cesium removal from hanford tank waste solution using resorcinol‐formaldehyde resin
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This article was downloaded by: [Moskow State Univ Bibliote]On: 18 February 2014, At: 21:14Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK
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Cesium Removal from HanfordTank Waste Solution UsingResorcinol‐Formaldehyde ResinNeguib M. Hassan a & Kofi Adu‐Wusu a
a Savannah River Technology Center , WestinghouseSavannah River Company , Aiken, SC, USAPublished online: 15 Feb 2007.
To cite this article: Neguib M. Hassan & Kofi Adu‐Wusu (2005) Cesium Removal fromHanford Tank Waste Solution Using Resorcinol‐Formaldehyde Resin, Solvent Extractionand Ion Exchange, 23:3, 375-389, DOI: 10.1081/SEI-200056519
To link to this article: http://dx.doi.org/10.1081/SEI-200056519
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Cesium Removal from Hanford Tank WasteSolution Using Resorcinol-Formaldehyde
Resin
Neguib M. Hassan and Kofi Adu-Wusu
Savannah River Technology Center, Westinghouse Savannah River
Company, Aiken, SC, USA
Abstract: Experiments with Hanford actual waste sample from Tank 241-AW-101 and
resorcinol-formaldehyde resin demonstrated that up to 208 BV of cesium (137Cs) can
be removed in a single-pass through an ion exchange column before a 50% break-
through occurs. This loading performance for the resorcinol-formaldehyde resin was
better than that previously obtained for the baseline resin (SuperLigw 644) under the
same experimental conditions. The elution of the resorcinol-formaldehyde resin with
0.5 M HNO3 was effective requiring only 16.5 BV to elute 99% of the cesium (i.e.
C/Co value ,0.01) loaded on the column. The peak concentration for 137Cs
occurred between 4 and 6 BV with concentration approximately 100 times that of
the feed. The metal ions found in the eluate solution above their detection limits
were Al, B, Ca, Cs, Na, and Si. Nitrate was the only anion detected and 238Pu,239/240Pu, and U were slightly enriched in the eluate solution. Large sample
dilutions prevented the detection of other species.
Keywords: Cesium, resorcinol-formaldehyde, Hanford, tank waste
INTRODUCTION
The US Department of Energy (DOE) is building a nuclear waste treatment
facility at the Hanford Site, in Richland, Washington, where millions of
gallons of high-level and low-level radioactive waste are currently stored in
Received 6 September 2004, Accepted 5 January 2005
Address correspondence to Neguib M. Hassan, Savannah River Technology Center,
Westinghouse Savannah River Company, Aiken, SC 29808, USA; E-mail: neguib.
Solvent Extraction and Ion Exchange, 23: 375–389, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0736-6299 print/1532-2262 online
DOI: 10.1081/SEI-200056519
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underground storage tanks. The Hanford Site has 177 underground tanks that
store 204 million liters (54 million gallons) of high-level and low-level radio-
active waste. Large portions of the waste exist as liquid solution (supernatant)
that contain the following radionuclides: 137Cs, 99Tc, 90Sr, and transuranic
actinides. The major contaminants in the supernatant prior to pretreatment
include 137Cs (t1/2 ¼ 30 y), 99Tc (t1/2 ¼ 2.13 � 105 y), and 90Sr (t1/
2 ¼ 28.6 y). The radioactivity in the Hanford Site waste supernatant is
primarily from the fission products 137Cs and 90Sr. These radionuclides are
produced by the fission of uranium or plutonium in relatively high yield and
they pose a serious radiation hazard to health and environment.
Removal of 137Cs from the bulk waste is required to produce a low-
activity waste (LAW) that can be vitrified into LAW glass. The design of
the facility provides for total cesium removal via ion exchange, recovery of
separated Cs concentration into a relatively small volume, and incorporation
in high-level waste sludge. This sludge is vitrified into HLW glass logs
suitable for permanent disposal in a federal repository. Cesium (137Cs)
removal from nuclear waste solutions using inorganic ion exchange
materials has been widely investigated.[1 – 8] The ion exchange materials
examined include potassium and cobalt hexacyanoferrates, ammonium
molybdophosphate incorporated in a polyacrylonitrile support (AMP-PAN),
and crystalline silicotitanate (CST). Prout and co-workers showed that
potassium hexacyanoferrates (K2CoFe(CN)6) was highly selective for
cesium, but the ion exchange material was not stable in very high alkaline
waste solutions.[1] The AMP PAN material exhibited good performance in
acidic waste solution and the elution of cesium from the resin with 8 M
nitric acid was effective.[2,3] Studies on crystalline silicotitanate (CST) resin
indicated that the material exhibits strong retention for cesium in both
acidic and alkaline solutions;[4 – 8] but it is chemically unstable in the
alkaline waste and it cannot be regenerated.
