α-Dialkylamino N,N-diisobutylacetamides: A new class of anion exchanger with intramolecular buffering properties

Article abstract of DOI:10.1039/c4ra03020f

A new class of ammonium based anion exchangers embedded with a terminal amide group, viz. α-dialkylamino N,N-diisobutylacetamides has been designed, synthesized and tested for their ability to extract oxometalate anions from nitric acid medium. As a representative example, the molybdate anion has been chosen for the present studies and its extraction behaviour was compared with routinely used anion exchangers like Alamine 336, Aliquat 336 and Primene JMT having no amide functionality. A higher %E value for molybdate was observed with α-dialkylamino N,N-diisobutylacetamides compared to Alamine 336, Aliquat 336 and Primene JMT, from the same HNO₃ acidity. The presence of amide group in the ligand is the key to the success of extraction from a relatively higher concentration of nitric acid medium. The amide group in the extractant leads to extra acidity through the intramolecular buffering effect thus enabling the ligand to extract the molybdate anion at higher acidities. Stoichiometry of the ion pair formed during extraction was ascertained by the slope analysis method. The composition of the complex was found to be (LH) ₂MoO₄·HNO₃. FTIR and NMR of the loaded extractant indicated that MoO₄^2- is associated with the ammonium site while binding of HNO₃ occurred at the amide group. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra03020f

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a-Dialkylamino N,N-diisobutylacetamides: a new
class of anion exchanger with intramolecular
buffering properties†
Cite this: RSC Adv., 2014, 4, 27837
a
a
b
c
Shikha Sharma, Sunil K. Ghosh,* Anitha M and Joti N. Sharma*
A new class of ammonium based anion exchangers embedded with a terminal amide group, viz.
a-dialkylamino N,N-diisobutylacetamides has been designed, synthesized and tested for their ability to
extract oxometalate anions from nitric acid medium. As a representative example, the molybdate anion
has been chosen for the present studies and its extraction behaviour was compared with routinely used
anion exchangers like Alamine 336, Aliquat 336 and Primene JMT having no amide functionality. A higher
%E value for molybdate was observed with a-dialkylamino N,N-diisobutylacetamides compared to
Alamine 336, Aliquat 336 and Primene JMT, from the same HNO acidity. The presence of amide group
3
in the ligand is the key to the success of extraction from a relatively higher concentration of nitric acid
medium. The amide group in the extractant leads to extra acidity through the intramolecular buffering
effect thus enabling the ligand to extract the molybdate anion at higher acidities. Stoichiometry of the
ion pair formed during extraction was ascertained by the slope analysis method. The composition of the
Received 4th April 2014
Accepted 16th June 2014
DOI: 10.1039/c4ra03020f
complex was found to be (LH)
2
MoO
ꢀ
is associated with the ammonium site while binding of HNO
4
$HNO
3
. FTIR and NMR of the loaded extractant indicated that
2
4
www.rsc.org/advances
MoO
3
occurred at the amide group.
TODGA has been replaced by secondary and tertiary imino
1
. Introduction
24
groups which acts as the anion exchanger site. Some of them
have shown good extraction behavior for oxometalates even
, TcO are usually present in various from higher nitric acid medium. However, the role of amide
2
ꢀ
246ꢀ
7
244ꢀ
O ,
Oxometalates such as MoO
UO
4
,
Mo
7
O
,
H
2
Mo
4
ꢀ
4ꢀ
4ꢀ
2
(CO
3
)
3
, UO (SO )
2 4 3
1
,2
nuclear waste streams. Amines are widely used as extractants groups in these extractants has not been discussed.
2–12
for these kinds of anions.
Trioctylamine (TOA), a major
It is known that the amide group in CMPO can suppress the
and retains its ability to work at
Ali- higher acidity. This behaviour is termed as intramolecular
component of Alamine 336 is known to extract oxometalates effect of competing HNO
3
1
3–17
25,26
from nuclear waste by an anion-exchange mechanism.
quat 336 and Primene JMT are also used for the same
purpose.
ketones is usually used as the diluent with these amines.
