Journal of Radioanalytical and Nuclear Chemistry
Supplementary information
Oxidation state of Pu desorbed from carbon samples
The results of the desorption experiments with C-CS and C-CS-COOH OMC
were in agreement with what was previously observed with nanocast mesoporous carbon.
Over 99% sorption to both C-CS and C-CS-COOH was observed from pH 4 perchlorate
samples with ionic strength approximately 1, 250 ± 13 µM Pu, after 23 hours contact.
From similar samples with a lower ionic strength of 0.13-0.15, over 99% sorption to CCS-COOH, and 91-97% sorption to C-CS occurred. After removal of the bulk liquid
phase and 24 hours contact with either 1 M HClO4 or 1 M HCl, the amount of Pu
remaining on the solid phase ranged from 14% to 34% ± 10%. Increasing the acid
concentration to 1.5 M had little effect on the total amount of Pu desorbed or the
absorbance spectra of the desorbed Pu. The Vis-NIR absorbance spectra of the Pu
desorbed from both materials showed distinct features of Pu(III), whether HCl or HClO4
was used for desorption. Fig. 1 shows examples of these spectra, along with the spectrum
of the Pu(VI) stock solution that was added to the carbon samples.
LLNL-JRNL-676901
1
Journal of Radioanalytical and Nuclear Chemistry
Fig. 1 Visible-NIR absorbance spectrum of Pu stock dilution in 1 M HClO4 (black), and
Pu desorbed from C-CS (blue) and C-CS-COOH (red) in 1 M HCl. In the sorption step
the carbon samples were contacted for 24 hours with pH 4, 250±13 µM Pu perchlorate
solution, in the batch ratio of 1.0 g/L. Although the Pu was added to the samples as
Pu(VI), the Pu that desorbed from the samples clearly shows spectral features of Pu(III).
Oxidation state changes of 1.25 ± 0.05 mM Pu(VI) in 1.25 ± 0.05 M HClO4,
in batch contact with carbons
The absorbance spectra of 1.25 ± 0.05 mM Pu(VI) in 1.25 ± 0.05 M HClO4 solution after
contact with the SBA-15 is shown in Fig. 2, and is very similar to those of the control
soloution (shown in Fig. 1, main text). No redox reaction occurred between Pu and silica,
as was expected. Figs. 3-7 show example absorbance spectra of 1.25 ± 0.05 mM Pu(VI)
in 1.25 ± 0.05 M HClO4, measured after various lengths of batch contact time with the
carbonaceous materials FDU-16, FDU-16-COOH, C-CS-COOH, activated carbon (AC),
and graphene nanoplatelet aggregates (GNA), respectively. The majority of Pu(VI) was
LLNL-JRNL-676901
2
Journal of Radioanalytical and Nuclear Chemistry
reduced to Pu(III) upon contact with the carbon powders, while LSC assays showed that
less than 7 ± 10 % of the Pu adsorbed to the carbon in all samples (see Table 1). The
contact time required for complete reduction of Pu varies with the specific properties of
each carbon powder.
Fig. 2 Vis-NIR absorbance spectra taken of 1.25 ± 0.05 mM Pu(VI) solution in 1.2 M
HClO4 after contact with SBA-15 mesoporous silica. The introduction of spectral features
of Pu(V) and Pu(IV) is similar to what was observed in the control sample due to
radiolysis effects. The inset shows the full Pu(VI) peaks at 829.4 ± 1.5 nm, while the
main plot is scaled to view the smaller peaks in the spectra.
LLNL-JRNL-676901
3
Journal of Radioanalytical and Nuclear Chemistry
Fig. 3 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.2 M HClO4,
after contact with FDU-16 mesoporous carbon. Reduction of Pu(VI) began immediately,
as evidenced by the approximate 50% decrease in absorbance at 829.4 nm after 51
minutes total contact with FDU-16. The reduction of Pu continued slowly, and after 11
days total contact, only spectral features of Pu(III) were observed.
LLNL-JRNL-676901
4
Journal of Radioanalytical and Nuclear Chemistry
Fig. 4 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.2 M HClO4,
after contact with FDU-16-COOH oxidized mesoporous carbon. After 52 minutes total
contact with FDU-16-COOH, absorbance at 829.4 nm was reduced to approximately
75% of that in the control sample. The reduction of Pu continued slowly, and after 11
days total contact, only spectral features of Pu(III), and to a lesser extent Pu(IV), were
observed.