Organic ion exchange resins, such as the resorcinol-formaldehyde (RF),
Duolitew CS-100, Diphonix-CSTM
, and SuperLigw 644, have been used for
cesium removal from Hanford Site nuclear waste solutions. The RF resin
developed by Bibler and Wallace[9] was tested for uptake of cesium in
alkaline radioactive waste at the Hanford Site and Savannah River Site.[10–12]
The performance of the earlier RF resin batches was highly variable
because the resin was subject to oxidation during storage and pretreatment.
Other investigators using the RF resin for cesium removal from nuclear
waste solutions were reported.[13,14] Studies to remove cesium from waste
supernatants with commercially available Duolitew CS-100 carboxylic acid
were reported.[15,16] Duolitew CS-100, a polymer of phenol-carboxylic, is
similar to the RF resin but the resin was less selective for cesium over
sodium and multiple loading and elution cycles were required to obtain the
desired performance. Chiarizia and co-workers developed Diphonix-CSTM
resin with phenol groups attached to the polymeric matrix to bind
cesium.[17 – 19] The resin can be used to simultaneously adsorb actinides,
N. M. Hassan and K. Adu-Wusu376
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cesium, and strontium from high-level waste solutions. Although the resin has
not yet been tested with actual waste it has performed well with Hanford Site
simulated waste solution. Extensive ion exchange testing was recently
performed at the Hanford and Savannah River sites using small-scale
columns with resin to remove cesium from actual waste samples retrieved
from various Hanford Site waste tanks.[20 – 23] SuperLigw 644 resin, a crown
ether ligand attached to an organic substrate, exhibited excellent loading
and elution performance with all Hanford Site waste categories. However,
pilot-scale tests revealed high pressure drops across the resin bed columns
during transition from regeneration to loading and elution. Therefore, due to
concerns of poor hydraulic performance and inability to maintain a homoge-
nously packed resin bed for efficient removal of cesium, the RF resin is under
consideration to replace SuperLigw 644 as the baseline ion exchange resin for
the Hanford Waste Treatment Plant. The RF resin was chosen because it has
high loading capacity per unit volume WTP process flow sheet and will
require minimal design changes. In addition, the RF resin is commercially
available in granular and, if desired, in spherical form to avoid hydraulic
problems.
EXPERIMENTAL
Ion Exchange Material
The resorcinol-formaldehyde (RF) resin was obtained as granular product
from Boulder Scientific Co. (Boulder, CO). The resin was prepared by
caustic condensation polymerization of resorcinol and formaldehyde. It is
highly selective for cesium, which primarily exists as dissociated ion in
highly alkaline waste solutions present in Hanford Site waste tanks. The ion
exchange mechanism for resorcinol formaldehyde involves a reversible equi-
librium exchange of cesium with sodium, the dominant bound species on the
resin. The major competitors against cesium for adsorption on RF active sites
are potassium and hydrogen ions. High selectivity for cesium over the compe-
titor ion is required for the overall effectiveness of the resorcinol formal-
dehyde resin for cesium removal from different Hanford Site waste types.
Since both potassium and sodium are present in Hanford tank wastes at con-
centrations that are orders of magnitude larger than the cesium ion concen-
tration. The equations representing the exchange of sodium with cesium and
potassium are as follows:
R� Naþh i
þ Csþ� �
R� Cs� �
þ Naþ� �
R� Naþ� �
þ Kþ� �
R� K� �
þ Naþ� �
Cesium Removal from Hanford Tank Waste Solution 377
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Where R-Naþwith the over bar represents the resin matrix in the sodium form.
