This document summarizes research on the adsorption, co-crystallization, and ion exchange mechanisms for technetium disposition in waste tanks at the Savannah River Site. Experiments studied technetium uptake by various sludge components including aluminosilicates, sodium oxalate, cryolite, iron and manganese oxides under oxidizing and reducing conditions. Key findings include: 1) Technetium showed low uptake by aluminosilicates like cancrinite and sodalite due to its large ion size excluding it from the crystal structure. 2) Under reducing conditions, technetium showed improved uptake by aluminosilicates and was more resistant to leaching.

1. ADSORPTION, CO-CRYSTALLIZATION AND ION EXCHANGE
AS MECHANISMS FOR TECHNETIUM DISPOSITION
IN SEVERAL SAVANNAH RIVER SITE WASTE TANKS
• K.Guerman, C. Delegard*, D. Hobbs**
• A. Ananiev, N. Budantseva,
• A. Fedoseev, S.Nikitenko,
• N. Popova, V. Shilov,
• V. Silin, V. Tarasov
Institute of Physical Chemistry of Russian Academy of Sciences
(Moscow, Leninsky pr.31, 119991,Russia)
* - Pacific Northwest National Laboratory,
(Richland, Washington 99352 U.S.A.)
**- Savannah River Site,

2. Institute of Physical Chemistry
Russian Academy of Sciences
D ir e c t io n
( E le c t io n s N o v e m b . 2 0 0 1 )
D e p a rtm e n t D e p a rtm e n t D e p a rtm e n t D e p a rtm e n t D e p a rtm e n t
S u r f a c e S c i. C o llo id S c i. R a d io c h e m is t r y P o ly m e r S c i. C o r r o s io n S c i.
250 2 5 0 re s . 3 5 0 re s 300 300
Lab. Lab. Lab. Lab. Lab. Lab. Lab. Lab.
TUE EX RCH IX IN J - 1 R A D -1 C a t a l. S O L ID
Lab. G RO UP G RO UP G RO UP Lab. Lab. Lab. Lab.
TP uE E L .C H . RCH&EC Tc IN J - 2 R A D -2 F IL T R . ANAL.
 Collaboration with US/DOE (Hanford, Savannah River and other
sites) was very important for IPC RAS in 1993-2001

3. Tc concentrations found in
99
various tank sludges at SRS
[Tc-99],
The discovery of relatively high Tank mCi/g dried Reference
99
Tc concentrations in Number solids
inorganic mineral sludge heels 17 0.462 d'Entremont et
taken from some tanks at the al. 1997
US-DOE Savannah River Site 20, white 0.34 d'Entremont and
(SRS) has prompted solids Hester 1996
investigations of Tc uptake 20, brown 0.94 d'Entremont and
from alkaline highly active solids Hester 1996
waste (HAW) by solid 42 0.22 Hay 1999
adsorbents
51 0.21 Hay 1999
8 0.22 Hay 1999
11 0.34 Hay 1999

4. The SRS waste volumes (Table 2.4 of "Integrated Database Report - 1993:
S.Spent Fuel and Radioactive Waste Inventories, Projections, and
Characteristics,”] Tc-99 quantities (Table 2.11), and
Tc-99 concentrations calculated from these data
Volume, Tc-99, Ci [Tc-99], [Tc], 106 Kd
liters Ci/liter g/liter total
Liquid 61.4 1.68E+04 2.74E-03 0.162 -
Sludge 13.9 1.14E+04 8.20E-03 0.483 3
Salt Cake 53.8 2.78E+03 5.17E-04 0.0305 0.2
Overall waste 129.1 3.098E+04 2.40E-03 0.141 -
Question to be studied : Which components absorb Tc with Kd
higher than 3 and are resistant to leaching?

5. Sludge components as carriers
for Tc(VII) and Tc(IV)
S O L ID S L U D G E C O M P O N E N T S
W H IT E S O L ID S B R O W N S O L ID S
A L U M IN O S IL IC A T E S M E T A L H Y D R O X ID E S
C A N C R IN IT E (F e , C r, M n )(O )(O H )
S O D A L IT E
. C R Y O L IT E . . P L A T IN U M G R O U P .
N a 3 A lF 6 M E T A L S
R h, R u, P d
. S O D IU M O X A L A T E .
N a 2C 2O 4
TiO2 was also tested

