MITNE -54
EQUILIBRIUM EXTRACTION CHARACTERISTICS
OF
ALKYL AMINES AND NUCLEAR FUELS METALS
IN
NITRATE
SYSTEMS
PROGRESS
REPORT J1
June I
-
August 31, 1964
BY
PHILIP J. LLOYD
EDWARD
DEPARTMENT
OF
A. MASON
NUCLEAR
ENGINEERING
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE, MASSACHUSETTS
02139
MITNE-54
Equilibrium Extraction Characteristics
of
Alcyl Amines and Nuclear Fuels Metals
in
Nitrate Systems
Progress Report for the Period
June 1 - August 31, 1964
Progress Report XIV
by
Philip J. Lloyd
Edward A. Mason
October 24, 1964
Work Performed Under Subcontract No.
1327
Under Contract No. W - 7405 - Eng - 26
with
Union Carbide Nuclear Corporation
Oak Ridge, Tennessee
Massachusetts Institute of Technology
Cambridge, Massachusetts 02139
1.0
1.1
Summary
Multicomponent Metal Extraction
Further tests were carried out on the technique of studying the variation of overall distribution ratio as a function
of phase ratio in order to determine the partition coefficients of two species being extracted simultaneously. Se7 5
and Agill tracers were extracted simultaneously from 1, 3,
6, 9 and 12M nitric acid solutions by 0.1 and 0.2M amine ni.trate solutions. Significant results were only odtained at
the highest acid and amine concentrations. This failure was
probably due partly to the low ratio of the partition coefficients concerned, and partly to the low values of the actual
partition coefficients,
1.2
Nitrosylruthenium Nitrato Complexes
Further studies of the behavior of nitrato complexes of
nitrosylruthenium were carried out using the PARTIFRAC analysis of the variation of overall distribution ratio with phase
ratio to determine the mole fractions of the extractable
species. Hydrolysis rates in 3M HNO3 were extended; the less
extractable species showed a rate constant for hydrolysis
ki;
0.01 per minute, and the more extractable a rate constant k2 Z 0.10-0.15 per minute, though there is some evidence that the more extractable species are actually two,
rather than one species, with different rates of hydrolysis.
Back extraction experiments showed that in the organic
phase, the less extractable species 1 was converted to the
more extractable species 2, with a rate constant kZ0.075
per min. Attempt to observe the rates of nitration by dissolving "RuNO(NO3)3" failed as it appeared that the preparation was a mixture containing at least 20% of the ruthenium
as species 2. Attempts to prepare radioactive nitrosylruthenium nitrato species by solution in nitric acid of irradiated RuNO(OH) also failed, as approximately 50% of the
active ruthenium present in the final aqueous solution was
evidently not a nitrosylruthenium complex.
A tentative scheme for the extraction of the nitrosykruthenium nitratocomplexes is outlined in which the probable structure of the complexes is suggested. The less
extractable species appears to be the trinitrato complex,
which is probably extracted with some coordinatively bound
water.
This water is then probably displaced during conversion of this species on standing in the organic phase. The
more extractable species are probably predominantly tetranitrato nitvosylruthenium, with possible traces of the pentanitrato complex.
-'
0,
.
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-.
9mm-
2.0
2.1
Multicomponent Metal Extraction
Introduction
It was suggested in the previous progress report (1)
that the technique of studying the variation of distribution
ratio with phase ratio, which had been employed in studying
the simultaneous distribution of two species of nitrosylruthenium, might be adaptable to the study of the simultaneous
distribution of two different metals. The theory of the method
was given and its disadvantages discussed. Preliminary tests
at that time were inconclusive, and it was decided to test
the method further using selenium and silver radiotracers, as
the behavior of these two metalsindividually was already
known.
2.2
Experimental
Seven-and-one-half day Agill tracer was purchased from
5
the Isotopes Division, ORNL, and 120 day Se7 was previously
Solutions
prepared by irradiatingSe powder in the MITR (2).
nitric
12M
an
9
of each of these were made up in 1, 3, 6,
acid, so that the final solutions contained roughly 50,000
cpm/ml of each activity.
Thercrganic phase was 0.2 or 0.lN tri-n-dodecylamine
(Eastman No. 7727) dissolved in A.R. grade toluene. Before
use the amine solution was pre-equilibrated by double contact
at 2:1 aqueous to organic phase ratio with nitric acid at the
relevant concentrations.