The RF resin is eluted with dilute nitric acid (0.5 M HNO3), which promotes
the protonation of the resin to release cesium into the aqueous solution,
leaving behind the resin in the hydrogen form.
The RF resin sample used in this work was prepared by combining a 6-L
production batch (BCS-187-1-0002) with a 600-g production batch (BCS-187-
4-0001). The combined resin was split several times using an open-pan riffle
sampler (Model H-3980, Humboldt Manufacturing, Co., Norridge, IL) to
produce representative sub-samples. Two 1-liter sub-samples were transferred
into air-tight polyethylene bottles and the headspace above the resin was
purged with nitrogen. The resin was stored dry in the potassium form. The
resin was converted to the sodium form immediately before being used in
the batch contact measurements.
Hanford Site Waste Solutions
In the tests, Hanford actual waste sample containing radioactive 137Cs and a
pretreated waste sample that was spiked with non-radioactive 133Cs were
used. The waste samples were retrieved from Hanford Site Tank 241-AW-
101. The as-received samples were homogenized, and then diluted with de-
ionized water to provide approximately 5 M Naþ concentration in the waste
sample. After dilution, the bulk solution was sampled and analyzed. The
bulk solution was then filtered through a 0.1-micron sintered metal Mott
filter to remove entrained solids. A total of 15 L of the AW-101 filtrate at
5 M Naþ was treated in a multiple ion exchange column tests with
SuperLigw 644 resin. A total of two liters of the pretreated waste sample
was later spiked with non-radioactive cesium (133Cs) and used for cesium
removal with the RF resin. The compositions of treated and actual waste
solution used are shown in Table 1.
Procedure
The apparatus used for cesium removal from Hanford waste samples with
resorcinol formaldehyde was described elsewhere.[23] The ion exchange
columns were made of borosilicate glass and had an inside diameter of
1.45 cm (i.e., 1.65 mL/cm of height). Graduations on the column walls were
used to monitor the height of the resin bed and liquid head space above it.
The glass columns were equipped with adjustable polypropylene plungers
(model 124108, Spectrum Chromatography, Houston, TX) at the top and
200 mesh stainless steel screens at the bottom. The plungers were used to
adjust the height of liquid above the resin beds, while the screen was used
to support the resin. A constant-temperature water bath (Model DC10-P5,
N. M. Hassan and K. Adu-Wusu378
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Table 1. Composition of Hanford waste sample from Tank 241-AW-101
Analyte Treated (mg/mL) Actual (mg/mL)
Ag 0.245 ,0.150
Al 12,000 12,305
B 35.5 ,16.2
Ba 0.323 ,0.150
Ca 7.32 ,4.53
Cd 1.46 ,0.200
Ce 2.87 ,2.48
Cr 34.0 45.1
Cu 1.22 ,0.310
Fe 1.78 0.820
Gd ,0.284 ,0.270
K 26,600 (0.68 M) 20,068 (0.52 M)
La 0.418 ,0.200
Li 1.00 ,0.850
Mg ,0.62 ,0.620
Mn ,0.22 ,0.220
Mo 32.2 33.3
Na 112,000 (4.87 M) 113,563
(4.93 M)
Ni 4.33 ,0.750
P 143 144
Pb 20.6 28.3
S 191 194
Sb 32.9 33.6
Si 205 157
Sn 60.2 730
Sr 2.27 ,1.00
Ti ,0.06 ,0.060
U ,7.55 ,7.55
V 3.40 3.54
Zn 4.96 ,0.55
Zr 5.45 2.97
F2 93.1 131
(HCOO)2 403 805
Cl2 2,290 2,623
NO22 42,550 33,718
NO32 79,680 89,600
PO42 257 380
SO42 134 163
(C2O4)22 185 229137Cs 0.073 (0.847) 2.04 (173)133Cs 8.12 5.43
(continued)
Cesium Removal from Hanford Tank Waste Solution 379
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Thermo-Haake, Newington, NH), circulating water through the column glass
jackets, was used to maintain the resin bed at the desired temperature. The
outer walls of the columns and jackets were coated with polyvinyl chloride
to help minimize hazard in case of breakage.
A portion of the RF resin (�12 mL) was weighed in HDPE container.