6. Experimental conditions for
precipitation and leaching tests:
Precipitation tests: Leaching modes:
 Wastes are alkaline  Surface leaching.
 Tc is redox sensitive  Complete dissolution.
 Sharp differences in the Leaching agents
redox potential within the  all precipitates : 0.1N NaOH
tanks are observed,
 aluminosilicates - NaHF2
So, both:
 oxidizing [Tc(VII)]  Na oxalate - 0.1N NaOH, NaNO2
 and reducing [Tc(IV)]  FeOOH - 0.1N NaOH, H2O2
 conditions were tested in  MnOOH - 0.1N NaOH, H2O2
0.1- 5 N NaOH + 0-5 N NaOH.
 TiO2 - 0.1- 3N NaOH
Methods: Liquid scintillation counting (LSC) of solutions, XRD, NMR, IR

7. Study of Tc uptake with Aluminosilicates
under oxidizing conditions at 70-130oC
 Literature data have demonstrated the possibility of
ClO4- and MnO4- co-crystallisaton with aluminosilicates :
purple Na8[AlSiO4]6(MnO4)2 (Weller,1999 etc.)
OUR EXPERIMENTS on TcO4- (reaction: NaAlO2+Na2SiO3+NaOH)
Solution Formed solid Kd
 TcO4- is too large
10-3-10-5M Tc and therefore it is
0.2-5M NaOH Cancrinite less 1
0.5-5 M NaNO3
excluded from the
aluminosilicate
10-3-10-5M Tc structure in both
0.2-5M NaOH Sodalite less 1
NaNO3 free
cancrinite and
sodalite

8. Case of Aluminosilicates formed
in concentrated Tc(VII) solution
 [Tc] = 0.2 M Fig. 1. NMR-99Tc spectrum of the aluminosilicate containing
 in NaNO3 solutions - cancrinite 57 mg-Tc/kg. Tc spectrum presents evidence for -30 ppm shift
characteristic of coordinated pertechnetate
 in NaNO3-free solutions - sodalite
 Although NMR spectrum presented
shift typical for coordinated Tc(VII)
its concentration is very low
 Dissolution in NaHF2 and LSC has
shown : [Tc] in solid cancrinite was
57 mg/kg ~ 100 times less than in
initial solution
 Tc is excluded from the
aluminosilicate structure

9. Study of Tc uptake with Aluminosilicates under
reducing conditions
(0.2M N2H5Cl, 1M NaNO3, T = 800С, t = 3 d)
Precipitation of Leaching conditions:
cancrinite↓
Leaching T, Leaching yield , Tc, %
NaOH Tc yield, agent: o
C
3 1 day 10 days
M %
hour
2.0 18.9 1M NaOH 20 0.8 1 3.7
4.0 32 2M NaOH 20 0.8 1.2 2.0
2.0 25.2 0.1M NaOH + 60 25 26.9 27
0.25 M H2O2
2.0 18.9 0.1M NaOH + 18 4 6.9 7
0.5 H2O2
4.0 32 0.1M NaOH + 18 6.5 6.9 11
0.5 H2O2
Under reducing conditions Tc uptake is important
Tc(IV) in aluminosilicates is resistant to leaching

10. Study of Tc(VII) sorption
by crystalline TiO2
under oxidizing conditions
 Tc(VII) was sorbed by TiO2
from neutral solution
with Kd = 30 ml/g.
 However, the Kd at pH=10
was only 3.3 ml/g  Among the
 No affinity to Tc(VII) was minerals tested for
noted for TiO2 at pH=12 Tc(VII) uptake,
and higher . high-density TiO2
MST and Silicotitanates was the most
yet not tested ..? efficient

11. Study of Tc uptake with
Na oxalate under
oxidizing and reducing conditions
NaOH + H2C2O4 = Na2C2O4
X-ray diffraction tests :
the precipitate is
sodium oxalate Na2C2O4
(PDF#20-1149)
 Tc(VII) is excluded from the Na oxalate structure
under oxidizing conditions (Kd = 1-2)
 Under reducing conditions Tc(IV) forms a separate
TcO2*1.6H2O phase - no interaction between Tc
hydroxide and Na oxalate were detected
 Tc precipitate is not resistant to leaching with 0.1 N
NaNO2

12. Study of Tc uptake with
Cryolite Na3AlF6 under
oxidizing and reducing conditions
6F-+NaAlO2+Na2CO3
X-ray diffraction tests :
the precipitate is cryolite Na3AlF6
 Reduced Tc :  Oxidizing
conditions:
 17-35% of Tc(IV) as
TcCl62- is co-  Kd is less 1
precipitated with
cryolite  Tc(VII) is excluded
 N2H5NO3 inhibits co- from cryolite
structure
precipitation