The extractions were carried out at various phase ratios
as described previously (1). 1.0 or 0.5 ml samples of each
phase were taken for counting in thin-walled glass vials.
A well-type scintillation counter was used, all counts above
0.12 Mev being recorded. The counting efficiencies of the
aqueous and organic phases were similar, while the difference
between the counting efficiency of 0.5 and 1.0 ml samples
amounted to roughly, 3%, and consequently was ignored.
The results are summarized in Table 1.
2.3
Discussion
The results were analyzed by the PARTIFRAC II program
described previously (1). On inspection it was obvious that
it would be difficult To analyze the results at the lower
acid concentrations and at the higher acid concentrations
for 0.lN amine, since under these conditions the distribution
ratios were so low that the statistical error in counting
the organic phase was of the same order of magnitude as the
variation in distribution ratio. Meaningful results could
V,
.
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.......
..
.
3
Table 1
Variation of Distribution Ratio With Phase Ratio
For Se and Ag Extracted Simultaneously at 2500
Amin e
Conc n.
Phase
Ratio
Distribution Ratio (o/A) at Given
Nitric Acid Concentration
iM
6M
12M
3M
9M
M
A/0
0.1
4
.oo49
2
1
.0052
.0047
.0048
.0047
0.4
0.2
.012
o.2
2
.011
1
.012
0.4
.010
0.2
.011
.0035
.0031
.0032
.0036
.0034
.0056
.0053
.0054
.0051
.0055
.015
.033
.014
.014
.015
.013
.029
.029
.027
.029
.0080
.0076
.0077
.0077
.0074
.026
.025
.024
.024
.025
.048
.047
.047
.044
.o40
.090
.087
.084
.076
.065
only be obtained for extraction by 0.2M amine from 9 and
12M acid solution. The results obtained here are compared
inFTable 2 to those previously determined for the metals
individually.
Table 2
Comparison of Distribution Ratios of Ag and Se Extracted
Individually or Simulatneously From 9 and 12M HNO
3
by 0.2M TLA
HNO 3
M
Distribution Ratio Determined:Individually
Simultaneously
Ag(1)
Se(2)
Ag
Se
9
0.12
0.004
12
0.21
0.006
o.oo4o
0.18
0.0057
In all other cases it appears that the method failed
partly because of the low distribution ratios involved,
leading to statistical counting errors in determining the
organic phase activity, and partly because of the limited
range of phase ratios employed. This is illustrated in
Table 3, where the expected distribution ratio is calculated
from the distribution ratios of the metals determined
4
individually for a particular case. The low activity of the
organic phase makes precise calculation of distribution ratio
impossible, while the effect studied is, in this case, so
slight that increasing the phase ratio by a factor of 400
only brings about a change of 3% in the distribution ratio,
Table 3
Calculation of Overall Distribution Ratio for the Simultaneous
Extraction of Ag (D 0.006) and Se (D 0.0015) From 3M HNO 3
by 0.lM Amine
Initial Activity of Each Metal in Aqueous Phase = 50,000 cpm/ml
Phase
Ratio
A/0
20
5
1
0.2
0.05
Ag Activity
cpm/ml
0
A
Se Activity
cpm/ml
A
0
49985
49940
49701
48543
44642
49996
49985
49925
49627
48543
300
300
298
291
268
75
75
75
74
73
Total Activity
cpm/ml
A
0
99981
99925
99626
98170
93185
375
375
373
365
341
D
O/A
.003751
.003753
.003744
.003718
.003659
Similar calculations indicate that the ratio between the
two distribution coefficients should be greater than 10, to
obtain meaningful results. At less than this, the variation
in distribution coefficient with phase ratio will be slight
over any reasonable range of phase ratios, artic larly in
the lower region of distribution ratios (10- - 1;e). Unsuccessful attempts were made to demonstrate this analyticallythe expression for D/ T, the partial of the distribution
ratio with respect to the phase ratio, did not reduce to any
readily comprehensible form in Pl and P2, the individual distribution ratios of the two species concerned.