Five bed volumes of 1 M NaOH solution were added to the container, and
then gently swirled to create resin slurry. Prior to resin transfer to the
column, 1 M NaOH solution was first poured into the column to a level that
is twice the column diameter. The resin slurry was then poured into the
column through a funnel while a drain valve was slowly opened to draw off
the excess liquid at the bottom of the column. To prevent air entering the
column from the bottom, the drain valve was connected to a hose with a
low point. The walls of the glass column were tapped simultaneously when
portions of the resin slurry were poured into the column. This was done to
ensure the resin bed was uniformly packed. When all the resin slurry was
added to the column, the resin height was measured. The quantity of resin
(dry mass) added to the column was recorded.
Two column tests were performed during this study. A shake-down test
was first conducted to verify that the resin bed column was properly function-
ing before proceeding with Hanford actual waste sample testing. This test was
conducted with previously treated waste from Tank AW-101 that was spiked
Table 1. Continued.
Analyte Treated (mg/mL) Actual (mg/mL)
135Cs 0.08 1.51
Total Cs 8.27 9.03137Cs/Total Cs 0.009 0.22660Co nm (2.11 � 1024)154Eu nm ,(9.92 � 1025)155Eu nm ,(3.41 � 1024)235U nm ,0.00015238U nm 1.24238Pu nm 5.04 � 1024
239Pu/240Pu nm 2.28 � 1024
241Am nm ,1.00 � 1024
Gross Alpha nm ,1.08 � 1022
Total Carbon
(mg/L)
TIC 14,115 nm
TOC 1,050 nm
Total Base, M 2.83 nm
Free OH2, M 2.09 nm
Density, g/mL 1.23 1.24
N. M. Hassan and K. Adu-Wusu380
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with non-radioactive cesium at initial concentration of 8.12mg 133Cs/mL. The
concentration of total cesium (all isotopes included) was 8.27mg/mL. The test
was conducted in a radiochemical hood. The second test was conducted in a
shielded cell.
The feed was transferred down through the columns at 3 BV/hr. The
loading of the column was considered to begin when the feed sample
reached the liquid above the resin bed. During loading, the height of the
resin, the liquid above the resin bed, and the temperature of water bath circu-
lator were measured. The temperature of liquid circulated through the column
jacket was maintained 25 + 28C. Aliquot (�6 mL) samples of the effluent
from the column were collected during the loading cycle at 10-BV increments.
A total 270 BV of the treated AW-101 sample had been processed during the
shake-down test. After loading was completed, the residual feed in the column
headspace was displaced from the column using 6 BV of 0.1 M sodium
hydroxide solution at 3 BV/hr. This was followed by 6 BV of deionized
water pumped down flow through the column at 3 BV/hr. The feed displace-
ment and deionized water effluents were collected from the column in 1 BV
increments.
At the end of feed displacement and water rinse steps, the column was
eluted with 0.5 M HNO3; elution was performed at 1.5 BV/hr. Eluate
samples from the were collected manually in 1.5 BV increments for the first
five samples, then every 3 BV for the next three samples, and the last five
samples were collected in 3.5 BV increments. Collection of the eluate
samples in different BV increments was necessary because of manpower con-
straints. After elution, the column was rinsed with 6 BV of water at 3 BV/hr.
Rinse solution was collected in 1 BV increments. The column was stored in
water for several weeks until they were transferred into shielded cell for hot
sample testing.
In the cell, the second column test was conducted using Hanford waste
sample that had a 137Cs concentration (initial) of 173mCi/mL; the total
cesium concentration was 9.03mg/mL. The column was regenerated by trans-
ferring 6 BV of 1 M sodium hydroxide solution in the down-flow direction at
3 BV/hr. Regeneration solution was collected in 1 BV increments. After
regeneration, the actual waste sample was pumped down flow through the
column at 3 BV/hr through. All process steps such as, column loading, feed
displacement, water rinse, and elution, were performed as previously
described. Experimental conditions and process solutions used in the shake-
down and actual waste column tests are given in Table 2.