13,18,19
A combination of kerosene and alcohols or
20,21
While the extraction is based on anion exchange mechanism,
the distribution ratio strongly depends on the concentration of
cations, anions and acidity of the aqueous phase. Alamine 336
and other amine based anion exchangers works well at lower
acidity but shows poor efficiency at higher acidity of aqueous
2
phase. Recently, imino analogs of TODGA (also known as
iminodiamides), have been introduced as extractants for oxo-
22–24
metalates from nitric acid medium.
The ether oxygen of
a
Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085,
India. E-mail: ghsunil@barc.gov.in; Fax: +91-22-25505151; Tel: +91-22-25595012
b
Rare Earths Development Section, Bhabha Atomic Research Centre, Trombay,
Mumbai 400085, India
c
Nuclear Recycle Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400085,
India. E-mail: jnsharma@barc.gov.in; Fax: +91-22-25505151; Tel: +91-22-25592959
Fig. 1 Structure of a-dialkylamino N,N-diisobutylacetamides 1–3,
TOA (major component of Alamine 336) 4, Aliquat 336 5 and Primene
JMT 6.
†
Electronic supplementary information (ESI) available: See DOI:
0.1039/c4ra03020f
1
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27
buffering effect. Therefore, there is a need to evaluate the role 1.2 equiv., 3.6 mmol) in dry CH
2
Cl
2
(6 mL) followed by drop-
of an adjunct amide group in an anion exchanger for oxome- wise addition of dry triethylamine (420 mL, 1 equiv., 3 mmol) at
ꢁ
talate extraction. We speculated the buffering effect principle of 10–15 C. The reaction mixture was allowed to attain to room
amide group might be useful to design new class of anion temperature and stirred for 24 h. The reaction mixture was
exchangers having simpler structures like dialkylamino-mono- diluted with water and extracted with ethyl acetate–petroleum
amides that might work at higher HNO concentrations. This ether mixture. The organic extract was dried over anhydrous
3
paper describes the synthesis and extraction behaviour of a- sodium sulfate and concentrated under reduced pressure. The
dialkylamino N,N-diisobutylacetamides 1–3 (Fig. 1), a new class residue was puried by distillation to give chloracetamide 7
1
of ammonium based extractants embedded with a terminal (523 mg, 85%). H NMR (200 MHz, CDCl
3
): d 0.82–1.0 (12H, m, 2
amide group. The extraction behavior of these amides was ꢂ CHMe ), 1.80–2.16 (2H, m, 2 ꢂ CH Me ), 3.14 (2H, d, J ¼ 7.6
2
2
compared with more commonly used anion exchangers like Hz, NCH CH), 3.20 (2H, d, J ¼ 7.6 Hz, NCH CH), 4.08 (2H, s,
2
2
Alamine 336 4, Aliquat 336 5 and Primene JMT 6 (Fig. 1) devoid COCH Cl).
2
of amidic groups.
a-Dipropylamino N,N-diisobutylacetamide (1). Dipropyl-
amine (20 mL, 3 equiv., 146 mmol) was added to a stirred
solution of chloracetamide 7 (10 g, 1 equiv., 48.7 mmol) in dry
THF (20 mL) and the solution was heated at 80 C for 3 days.
The reaction mixture was diluted with water and extracted with
2. Experimental
ꢁ
2.1 Chemicals
Nitric acid, n-dodecane and isodecyl alcohol (IDA) were 10% ethyl acetate–petroleum ether. The combined organic
obtained from local sources. Alamine 336, Aliquat 336, extract was dried over anhydrous sodium sulfate and concen-
Primene JMT, diisobutylamine, dioctylamine, dihexylamine, trated under reduced pressure. The residue was distilled to give
1
dipropylamine,
(NH Mo 24$4H
analytical grade. The solvents were dried and distilled from the 1.59 (4H, m, 2 ꢂ CH
indicated drying agents: THF from sodium/benzophenone; (4H, t, J ¼ 7.4 Hz, 2 ꢂ CH
triethyl amine from CaH and then stored over calcium metal. NCH CHMe
), 3.27 (2H, d, J ¼ 7.8 Hz, NCH
CO). C NMR (150 MHz, CDCl ): d 11.8, 19.9, 20.1 (4C), 26.1
silica gel plates (about 0.5 mm) and column chromatography (2C), 27.3 (2C), 52.5, 54.3, 56.1 (2C), 57.8, 171.1. Calcd. for
was performed using silica gel of 230–400 mesh. Characteriza-
O; C, 71.06; H, 12.67; N, 10.36%; found: C, 71.16; H,
tion of synthesized compounds was done by H NMR, C NMR 12.67; N, 10.46%.
