Mechanism and kinetics of Rh(IV) radiation-chemical reduction in HNO 3 solutions

Article abstract of DOI:10.1023/A:1022313300868

Reduction of Rh(IV) in γ-irradiated and nonirradiated solutions of HNO₃ (0.3-3.0 M) was studied. In both systems, Rh(IV) is completely reduced to Rh(III). The reduction rates in nonirradiated solutions amount to 50-90% of rates in irradiated so

Full text of DOI:10.1023/A:1022313300868

Radiochemistry, Vol. 45, No. 1, 2003, pp. 33 39. Translated from Radiokhimiya, Vol. 45, No. 1, 2003, pp. 32 37.
Original Russian Text Copyright 2003 by Vladimirova, Khaperskaya.
Mechanism and Kinetics of Rh(IV) Radiation-Chemical
Reduction in HNO3 Solutions
M. V. Vladimirova and A. V. Khaperskaya
Bochvar Research Institute of Inorganic Materials, State Scientific Center of the Russian Federation,
Moscow, Russia
Received January 28, 2002
Abstract Reduction of Rh(IV) in -irradiated and nonirradiated solutions of HNO3 (0.3 3.0 M) was studied.
In both systems, Rh(IV) is completely reduced to Rh(III). The reduction rates in nonirradiated solutions
amount to 50 90% of rates in irradiated solutions. Reduction of Rh(IV) with water is postulated. The rates
of Rh(IV) reduction in both irradiated and nonirradiated solutions increase with [Rh(IV)] growth and decrease
with an increase in [HNO3] from 0.5 1 to 2 3 M. The dependence of the reduction rates on the dose rate is
weak. Mathematical simulation was used to reveal the mechanism and kinetics of radiation-chemical reduction
of Rh(IV) in HNO3 solutions. The rate constant of Rh(IV) reduction with water was calculated by fitting to
the experimental data.
Rhodium has several oxidation states, and in nitric
acid solutions of the irradiated nuclear fuel it should
undergo redox transformations. Published data on the
rhodium radiolytic behavior are scarce. In [1, 2] we
sodium bismuthate [3]. The Rh(IV) concentration was
monitored spectrophotometrically using an absorption
band at 550 nm with the extinction coefficient of 4.0
10 l mol cm [4] on a Perkin Elmer Lambda 40
recording spectrophotometer. The error of determina-
tion of the Rh(IV) concentration was 5%.
2
1
1
studied the behavior of Rh(III) and Rh(IV) in HNO
3
and HClO and found that Rh(IV) is reduced in both
4
irradiated and radiation-free solutions. In HClO solu-
60
4
The rhodium solutions were irradiated with a Co
tion containing ethanol, isopropanol, or butanol,
Rh(III) is reduced to metallic Rh in the form of rhodi-
um black. The Rh(IV) reduction yields obtained in [2]
are characterized by a large scattering and do not
1
-ray source at a dose rate from 0.4 to 1.1 1.4 Gy s .
The radiation dose was determined by the ferrosulfate
method. Two samples were studied simultaneously:
one was irradiated and the second (blank) was radia-
tion free.
show clear dependences on the rhodium and HNO
concentrations.
3
Reduction of Rh(IV) in blank experiments. The
kinetics of Rh(IV) reduction was studied at various
In this work, we studied the reduction of Rh(IV) in
0.5 3 M HNO without radiation (blank experiment)
3
concentrations of Rh and HNO . Some of the results
60
3
and under irradiation with Co -quanta at widely
are listed in Table 1. As seen, the rhodium(IV) con-
varied initial parameters. A mathematical model of
radiolysis of Rh nitric acid solutions was developed,
and the Rh(IV) concentrations were calculated for
various experimental conditions. It was shown that
this model adequately describes the experimental data.
Basing on the calculations, we interpreted the results
obtained, found the yield of Rh(IV) reduction, and
proposed the mechanism of radiation-chemical proc-
esses.