RESULTS AND DISCUSSION
Fig. 1 shows the results of the column shake-down test with RF resin and
treated waste sample containing non-radioactive cesium (133Cs) at the
Cesium Removal from Hanford Tank Waste Solution 381
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concentration of 8.12 mg/mL. The C/Co (i.e., the concentration in the
effluent divided by the concentration of the feed) was plotted in Fig. 1
(open circles) as a function of the number of bed volumes (BV) processed
through the column. The onset of cesium breakthrough, defined as
C/Co � 0.01, was detected after processing 90 BV of waste solution
through the lead column. After 90 BV, the breakthrough sharply increased
upward and reached 46% breakthrough at 270 BV. At this point, the run
was terminated due to insufficient feed. Extrapolation of the data to 50%
breakthrough would indicate a 280 BV could be processed. From previous
batch Kd data,[24] the amount of waste to process at 50% breakthrough
was predicted as 246, which is very close (i.e., within 12% difference) to
Table 2. Experimental conditions for column tests
Process step Solution
Bed volume
processed
Flow rate,
(BV/hr)
Process
time (h)
Regeneration 1 M NaOH 6 3 2
Feed loading Treated AW-101 270 3 90
Actual AW-101 160 3 53
Feed displacement 0.10 M NaOH 6 3 2
Caustic rinse DI water 6 3 2
Lead column elution 0.5 M HNO3 52 1.5 �35
36 1.5 �24
Post-elution rinse DI water 6 1.5 4
Temperature ¼ 25 + 28C.
Bed volume (BV) ¼ 12 mL (in treated AW-101 waste sample).
Figure 1. Cesium breakthrough curve (shake-down test).
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projected value from this results. The amount of cesium loaded on the
column was calculated from the area above the breakthrough curve
(Fig. 1) at 46% breakthrough. The amount of cesium loaded on the
column was calculated as 23902mg. Using a dry mass of 4.297 g Na-form
resin in the column, the cesium loading was 5562mg 133Cs/g dry resin.
The cesium loaded on the column from the shake-down test was eluted
with 0.5 M HNO3 at 1.5 BV/hr (0.3 mL/min). Fig. 2 displays the elution
results, where the C/Co was plotted in a semi-log scale as a function the
number BV of eluate. The elution started (zero BV) when the nitric acid
(0.5 M) initially contacted the liquid in the column head space above the
resin bed. It required approximately 4 BV of the acid to displace the liquid
in the column and resin void volume. The pH data shown on the right axis
of Fig. 2 (open circles) indicate a steep drop of the pH to �1 at 4 BV and
the peak C/Co of the elution curve shown on the left axis of Fig. 2 was
observed at 5–6 BV (i.e., immediately after the pH drop). After the peak,
the elution curve decayed exponentially to C/Co ¼ 0.01 at 18–20 BV. The
column was eluted with a total 52 BV of 0.5 M HNO3, after which the
C/Co approached 0.001.
The amount of cesium eluted from the column (23.678 g) was calculated
from the area under the elution curve. This compares very well with the
amount of cesium (23.902 g) loaded on the column, which was calculated
from the area above the breakthrough curve. From these two numbers, the
cesium elution was complete. In previous work,[25] the cesium elution from
RF resin exhibited a peak C/Co at 4–6 BV and the C/Co value at the peak
was less than 40. Also, a long elution tail was reported.
Figure 2. Cesium elution (shake-down test)
Cesium Removal from Hanford Tank Waste Solution 383
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Fig. 3 shows the breakthrough curve for 137Cs on the RF resin, along with
the breakthrough data for the baseline, SuperLigw 644 resin. Very little cesium
was detected (C/Co ,0.01) in the effluent from the RF column until 80 BV
was processed. After this point, the breakthrough sharply increased and
reached 19% at 160 BV; extrapolation of the RF breakthrough data to 50%
would show 212 BV. In contrast, cesium was detected in the effluent from
SuperLigw 644 resin columns only after processing 20 BV and the break-
through was more rapid, reaching 45% at 130 BV.[21] Similar results of
cesium early breakthrough behavior from the SuperLigw 644 resin column
were reported by Kurath.[1] The amount of cesium loaded on the RF resin
during the actual waste test (319,087mCi or 3,668mg) was calculated from
the area behind the curve in Fig. 3 up to 19% breakthrough. Based on the
dry mass of resin used in the column (4.297 g), the cesium loading was
�7.43 � 104mCi/g dry resin or 854mg/g resin on a dry weight basis. The
difference in the amount of cesium loaded on the RF resin bed during the
shake-down and the actual waste column testing is higher than expected.