LLNL-JRNL-676901
5
Journal of Radioanalytical and Nuclear Chemistry
Fig. 5 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.2 M HClO4,
after contact with C-CS-COOH oxidized mesoporous carbon. The majority of the Pu(VI)
is reduced to Pu(III) within 23.5 hours total contact. The inset shows the full Pu(VI)
peaks at 829.4 ± 1.5 nm, while the main plot is scaled to view the smaller peaks in the
spectra.
LLNL-JRNL-676901
6
Journal of Radioanalytical and Nuclear Chemistry
Fig. 6 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.3 M HClO4,
after contact with amorphous AC. Most of the Pu(VI) is reduced to Pu(III) within the first
hour of total contact.
LLNL-JRNL-676901
7
Journal of Radioanalytical and Nuclear Chemistry
Fig. 7 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.2 M HClO4,
after contact with GNA. Most of the Pu(VI) is reduced to Pu(III) within twenty hours of
total contact. The inset shows the full Pu(VI) peaks at 829.4 ± 1.5 nm, while the main
plot is scaled to view the smaller peaks in the spectra.
Table 1 Average percent sorption of Pu (initially Pu(VI)) in 1.25 ± 0.05 mM Pu, 1.25 ±
0.05 M HClO4 solution, in contact with carbon powders. Percent sorption was determined
by LSC counting of the solution phase.
% sorption 5
%sorption 29 days
Sample
days
(± 10%)
(± 10%)
C-CS
0
N/A
C-CS-COOH
7
N/A
SBA-15
4
6
FDU-16
7
N/A
FDU-165
3
COOH
AC
3
N/A
GNA
3
N/A
Oxidation state changes of 1.25 ± 0.05 mM Pu in other acids, in batch
contact with C-CS and C-CS-COOH OMCs
LLNL-JRNL-676901
8
Journal of Radioanalytical and Nuclear Chemistry
Samples of C-CS and C-CS-COOH were prepared with 1.25 ± 0.05 mM Pu in other
acidic matrices, to test the versatility of the redox reaction. Table 2 summarizes LSC
results from these samples, demonstrating that no significant Pu sorption to C-CS
occurred, and small amounts of Pu adsorbed to C-CS-COOH is some of the samples.
Table 2 Average percent sorption of Pu (initially Pu(VI)) in 1.25 ± 0.05 mM Pu,
solution, in contact with C-CS and C-CS-COOH OMC powders. Percent sorption was
determined by LSC counting of the solution phase.
% Sorption to CDays
% Sorption to C-CSAcid
CS
contact
COOH (± 10%)
(± 10%)
1 M HCl/0.3 M
5
1
12
HClO4
1.45 M HCl
5
0
0
1.3 M HNO3
5
1
4
1.3 M HNO3
29
0
10
Figs. 8 and 9 show spectra of a solution of Pu(VI) in 1 M HCl, and 0.3 M HClO4,
monitored over time with no solid, and after contact with C-CS, and C-CS-COOH. This
solution was prepared by adding Pu(VI) stock solution in concentrated HClO4 to 1 M
HCl. The shoulder peak at 836.0 ± 1.5 nm may be attributed to the first Pu(VI) chloride
complex, [PuO2Cl]+. Without contact with any solid, the spectrum does not change
significantly over the course of 30 days. Within one day of contact with either C-CS or
C-CS-COOH, the Pu(VI) in this solution is reduced to Pu(III).
LLNL-JRNL-676901
9
Journal of Radioanalytical and Nuclear Chemistry
Fig. 8 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1 M HCl, 0.3 M
HClO4. The Pu(VI) in solution is stable over the course of 30 days. The inset magnifies
the Pu(VI) peaks at 829.4 ± 1.5 nm, with the shoulder at 836.0 ± 1.5 nm, which may be
attributed to the first Pu(VI) chloride complex.
LLNL-JRNL-676901
10
Journal of Radioanalytical and Nuclear Chemistry
Fig. 9 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1 M HCl, 0.3
M HClO4 after contact with C-CS and oxidized C-CS-COOH mesoporous carbons. The
majority of Pu(VI) is reduced to Pu(III) within one day of contact with either C-CS or CCS-COOH, with a trace amount of Pu(IV) in the C-CS-COOH sample that is evidenced
by the small peak at 471.0 ± 1.5 nm.