and elemental analyses.
a-Dihexylamino N,N-diisobutylacetamide (2). A mixture of
chloracetamide 7 (1 g, 1 equiv., 4.87 mmol) and dihexylamine
ammonium
O] and other chemicals used were of NMR (200 MHz, CDCl
CH
molybdate
tetrahydrate a-dipropylamino N,N-diisobutylacetamide 1 (10.52 g, 80%). H
[
4
)
6
7
O
2
3
): d 0.80–0.95 (18H, m, 6 ꢂ CH
N), 1.82–2.07 (2H, m, 2 ꢂ CHMe
CH
N), 3.16 (2H, d, J ¼ 7.4 Hz,
CHMe ), 3.35 (2H, s,
3
), 1.40–
2
2
2
), 2.53
2
2
2
2
2
2
2
1
3
Analytical thin layer chromatography was performed using CH
2
3
C H N
16 34 2
1
13
(
1.42 mL, 1.25 equiv., 6.09 mmol) in triethylamine (3 mL) was
2
.2 Synthetic procedures for 1–3
ꢁ
heated at 90 C for 20 h. The reaction mixture was diluted with
water and extracted with 10% ethyl acetate–petroleum ether.
The combined organic extract was dried over anhydrous sodium
sulfate and concentrated under reduced pressure. The residue
was puried by column chromatography to give amide a-
a-Dialkylamino N,N-diisobutylacetamides 1–3 were synthesized
in our laboratory as described in Scheme 1. For this, chlor-
oacetyl chloride was reacted with diisobutylamine to give the
amide 7 which was subsequently reacted with different dialkyl
amines to give the desired a-dialkylamino N,N-diisobutylaceta-
mides 1–3 in very good overall yields.
1
dihexylamino N,N-diisobutylacetamide 2 (1.31 g, 76%). H NMR
(500 MHz, CDCl
(12H, m, 6 ꢂ CH
(1H, m, CHMe ), 1.96–2.05 (1H, m, CHMe
3
): d 0.83–0.93 (18H, m, 6 ꢂ CH
), 1.39–1.47 (4H, m, 2 ꢂ CH CH
), 2.48 (4H, t, J ¼ 7.5
3
), 1.22–1.33
N) 1.86–1.95
N,N-Diisobutylchloroacetamide (7). A solution of diisobutyl-
2
2
2
amine (525 mL, 1 equiv., 3 mmol) in dry CH
wise added to a stirred solution of chloroacetyl chloride (290 mL,
2 2
Cl (3 mL) was drop-
2
2
Hz, 2 ꢂ CH NCH CO), 3.16 (2H, d, J ¼ 7.5 Hz, NCH CHMe ),
2
2
2
2
1
3
3
.28 (2H, s, CH CO), 3.29 (2H, d, J ¼ 9 Hz, NCH CHMe ).
C
2
2
2
NMR (125 MHz, CDCl ): d 13.9 (2C), 20.0 (2C), 20.2 (2C), 22.6,
3
2
5
7
6.2 (2C), 27.0 (2C), 27.2 (2C), 27.4, 31.8 (2C), 52.6, 54.4 (2C),
4.5, 57.7, 171.2. Calcd. for C22 O; C, 74.51; H, 13.07; N,
46 2
H N
.9%; found: C, 74.46; H, 13.0; N, 7.92%.
a-Dioctylamino N,N-diisobutylacetamide (3). A mixture of
chloracetamide 7 (1 g, 1 equiv., 4.87 mmol) and di-n-octylamine
(
1.84 mL, 1.25 equiv., 6.09 mmol) in triethylamine (3 mL) was
ꢁ
heated at 90 C for 20 h. The reaction mixture was diluted with
water and extracted with 8% ethyl acetate–petroleum ether. The
combined organic extract was dried over anhydrous sodium
sulfate and concentrated under reduced pressure. The residue
was puried by column chromatography to give amide a-dio-
1
ctylamino N,N-diisobutylacetamide 3 (1.46 g, 73%). H NMR
Scheme 1 Synthesis of a-dialkylamino N,N-diisobutylacetamides.