In conclusion, the suggested method for the simultaneous
determination -ofditribton
coefficients is capable of
giving reasonably good results provided certaintlimitations
are fulfilled. It is simple and rapid and as such would
seem to lend itself to simultaneous determinations in, for
instance, activation analysis. The limitations are as yet not
completely explored, but numerical calculations of a few
test cases will show whether the limitations may apply to the
particular case under consideration.
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3.0
3.1
Nitrosylruthenium Complexes
Introduction
Previous studies (1), (3) attempted to determine the
rates of hydrolysis of the two extractable nitrosylruthenium
nitrato complexes. It was pointed out (1) that the increase
in distribution ratio with contact time was larger than could
be accounted for on a basis of rates of nitration to extractable complexes in the aqueous phase. The experiments on the
rates of hydrolysis were therefore extended, and attempts
were made to study the effect of increasing contact time on
the apparent mole fractions and to determine rates of nitration in the aqueous and organic phases. It should be stressed
that these experiments were of a scouting nature; neither
experiments nor analyses were duplicated. However, while too
much emphasis should not be placed upon quantitative aspects
of the results, the qualitative aspects are probably correct.
3.2
Ruthenium Analysis
In order to speed up the determination of distribution
ratios, a direct colorimetric method for the determination
of ruthenium in the organic phase suggested by Vaughen (4)
was studied. The color of the organic phase containing ruthenium was measured at 490 m. in 1 cm cells between 1/2 and 1
hour after extraction. The ruthenium content of the organic
phase was then determined by KOH fusion (1).
The resulting
calibration curve is shown in Figure 1. While the curve is
non-linear, the method is apparently of the same order of
precision as the fusion method.
3.3 Rates of Hydrolysis and the Effect of Contact Time
3.31 Experimental
Aged solutions of RuNO in ll.5M HN0 3 were rapidly diluted
to 3.OM HNO 3 and mixed in a centrifuge tube. A known volume
of pre-equilibrated tri-n-dodecyl amine (TLA) in toluene was
carefully introduced above the aqueous layer. At a known time
(the "delay" time) after the mid-point of the dilution, the
extraction was performed by hand-shaking- 1or a known time
(the "mixing" time). The phases were centrifuged and separated
as rapidly as possible, and the color of the organic phase
was determined against an amine nitrate blank 1/2 hour after
the start of contact. The ruthenium content of the initial
aqueous phase was determined by the fusion method, so that
the content of the equilibrium aqueous phase could be calculated assuming a perfect mass balance. Check samples of
various equilibrium aqueous phases showed that this assumption was essentially valid.
6
1.6
1.5
1.4
1.3
1.2
1.1
1.0
I-
z 0.9
Lu
0
0j
0
0.80.7
0.60.5 -1,
0.4-
+
x
0.3 -+
0.2 0.1
0
.00 2
.004
.006
.008
RUORG
.010
.012
.014
.016
M
FIGURE I COLOR OF AMINE SOLUT IONS OF RuNO AT 490 mp
(AMINE BLANK) IN I CM CELLS VS RUTHENIUM
CONTENT OF SOLUTION
rn
m
7
3.32
Results and Discussion
The results are summarized in Table 4. PARTIFRAC analyses (1) of these results gave the mole fractions of the two
species involved, as shown in Figure 2.
Table 4
Variation of Distribution Ratio of RuNO Nitrato Complexes Aged
in 11.5M HN0 3 , Rapidly Diluted to 3.OM HNO 3 and Extracted into
0.26ff TLA in Toluene at Varying Phiase Ratios, Delay and
Mixing Times
Mixing
Time
Secs.
30
90
Delay
Time
Secs.
.146
.215
.290
.380
.107
.041
.194
.077
.059
.047
.252
.105
.029
.146
.057
.045
.036
.115
.089
.165
.230
.314
.410
.117
.214
.046
.o63
.275
.134
.047
.036
.085
.056
.105
900
.036
.029
.160
.083
.065
.045
90
.116
300
600
.072
.059
.150
.105
.209
.120
.263
.137
.315
.197
.085
.098
.112
.140
30
90.
300
600
900
:098
.o68
30
90
300
600
180
Distribution Ratio, 0/A, at Given Phase Ratio, A/0
4
2
1
.25
.5
.027
.023
.021
.033
.106
.077
.059
.o68
Study of Figure 2 shows that the apparent mole fraction of
the more extractable species, X2 , is constant with mixing time
for a given delay time, whereas the apparent mole fraction of
the less extractable increases markedly.