Spectra of a solution of Pu in 1.45 ± 0.05 M HCl monitored over time with no solid, and
after contact with C-CS, and C-CS-COOH are shown in figures 10 and 11. The spectra
shown in Fig. 10 indicate that the solution contained a mixture of roughly equal amounts
of Pu(III) and Pu(IV), and the features of this spectrum did not change significantly over
the course of 30 days. Within one day of contact with C-CS or C-CS-COOH, most of the
Pu(IV) in solution was reduced to Pu(III) (Fig. 11). This reduction is easier to achieve
than that of Pu(VI), but these results still confirm that the presence of perchloric acid is
not necessary in order for Pu to be reduced by carbon surfaces.
LLNL-JRNL-676901
11
Journal of Radioanalytical and Nuclear Chemistry
Fig. 10 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu solution in 1.45 ± 0.05 M
HCl. The Pu in solution is a mixture of Pu(III) and Pu(IV), and the spectral features do
not change significantly over the course of 30 days.
LLNL-JRNL-676901
12
Journal of Radioanalytical and Nuclear Chemistry
Fig. 11 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu(VI) solution in 1.45 ± 0.05 M
HCl after contact with C-CS and oxidized C-CS-COOH mesoporous carbons. The
majority of Pu(IV) is reduced to Pu(III) within one day of contact with either C-CS or CCS-COOH.
Figs. 12, 13 and 14 show spectra of a solution of Pu in 1.3 M HNO3, monitored over time
with no solid, and after contact with C-CS, and with C-CS-COOH. The presence of
HNO3 slows the reduction of Pu dramatically compared to the HClO4 matrix. Pu redox
chemistry is complicated by the reduction of NO3- to NO2-. The relative concentrations of
Pu(IV) and Pu(VI) were estimated by assuming those were the only two oxidation states
present, and by using the molar extinction coefficients determined for the peaks at 476
nm for Pu(IV) and 831 nm in 1 M HNO3 by Hagan and Miner [1]. In the absence of any
solid, the solution is a mixture of approximately 43% Pu(VI) and 57% Pu(IV), and the
composition does change significantly over the course of 30 days (Fig. 12). In the
presence of C-CS or CS-COOH, the Pu(VI) is slowly reduced over time, and after 29
days contact the Pu(IV) dominates the solution, although a small amount of Pu(VI)
remains (approximately 5% in the C-CS sample, and 10% in the C-CS-COOH sample).
LLNL-JRNL-676901
13
Journal of Radioanalytical and Nuclear Chemistry
The reduction is initially faster when in contact with the C-CS compared to the C-CSCOOH, but after 13 months of contact, approximately 3% of the Pu remained in the
hexavalent state in both samples.
Fig. 12 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu solution in 1.30 ± 0.05 M
HNO3. The solution contains approximately 43% Pu(VI) and 57% Pu(IV), and the
spectral features do not change significantly over the course of 30 days. The inset
magnifies the Pu(VI) peaks at 829.4 ± 1.5 nm.
LLNL-JRNL-676901
14
Journal of Radioanalytical and Nuclear Chemistry
Fig. 13 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu solution in 1.30 ± 0.05 M
HNO3 after contact with C-CS mesoporous carbon. The Pu(VI) was reduced to Pu(IV)
upon contact with the carbon. After one day contact the solution contains approximately
21% Pu(VI) and 79% Pu(IV), and after 29 days contact the Pu(VI) content was reduced
to approximately 5%. The inset shows the full Pu(VI) peaks at 829.4 ± 1.5 nm, while the
main plot is scaled to display all spectral features.
LLNL-JRNL-676901
15
Journal of Radioanalytical and Nuclear Chemistry
Fig. 14 Vis-NIR absorbance spectra of 1.25 ± 0.05 mM Pu solution in 1.30 ± 0.05 M
HNO3 after contact with oxidized C-CS-COOH mesoporous carbon. The Pu(VI) was
reduced to Pu(IV) upon contact with the carbon. The reaction began much more slowly
than that with C-CS. After one day contact the solution contains approximately 48%
Pu(VI) and 52% Pu(IV), and after 29 days contact the Pu(VI) content was reduced to
approximately 10%. The inset shows the full Pu(VI) peaks at 829.4 ± 1.5 nm, while the
main plot is scaled to display all spectral features.