There are several reasons for the reported low performance for SuperLigw
644 columns. First, the initial concentration of 137Cs in the AW-10 waste
sample tested with SuperLigw 644 resin was 204mCi/mL as compared to
173mCi/mL in the sample used with RF resin. Second, the SuperLigw 644
resin batch previously used may not have been protected from air oxidation,
which severely degrades the resin and lowers performance. Significant
improvements have been made since then both in the manufacturing
process and laboratory handling of the SuperLigw 644 resin samples. A
more recent test[23] using SuperLigw 644 with the AW-101 waste sample con-
taining 173mCi/mL 137Cs exhibited less than 8% breakthrough after 194 BV,
Figure 3. Cesium breakthrough curve for RF resin (actual column test)
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but the flow rate (0.69 BV/h) was 4 times lower than that used for the RF resin
testing (3 BV/h).
Fig. 4 shows the elution data for 137Cs on RF resin. The elution was
performed at a flow rate of 1.5 BV/h with 0.5 M HNO3. The elution of the
RF resin with actual waste sample was similar to that observed in the
shake-down test. Very little cesium eluted from the column during the first
4 BV when the eluent had passed through the column. During this time, the
NaOH in the column head space was neutralized and, because the pH was
still at 12, no cesium was eluted from the resin. After 4 BV, the effect of
the acid (Hþ) exchange with cesium was noted at the bottom of the column,
where the pH of the eluate solution started dropping to 10. At 6 BV, the pH
dropped to 2.5 and the C/Co peak for 137Cs was occurred. After the peak,
an exponential decay of C/Co to 0.01 was observed at 17 BV. The elution
was continued until 36 BV of eluate was processed and at this point, the
C/Co dropped to 0.0018.
The amount of cesium eluted from the column was calculated from the
area under the elution curve, the initial concentration of 137Cs in the feed,
and the volume of the resin bed. The amount of 137Cs eluted was
319,704mCi (3.668 mg) vs the amount 319,087mCi or 3.668 mg loaded on
the resin. Thus, the cesium elution was again complete as indicated by the
cesium recovery of �100%.
Table 3 shows the swelling and shrinking history of the column of the
shake-down test during exposure to different process solutions during. The
solutions were alkaline waste (loading), 0.1 M NaOH (feed displacement),
0.5 M HNO3 (elution), and 1 M NaOH (regeneration). The results indicated
Figure 4. Cesium elution curve and eluate pH (actual waste column test)
Cesium Removal from Hanford Tank Waste Solution 385
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that the RF resin had swollen in 1 M NaOH preconditioning solution and con-
tracted in 0.5 M HNO3 solution during elution. The percent volume change
between fully swollen bed in 1 M NaOH (Na-form) and fully contracted bed
in 0.5 M HNO3 solution (H-form) was 26. This swelling/shrinking behavior
of RF resin is similar to that of most recent SuperLigw 644 resin batch
(1 gallon batch: I-D5-03-06-02-35-60), which recorded a percent volume
change of �22% between elution and preconditioning.[23] The feed displace-
ment solution (0.1 M NaOH) and DI water had no swelling/shrinking effect on
the RF resin. Swelling is often observed when the resin converts from
hydrogen to sodium form. Generally, some swelling of the resin is desirable
for the ion exchange process to take place. A swollen resin, allows faster
mass transfer by reducing intra-particle resistance. Resin swelling and
shrinking, however, can become undesirable from operations point of view
since excessive swelling could potentially cause hydraulic problems and chan-
neling. The swelling and shrinking behavior of this resin batch was essentially
invariant with superficial velocity under the present experimental conditions.
