Effect of some reducing and complexing agents on the extraction behavior of technetium in the TBP-HNO3 system

Article abstract of DOI:10.1134/S1066362211030052

The effect of a series of complexing and reducing agents on the extraction-chemical behavior of technetium as applied to extraction splitting of uranium and plutonium in the Purex process was examined. Kinetic parameters of the catalytic decomposition of

Full text of DOI:10.1134/S1066362211030052

ISSN 1066-3622, Radiochemistry, 2011, Vol. 53, No. 3, pp. 256–263. © Pleiades Publishing, Inc., 2011.
Original Russian Text © A.B. Melent’ev, A.N. Mashkin, O.V. Tugarina, D.N. Kolupaev, B.Ya. Zilberman, I.G. Tananaev, 2011, published in Radiokhimiya,
2011, Vol. 53, No. 3, pp. 219 –224.
Effect of Some Reducing and Complexing Agents
on the Extraction Behavior of Technetium
in the TBP–HNO3 System
A. B. Melent’ev*a, A. N. Mashkina, O. V. Tugarinaa, D. N. Kolupaeva,
B. Ya. Zilbermanb, and I. G. Tananaev**c
a Mayak Production Association, Federal State Unitary Enterprise,
pr. Lenina 31, Ozersk, Chelyabinsk oblast, 456780 Russia; * e-mail: Melentev74@mail.ru
b Khlopin Radium Institute, Research and Production Association, Federal State Unitary Enterprise,
St. Petersburg, Russia
c Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
Received August 30, 2010
Abstract—The effect of a series of complexing and reducing agents on the extraction-chemical behavior of
technetium as applied to extraction splitting of uranium and plutonium in the Purex process was examined.
Kinetic parameters of the catalytic decomposition of N2H5NO3 under the action of Tc in the presence of these
agents were evaluated. Variation of the ratio of the oxidized and reduced Tc species in the course of the process
and in the hydrazine-free systems was determined. Reagents preventing oxidation of the reduced technetium
and decomposition of N2H5NO3 in nitric acid solutions (acetohydroxamic acid, hydroxylamine, ascorbic acid,
etc.), inhibiting the reduction of Tc with hydrazine nitrate (Н2О2, HN3, etc.), and known as complexing agents
toward quadrivalent actinides but indifferent to Tc were considered. The possibilities of using these reagents
for modifying the Tc behavior in the course of SNF extraction reprocessing with the aim to direct this element
to different process streams were discussed.
Keywords: SNF reprocessing, uranium/plutonium splitting, technetium, hydrazine nitrate, redox processes,
complexing agents
DOI: 10.1134/S1066362211030052
The presence of Tc strongly affects the course of
reductive splitting of uranium and plutonium in the
Purex process. Hydrazine nitrate used in this step as
stabilizer efficiently converts Тс to the nonextractable
Tc(IV) form, but Tc(IV) can undergo back oxidation to
Tc(VII), which leads to its circulation within the ex-
traction apparatus, excess consumption of the reduc-
tant, and worse process stability [1].
operation and favors removal of Tc into the plutonium
stream. Some complexones such as urea, on the con-
trary, do not interact with Tc but form stable com-
plexes with Pu and Np, so that it becomes possible to
perform the U/Pu splitting without altering the extrac-
tion behavior of Тс [3].
In this study we considered the effect exerted on the
Tc behavior in the TBP–HNO3–N2H5NO3 system by a
series of practically used or promising agents exhibit-
ing both complexing and reducing properties. In addi-
tion, we studied how these reagents affect the
N2H5NO3 decomposition in the presence of Тс or inter-
act with Tc in hydrazine-free systems.
To modify the behavior of Tc, additional agents
exerting complexing or mixed complexing/reducing
effect can be introduced into the system. The course of
the U/Pu splitting will largely depend on the perform-
ance of these agents and on their capability to fix Tc in
the reduced state.
EXPERIMENTAL
As shown previously [2], such complexing agents
as DTPA can inhibit the Тс(IV) oxidation and decrease
in a certain manner the degree of the N2H5NO3 decom-
position, which enhances the stability of the reduction
To study experimentally the variation of the ratio of
Tc valence forms in the course of the experiment and
the catalytic decomposition of N2H5NO3, to 1 M HNO3
256

EFFECT OF SOME REDUCING AND COMPLEXING AGENTS
257
solutions we added definite amounts of N2H5NO3,
Tc(VII) (in the form of HTcO4), and the tested com-
plexing/reducing agent. At definite time intervals after
the start of the experiments, aliquots were taken for the
analysis. The aliquots were brought in contact with
100% TBP preequilibrated with a solution containing
1 M HNO3. The phase ratio was kept equal to 1 : 1,
and the aqueous phase temperature, within 40 ± 1°С.
