–3
–3
–3
The article is published in the original.
.
468

EXTRACTION OF U(VI)
469
DU
DU
1
00
0.10 M DMDOMA
.20 M TBMA
5
4
3
0
0
0
0
8
6
4
0
0
0
2
0
0
1
20
0
0
1
2
3
4
5
1
2
3
4
5
cHNO3
cNaNO3
Fig. 2. Effect of NaNO3 concentration on the extraction of U(VI);
–3
–3
cU = 5.00
= 0.01 mol dm–3
cH
×
10–3 mol dm , cDMDOMA = 0.10 mol dm ,
Fig. 1. Effect of HNO3 concentration on the extraction of U(VI);
cU = 5.0
10–3 mol dm–3 cDMDOMA = 0.10 mol dm–3
×
,
.
+
.
Preparation and Characterization of Extracted Species malonamide extractants bring big steric hindrance
effect in the formation of the extracted species of uraꢀ
The extracted species were prepared, presumedly
nyl ion.
identical to those existing in the extracts. The extractꢀ
ant solutions were shaken with a concentrated solution
of UO (NO3)2, centrifuged and the organic phase sepꢀ
arated. The organic solvents were removed by evaporaꢀ
2
Effect of the Concentration of Extractant
on the Extraction of U(VI)
tion and FTꢀIR spectra of the residuals were recorded on
–1
an FTSꢀ165 Spectrometer in the range 400–4000 cm
.
The variation in the distribution ratio of U(VI) with
DMDOMA in toluene is given in Fig. 3. The logꢀlog
plots of the distribution ratio vs. the initial extractant
concentration show that the lines have a slope of
nearly 1. It implies that the stoichiometrics of the
The samples were used in the spectrometer between
potassium bromide windows. The scan times and the
resolution were 60 and 2 cm–1, respectively.
extracted species in toluene is UO (NO )
⋅
RESULTS AND DISCUSSION
2
3 2
DMDOMA, which is distinct from the result of the
extraction of U(VI) with TBMA which forms
Effect of Nitric Acid Concentration
on the Extraction of U(VI)
The extraction of U(VI) with 0.10 mol dm–3
UO (NO ) 2TBMA [12].
⋅
2
3 2
DMDOMA from nitric acid solutions in the range of
–3
1
(
.00–5.00 mol dm at 298 K has been investigated
Fig. 1). The results show that the distribution ratio of
U(VI) increases with the increase in the concentration
of HNO3
1
1
1
1
.5
.4
.3
.2
.
s = 1.09
Effect of Sodium Nitrate Concentration
on the Extraction of U(VI)
The effect of sodium nitrate concentration in the
–3
presence of 0.01 mol dm HNO3 on the distribution
ratio of U(VI) is shown in Fig. 2. The distribution ratio
of U(VI) increases significantly with increasing
NaNO3 concentration in which the coꢀion effect plays
a crucial role. Compared with the result of the extracꢀ
1.1
.0
1
–1.1
–1.0
–0.9 –0.8
logcDMDOMA
–0.7
tion of N,N,N',N'ꢀtetrabutylmalonamide (TBMA]
[
12, 13], we find that the adoption of unsymmetrical
Fig. 3. Effect of extractant concentration on the extraction of
substituted alkyl does improve the extractability of
malonamides markedly, which indicates that the two
straight long chain alkyls adjacent to nitrogen atom in
10–3 mol dm , cH = 0.01 mol dm–3,
–3
U(VI); cU = 5.00
×
+
= 3.00 mol dm–3
.
c
NaNO3
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 3 2010