(500 MHz, CDCl
): d 0.83–0.96 (18H, m, 6 ꢂ CH
3
), 1.20–1.34
3
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(
20H, m, 10 ꢂ CH
2
), 1.39–1.48 (4H, m, 2 ꢂ CH
2 2
CH N), 1.86–1.96
(
2
1H, m, CHMe ), 1.96–2.07 (1H, m, CHMe ), 2.48 (4H, t, J ¼ 8 Hz,
2
2
ꢂ CH NCH CO), 3.17 (2H, d, J ¼ 7.5 Hz, NCH CHMe ), 3.29
2
2
2
2
1
3
(
(
2H, s, CH CO), 3.30 (2H, d, J ¼ 7.5 Hz, NCH CHMe ). C NMR
2
2
2
3
125 MHz, CDCl ): d 14.1 (2C), 20.1 (2C), 20.2 (2C), 22.6 (2C),
2
5
6.3, 27.1 (2C), 27.5, 27.6 (2C), 29.3 (2C), 29.6 (2C), 31.8 (2C),
2.7, 54.4 (2C), 54.5, 57.8, 171.3. Calcd. for C26 O; C, 76.03;
54 2
H N
H, 13.25; N, 6.82%; found: C, 76.07; H, 13.01; N, 6.72%.
2.3 Molybdenum feed solutions
Ammonium molybdate solutions were prepared by dissolving
appropriate amount in nitric acid. Nitric acid concentration
range of our extraction studies was 0.5–2.0 M, where molyb-
28
2
denum mainly exists as H MoO4. Quantitative determination
of molybdenum was carried out using ICP-AES (inductively
coupled plasma atomic emission spectrophotometry tech-
nique). Detection limit for molybdenum was 1 ppm. Error in
molybdenum analysis was within ꢃ5.0%.
Fig.
2
%E for anion exchangers 1–6 at varying nitric acid
concentrations.
2.4 Extraction studies
Prior to extraction experiments, organic phase containing the
anion exchangers was pre equilibrated with equal volume of 0.5
M HNO to minimize variation in nitric acid concentration
3
But at higher concentrations of nitric acid, %E of Mo is much
better for acetamides 1–3 compared to extractants 4–6. This
behavior can be explained by the presence of amidic group in
acetamides 1–3, which allowed retaining the extraction ability at
high nitric acid medium by intramolecular buffering effect of
amidic group. Acetamide 1 was chosen for further studies as it
has shown better extraction behavior.
during extraction. For determination of distribution ratio (DMo),
organic phase was equilibrated with equal volume of aqueous
phase containing molybdate anion for 1 h in a glass vial. All the
extraction experiments were carried out in a thermostated water
ꢁ
bath maintained at temperature 25 ꢃ 1 C. Aer phase sepa-
ration by centrifugation, the organic and the aqueous phase was
separated and the aqueous phase was analyzed for molyb- 3.2 Determination of organic phase composition
denum concentration by ICP-AES aer suitable dilutions. The
concentration of molybdenum in the organic phase was calcu-
lated by mass balance. The distribution ratio DMo was deter-
mined as the ratio of metal concentration in organic phase to
that in aqueous phase. Percentage extraction of metal ion was
determined by equation:
Considering the polar nature of metal–ligand complex and their
poor solubility in n-dodecane, IDA has been chosen as a phase
29,30
modier to mitigate the third phase formation.
In order to

nd out the most suitable solvent composition, extraction
studies were carried out at different concentrations of phase
modier and acetamide 1. Concentration of IDA was varied
form 0–100% and acetamide 1 from 0.1–0.3 M (Fig. 3).