Analysis of the solution aliquots for Тс and N2H5NO3
and mathematical processing of the analysis results
were performed by the procedure used previously for
determining the ratio of the Tc valence forms and the
main parameters of the catalytic decomposition of
N2H5NO3 in nitric acid solutions in the presence of
DTPA and Н2С2О4 [2].
Similar parameters were considered for the systems
studied in this work: τ1/2, time at which a half of the
initial amount of N2H5NO3 ([N2H5NO3]0) decomposed;
Сf, fraction (% of [N2H5NO3]0) characterizing the re-
sidual (steady-state) amount of the reductant in the
final step of the reaction; τstab, time in which Сf was
attained; k', apparent rate constant of the N2H5NO3 de-
composition in the fast step of the reaction; Dmin and
Tc(VII)min, minimal distribution ratio of technetium
(DТс) in extraction with 100% TBP and minimal frac-
tion (%) of the oxidized form of Tc in the solution,
attained in the given experiment; Df and Tc(VII)f, DТс
Fig. 1. (a) Decomposition of N2H5NO3 and (b) variation of
the Тс(VII) fraction in nitric acid solutions in the presence
of additives. [Тс] = 2 × 10–3, [HNO3] = 1 M, 40°C; the
same for Figs. 2–4. [N2H5NO3] = 0.2–0.3 M. Additives
(0.05 M): (1) H2SO4, (2) AA, (3) СS(NH2)2, and (4) H2O2.
and content of the oxidized form of Tc in solution by [5]); СН3СООН and H2SO4; H2O2; hydroxylamine
the end of the experiment. The time that passed from nitrate (HAN); acetohydroxamic acid (AHA); urea and
the beginning of the experiment was designated as τ.
thiourea; halides and pseudohalides; and also β-hy-
droxyethylhydrazine (β-HEH) suggested previously as
reagent for plutonium reduction [6]. HAN and AHA
were prepared directly before experiments by proce-
dures of laboratory synthesis; the other chemicals were
of chemically pure grade.
Previously we found that, in the Тс–HNO3–
N2H5NO3 system, the minimal distribution ratio Dmin
of Tc was attained when the degree of the reductant
decomposition was close to 1/2 [4] However, in the
present study, with some reagents introduced into the
system, this relationship was not observed. Therefore,
we additionally took into account the parameter τDmin
characterizing the time in which Dmin was attained in
the course of the experiment.
RESULTS AND DISCUSSION
We found that, under the examined conditions, in-
troduction of such agents as H2SO4, CH3COOH, and
thiourea did not noticeably affect the course of the
N2H5NO3 decomposition. The process was, on the
whole, similar to that occurring in the base system
without additives, whose behavior was considered in
more detail in the previous study [2]. At the same time,
it was noted that, with sulfuric acid additive, the induc-
tion period usually observed in catalytic decomposition
of N2H5NO3 was practically absent (Fig. 1a, curve 1);
therefore, τ1/2 was as short as 1 h. At the same time, Сf
and k' were comparable to those observed in the base
The absorption spectra of the solutions were re-
corded in the visible and near-UV ranges with a
Perkin–Elmer Lambda 35 spectrophotometer. Solution
aliquots taken for the spectrophotometry were prelimi-
narily cooled to 0°С, which allowed the N2H5NO3 de-
composition and concomitant gas evolution negatively
affecting the spectrum quality to be practically fully
stopped.
As complexing or complexing/reducing agents we
used ascorbic acid behaving as reductant toward Тс
RADIOCHEMISTRY Vol. 53 No. 3 2011

258
MELENT’EV et al.
Table 1. Summary of data on the effect of various substances on the redox behavior of Tc and oxidation of hydrazine nitrate.