From previous results, and from the results given in
section 3.5 below, the value of X2 in equilibrium in 3.OM HNO
is X 0.0095. If it is assumed that the species is hydrolyze
according to first order kinetics, then a plot of log (X2 - X )
vs t should be linear, and the slope should yield the rate
constant for the hydrolysis reaction. Such a plot is shown
in Figure 3. The slope of the best straight line through
the points is -1.0/900 per sec., which gives a value of
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0--
X
X @ 90 SEC
x
X @30 SEC+
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0.10
X2
x
4
X
4:
x
180 SECS SHAKING
x 90 SECS SHAKING
30 SECS SHAKING
+
h 30 SECS SHAKI NG,
PREVIOUS RESULTS (1)
0
0.01
U
0.001
- I-I
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_
I
I
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I
I
200
400
600
1000
800
DELAY TIME (1/2 POINT OF ADDITION TO START
OF SHAKI NG) SECS -+
FIGURE 2 RAPID DILUTION FROM 11.5 M TO 3M
HNO 3 , DELAY FOR THE GIVEN TIME,
AND EXTRACTION FOR THE GIVEN
TIME BY O.26M TLA
9
-0.8
- 1.0
-1.2
x+
+
-1.4
0
N
'~o
-1.8
I
-2.0
0
200
400
DELAY TIME,
600
800
1000
SECS--+
FIGURE 3 SEMILOG PLOT OF MOLE FRACTION DIFFERENCE
AGAINST TIME, FOR SLOPE ANALYSIS TO
DETERMINE THE RATE OF HYDROLYSIS
10
k2 = 2.303/900 per sec., or k2 = 0.15 per min.
The previous
report (1) gave a preliminary value of 0.20 per min.
However, it was previously (1) pointed out that there is
a discrepancy between these resulfs and the results for the
overall hydrolysis of all the anionic species. It will be
noted in Figure 3 that a smooth curve may be drawn through
the points. This was initially ignored, but experiments at
longer delay times (see below, section 3.5 ) confirmed that
this curvature persisted. Secondly, a few careful experiments
on the extraction of RuNO aged in 3.OM HNO showed the
striking temperature dependance of thi dis ribution, as indicated in Table 5.
Table 5
Dependance of Distribution Ratio on Room Temperature
RuNO Complexes Aged in 3.OM HIN0 3 Extracted
by 0.26M TLA Nitrate at 2:1 Phise Ratio for 30 Sec.
Temperature
OF
81
74
73
72
71
Distribution Ratio
O/A
0.0161
0.0179, 0.0183
0.0181, 0.0183, 0.0184
0.0185, 0.0190
0.0192
69
0.0192
It is important to consider such an effect, since when
ll.5M HNO3 is diluted to 3M HNO3, there is a temperature rise
of approximately 300F. ThTs wil be important at shorter
delay times, and may explain some of the observed curvature.
Finally it proved difficult to determine a rate of hydrolysis for the less extractable species, Xl.
Attempts were made to solve by tri&l and error sets of
equations of the type
(X
-
X*) = (XO - X*) e-kit +
k2
(Xo - Xl)(eklt _ e-k2t)
which governs the first order decay of species 1 when it is
bgth gresgnt 8nd formed by the decay of species 2 (1). Xi,
X1 , X., X2, X2 and k2 could be estimated from experimental
11
results, but in all cases no single value of k2 could be
found which would fit the data within reasonable limits.
The increase in the mole fraction of species 1 with contact time requires elucidation. It seemed possible that the
rate of extraction of this species might be low which would
be in agreement with the previous suggestion (1) that the
species might be polynuclear. This seems unliRely, however,
as the measured partition coefficient of this species did not
increase markedly with increasing contact time, and since
the results at, say, 90 seconds' delay time and 180 seconds'
mixing time would indicate that over 70% of the ruthenium
originally present was in an extractable state. What seems
more likely is that some conversion of the species 1 may take
place, to "fix" it in the organic phase and thus raise the
apparent mole fraction. To test this, back extraction experiments were performed.