Table 1. Variation of Rh(IV) concentration in blank
experiments (22 25 C)
[HNO3], M
Time,
min
0.5
1.0
2.0
3.0
[Rh(IV)] 103, M
0
5
10
15
75
1.87
1.76
1.65
1.55
1.17
0.98
0.58
1.92
1.81
1.72
1.63
1.28
1.10
0.60
1.95
1.83
1.73
1.65
1.31
1.10
0.60
1.96
1.83
1.75
1.60
1.23
1.02
0.57
EXPERIMENTAL
The initial solution of Rh(III) nitrate was prepared
from a commercial (pure grade) solution of Rh(NO )
3 3
2
by dilution to (2 4) 10
M and addition of
135
1155
HNO to 2 3 M. Solutions of Rh(IV) were prepared
3
by Rh(III) oxidation in HNO solution with solid
3
1066-3622/03/4501-0033$25.00 2003 MAIK Nauka/Interperiodica

34
VLADIMIROVA, KHAPERSKAYA
Table 2. Variation of Rh(IV) concentration in irradiated solutions
[Rh(IV)] 103, M, at indicated [HNO3], M
Time, min
0.5
1.0
2.0
3.0
0.5
1.0
2.0
3.0
1
1
D = 0.4 Gy s
D = 1.4 Gy s
0
12
24
36
2.64
2.26
1.83
1.45
2.72
2.48
2.02
1.75
2.75
2.74
2.41
2.08
1.81
2.64
2.11
1.55
1.21
2.72
2.34
1.94
1.58
2.75
2.44
2.05
1.66
2.74
2.28
1.85
1.60
2.55
2.18
1.90
centration decreases with time and is virtually in-
formal reaction:
Rh(IV) + H2O
The rate of reaction (1) is
d[Rh(IV)]/dt = K1[Rh(IV)][H2O].
dependent of HNO concentration at a given time of
3
storage. In 2 h, the Rh(IV) concentration decreases by
a factor of 2, i.e., the reduction rate is relatively high.
We believe that Rh(IV) is reduced with water. Such a
reaction is thermodynamically feasible because, in
the blank run, the redox potential of the H O/O
Rh(III).
(1)
(I)
2
2
couple (E = 1.229 V) is less positive than that of the
Rh(IV)/Rh(III) couple (E = 1.4 V). It follows from
kinetic curves that the reaction order with respect to
rhodium is unity, which corresponds to the following
To calculate the rate constant of reaction (1), K ,
1
we used a model of radiolysis of aqueous solutions
described in [5]. At a dose rate equal to zero, for given
[H O] and [Rh(IV)], we preset various values of K ,
2
1
calculated the running Rh(IV) concentrations, and
compared with the experiment. For 0.5, 1, 2, and 3 M
HNO , the water concentration of 54.4, 53.8, 52.1, and
3
49.8 M, respectively, was used in calculations. Curves
calculated for various K are shown in Figs. 1 and 2.
1
As seen, the calculated and experimental values are
6
1
1
in good agreement at K = (3 4) 10 l mol cm
1
for nitric acid concentration of 0.5 M and 3
10 l mol cm for 2 M. The K values were re-
6
1
1
1
fined in experiments with irradiated solutions. The
best agreement with the experiment was obtained at
Fig. 1. Kinetics of Rh(IV) reduction in 0.5 M HNO in
3
6
blank experiments: (1 3) calculated at K = 2 10
,
1
6
6
1
1
6
6
1
1
3
10 , and 4 10 l mol
s
, respectively; (points)
K 4 10 and 3 10 l mol cm for 0.5 1 and
1
experiment.
2 3 M HNO , respectively.
3
It follows from the calculation that, at [Rh(IV)]
3
3
3
1 10 , 2 10 , and 5 10 M and [H O] 54 M the
2
rates of rhodium(IV) reduction with water ( = 1 h)
4
4
4
1
1
are 1.5 10 , 3.0 10 , and 7.5 10 mol l h ,
respectively, and 97% reduction in all cases is attained
within 20 h.