Solution components: [Tc] = 2 × 10–3, [HNO3] = 1.0, [reagent] = 0.05 M; 40°C; the same for Table 2
Initial parameters of systems
N2H5NO3 decomposition
Tc behavior
Reagent
N2H5NO3, M τ1/2, h τstab, h Cf, % k', h–1 τDmin, h Dmin Tc(VII)min, %
Df
Tc(VII)f, %
None
AHA
HAN
AA
0.24
0.26
0.26
0.30
0.20
0.21
0.20
0.30
0.25
0.25
0.23
0.05
0.05
0.20
0.28
0.30
1.6
3.0
–
–
10
–
–
13
51
6
10
5
7
6
8
56
25
62
99
37
0.83
–
–
1.5
1.5
3.0
2.0
1.0
1.5
1.5
1.5
1.5
1.5
1.5
2.0
1.0
2.0
3.0
1.5
<0.10
0.15
0.20
<0.10
0.16
0.14
0.13
0.12
0.28
0.77
0.59
7.94
1.52
13.8
19.2
0.42
<1
4
9
<1
7
4
4.2
82
24
21
3
b
–
–
0.43
0.38
0.13
0.41
5.7
b
2.4 >6.0c
0.82
0.36
1.67
1.11
1.12
1.60
1.73
1.50
0.09
0.64
0.28
–
Thiourea
Urea
H2SO4
СН3СООН
F–
2.9
1.3
1.1
1.4
1.1
1.4
1.5
3.0
3.0
23
86
83
87
84
69
86
98
97
97
98
35
2.5
3.0
2.5
2.5
2.5
>6.0c
3.0
3.0
0.0
3
2
4.7
6.22
5.06
2.35
5.79
15
39
32
90
58
95
97
23
Cl–
N3–
d
N3–
–
23.4
N3– а
1.0
19.1
19.0
23.4
CNS–
H2O2
–
–
d
d
β-HEH
4.0 >6.0c
0.19
0.67
a
Reagent concentration 0.025 M.
Analysis for N2H5NO3 content was not performed
The N2H5NO3 content decreased throughout the monitoring period, but after τ = 3 h the hydrazine nitrate oxidation considerably
decelerated.
b
c
d
Decomposition of 1/2 of [N2H5NO3]0 was not attained in the monitoring period.
system (Table 1). In the presence of acetic acid and
urea, the induction period was well pronounced, as in
the system without additives.
traction behavior of Тс (Figs. 1a and 1b, curves 2–4).
For example, addition of 0.05 M Н2О2 fully prevented
formation of nonextractable Tc species, and N2H5NO3
decomposition was not observed.
The maximal yield of the reduced Тс in the systems
in which the effect of additives was insignificant was
observed at τ1/2; at that moment, the residual content of
Тс(VII) was 2, 3, and 4% in the presence of H2SO4,
CH3COOH, and urea, respectively. Also, appreciable
oxidation of the reduced Tc under the action of the
nitric acid medium was observed in these systems. As
in the base system, the process practically stopped af-
ter reaching τstab, when the reductant content in the so-
lutions stabilized on a definite level. For the system
with urea, the parameter Сf characterizing this state
was 6%, and with H2SO4 it was 10%. Variation of the
fraction of Тс(VII) in the reaction with N2H5NO3 in the
presence of the above additives (with H2SO4 as exam-
ple) is shown in Fig. 1b (curve 1). It should be noted
that, after keeping the solutions for 6 h, the Тс(VII)
content exceeded 80% in all the systems where the
effect of additives was not manifested (Table 1).
On adding thiourea [СS(NH2)2], technetium rapidly
(τDmin = 1 h) passed into the reduced state. The subse-
quent oxidation of Тс was minimal, and, after reaching
τstab equal to 3 h, the Тс(VII) content kept on the level
of 23%. The reagent also exerted a strong protective
effect on the reductant: Its decomposition was consid-
erably inhibited, and Сf was 51% (Table 1). These ef-
fects were apparently caused by the fact that thiourea
not only exhibits reducing properties, but also forms
stable compounds with reduced technetium [7].
Ascorbic acid (AA) exerted a similar but more pro-
nounced effect on Tc. In the presence of this reagent,
noticeable oxidation of the reduced Tc was not ob-
served throughout the observation period. The Тс(VII)
fraction at τ = 6 h was as low as 3%, i.e., the stabiliz-
ing power of AA in mixtures with N2H5NO3 is very
high. At the same time, N2H5NO3 was consumed more
intensely than in the above-considered system with
thiourea. At τ = 3 h, the N2H5NO3 decomposition rate
Some reagents, on the contrary, significantly af-
fected both the reductant decomposition and the ex-
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EFFECT OF SOME REDUCING AND COMPLEXING AGENTS
259
Table 2. Reduction of technetium with various agents in the
decreased considerably, but full stabilization (cessation
of N2H5NO3 decomposition), as in the other systems,
was not observed. Gradual decomposition of the reduc-
tant continued even 6 h after the start of the experiment
(Fig. 1a, curve 2).