3.4
Back Extraction Experiments
It was the aim of these experiments to attempt to observe
conversion taking place in the organic phase with increasing
time of, or after, extraction. Ruthenium was therefore extracted under standard conditions. Aged solutions of RuNO in
ll.5M HNO3 were rapidly diluted to 3.OM HNO3 , and after 30
secs. delay time extracted for 90 secs. at 0.5 A/0 phase ratio
by 0.26M TLA nitrate.
After extraction the separated organic phase was aged
for a known time (the "back delay" time, defined from the midpoint of the forward extraction to the start of the back
extraction) and back extracted to 3.0M HN03 at various phase
ratios for a given mixing time (the "Sack mixing time").
By measuring the ruthenium concentration in the organic phase
before and after back extraction, the back distribution coefficient, A/0, could be determined, and by defining the phase
ratio as 0/A, the results could be submitted for PARTIFRAC
analysis directly.
The results are shown in Table 6, and the mole fractions
determined by analysis of these results are shown in Figure 4.
The data at 30 and 90 seconds.' back mixing time, as analyzed
in Figure 4, clearly show that in fact conversion is taking
place. Between 120 and 500 seconds'delay, X1 0 , the mole fraction of species 1 in the organic phase, decrease from 0.19
to 0.12, while X 20 increased from 0.47 to 0.53, i.e., the
decrease in species 1 is balanced by the increase in species
2. It is also evident that there is a rate of mass transfer
effect-since all the ruthenium is in the organic phase, it
must all be "extractable," and the mole fractions should
total 1.0.
In fact, at 30 secs.' mixing time, only 75% of
12
1.0
X20
x
t
0
+X
0
+1
w
U)
0.1
z
+ 30 SEC BACK EXTRACTION
x 90 SEC BACK EXTRACTION
o 120 SEC BACK EXTRACTION
& CALCULATED FOR ZERO TIME
0
z
w
w 0.01
(cl)
LjL
0
(I)
0
C-
w
-J
0
7
0
I
I
I
I
I
I
I
800
1000
400
600
200
AGE OF ORGANIC PHASE, FROM MIDPOINT OF
FORWARD TO START OF BACK EXTCN. (SECS.)
FIGURE 4 BACK EXTRACTION; RADID DILUTION FROM
II TO 3M HNO 3 , 30 SEC DELAY, EXTRACTION
AT 2 A/O PHASE RATIO FOR 90 SEC; DELAY
FOR GIVEN TIME 8 BACK EXTRACTION FOR
GIVEN TIME
13
Table 6
Variation of Back Distribution Ratio with Varying Back Delay
and Back Mixing Time as a Function of the Back Phase Ratio
Back
Mixing
Time
Secs.
30
Back
Delay
Time
Secs.
120
250
90
500
250
120
500
250
Back Distribution Ratio (A/0)
At Phase Ratio (0/A)
.25
.5
1
2
4
.140 .190 .263 .338 .442
.132 .180 .231 .305 .378
.140 .178 .232 .278 .328
.209 .282 .382 .522 .647
.212 .291 .383 .496 .565
.216 .288 .379 .527 .649
the ruthenium is equilibrated. By90 secs. mixing time, this
has risen to 93A and by 120 secs. to 99%.
3.5
Attempts to Determine the Rate of Nitration
On a basis of the time for spectra of solutions of
nitrosylruthenium hydroxide dissolved in nitric acid, to
reach equilibrium, Skavdahl had suggested (3) that the rate
of formation of extractable complexes, i.e., the rate of
nitration, is very slow. As pointed -out above (section
and (1)), this is at variance with the results on the increase
of exTraction with increased mixing time. Part of this increase is already explained by the effects of rate-of-extraction and conversion in the organic phase, but it seemed desirable to check the rates of nitration.
"Trinitrato nitrosylruthenium," RuNO(NO3 ) was prepared
according to the method of Fletcher (5) The material was
dissolved in 3M nitric acid, and after aging for a known
period, samples of the solution were extracted at various
phase ratios by 0.26M TLA nitrate in toluene. The experiments were performed in an air conditioned laboratory to
avoid temperature effects as noted above, and the ambient
temperature was constant at 730 F + 10. The results are given
in Table 7, and the PARTIFRAC analysis is summarized in
Figure 5.