Dissolution experiments
Experiments were performed to test whether the dissolution of Pu(IV) colloids and
precipitates by 1 M acids would occur faster in the presence of porous carbon solids. A
1.1 ± 0.1 mM Pu(IV) colloid solution was prepared by drop-wise addition Pu(IV) stock in
concentrated HCl to Milli-Q water. A small volume of 10 M NaOH was added to the side
of the vial halfway through addition of the Pu stock solution, and quickly mixed in to
maintain only slightly acidic conditions, without precipitation. The solution pH rose to
1.9 during 6 days of gentle rocking, then remained constant until the colloidal solution
was partitioned for batch and column experiments, a total of 11 days after preparation.
The absorbance spectrum showed the characteristic broad peak at 613 nm, and was
LLNL-JRNL-676901
16
Journal of Radioanalytical and Nuclear Chemistry
unaltered by centrifugation for 10 minutes at 7000 RPM. In the control sample, a small
volume of concentrated HClO4 was added to the colloidal solution to give a total acidity
of 1.0 ± 0.1 M, and the absorbance spectrum of the solution was measured after various
lengths of time, both in a control sample with no solid, and in batch contact samples with
200 ± 10 mL/g C-CS and AC powders. Another 1.00 ± 05 mL aliquot of the colloid
solution was acidified and immediately pushed through a glass column packed with 40 ±
4 mg AC particles (~3 cm × 2.5 mm diameter) with argon gas at an approximate rate of
25 min/mL. The absorbance spectra and LSC analysis of colloidal solution, measured at
various lengths of time after HClO4 was added showed features of both aqueous and
colloidal Pu(IV) after 15 hours but only aqueous Pu(IV) after 87 hours (see Fig. 15). LSC
measurements indicated 7 ± 10 and 28 ± 10 percent Pu missing from the solution phase at
15 h and 87 h, respectively. It is not clear whether this is due to Pu(IV) adsorption to the
polypropylene vial, or colloidal particles that aggregated into larger particles and were
centrifuged out of solution. In batch samples of acidified colloidal solution with C-CS
(Fig. 16) and AC, colloidal Pu(IV) particles seemed to adsorb or aggregate to carbon
particles, but dissolved completely to aqueous Pu(III) within the 87 hours. After 15 hours
contact with C-CS or activated carbon, only spectral features of Pu(III) were observed in
the absorbance spectra of the solutions, but LSC measurements indicated 15 ± 10 and 38
± 10 percent of the Pu was still sorbed to C-CS and AC, respectively. After 87-88 hours
of contact, only 4 ± 10 percent of the Pu was missing from solution phase in the carbon
samples, indicating near complete dissolution to Pu(III) occurred.
LLNL-JRNL-676901
17
Journal of Radioanalytical and Nuclear Chemistry
Fig. 11 Vis-NIR absorbance spectra of the colloidal Pu solution before and after addition
of concentrated HClO4 to give a 1.0 ± 0.1 M HClO4 solution. As the colloidal Pu(IV)
slowly dissolved into aqueous Pu(IV) , the broad peak at 615 nm disappeared, absorbance
of light around 650 nm increases, and the sharp peak at 472.6 ± 1.5 nm appears.
LLNL-JRNL-676901
18
Journal of Radioanalytical and Nuclear Chemistry
Fig. 12 Vis-NIR absorbance spectra of the colloidal Pu solution after addition of
concentrated HClO4 to give a 1.0 ± 0.1 M HClO4 solution, in batch contact with C-CS
mesoporous carbon powder. In the presence of C-CS, the Pu colloids dissolve into
aqueous Pu(III).
The AC column test showed that a porous carbon column may be used to partially
dissolve Pu(IV) colloids in 1 M acid on a much shorter timescale. LSC analysis of the
eluted solution showed that it contained 67 ± 7 % of the Pu that was loaded, and the
absorbance spectrum (Fig. 17) showed features consistent with aqueous Pu(III). It is
particularly interesting that the undissolved portion of Pu(IV) colloid appears to have
remained on the column, thereby separating it from the Pu solution. The effects of Pu
colloid particle size and carbon pore size on the adsorption and reductive dissolution of
Pu colloids is an interesting area for future studies.