Rh(IV) reduction in irradiated solutions. Several
series of experiments on Rh(IV) reduction kinetics
were performed: at a given dose rate (0.4, 1.1
1
1.4 Gy s ), constant [HNO ], and variable rhodium
3
concentration; at a given dose rate, constant [Rh(IV)],
Fig. 2. Kinetics of Rh(IV) reduction in 2.0 M HNO in
3
6
and variable [HNO ]; and at given [Rh(IV)], and
blank experiments: (1 3) calculated at K = 2 10
,
3
1
6
6
1
1
[HNO ] and variable dose rate. Some of the data ob-
3
10 , and 4 10 l mol
s
, respectively; (points)
3
experiment.
tained are listed in Table 2.
RADIOCHEMISTRY Vol. 45 No. 1 2003

MECHANISM AND KINETICS OF Rh(IV) RADIATION-CHEMICAL REDUCTION
35
Table 3. Experimental and calculated rates of Rh(IV) reduction V in irradiated and nonirradiated solutions at t = 12
20 min
1
1
1
[HNO3]
[Rh(IV)] 103
D = 0 Gy
D = 0.4 Gy s
D = 1.4 Gy s
calculated
experimental
calculated
experimental calculated experimental
M
1
1
V 105, mol l min
0.5
1.0
2.0
2.0
2.0
2.0
3.0
2.64
1.92
0.35
1.86
2.75
4.87
2.74
3.0
2.1
0.2
1.3
2.3
3.7
2.2
3.5
2.0
3.15
3.6
3.4
2.5
0.42
2.3
2.8
4.5
3.1
4.4
2.9
0.37
2.0
2.6
4.3
3.8
2.1
2.4
2.4
2.5
2.4
2.8
Table 4. Scheme of radiation-chemical reactions in nitric acid solutions of rhodium
1
Reaction no.
Reaction
Rate constant, l mol 1 s
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Rh(IV) + H2O
Rh(III)
See Table 5
2.4 1010 [7]
2.0 1010 [7]
6.0 106 [7]
5.0 105 [7]
2.0 1010 [7]
8.0 105 [7]
1.0 108 [8]
See Table 5
1.0 107 [9]
See Table 5
1.4 108 [8]
See Table 5
5.0 1010 [10]
1.0 108*
eaq + H+
H
NO3 + eaq
NO3 + H
NO3 + OH
H + O2
NO2
NO2
NO3
HO2
HO2 + HO2
NO2 + NO2 + H2O
HNO2 + HNO3
HNO2 + NO3
HNO2 + H2O2
HNO3 + OH
H2O2 + O2
HNO2 + HNO3
NO2 + NO2
NO2
HNO3
NO3
4HNO2
N2O4 + 2NO
Rh(IV) + eaq
Rh(IV) + H
Rh(III)
Rh(III) + H+
Rh(IV) + HO2
Rh(IV) + H2O2
Rh(IV) + HNO2
Rh(III) + OH
Rh(III) + NO3
Rh(III) + O2 + H+
Rh(III) + HO2 + H+
Rh(III) + NO2 + H+
Rh(IV) + OH
1.0 105*
4
2.5 10 [11]
See Table 5
1.0 109*
Rh(IV) + NO3
1.0 106*
* Probable values.
As seen, at the chosen irradiation time in 1 3 M
of Rh(IV) reduction with water and small variation of
the rhodium concentration.
HNO , the Rh(IV) concentration only slightly depends
3
on the dose rate. The experimental rates of Rh(IV)
To find the kinetic parameters of radiation-chemi-
cal reduction of rhodium(IV), we used mathematical
simulation.
reduction as functions of the dose rate and HNO and
3
Rh(IV) concentrations are presented in Table 3.
With regard to rhodium(IV) reduction in blank ex-
periments, we calculated the radiation-chemical yields
of Rh(IV) reduction for various experimental condi-
tions and found that they vary within almost an order
of magnitude. This is caused by a large contribution
Mathematical model. We took the model of
HNO radiolysis [5, 6] as a basis and added reactions
3
involving Rh(IV) and Rh(III). All the reactions are
listed in Table 4.