It was somewhat surprising to observe during the course
of the experiments an obvious decrease with time in the amount
of ruthenium in the organic phase where an increase due to
the formation of extractable species had been expected. The
analysis shown in Figure 5 makes it clear that the more
extractable species, species 2, was present in significant
14
1.0
.10
X2
x
.01
x
.00I
8
32
24
16
TIME SINCE DILUTION,
40
HOURS
48 --- 100
FIGURE 5 MOLE FRACTIONS OF EXTRACTABLE SPECIES
FOR " RuNO(NO 3 )3 " DISSOLVED IN 3M HNO 3 AND
EXTRACTED BY O.26M AMINE AT 73±11 AT
GIVEN TIMES AFTER DILUTION
..
.........................
15
Table 7
Extraction of Freshly Dissolved RuNo(NOg) in 3M HNO 3 at
Increasing Time After Solution, by 0.26M LA Nitrate in
Toluene at Varying Phase Ratios and with 30 Sec. Mixing Time
Time After
Solution
hrs.
0.167
0.534
1.0111
2
14.3
23.5
46.5
109
Phase Ratio (A/0) of
Distribution Ratio (o/A) at
O,.25 0.5
1
2
4
.0246 .0390 .0649 .0957 .1315
.0165 .0234 .0319 .0411 .0551
.0097
.0084
.0084
.0084
.0083
.0146
.0125
.0112
.0108
.0111
.0111
.0212
.0172
.0161
.0140
.0140
.0140
.0263
.0222
.0189
,0178
.0187
.0185
.0369
.0295
.0258
.0241
.0237
.0245
quantities in the preparation, and that there was probably
also some of species 1. The starting material was certainly
not, therefore, pure tri-nitrato nitrosylruthenium.
It seemed possible that all the nitric acid had not been
removed from the preparation, even after standing over KOH
pellets for 1 month. Fresh material was therefore prepared
in which every attempt was made to remove excess nitric acid.
The nitric acid solution of the RuNO complexes was distilled
under vacuum and in a nitrogen atmosphere. Once most of the
nitric acid had been removed, a slow stream of distilled water
was introduced into the distillation flask, which distilled
carrying off, it was hoped, the last traces of nitric acid.
After several hours, the pH of the distillate actually distilling over had risen to pH 6.7. Water addition was stopped,
and the distillation temperature slowly raised to 430C,
when ruthenium complexes suddenly commenced to distill over,
as evidence by the appearance of purple-red droplets at the
lower end. of the condenser. The distillation was immediately
stopped, and the residue was stored over KOH pellets for two
weeks in a vacuum dessicator. Before use, a sample was
analyzed for the N0 to Ru ratio; the ratio found was 3.03
to 1, and it was assumed that the material produced was indeed
the tri-nitrato nitrosylruthenium. The experiment described
above was therefore repeated. The results are not given as
in all essential respects they are identical with those in
Table 7.
It thus appears impossible by this means to study the
rate of formation of extractable species. However, the decay
..
........
....
........
curves shown in Figure 5 lend themselves to analysis for the
rates of hydration of the extractable species, though it is
necessary to make assumptions as to the mole fractions present
at zero time. However, by extrapolation X1 0t 0.01 and X 2 00.20
and
By trial
while k2,z0.15 per minute as shown previously.
error, kiZ0.01 per minute.
One phenomenon of nite is the apparent curvature of a
semi-log plot of (X2 - X 2 ) against time, as shown in Figure 6.
This is in the same direction as the plot in Figure 3, and does
not seem likely to be due to temperature effects. It may
indicate the presence of a third extractable species which is
hydrolyzed somewhat faster than the second species.
3.6
Variation of Partition Ratio with Amine Concentration
In some cases it is possible to obtain an indication of
the charge on an extracted species by means of a slope analysis
of a log-log plot of the distribution ratio of a species
versus the extractant concentration. This technique is by
no means rigorous, and there are many effects which can
cause such a slope analysis not to indicate the charge on the
extracted species. Nevertheless, it was of interest to study
the effect of amine concentration.
In order to overcome any effect of ruthenium concentration, a ruthenium tracer was used. RuNO(OH) 3 was irradiated
in the MITR, and dissolved after two days in llM HNO3 . Two
days later, a portion of this stock was diluted to 3.OM HNO
and aged for 30 days. No activity other than that of 740 day3
Rul0 3 could be observed in the 7-spectrum of the product.