LLNL-JRNL-676901
19
Journal of Radioanalytical and Nuclear Chemistry
Fig. 13 Vis-NIR absorbance spectra of a colloidal Pu solution before and after addition of
concentrated HClO4 to give a 1.0 M HClO4 solution, and after being eluted from a
column packed with activated carbon in 1 M HClO4. The AC column partially dissolved
and reduced the Pu colloids to aqueous Pu(III).
A 1.5 ± 0.1 mM Pu colloid solution with pH 2.04 was prepared as described above,
and rocked gently for 9.3 weeks before it was used for the dissolution/reduction
experiment. The Pu particles had grown or aggregated, such that 81 ± 4 % of the Pu was
removed from the solution by centrifuging 10 minutes at 7000 rpm, with a green
precipitate visible at the bottom of the conical vial after centrifugation. The particulates
were evenly distributed into a slurry by shaking the sample before portions were removed
and acidified to 1.09 ± 0.01 M HCl to test the dissolution of a control sample, and one in
contact with activated carbon (200 ± 10 mL/g). The concentration of Pu in the solution
phase of each sample after various lengths of time was determined via LSC, following
centrifugation of the samples for 10 minutes at 7000 rpm. The same experiment was
performed with C-CS and C-CS-COOH after the precipitate aged a total of 14 weeks.
LLNL-JRNL-676901
20
Journal of Radioanalytical and Nuclear Chemistry
Fig. 18 plots the Pu concentration measured in the samples described above, and
shows the carbon containing samples initially have less plutonium in the solution phase
than the acidified control samples. This likely occurs because as the particles dissolve to
become smaller, they remain in colloidal suspension in the control samples, but adsorb or
aggregate with the carbon particles. This is particularly evident with the C-CS-COOH
sample, where the high concentration of functional groups promotes adsorption of Pu,
even in acidic solutions. However, it appears that the reduction of Pu by the carbon
promotes faster dissolution of the Pu precipitates in the long run, especially the
unoxidized activated carbon and C-CS mesoporous carbon. Example absorbance spectra
measured of the supernatant after various lengths of dissolution time are shown with HCl
only (Fig. 19) and in the presence of C-CS (Fig. 20). These spectra confirmed that
reductive dissolution took place for all of the carbon samples. In 1.09 ± 0.01 M HCl
alone the precipitates only partially dissolved within the experimental timeframe, into
primarily aqueous Pu(IV). In the presence of activated carbon and C-CS the precipitate
dissolved completely into aqueous Pu(III). The oxidized C-CS-COOH also reduced the
Pu to Pu(III) as it dissolved, but in that sample some of the Pu remained associated with
the solid phase.
LLNL-JRNL-676901
21
Journal of Radioanalytical and Nuclear Chemistry
Fig. 14 Concentration of soluble Pu in mM vs. hours following acidification of Pu(IV)
precipitate slurries with 1. 09 ± 0.01 M HCl only (Control 1 and 2, hollow and black
squares) or in batch contact with AC (green circles) C-CS (blue triangles) and C-CSCOOH (red diamonds) carbon powders.
LLNL-JRNL-676901
22
Journal of Radioanalytical and Nuclear Chemistry
Fig. 15 Vis-NIR absorbance spectra measured in the supernatant from centrifugation of a
1. 09 ± 0.01 M HCl solution containing a Pu precipitate (aged 14 weeks in pH 2 solution
before HCl was added), after different lengths of time since HCl addition. The data shows
that the precipitate dissolved primarily to aqueous Pu(IV), with traces of higher oxidation
states.
LLNL-JRNL-676901
23
Journal of Radioanalytical and Nuclear Chemistry
Fig. 6 Vis-NIR absorbance spectra measured in the supernatant from centrifugation of a
1. 09 ± 0.01 M HCl solution containing a Pu precipitate (aged 14 weeks in pH 2 solution
before HCl was added), after different lengths of time since addition of HCl and C-CS
OMC. The data shows that the precipitate dissolved primarily to aqueous Pu(III).