It was observed that with increase in IDA concentration in
solvent, initially there was considerable increase in the DMo
values for all extractant concentrations, but, remained
unchanged beyond 30% IDA. From these observations, 0.2 M a-
amino-acetamide 1 in 30% IDA/n-dodecane was chosen as the
optimum organic phase composition for extraction studies.
%
E ¼ (DMo/DMo + 1) ꢂ 100
(1)
Errors in D
M
values were within ꢃ5%. The nitric acid
concentrations of aqueous and organic phases were determined
by potentiometric titration with 0.1 M NaOH using a Metrohm
905 Titrando device.
3. Results and discussion
3.3 Stoichiometry of the extracted metal complex
3.1 Extraction behavior of amines 1–6
Nitric acid uptake is a common property exhibited by amidic
A solution of 0.2 M each of extractants 1–6 dissolved in 30% extractants. a-Amino-acetamide 1, having both the amine and
IDA/n-dodecane was equilibrated with aqueous solution con- amidic functional groups, also expected to show similar prop-
ꢀ
1
taining 450 mg L
concentrations from 0.5 M to 2.0 M (Fig. 2). It can be seen that exchangers Alamine 336 and acetamide 1 in 30% IDA/n-
E decreases with increase in nitric acid concentration for all dodecane was studied at different initial nitric acid concentra-
the extractants, but the relative decrease in case of Alamine 336 tions (0.1–4.0 M). The acid concentration in the organic and
, Aliquat 336 5 and Primene JMT 6 is much higher compared to aqueous phase was estimated by potentiometric titration
acetamides 1–3. At lower concentration of nitric acid, %E for Mo with 0.1 M NaOH. The variation of [HNO org as a function of
is similar and high for all the extractants except Primene JMT 6. initial aqueous nitric acid concentration is depicted in Fig. 4.
molybdenum at varying nitric acid erties. Therefore, extraction of nitric acid by 0.2 M anion
%
4
3
]
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Fig. 3 Variation in DMo with IDA concentration at 0.5 M nitric acid.
3
Fig. 5 Dependency of DMo on concentration of HNO .
For a-amino-acetamide 1, the ratio of [HNO3]org to [acetamide 1]
increases from 1 : 1 to 2 : 1 as the aqueous nitric acid concen-
log DMo vs. log[HNO
3
] is a straight line with a slope of ꢀ0.85 ꢃ
0.02 indicating participation of one molecule of nitric acid in
tration increases from 0.5 M to 4.0 M. At 0.5 M HNO all the
3
the extraction process.
The stoichiometry of extracted complex with respect to a-
amino-acetamide 1 (L) was determined by plotting variation of
ammonium site of a-amino-acetamide 1 is protonated by HNO
3
and shows 1 : 1 composition, above it the amide group of a-
amino-acetamide 1 starts taking up of nitric acid, partial
DMo as a function of concentration of 1 (Fig. 6). It was observed
protonation of amide group was seen at 2 M HNO
complete protonation was observed at 4 M HNO . The above
ndings also indicate that during pre-equilibration with 0.5 M
3
and
that DMo values increases with an increase in the concentration
of 1. The plots are straight line with slops of 2.34 ꢃ 0.05 and
3

2.04 ꢃ 0.02 for 0.5 M and 2 M HNO
3
, respectively. The results
nitric acid the species formed in the organic phase is L$HNO3.
indicate that in the range of 0.5 to 2 M HNO
the metal ligand composition in the organic phase is
LH) MoO $HNO (Fig. 7).
Based on the above ndings the anion exchange process in
3
concentrations,
As evident from the Fig. 4, the ratio of [HNO3]org to [Alamine
3
36] is 1 : 1 while that of a-amino-acetamide 1 it was 1.5 : 1 in
the range of 0.5 to 2 M aqueous phase HNO concentration and
nally 2 : 1 above 4 M nitric acid.
The effect of HNO on the DMo was established for nitric acid
concentration varying from 0.5 M to 2 M (Fig. 5). The plot of
(
2
4
3
3

the acid range 0.5 to 2 M HNO
3
may be represented as
3
2
H MoO4(aq) + 2L$HNO3(org) $
(
LH)
2
MoO
4
$HNO3(org) + HNO3(aq)
(2)
Fig. 4 Extraction of HNO
acetamide 1 or Alamine 336 4.