RADIOCHEMISTRY Vol. 45 No. 1 2003

36
Table 5. Variable parameters of the model
Values at indicated [HNO3], M
1.0 2.0
Radiation-chemical yields, particles/100 eV ( -radiolysis)
VLADIMIROVA, KHAPERSKAYA
Parameter
References
0.5
3.0
G(eaq)
G(H2)
G(H2O2)
G(OH)
G(NO2)
G(NO3)
5.2
0.15
1.0
3.5
0.12
0.12
5.9
0.1
1.1
3.3
0.3
0.3
6.0
0.05
1.2
3.0
0.35
0.35
6.2
0.04
1.2
2.8
0.7
0.7
Rate constants*
6
6
6
6
K
4.0 10
0.007
1.0 103
25
4.0 10
0.015
2.5 103
75
3.0 10
3.0 10
0.04
**
1
K9
0.025
5.0 103
100
[12], [13]
[12], [14]
[12]
K11
K13
K18
7.5 103
125
82
41
21.3
14.7
***
1
1
3
3
1
* Dimension: K , K , K , K , l mol
s
; K , l mol
s .
1
9
11
18
13
** This work.
*** Our calculation from data of [15].
For calculations, the model parameters (radiation-
chemical yields of products and rate constants of ele-
mentary stages) and external parameters [concentra-
equation
d[Rh(IV)]/dt = K17[Rh(IV)][H2O2].
(II)
+
tions of H , NO , HNO , and Rh(IV), dose rate, and
3
3
The rate constant K is independent of acidity and
is equal to 2.5 10 l mol
17
time of irradiation] should be given.
4
1
1
s
[11].
In HNO radiolysis, e , H, OH, NO , and NO
3
3
aq
2
The kinetics of reaction (18) was studied in [15]. It
was found that the reaction rate is described by the
equation
radicals and H O and H molecules are formed as
2
2
2
primary products. HNO is the secondary product of
2
reaction (8). The radiation-chemical yields of primary
products of HNO radiolysis and rate constants of
3
d[Rh(IV)]/dt = K18[Rh(IV)][HNO2]/[H+].
(III)
reactions depending on [HNO ] are listed in Table 5.
3
1
The kinetics of reaction (17) was studied in [11]. It
was found that the reaction rate is described by the
K
= 41 s at 25 C [15].
18
Using this value of the constant, we calculated
K , l mol s , for the given H concentration
1
1
+
18
with regard to the degree of nitric acid dissociation
(Table 5).
CALCULATION RESULTS
Using the model parameters, we calculated the
Rh(IV) concentrations in irradiated and nonirradiated
solutions and the rates of its reduction from the time
dependences of the calculated concentrations. The
results are presented in Figs. 3 6 and in Table 3. As
seen, the calculated values are in satisfactory agree-
ment with the experiment. This correlation indicates
that the scheme of reactions in Table 4 adequately
Fig. 3. Kinetics of Rh(IV) reduction in 0.5 M HNO in
3
irradiated solutions: (1, 2) calculated at D = 0.4 and
1
1.08 Gy s , respectively; (points) experiment.
RADIOCHEMISTRY Vol. 45 No. 1 2003

MECHANISM AND KINETICS OF Rh(IV) RADIATION-CHEMICAL REDUCTION
describes radiation-chemical processes in nitric acid
37
solutions of rhodium and that the rate constants and
radiation-chemical yields of HNO radiolysis products
3
are correct.