Pre-equilibrated amine solutions were prepared over a
range of amine concentrations. Ruthenium distribution to each
of those was followed as a function of phase ratio. The
results are summarized in Table 8.
Table 8
Effect of Varying the Amine Concentration on the
Distribution Ratio of RuNO from 3.OM HNO 3, 90 Secs!
Mixing, at Room Temperature
Amine
Conen.
M
Distribution Ratio (0/A) at
4
2
1
0.4
0.2
Phase Ratio (A/0) of
0.520
0.260
.0229
.0146
0.130
0.065
.0170
.0103
.00885 .00644
.00544 .00389
0.0325
.00201 .00169 .00150 .00100 .00072
IonNO"MMI"
M
17'
T""t -
.0118
.00733
.00467
.00284
.00787 .0059
.00468 .00363
.00289 .00211
.00195
.00136
17
1.0
I
I I
I 1
I
I I
-
.01
x
0
z
ir_
U-
+
z
0
001
ULU
I
0
1k
I
I
1
.1
.1
1.
1
1
10 20 30 40 50 60 70 80 9010011O
TIME, MINUTES -
FIGURE 6
_ __ _ -""''-
I
1
1
120
1
130
VARIATION OF MOLE FRACTION OF SPECIES
2 WITH TIME
I.,II I._1_-_11____-
I.. -_ _.....
....
18
Comparison of the results for 0.26M amine with the
results of Table 7 for 23.5-109 hours"aging indicates that
the results here are too low by a factor of roughly 2. This
may be due to some of the activity in the aqueous phase not
being present as RuNO complexes, as had been assumed.
It was not therefore surprising, on the submitting the
results to PARTIFRAC analysis, to find that the output did
not make much sense. This is indicated in Table 9, where
the best values of the partition ratio mole fractions of the
various species are listed.
Table 9
Partition Ratio and Mole Fractions Calculated
From the Data of Table 8
Amine
Concn.
M
Partition Ratio
P1
Mole Fraction
P2
0.52
0.048
4.8
0.113
0.008
0,26
0.030
$.2
0.005
0.13
0.025
3.0
0.099
0.058
0.065
0.010
0.006
2.4
0.7
0.072
0.045
0.0325
0.004
0.003
0.003
There is certainly a trend towards decreasing values of
P2 with decreasing amine concentration, but the caland
Pl
culated mole fractions should not vary with amine concentration, but should be constant at the equilibrium values for
3.OM HNO 3 shown in Figure 5. The fact that the mole fractions
are, in all cases, considerably lower than the equilibrium
values would indicate that assumption that some of the ruthenium is not present as nitrosylruthenium complexes is valid.
3.7
Conclusions
The technique of following the variation of distribution
ratio with changing phase ratio in order to determine the mole
fractions of extractable species present, has been adopted
for the study of various phenomena involving nitrosylruthenium
nitrato complexes. An estimate has been made of the rates
of hydrolysis of the extractable species, ki%0.01 per min. and
k 2 to.15 per min., where ki and k2 refer to the less and more
extractable species, respectively.
A resistance to transfer of the less extractable species
of ruthenium in the reverse direction has been observed.
Conversion of this species to the more extractable species
takes place in the organic phase on standing. In forward
------------------
19
extraction, increasing the time of shaking increases the
apparent amount of less extractable species in the aqueous
phase. This is probably due both to conversion in the organic
phase and to a rate of mass transfer effect, though the possibility of formation of this complex from lower species should
not be overlooked. This seems somewhat unlikely, however,
in view of the generally relatively slow rates of nitration
of lower to higher species observed by Scargill and others
(6), an observation in accord with Skavdahl's previous sugIt is unfortunate that the rate of conversion
gestion (3).
studies could not be carried out to equilibrium. However,
assuming that at equilibrium at least 90% of the less extractable species 1 is converted to species 2, then the data
shown in Figure 4 correspond to a rate constant for the
reaction lorg-9 2 org of ki0.075 per min.