3
from aqueous solution by 0.2 M a-amino- Fig. 6 Dependency of DMo on concentration of a-amino-acetamide 1
(0.1–0.3 M) at different aqueous phase HNO acidity.
3
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Fig. 7 Extracted metal–ligand complex in the organic phase.
The above complexation was further supported by FTIR and
H-NMR studies. FTIR of loaded organic indicated binding of
1
HNO
3
at amide group as evidenced by lowering of nC]O. The
ꢀ1
value of nC]O of the organic phase was 1639 cm
contact to aqueous phase. Aer contact with 450 mg L Mo in 1
M HNO
tion to the 1639 cm peak (Fig. 8). This lowering in nC]O can be
attributed to coordination of HNO to the amide C]O.
before
ꢀ1
ꢀ
1
3
, a shoulder for nC]O at 1554 cm appeared in addi-
ꢀ
1
3
To ascertain the binding site for Mo, organic phase con-
taining 0.2 M a-amino-acetamide 1 in 30% IDA/n-dodecane was
saturated with metal ion by giving sufficient number of contacts
ꢀ
1
with fresh 1 M HNO aqueous phase containing 450 mg L of
3
Mo. The resultant yellow precipitate of metal ligand complex in
the organic phase was ltered and the residue was washed with
chloroform. While recording H NMR of the solution of the
1
1
Fig. 9 (a) H NMR of a-amino-acetamide 1; (b) H NMR of complex of
1
2ꢀ
MoO
4
with a-amino-acetamide 1.
complex in CDCl
of the peaks corresponding to CH
4H, t, J ¼ 7.4 Hz, 2 ꢂ CH CH N) vs. 2.71–2.95 (4H, brs, 2 ꢂ
CH CH N) and 3.35 (2H, s, CH CO) vs. 3.6–3.78 (2H, brs,
CH CO) are clearly discernable indicating the exchange of
3
, a downeld shi of d values and broadening
2
a-to amine group viz. 2.53
(
2
2
3
.4 Back extraction studies
2
2
2
For back extraction studies the organic phase 0.2 M a-amino-
acetamide 1 in 30% IDA/n-dodecane was equilibrated with
aqueous phase containing 450 mg L of Mo dissolved in 0.5 M
nitric acid. Loaded organic phase was contacted with 10% NH
solutions. It was observed that 10% NH is suitable for 90%
2
2
ꢀ
MoO4 at ammonium site (Fig. 9).
ꢀ
1
3
3
recovery of molybdenum from loaded organic phase aer three
contacts.
4. Conclusions
In conclusion, a-amino-acetamides have been designed and
synthesized as a new class of anion exchangers to extract
molybdate anions from higher nitric acid medium. These
acetamides showed better extraction behavior compared to the
conventional only amine-based anion exchangers, Alamine 336,
Aliquat 336 and Primene JMT. The presence of amide group was
critical to this success because of its intramolecular buffering
effect. This study has highlighted the exact role of the amide
group in retaining the extraction ability at higher acidities.
Stoichiometry of metal ligand complex was ascertained by slope
analysis method and was found to be (LH)
and NMR of loaded organic indicated MoO
2
MoO
4
$HNO
exchanged at
3
. FTIR
2
ꢀ
4
ammonium site while buffering effect takes place at amide
group.
References
1
F. Poineau, J. D. Mazaubrun, D. Ford, J. Fortner, J. Kropf,
G. W. C. Silva, N. Smith, K. Long, G. Jarvinen and
K. Czerwinski, Radiochim. Acta, 2008, 96, 527.
Fig. 8 IR spectra of organic phase: (a) before contact; (b) loaded
organic phase.
2 R. Shanker and K. S. Venkateswarlu, Sep. Sci., 1976, 11, 591.
This journal is © The Royal Society of Chemistry 2014
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Paper
3
4
5
6
7
8
9
P. K. Parhi, K. H. Park, H. I. Kim and J. T. Park, 18 P. Nekov ´a ˇr and D. Schr ¨o tterov ´a , Chem. Eng. J., 2000, 79, 229.