Column Experiments
Approximately 30 mg of activated carbon or C-CS was packed into a glass
column (2 cm x 2.5 mm) as a slurry in 1 M HClO4, and solutions of Pu (1.25 ± 0.05 M
HClO4 and 1.20 ± 0.1 mM Pu(VI)) were reduced by passing through the columns. Fig. 21
shows the Vis-NIR absorbance spectra of the solution both before and after passing
through the AC column, and clearly illustrates that Pu(VI) was reduced to Pu(III) by
passing through the column of AC particles. Fig. 22 shows results from a similar
experiment with a column of C-CS particles. No preconditioning or changes of solution
matrix were necessary. The average elution rate was ~10 seconds per drop, which
required pressure in the AC column, but not the C-CS column, corresponding to
approximately 15 minutes per 1 mL aliquot of Pu (VI) solution reduced. Thus, it was
LLNL-JRNL-676901
24
Journal of Radioanalytical and Nuclear Chemistry
demonstrated that a column packed with mesoporous carbon is a convenient way to
reduce oxidized Pu to Pu(III) in acidic solutions.
Fig. 21 Vis-NIR absorbance spectra of a 1.25 ± 0.05 mM Pu in 1.25 ± 0.05 M HClO4
solution both before and after passing through a glass column packed with activated
carbon particles (2 cm x 2.5 mm). The Pu(VI) was quickly reduced to Pu(III) by passing
through the column.
LLNL-JRNL-676901
25
Journal of Radioanalytical and Nuclear Chemistry
Fig. 22 Vis-NIR absorbance spectra of a 1.25 ± 0.05 mM Pu in 1.25 ± 0.05 M HClO4
solution both before and after passing through a glass column packed with C-CS
mesoporous carbon particles (2 cm x 2.5 mm). The Pu(VI) was quickly reduced to Pu(III)
by passing through the column.
LLNL-JRNL-676901
26
Journal of Radioanalytical and Nuclear Chemistry
a
b
LLNL-JRNL-676901
27
Journal of Radioanalytical and Nuclear Chemistry
Fig. 23 Example visible absorbance spectra measured from 1.0 ± 0.2 mL fractions of 1.28
± 0.06 mM Pu in 1.13 ± 0.05 M HClO4, initially Pu(VI), eluted from a 2.5 mm diameter
glass column containing 33 ± 1 mg activated carbon powder. The Pu(VI) in the first 1 mL
(F2) Pu solution to pass through the column was reduced completely to Pu(III), and
subsequent fractions were partially reduced. Evidence of Pu(V) eluting from the column
is observed for F3-17 (Fig. 23a), while the Pu(VI) peak is only significant after 6 mL
eluted (F7-17, Fig. 23b).
To put constraints on the overall capacity of the carbons for the Pu(VI) to Pu(III)
reduction, batch samples of activated carbon and OMC spheres were prepared with 1.25
± 0.05 mM Pu(VI) in 1.25 ± 0.05 M HClO4, and liquid-to-solid ratios of 374 ± 10 mL/g
or 750 ± 20 mL/g, and one week total contact time. These samples contained 0.47 ± 0.02
and 0.94 ± 0.05 mmol Pu per g carbon, and the absorbance spectra of their supernatants
are shown in Fig. 24. These tests showed that the OMC spheres have a larger capacity to
reduce Pu(VI) to Pu(III) than the AC, as the solution with 0.94 mmol/g of OMCS is
completely reduced to Pu(III), while that in contact with AC is a mixture of Pu(III) and
Pu(IV).
LLNL-JRNL-676901
28
Journal of Radioanalytical and Nuclear Chemistry
Fig. 24 Absorbance spectra of initially 1.25 ± 0.05 mM Pu(VI) in 1.25 ± 0.05 M HClO4
solutions after one week of batch contact with AC and OMCS in the ratio of 0.47 ± 0.02
and 0.94 ± 0.05 mmol Pu per g carbon. The solutions in contact with OMCS reduced
completely to Pu(III) while samples with 0.94 ± 0.05 mmol Pu per g activated carbon
were reduced to a mixture of Pu(III) and Pu(IV).
Supplementary References
1. Hagan P G, Miner F J (1969) Spectrophotometric determination of plutonium III, IV,
and VI in nitric acid solutions. Report prepared for U.S. Atomic Energy Commission,
RFP-1391, UC-4 Chemistry, TID-4500-54th Ed.
LLNL-JRNL-676901
29