Let us analyze data of Table 3. It is seen that, in
most cases, the calculated and experimental rates for
both irradiated and nonirradiated solutions are fairly
close. However, in some cases the disagreement is
substantial. This may be connected with the influence
of the temperature on the rate of reaction (1) whose
3
contribution at [Rh(IV)] > 0.35 10 M, as seen
Fig. 4. Kinetics of Rh(IV) reduction in 1.0 M HNO in
from Table 3, amounts to 70 90% of the rates in ir-
radiated solutions (in our experiments, the temperature
of solutions was not controlled). However, we may
definitely conclude that the rate of rhodium(IV) reduc-
3
irradiated solutions: (1 3) calculated at D = 0.4, 1.4, and
1
1.08 Gy s , respectively; (points) experiment.
tion decreases when [HNO ] increases from 0.5 to
3
2 3 M at given [Rh(IV)]; it increases approximately
in proportion with the rhodium concentration and
weakly depends on the radiation dose rate because of
major contribution of the chemical reduction with
water.
To reveal the role of particular radiation-chemical
reactions in Rh(IV) reduction and Rh(III) oxidation
and to find the radiation-chemical yields of Rh(IV)
reduction, we calculated the rates of these reactions at
Fig. 5. Kinetics of Rh(IV) reduction in 2.0 M HNO in ir-
varied [Rh(IV)], dose rate, and integral dose of the
3
1
3
radiated solutions: (1, 2) calculated at D = 1.4 and 1.08 Gy s
,
radiation. The results for [Rh(IV)] 2.6 10
M,
respectively; (points) experiment.
1
2
D 0.4 Gy s , and dose of 1.5 10 Gy are listed in
Table 6. The rate of rhodium(IV) reduction with hy-
drogen peroxide (17) was not given, since it is many
times lower than the rates of the other reactions. The
low rate of reaction (17) is caused by both small value
of K (2 10 l mol s ) and low concentration of
H O , which is decomposed, reacting with HNO
4
1
1
17
2
2
2
[reaction (11)]. The equations for the rate of the
Rh(IV) radiation-chemical reduction are as follows:
d[Rh(IV)]/dt = d[Rh(III)]/dt = [Rh(IV)](K14[eaq]
Fig. 6. Kinetics of Rh(IV) reduction in 3.0 M HNO in ir-
3
+ K15[H] + K16[HO2] + K18[HNO2]) [Rh(III)](K19[OH]
radiated solutions: (1 4) calculated at D = 0.4, 1.4, 1.4, and
1.08 Gy s , respectively; points are experimental.
1
+ K20[NO3]),
(IV)
It follows from Table 6 that reactions with HO
2
radicals and HNO [reactions (16) and (18)] make the
Vrch = V14 + V15 + V16 + V18
V19
V20. (V)
2
main contribution to the overall rate of the radiation-
chemical reduction of Rh(IV). The total rate of these
reactions and overall rate of Rh(III) oxidation [reac-
Then, the radiation-chemical yield of Rh(IV) reduc-
tion, G[ Rh(IV)], is
tions (19) and (20)] decrease with increasing [HNO ]
3
G[ Rh(IV)] = Vrch/(aD).
(VI)
from 0.5 1 to 2 3 M. However, these overall rates
decrease to a different extent, so that the overall rate
and radiation-chemical yield of Rh(IV) reduction de-
1
1
When the rate is expressed in mol l
s
and the
1
dose rate D in Gy s , the coefficient a in (VI) is equal
crease in the [HNO ] range considered. The total rate
3
7
to 1.04 10 .