absence of hydrazine nitrate
Tc(VII) fraction, %, after
Reagent con-
keeping for indicated time, h
Reagent
HN3
AA
AHA
HAN
DTPA
Urea
CH3COOH
centration, M
2
4
6
0.10
0.05
0.10
0.10
0.05
0.10
0.05
0.11
99
<1
98
97
97
98
99
42
99
<1
96
95
95
98
99
<1
98
<1
93
91
94
98
99
<1
It should also be noted that AA exhibits strong in-
trinsic reducing properties with respect to Tc. The re-
duction of pertechnetate ion under the action of AA in
a hydrochloric acid medium was studied in detail pre-
viously [8]. In this study we showed that, in nitric acid
solutions without N2H5NO3, in the presence of 0.05 M
AA, on keeping the system for more than 2 h, Тс(VII)
was practically completely converted into the reduced
form nonextractable with TBP. The fraction of the re-
duced Тс remained on the attained level for a long time
(Table 2).
β-HEH nitrate
tant was not attained throughout the observation period
(Table 1). At the same time, the presence of colored
compounds, untypical of Тс(VII), in both the aqueous
and organic phases suggests the occurrence of more
complex processes in the system.
The course of the N2H5NO3 decomposition in the
presence of halides was, on the whole, similar to the
systems without additives. At the same time, in solu-
tions containing fluoride ion, the induction period
decreased relative to the system with chloride ions
(Fig. 2a, curves 1, 2). For these systems, τ1/2 was equal
to 1.1 and 1.4 h, respectively (Table 1).
The data obtained in the experiments with azide
ions confirm the previously revealed protective effect
It was noted that halides decrease the yield of the
reduced Tc: In the presence of fluoride and chloride
ions, the Тс(VII)min fraction was 15 and 27%, respec-
tively. The additives also affected the fraction of the
reduced Tc remaining in the final step of the reaction.
The parameter Тс(VII)f appeared to be the smallest
with chloride ions: 69%. These facts suggest that hal-
ides present in the system can shift the equilibrium in
the redox cycles observed with Tc in these media.
Similar effect was observed with pseudohalides. In
the presence of 0.05 M azide ions, the N2H5NO3 de-
composition occurred similarly to the systems with
halides, also with decreased degree of Tc reduction
(Fig. 2b, curve 4). Introduction of azide ions into the
systems in amounts corresponding to the ratios
N2H5NO3 : N3– = 2 : 1 and 1 : 1 led to further decrease
in the degree of Тс(VII) reduction. The parameter
Тс(VII)min was 58% in the first case and 90% in the
second case, after which both systems returned to the
initial state (Fig. 2b, curve 5; Table 1). The reductant
after τ = 3 h decomposed at a considerably lower rate
than in the fast step of the reaction, and Сf was 56%
(Fig. 2a, curve 5). Introduction of thiocyanate ions ex-
erted a similar effect. It should be noted that, in the
process, technetium remained practically fully in the
extractable form, and half decomposition of the reduc-
Fig. 2. (a) Decomposition of N2H5NO3 and (b) variation of
the Тс(VII) fraction in nitric acid solutions in the presence
of halides and pseudohalides. [N2H5NO3], M: (1–4) 0.23–
0.25 and (5) 0.05. Additives (0.05 M): (1) F–, (2) Cl–,
(3) CNS–, and (4, 5) N3–.
RADIOCHEMISTRY Vol. 53 No. 3 2011

260
MELENT’EV et al.
preceding the fast step of the Tc reduction. In both sys-
tems, we noted relatively high yield of reduced techne-
tium species. The parameter Тс(VII)min was 4 and 9%
in the systems with AHA and HAN, respectively. It
should be noted that the curve reflecting variation of
the Тс(VII) content in the system with HAN was less
steep than in the system with AHA (Fig. 3, curves 1
and 2). The minimum in the Тс(VII) content was at-
tained at τDmin = 3 h; at the same time, the values of
D
Тс were relatively low already in 2 h after the start of
the experiment (Table 1).