13. Study of Tc(IV) uptake
with Cryolite Na3AlF6
under reducing conditions
[NH4F] [Na2CO3] in [N2H5NO3], in Tc(IV)
No initial, final solution, final solution, uptake,
M M M %
1 2,0 0,6 - 20
2 2.5 0.6 - 23
3 3.0 0,6 - 26
4 4,0 0.6 - 28
5 6,0 0,6 - 35
8 2,0 0,4 - 25
9 2,0 0,8 - 17
10 2,0 0,6 0,1 0
• Tc(IV) is added as Na2TcCl6 to (NH4F+NaAlO2) solution
• No additional reducing agent in exp. No 1-9
• Leaching test were impossible to quantify relative to
real cryolite in tanks as complete peptization occurred.

14. Study of Tc(IV) uptake with
FeOOH under reducing conditions
 Reducing agent: 0.02M FeSO4, T = 600С, time = 3 h
 Precipitate : FeOOH/Fe2O3
Precipitation test: Leaching test (t=18 oC, d = days):
NaOH Tc in solid Leaching Leaching yield ,Tc, %
M phase, % agent: 1 d 10 d 29 d 105d
0.6 97 0.1M NaOH 1.0 9.8 14.9 24
2.0 88.0 1M NaOH 2.9 16.5 40.2 58
4.0 90 2M NaOH 0.8 2 3 8.2
Though Tc adsorbed better on iron hydroxides from 0.5–2.0 M NaOH
than from 3.0-4.0 M NaOH, the precipitates formed at lower NaOH
concentration were more easily leached by the NaOH leachant
Tc leaching with H2O2 was 20 % and with Na2S2O8 was70-100% in 100 days

15. Study of Tc(IV) uptake with
MnOOH under reducing conditions
 Reaction NaOH + Na2MnO4+ N2H5OH= MnOOH
X-ray diffraction tests : the freshly precipitated
solid was Mn2O3 , the aged precipitate was
manganite MnOOH (PDF#18-805)
MnOOH precipitation MnOOH leaching to 0.1 NaOH (1,3,4) and Na2S2O8(2)
12
1) Mn/Al=1/10
90 2) Mn/Al=1/40
10
3)Mn/Al=1/10
75
Tc uptake by precipitate, %
8 4) Mn/Al=1/40
Leached Tc, %
60
Mn/Al=1/10 6
45
30 Mn/Al=1/40 4
15 2
0
0
0 5 10 15 20 25 30
0 2 4 6 8 10 12
Time,d Time. d
 Manganese(III) oxides were effective Tc carriers and underwent
chemical transformations on ageing that increased leaching resistance
to most agents.

16. What additional work is necessary to clarify
results obtained in the present work
 It is still possible that some polymeric inorganics involving larger ions
(like titanium, forming hydroxides, complex titanates and Silicotitanates)
could be better sorbents for TcO4-, - additional tests of different (Ti?)
compounds could explain some cases of Tc presence in sludge, and
possibly result in efficient inorganic Tc(VII)-sorbent for long-term storage.
 Tests of the Tc/Fe hydroxide co-precipitate formed at 4M NaOH could be
continued aiming to demonstrate the nature of the precipitate and its
stability domain. EXAFS/XANES, Tc-NMR and γ -resonance spectroscopy
could be useful for Tc speciation under these conditions.
 Co-precipitation tests could be continued with the transition metal
hydroxide mixtures (Fe/Ti, Mn/Al, Ti/Cr, Ti/Zr and others) as these could
provide higher affinity to reduced technetium, or even Tc(VII) and higher
resistance to leaching. Tc speciation experiments in these cases are
desirable.

17. Acknowledgements
• This work was supported by the U.S. Department of Energy Under a
contract to the Institute of Physical Chemistry RAS by the Office of
Environmental Management, Efficient Separations and Processing
Cross cutting Program.
• We recognize the organizational skill of Dr. M. Khankhasaev in
contract implementation, Liliya Petrachenkova (SAIC), Dr. V.
Polyanichko, IPC financial manager Edouard German and RAS corr.-
member A.K. Pikaev for administrative assistance.
• We are thankful to Dr.D. Hobbs for his encouraging attention to this
work, useful discussions and elaboration of the experimental program