of reactions (19) and (20) decreases owing to a de-
RADIOCHEMISTRY Vol. 45 No. 1 2003

38
VLADIMIROVA, KHAPERSKAYA
1
1
Table 6. Rates of particular reactions (mol l 1 s ) at a dose rate of 0.4 Gy s , dose of 1.5 102 Gy, and [Rh(IV)]
3
2.6 10
M
Rh(IV) + Rh(IV) + Rh(IV) + Rh(IV) +
Rh(IV) + Rh(III) + Rh(III) +
[HNO3],
M
,*
rch**
G[ Rh(IV)],**
ions/100 eV
H2O,
eaq,
V14
H,
V15
HO2,
V16
HNO2,
OH,
V19
NO3,
V20
V
V1
V18
7
7
7
7
9
9
9
9
9
8
8
8
8
7
7
7
7
8
7
7
7
7
8
8
8
8
0.5
1.0
2.0
3.0
5.3 10
5.2 10
3.9 10
3.7 10
1.0 10
7.0 10
4.0 10
2.7 10
4.0 10
3.5 10
2.2 10
1.7 10
6.2 10
5.0 10
3.3 10
2.6 10
1.36 10
1.35 10
1.21 10
1.27 10
4.4 10
1.6 10
1.6 10
6.0 10
1.07 10
1.29 10
1.23 10
1.20 10
5.2 10
5.6 10
3.2 10
3.4 10
1.2
10
10
10
8
1.07
0.75
0.8
9
10
* Overall reaction of radiation-chemical reduction.
** V and G[ Rh(IV)] were calculated by Eqs. (V) and (VI).
rch
crease in the sum of radiation-chemical yields of
The expressions for the minimum and maximum
possible theoretical yields of rhodium(IV) reduction
are as follows:
radicals OH and NO (Table 5). It follows from
3
Table 6 that the total rate of reactions (16) and (18)
decreases mainly at the expense of reaction (16). Cal-
culations showed that the decrease in its rate is caused
by increase in the rate of reaction (4) and decrease in
Gmin[ Rh(IV)] = G(eaq) G(H2O2) + G(NO2) G(OH)
G(NO3),
(VII)
the rate of reaction (6) with increase in [NO ]. Weak
3
dependence of the rate of Rh(IV) reaction with
HNO on [HNO ] [reaction (18)], despite a substantial
G
max[ Rh(IV)] = G(eaq) + 2G(H2O2) + G(NO2)
2
3
decrease in K in going from 0.5 to 3 M HNO
18
3
G(OH) G(NO3). (VIII)
(Table 5), is caused by substantial increase in the
radiation-chemical yield of HNO formation. In [16],
2
After substituting the radiation-chemical yields
we showed that, with increase in [HNO ] from 0.5
3
min
from Table 5 in Eqs. (VII) and (VIII), we obtain G
to 3 M, G(HNO ) increases by a factor of approxi-
2
max
0.7, 1.5, 1.8, and 2.2 and G
3.7, 4.8, 5.4, and
mately ten.
5.8 ions/100 eV in 0.5, 1, 2, and 3 M HNO , respec-
3
It follows from Table 6 that, under the experi-
mental conditions considered, the contribution of
reaction (1) to the overall rate of Rh(IV) reduction
amounts to about 90%. Calculations showed that, the
lower the rhodium concentration and the higher the
dose rate, the smaller the contribution of reaction (1).
tively.
It follows from Table 7 that, at [HNO ] = 1 and
3
3
[Rh(IV)] = 5 10 M, G[ Rh(IV)] is equal to the
minimal value (1.5 ions/100 eV). In the other cases,
min
the radiation-chemical yields are lower than G
.
This means that the kinetics of radiation-chemical
processes does not correspond to the balance of radia-
tion-chemical yields in Eq. (VII).
To reveal the effect of [Rh(IV)], [HNO ], and dose
3
rate on the radiation-chemical yield of reduction, we
calculated the rates of particular reactions and V
.
rch
Earlier, we found that the experimental radiation-
From Eq. (VI) we found the values of G[ Rh(IV)],
which are listed in Table 7. As seen, the radiation-
chemical yields are virtually independent of the dose
rate; with doubling of [Rh(IV)] they increase by a
factor of 1.2 only. Other conditions being equal, in
chemical yields of Ce(IV) reduction in 1 3 M HNO
3
at -radiolysis are equal to the above-indicated maxi-
mum possible theoretical radiation-chemical yields
(5 6 ions/100 eV) [17]. These high yields are caused
by the fact that the rate constant of the reaction bet-
the range of [HNO ] 0.5 1.0 M G[ Rh(IV)] is ap-
3
4+
6
1
1
ween Ce and H O is equal to 1 10 l mol
[7].
s
proximately 1.5 times higher than in the range 2 3 M.