Fig. 3. Variation of the Тс(VII) fraction in the reaction with
N2H5NO3 in nitric acid solutions in the presence of AHA
and HAN. [N2H5NO3], M: (1, 2) 0.26 and (3, 4) 0. Addi-
tives: (1) HAN, 0.05 M; (2) AHA, 0.05 M; (3) HAN,
0.1 M; and (4) AHA, 0.1 M.
Reliable retention of Tc in the reduced nonex-
tractable form under the action of AHA and HAN may
be due to the occurrence of a complex reaction of re-
ductive nitrosylation of Tc in the presence of these re-
agents with the formation of a series of stable com-
pounds. For example, Gong et al. [12] showed that, in
a nitric acid solution in the presence of AHA, the com-
plex [Tс(NO)(AHA)2H2O]+, nonextractable with TBP,
is formed via several intermediates. The Тс(IV) ions
are considerably more reactive in the process and more
susceptible to reductive nitrosylation than Тс(VII).
The near-UV and visible absorption spectra of the
solution containing AHA in the initial reaction step
(Fig. 4, curves 1 and 2), on the whole, reproduced the
absorption spectra of the system without additives un-
der similar conditions. In 1.5 h after the start of the
experiment in the system with AHA, the optical den-
sity of the solution increased, with a maximum ob-
served at λ = 470 nm (Fig. 4, curve 3). This peak ap-
parently characterizes a Tc complex compound formed
in the process. Further keeping of the solution was ac-
companied by a slow decrease in the optical density
throughout the examined wavelength range (Fig. 4,
curves 4 and 5). In the system without additives at τ =
1.5 h, the absorption maximum at λ = 470 nm was ab-
sent (Fig. 4, curve 6). The spectra similar to those ob-
served in the Тс–HNO3–N2H5NO3–AHA system at
τ > 1.5 h are known for the product of the reaction of
NH4TcO4 with a mixture of AHA and HAN [12].
Fig. 4. Variation of the absorption spectra of Tc in the
presence of N2H5NO3 and AHA. [N2H5NO3] = 0.26 M.
Time from the start of the experiment, h: (1) 0, (2) 0.5,
(3, 6) 1.5, (4) 2, and (5) 4. AHA added, M: (1–5) 0.05 and
(6) 0.
of hydrogen azide (product of catalytic decomposition
of N2H5NO3 in the systems under consideration) to-
ward N2H5NO3, which may be due to competition be-
tween these compounds for the reaction with HNO2,
also playing an important role in catalytic cycles in-
volving Тс [3, 9]. Introduction of N–3 into the Тс-
containing nitric acid solutions under the examined
conditions without N2H5NO3 did not affect the fraction
of Тс(VII) (Table 2).
The reaction of Tc with HAN cal also yield several
complex products [13, 14]. It should be noted that
AHA in a nitric acid solution undergoes hydrolysis to
HAN and acetic acid [15], which further complicates
the reaction pattern in the system.
Systems with additions of AHA and HAN should
be considered in more detail, because these agents can
both affect Tc in mixtures with hydrazine nitrate and
exert a reducing effect independently [10, 11]. Here we
present the refined data on the behavior of Tc in the
presence of AHA and HAN (Fig. 3).
These facts suggest that accumulation of Тс(IV) in
the initial step of the reaction under the action of hy-
drazine nitrate in a nitric acid solution can lead subse-
quently to fast formation of stable compounds of Tc
In the presence of AHA and HAN in the hydrazine-
containing systems, we observed an induction period
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EFFECT OF SOME REDUCING AND COMPLEXING AGENTS
261
Today the traditional way of uranium/plutonium
splitting is reduction of plutonium to a nonextractable
state, which is attained, as a rule, under the action of
U(IV). The process is performed in the presence of
hydrazine nitrate, with technetium removed together
with the nonextractable Pu form and then separated
from Pu in the corresponding refining cycle. However,
the use of N2H5NO3 gives rise to certain problems. The
most serious problem is contamination of the solutions
with undesirable products of decomposition of this
reductant, namely, with the already mentioned azide
and also ammonium compounds, which makes utiliza-
tion of the raffinates obtained fire- and explosion-
hazardous [17]. Also, under the conditions of hydra-
zine deficiency, characteristic of some zones of extrac-
tion apparatuses, technetium can be partially oxidized
again, leading to disturbances of the reduction process
[18].
(in lower oxidation states) both with AHA and with
HAN, so that the major fraction of Tc is fixed in the
nonextractable state.
The pattern we observed can also be accounted for
by blocking of the autocatalytic decomposition of hy-
drazine owing to fast scavenging of the generated ni-
trogen oxides (NO, NO2), which are reduced to N2 or
N2O.