Hydrometallurgy, 2011, 105, 195.
J. Marchese, F. Valenzuela, C. Basualto and A. Acosta,
Hydrometallurgy, 2004, 72, 309.
19 P. Nekov ´a [rbreve] and D. Schr ¨o tterov ´a , Solvent Extr. Ion
Exch., 1999, 17, 163.
20 T. Cosar and R. Ziyadanogullari, Turk. J. Chem., 1998, 22,
379.
J. Y. Lee, J. R. Kumar, H. S. Jeon and J. S. Kim, Chem. Eng.,
2
010, 54, 27.
21 E. Goralska, M. T. Coll, A. Fortuny, C. S. Kedari and
A. M. Sastre, Solvent Extr. Ion Exch., 2007, 25, 65.
22 M. C. Ali, T. Kawasaki, M. Nogami, M. Saeki, Y. Sasaki and
Y. Ikeda, Prog. Nucl. Energy, 2011, 53, 1005.
23 M. C. Ali, T. Suzuki, Y. Tachibana, Y. Sasaki and Y. Ikeda,
Sep. Purif. Technol., 2012, 92, 77.
24 Y. Sasaki, M. Ozawa, T. Kimura and K. Ohashi, Solvent Extr.
Ion Exch., 2009, 27, 378.
25 E. P. Horwitz, A. C. Muscatello, D. G. Kalina and L. Kaplan,
Sep. Sci. Technol., 1981, 16, 417.
L. E. Noronha, G. S. Kamble, S. S. Kolekar and M. A. Anuse,
Radiochim. Acta, 2013, 3, 15.
J. R. Kumar, J. S. Kim, J. Y. Lee and H. S. Yoon, J. Radioanal.
Nucl. Chem., 2010, 285, 301.
C. J. Kim, J. R. Kumar, J. S. Kim, J. Y. Lee and H. S. Yoon, J.
Braz. Chem. Soc., 2012, 23, 1254.
N. I. Gerhardt, A. A. Palant, V. A. Petrova and R. K. Tagirov,
Hydrometallurgy, 2001, 60, 1.
1
0 R. R. Rao and S. M. Khopkar, Analyst, 1983, 108, 346.
1
1 V. R. Bhandiwad, R. Swarup and S. K. Patil, J. Radioanal. 26 E. P. Horwitz, K. A. Martin, H. Diamond and L. Kaplan,
Nucl. Chem., 1979, 52, 5. Solvent Extr. Ion Exch., 1986, 4, 449.
2 M. Ghadiri, S. N. Ashrazadeh and M. Taghizadeh, 27 V. Kumar, J. N. Sharma, P. V. Achuthan and R. C. Hubli, RSC
Hydrometallurgy, 2014, 144–145, 151. Adv., 2014, 4, 805.
3 E. A. Mezhov, V. V. Druzhenkov and A. N. Sirotinin, 28 M. A. Olazabal, M. M. Orive, L. A. Fern ´a ndez and
Radiochemistry, 2002, 44, 146. J. M. Madariaga, Solvent Extr. Ion Exch., 1992, 10, 623.
4 D. Desideri, L. Feduzi, M. A. Meli and C. Roselli, Microchem. 29 A. S. Kertes, in Solvent extraction chemistry of metals, ed. H. A.
1
1
1
1
J., 2011, 97, 264.
C. McKey, T. V. Healy, I. L. Jetkins and A. Naylor, MacMillan,
London, 1965, p. 377.
5 H. Rameb ¨a ck, Y. Albinsson, M. Sk ˚a lberg, U. B. Eklund,
L. Kjellberg and L. Werme, J. Nucl. Mater., 2000, 277, 208.
6 A. Senol, Sep. Purif. Technol., 2014, 131, 35.
7 Y. Xu, S. Y. Kim, T. Ito, H. Tokuda, K. Hitomi and K. Ishii, J.
Chromatogr. A, 2013, 1312, 37.
30 A. Keshav, K. L. Wasewar, S. Chand and H. Uslu, Fluid Phase
Equilib., 2009, 275, 21.
1
1
27842 | RSC Adv., 2014, 4, 27837–27842
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