It was shown that the supposed "RuNO(NO3)3" was a mixture of nitrosylruthenium nitrato complexes. Unsuccessful
attempts were made to produce the pure trinitrato nitrosylruthenium. This raises the question of the exact nature of
the complexes. van Raaphorst (7) reports that roughly 10%
of the RuNO is in higher complexes than dinitrato in 3M HNO3 ,
and 70% in 11M HNO 3 . Fletcher (8) reached essentiallyfsimilar
conclusions but mistakenly identified these species as being
higher than trinitrato. Later work (6) has suggested that
these higher than dinitrato species may also be split into
two groups, a trinitrato group, 12% in 3M and 55 in 11M, and
Species~1
a tetranitrato group, 1% in 3M and 35% ii 11.
in this study is 13% in 3M and 45-560% in 1114, while species
The correspondence
2 is 0.095% in 3M and 16% in llM HNOq
3.
between these figures and those of Scargill (6) would seem to
indicate that species 1 is the trinitrato and species 2 the
tetranitrato complexes. However, if species 1 is the trinitrato complex, it is most surprising that this particular
species should build up rapidly in 3M HNO3 on dissolving a
material purporting to be trinitrato nitrosylruthenium.
This is the main anomaly in the picture of the extraction
of nitrosylruthenium nitrato complexes by alkyl amines which
is beginning to emerge. The trinitrato complex (species 1)
is probably extracted by
RuNO(NO 3 ) 2H2 0 + R3 HNO 3
:: R3NHI.
RuNO(N0 3 )4 . H 2 0 + H2 0
The organic phase complex is then converted by reaction with
more amine.
R 3 NH. RuNO(NO 3 )4.H2 0 + R 3 NHNO03 .-..
(R3 NH)2 RuNO(NO 3 )5 + H20
This reaction takes place slowly in the organic phase.
It is suggested that the water released by this reaction is
capable of removing some of the unbound nitric acid present,
thus leading to the apparently low values for unbound nitric
acid determined conductumetrically (1), and the apparently
high nitrate-to-ruthenium ratio observed (1) for this species.
....
....
..
20
The tetranitrato species (species 2) is probably extracted
by
[RuNO(NO 3 )4 H 2 0] + 2R 3 NHN0 3 ,;::(R
3 NH)2 RuNO(NO3) 5 + NO3 + H 2 0
thus giving the same species in the organic phase as the
extracted trinitrato complex, after conversion, and explaining
why after 1/2 hour the spectrum of the organic phase becomes
independant of the species involved.
It is also possible that trace quantities of the pentanitrato species may be present. The above equations suggest
that the nitrosylruthenium in the organic phase has all five
available coordination sites filled with nitrate ions, and
there seems to be no particular reason why the same may not
be true in the aqueous phase, though as proposed earlier
(6, 7) the coordination opposite the nitrosyl group may be
weak. There was some evidence (see Figures 3 and 6) that a
second species was present with species 2. In fact the hydrolysis rate determined in Figure 3 is somewhat higher than that
corresponding to the data of Figure 6; in Figure 3, hydrolysia
of species present in llM HNO is taking place, and in Figure
6, hydrolysis of speciesin 3M HNO is taking place, and more
of the pentanitrato species would 5e expected to be present
in the llM acid solution. The weakness of coordination opposite the nEitrosyl group may imply that primary extraction of
the trinitratoconiex takes place by replacement of the water
in this position by an amine nitrate, and that the water displaced in the conversion reaction is that present in planar
position 5.
21
5.0
References
(1) P. J. Lloyd and E. A. Mason, Progress Report XIII,
MITNE-50 (1964).
(2) P. J. Lloyd and E. A. Mason, Progress Report XII,
MITNE-43 (1963), J. B. Goodblatt, M.S. Thesis, Department of Nuclear Engineering, M.I.T., February 1964.
(3)
R. E. Skavdahl and E. A. Mason, MITNE-20 (1962).
(4)
V. C. A. Vaughen and E. A. Mason,
(5)
J. M. Fletcher, et.al., J. Inorg. Nucl. Chem. 1, 378
TID-12665 (1960).
(1955).
(6)
D. Scargill, C. E. Lyon, N. R. Large and J. M. Fletcher,
"Nitrato Aquo Complexes of Nitrosylruthenium III,"
Personal Communication, June, 1964.
(7) J. G. van Raaphorst and P. A. Deurloo, KR-52 (1963).
(8)
J. M. Fletcher, et.al., J. Inorg. Nucl. Chem. 12, 154
(1959).