Calculations showed that the radiation-chemical yields
decrease with increase in the radiation dose owing to a
decrease in the rate of reaction (18) and an increase
in the rate of reaction (20).
2
2
We also calculated the effect of the rate constant of
the reaction between Rh(IV) and H O , K , on the
2
2
17
rates of separate reactions and on the radiation-chemi-
cal yields of Rh(IV) reduction and found that these
yields become equal to the above maximal values in
We also calculated the radiation-chemical yields
when K is equal to zero. They increase by a factor
1
of 1.1.
0.5, 1, 2, and 3 M HNO at K
5, 50, 100,
3
17
RADIOCHEMISTRY Vol. 45 No. 1 2003

MECHANISM AND KINETICS OF Rh(IV) RADIATION-CHEMICAL REDUCTION
39
Table 7. Calculated radiation-chemical yields of Rh(IV)
1992, vol. 34, no. 4, pp. 35 41.
reduction at a -radiation dose of 1.5 102 Gy
4. Dorfman, L.M. and Adams, G.E., Talanta, 1979,
vol. 26, no. 5, pp. 415 419.
G[ Rh(IV)], ions/100 eV
5. Vladimirova, M.V. and Golub’, E.A., Radiokhimiya,
[Rh(IV)]
103, M
[HNO3],
M
1988, vol. 30, no. 4, pp. 547 557.
1
1
D = 0.4 Gy s
D = 1.4 Gy s
6. Vladimirova, M.V., Radiokhimiya, 1998, vol. 40,
no. 5, pp. 385 392.
0.5
1.0
2.0
3.0
2.6
2.6
2.6
2.6
1.2
1.29
1.27
0.76
0.7
7. Pikaev, A.K. and Kabakchi, S.A., Reaktsionnaya spo-
sobnost’ pervichnykh produktov radioliza vody. Spra-
vochnik (Reactivity of Primary Products of Water
Radiolysis. Handbook), Moscow: Energoizdat, 1982.
1.07
0.75
0.8
0.5
1.0
2.0
3.0
5.0
5.0
5.0
5.0
1.4
1.5
1.0
1.0
1.45
1.6
1.05
0.9
8. Lee, Y.N. and Schwartz, S.B., J. Phys. Chem., 1981,
vol. 85, pp. 1684 1685.
9. Kaysumura, Y., Jiang, P., and Nagaishi, R., J. Phys.
Chem., 1991, vol. 95, pp. 4435 4439.
10. Broszkiewicz, K.K., Radiat. Phys. Chem., 1977,
1
1
vol. 10, pp. 1 10.
and 100 l mol s , respectively. These results con-
firm the validity of the radiation-chemical yields
11. Koltunov, V.S. and Khaperskaya, A.V., Radiokhimiya,
4
1
1
1993, vol. 35, no. 4, pp. 93 99.
(Table 7) calculated for K = 2.5 10 l mol s .
17
12. Vladimirova, M.V., Radiokhimiya, 1992, vol. 34,
Thus, the rates of Rh(IV) reduction in nonirradiated
solutions range from 50 to 90% of the rates in ir-
radiated solutions, depending on the initial conditions.
no. 6, pp. 116 127.
13. Lee, Y.N. and Schwartz, S.B., J. Phys. Chem., 1980,
vol. 84, pp. 840 845.
Since reduction with water is significant, it is im-
possible to obtain the radiation-chemical yields of
reduction from the difference in the concentrations
in the blank and irradiated solutions.
14. Shilov, E.A. and Stepanova, Z.S., Zh. Fiz. Khim.,
1950, vol. 24, no. 6, pp. 820 825.
15. Koltunov, V.S. Khaperskaya, A.V., and Shapova-
lov, M.P., Radiokhimiya, 1995, vol. 37, no. 1, pp. 33
37.
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RADIOCHEMISTRY Vol. 45 No. 1 2003