In the systems without hydrazine nitrate in the pres-
ence of AHA and HAN, the technetium reduction un-
der the examined conditions, on the contrary, was
rather slow, with the Тс(VII) fraction decreasing uni-
formly throughout the experiment (Fig. 3, curves 3 and
4). After 6 h of the reaction, the Тс(VII) fraction was
93 and 91% for the solutions with AHA and HAN,
respectively (Table 2).
Gradual and insignificant decrease in the Тс(VII)
fraction on keeping for 6 h was also noted in the hy-
drazine-free system with the addition of DTPA. Appar-
ently, this reagent is not only a complexing agent for
Тс reduced, e.g., under the action of N2H5NO3, but
also a weak reductant.
Introduction into the stripping solution of complex-
ing agents used today, e.g., of DTPA [19], somewhat
decreases the rate of hydrazine nitrate oxidation, which
allows only partial solution of the problem of the proc-
ess instability [2]. Therefore, search for flowsheets in
which hydrazine will be used to a smaller extent or
abandoned at all remains topical.
Urea and acetic acid in hydrazine-free systems ex-
erted no reducing effect on technetium under the con-
ditions of the experiment (Table 2). β-HEH suggested
as alternative to hydrazine nitrate and forming no un-
desirable decomposition products [16] ensured com-
plete reduction of Тс(VII), but the process was, on the
whole, slower than with N2H5NO3 (Table 1). At τ =
2 h, the Тс(VII) fraction in the system was 42%. The
maximal yield of the reduced Tc was observed after
keeping for 4 h (Table 2). At the same time, a mixture
of hydrazine and β-HEH reduces Тс rapidly and com-
pletely, and the N2H5NO3 decomposition rate in the
presence of β-HEH is considerably lower than in the
base system, with only weak back oxidation of Tc
(Table 1). The observed pattern is similar to that in mix-
tures of hydrazine with AHA, HAN, or ascorbic acid
and is apparently caused by the same factors. Because
complexation of β-HEH with Тс(IV) can hardly be as-
sumed, the alternative mechanism gains additional sup-
port, but studies in this field should be continued.
The use of AHA and HAN as stabilizing agents can
ensure in the presence of N2H5NO3 reliable fixation of
Tc in the nonextractable state, which should apprecia-
bly reduce the hydrazine nitrate consumption. Another
important factor is that the decomposition products of
AHA and HAN contain no substances complicating
the subsequent solution reprocessing.
Among reagents alternative to hydrazine nitrate but
ensuring complete reduction of Tc under the condi-
tions of the experiment are β-HEH and ascorbic acid.
AA behaves as reductant when taken both separately
and in combination with N2H5NO3, which allows it to
be considered, in particular, as complexing agent for
Тс. Whereas the rate of technetium reduction with
ascorbic acid is sufficiently high, the rate of techne-
tium reduction with β-HEH is relatively low and can
be insufficient for complete reduction of Tc in fast ex-
traction processes. To attain the acceptable characteris-
tics, more severe conditions (e.g., elevated tempera-
ture) are required than when performing the corre-
sponding operations within the framework of the Purex
process. At the same time, possible effect of AA de-
composition products in nitric acid solutions on the
course of reductive U/Pu splitting can also restrict the
applicability of this reagent in the industrial process.
The results given in this paper can be important for
the development of new or modification of existing
technologies for extractive reprocessing of SNF, so as
to control by using combinations of reducing and com-
plexing agents the extraction behavior of SNF compo-
nents being separated [3].
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MELENT’EV et al.
In contrast to the above reagents, hydrogen perox-
N2H5NO3–AHA, N2H5NO3–HAN, or N2H5NO3–
β-HEH mixtures, as well as other high-performance
reducing and complexing agents.
ide practically fully blocked the technetium reduction
in nitric acid solutions. This may be due to the effect of
this reagent on the initial steps of the technetium cata-
lytic cycle, preventing generation of Тс(IV) in an
amount sufficient for the normal progress of the reac-
tion of Tc with hydrazine nitrate. The reaction is also
inhibited by azide ions formed by decomposition of
hydrazine.
ACKNOWLEDGMENTS
The study was supported by the Russian Founda-
tion for Basic Research, project no. 09-08-00153-а.
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A number of other substances known as complex-
ing agents appeared to be practically indifferent to the
technetium reduced with hydrazine. For example, urea
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