Table 4 shows the concentrations of some cations of interest in the feed,
column effluent, and column eluate solutions. Uranium in the eluate product
was enriched 1.6 times its feed composition and depleted in the effluent
solution. Chromium and lead were not detected in the eluate product due to
Table 3. Bed swelling and shrinking history (shake-down test)
Process step Solution
Bed volume (mL)
shakedown
Bed volume
(mL) actual
Resin preconditioning 1.0 M NaOH 12.5 12.5
Treated waste loading AW-101 waste 12.1 12.2
Feed displacement 0.1 M NaOH 12.1 12.2
De-ionized water rinse De-ionized water 12.2 12.2
Elution 0.5 M HNO3 9.6 9.6
Post-elution rinse De-ionized water 9.2 9.2
Table 4. Concentration of metal competitors
Total volume (mL) Na Cr Pb 238U
Feed, mg/mL 2094 1.14 � 105 (4.93) 45.1 28.3
1.24
Effluent, mg/mL 1998 1.02 � 105 (4.41) 38.9 22.2
0.476
Eluate, mg/mL 430 8.97 � 102 ,4.43 ,36.3
2.05
Values in bracket () are molar units.
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large sample dilutions required to remove samples from the shielded cell. Both
chromium and lead were depleted in the column effluent product.
Table 5 shows a summary of radionuclude partitioning in the feed,
column effluent, and eluate solutions. The 137Cs was the only gamma
emitting radionuclide detected in the eluate solution; large quantity of 137Cs
prevented the detection for other gamma emitters, such as 60Co, 154Eu, and155Eu. Alpha emitting actinides, 238Pu, 239/240Pu, and, 241Pu were detected
in the column eluate, although they were only slightly enriched by 2.7 and
1.6 times their feed concentration. It is not clear from this limited study if
the resin has affinity to adsorb the actinide species.
To meet the Low Activity Waste (LAW) vitrification criteria for Hanford
wastes samples from Tank 241-AW-101, the 137Cs concentration in the
column effluent product should be less than 8.7 � 1022mCi 137Cs/mL. As
shown in Table 5, the average concentration of 137Cs in the column effluent
product was 4.2 � 1023mCi/mL, which is 20 times below the concentration
limit for LAW waste samples at �5 M sodium. Thus, the percent removal
of 137Cs was better than 99.99%, and the overall DF for 137Cs was
4.11 � 104. The percent removal and the DF were calculated from the concen-
trations of 137Cs in waste sample feed (173mCi/mL) and in the column
effluent product (Table 5). The results generally demonstrate that the perform-
ance of the RF resin has exceeded the LAW vitrification criteria under the
current experimental conditions.
CONCLUSION
Experimental study to evaluate cesium removal from Hanford actual waste
sample from Tank 241-AW-101 using resorcinol-formaldehyde (RF) resin
has been conducted. The cesium loading on the RF resin with non-
radioactive cesium (133Cs) that was spiked into previously treated
AW-101 waste at an initial concentration of 8.12mg/mL was approximately
Table 5. Summary of radionuclide/actinide partitioning
Volume (mL) 137Cs 238Pu 239/240Pu 241Am
Feed, mCi/mL 2094 1.73 � 102 5.40 � 1024 2.28 � 1024
,1.00 � 1024
+6.48 � 1025 +3.73 � 1025
Effluent, mCi/mL 1998 4.20 � 1023 1.19 � 1025 1.43 � 1025
,6.69 � 1026
+3.65 � 1026 +4.62 � 1026
Eluate, mCi/mL 430 8.0 � 102 1.47 � 1023 3.58 � 1024
,1.14 � 1024
+1.62 � 1024 +8.95 � 1025
Cesium Removal from Hanford Tank Waste Solution 387
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280 BVs at projected 50% breakthrough. The loading on the resin with actual
AW-101 waste containing 137Cs at initial concentration of 173mCi/mL (total
cesium 9.03mg/mL) was 208 at projected 50% breakthrough. The percent
volume change of the resin bed volume between elution and regeneration
was 26%. This low swelling/shrinking behavior of the RF resin with
varying pH and ionic strength of the process solutions is desirable to
avoid certain hydraulic problems. The elution of the RF resin with 0.5 M
HNO3 was effective, requiring only 16 BV to remove up to 99% of
cesium loaded. The peak 137Cs concentration was sharp and the elution
tail was short.
ACKNOWLEDGMENTS
This work was conducted by Savannah River National Laboratory (SRNL) in
Aiken, South Carolina. The Hanford River Protection Project-Waste
Treatment Plant (RPP-WTP) funded this work. The authors are very
grateful to Karen Palmer, Betty Mealer, and Yvonne Simpkins for their
assistance in the experimental work.
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