470
CUI et al.
1
00
1
.4
.2
DMDOMA
1
80
DMDOMAꢀU(VI)
1.0
0.8
0.6
0.4
6
4
2
0
0
0
0
3.1
3.2
3.3
000/T (K )
3.4
3.5
–
1
1
Fig. 4. Dependence of extraction of U(VI) on the experiꢀ
mental temperature; cDMDOMA = 0.10 mol dm–3
3000
2000
Wavenumber (cm )
1000
–1
,
×
10–3 mol dm , cNaNO3 = 3.00 mol dm ,
ꢀ3
–3
cU = 5.00
= 0.01 mol dm–3
cH
+
.
Fig. 5. IR spectra of the extractant loaded uranyl nitrate.
Hence the equilibrium expression, written as the the coordinated nitrate ions [14, 15]. An additional
solvating reaction of U(VI) is given as follows band described as the U–O stretching vibration of the
–
1
2
2
+
−
uranyl ion is noted at 926 cm .
UO + 2NO + DMDOMA
(O)
3
(1)
=
UO (NO ) ⋅ DMDOMA
2 3 2 (O)
in which the equilibrium constant for U(VI), Kex, is
CONCLUSIONS
U(VI) can be extracted effectively from nitric acid
solution employing toluene as diluent by the new
unsymmetrical diamide, N,N'ꢀdimethylꢀN,N'ꢀdioꢀ
ctylmalonamide. The stoichiometry of the extracted
[
UO (NO ) ⋅ DMDOMA]
2
3 2
−
(O)
Kex
=
.
(2)
2+
2
[
UO ]⋅[NO ] ⋅[DMDOMA]
From Fig. 3 we can obtain the values of
equation (2), which is 17.25 ± 0.75 mol dm
2
3
(O)
K
through
ex
–3
9
species in toluene is UO (NO )
⋅
DMDOMA. The
±
.
2
3 2
–
1
value of H for the extraction is –44.23 4.20 kJ mol .
Δ
The adoption of unsymmetrical substituted alkyl does
improve the extractability of malonamides markedly
compared with symmetrical extractant whose substitꢀ
uents possess similar number of carbon atoms.
Influence of Temperature on the Extraction of U(VI)
Figure 4 illustrates the influence of temperature on
the values of
D. The extraction distribution ratio
decreases with the increase in the temperature, which
shows that the extraction reaction is exothermic. The
ACKNOWLEDGMENTS
log
D
values increase linearly with the increase in 1/
T.
The change in enthalpy,
Δ
H, associated with reaction
The authors are grateful for the support from the
(
1), can be evaluated by means of the Van’t Hoff Equaꢀ National Natural Science Foundation of China
±
tion. The value of
Δ
H
obtained from Fig. 4, is –44.23
(20301008), Natural Science Foundation of Shanꢀ
dong Province (Q2003B01) and Doctoral Foundation
of University of Jinan (B0417).
4
.20 kJ mol–1
.
IR Spectra Analysis of the Extracted Species
An analysis of the spectra (Fig. 5) of the loaded
organic phase in the C=O stretching region (1550–
REFERENCES
1. N. I. Steblevskaya, M. A. Medkov, N. V. Batyrbaeva,
–1
and L. N. Kurilenko, Rus. J. Inorg. Chem. 52 (4), 635
1
760 cm ) was carried out using a curve fitting proceꢀ
(
2007).
dure. The broad band of C=O consists of three subbands
and the peaks are at 1593.1, 1629.6 and 1659.5 cm
–
1
,
2. V. A. Keskinov, V. V. Lishchuk, and A. K. Pyartman,
Rus. J. Inorg. Chem. 53 (1), 153 (2008).
3. E. A. Mowafy, H. F. Aly, Solvent Extr. Ion Exch. 20 (2),
respectively. Compared with the IR spectra of free
extractants, the carbonyl group (C=O) stretching
vibration of the extracted species is shifted from about
177 (2002).
1
660 to 1593.1 and 1629.6 cm–1, which implies that the
4. C. Cuillerdier, C. Musikas, and P. Hoel, et al., Sep. Sci.
Technol. 26 (9), 1229 (1991).
5. Y. Cui, G.ꢀX. Sun, Z.ꢀW. Zhang, and S.ꢀX. Sun,
amide ligand directly coordinates to the uranyl ion
through its carbonyl group. The appearance of bands
at about 1046, 1281 and 1520 cm–1 can be attributed to
J. Serb. Chem. Soc. 71 (5), 513 (2006)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 3 2010

EXTRACTION OF U(VI)
471
6
7
8
9
. L. Nigond, N. Condamines, P. Y. Cordier, et al., Sep. 11. Y. Cui, G. X. Sun, Z. W. Zhang, et al., J. Radioanal.
Sci. Technol. 30 (7&9), 2075 (1995).
Nucl. Chem. 272 (1), 199 (2007).
. M. C. Costa, A. Carvalho, A. Uryga, et al., Solv. Extr.
Ion Exch. 21 (5), 653 (2003).
. L. Spjuth, O. J. Liljenzin, M. Hudson, et al., Solv. Extr.
Ion Exch. 18 (1), 1 (2000).
1
1
1
2. M. Bao and G. X. Sun, J. Radioanal. Nucl. Chem.
(
Lett.) 231 (1–2), 203 (1998).
3. Y. Sh. Wang and G. X. Sun, J. Radioanal. Nucl. Chem.
Lett.) 224 (1–2), 151 (1997).
4. J. R. Ferraro, J. Inorg. Nucl. Chem. 10, 319 (1959).
(
. C. Musikas and H. Hubert, Solv. Extr. Ion Exch.
1987).
5, 877
(
1
0. T. Nakamura and C. Miyake, Solv. Extr. Ion Exch. 15. C. Berthon and C. Chachaty, Solv. Extr. Ion Exch.
13
(2), 25 (1995). 13 (5), 781 (1995).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 3 2010