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ADSORPTION, CO-CRYSTALLIZATION AND ION EXCHANGEADSORPTION, CO-CRYSTALLIZATION AND ION EXCHANGEAS MECHANISMS FOR TECHNETIUM AS MECHANISMS FOR TECHNETIUM DISPOSITIONDISPOSITION
IN SEVERAL SAVANNAH RIVER SITE WASTE TANKSIN SEVERAL SAVANNAH RIVER SITE WASTE TANKS
• K.Guerman,K.Guerman, C. Delegard*, D. Hobbs**C. Delegard*, D. Hobbs**• A. Ananiev, N. Budantseva, A. Ananiev, N. Budantseva, • A. Fedoseev, S.Nikitenko, A. Fedoseev, S.Nikitenko, • N. Popova, V. Shilov, N. Popova, V. Shilov, • V. Silin, V. TarasovV. Silin, V. Tarasov
Institute of Physical Chemistry of Russian Academy of SciencesInstitute of Physical Chemistry of Russian Academy of Sciences(Moscow, (Moscow, Leninsky pr.31, Leninsky pr.31, 119991,Russia)119991,Russia)
* - Pacific Northwest National Laboratory, * - Pacific Northwest National Laboratory, (Richland, Washington 99352 U.S.A.)(Richland, Washington 99352 U.S.A.)
**- Savannah River Site, **- Savannah River Site,
Institute of Physical Institute of Physical Chemistry Chemistry
Russian Academy of Russian Academy of SciencesSciences
D epartm entSurface Sci.
250
D epartm entC ollo id Sci.
250 res.
Lab.TPuE
Lab.TU E
Lab.EX
G R O U PEL.C H .
G R O U PR C H &EC
G R O U PTc
Lab.R C H
Lab.IX
Lab.IN J-2
Lab.IN J-1
Lab.R AD -2
Lab.R AD -1
Lab.F ILTR .
Lab.C ata l.
Lab.AN AL.
Lab.SO LID
D epartm entR adiochem istry
350 res
D epartm entPolym er Sci.
300
D epartm entC orrosion Sci.
300
D irection(E lections N ovem b. 2001)
Collaboration with US/DOE (Hanford, Savannah River and other sites) was very important for IPC RAS in 1993-2001
9999Tc concentrations found in Tc concentrations found in various tank sludgesvarious tank sludges at at SRSSRS
Tank Tank NumberNumber
[Tc-99], [Tc-99], mCi/g mCi/g dried dried solidssolids
ReferenceReference
1717 0.4620.462 d'Entremont et d'Entremont et al. 1997al. 1997
20, white 20, white solidssolids
0.340.34 d'Entremont d'Entremont and Hester and Hester 19961996
20, brown 20, brown solidssolids
0.940.94 d'Entremont d'Entremont and Hester and Hester 19961996
4242 0.220.22 Hay 1999Hay 1999
5151 0.210.21 Hay 1999Hay 1999
88 0.220.22 Hay 1999Hay 1999
1111 0.340.34 Hay 1999Hay 1999
The discovery of relatively The discovery of relatively high high 9999Tc concentrations in Tc concentrations in inorganic mineral sludge inorganic mineral sludge heels taken from some heels taken from some tanks at the US-DOE tanks at the US-DOE
Savannah River Site (SRS) Savannah River Site (SRS) has prompted has prompted
investigations of Tc uptake investigations of Tc uptake from alkaline highly active from alkaline highly active
waste (HAW) by solid waste (HAW) by solid adsorbentsadsorbents
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], Volume, Tc-99, Ci [Tc-99], [Tc], 10[Tc], 106 6 KdKd
liters liters Ci/liter Ci/liter g/liter total g/liter total
Liquid 61.4 1.68E+04 2.74E-03 Liquid 61.4 1.68E+04 2.74E-03 0.162 -0.162 -
Sludge 13.9 1.14E+04 8.20E-03 Sludge 13.9 1.14E+04 8.20E-03 0.483 30.483 3
Salt Cake 53.8 2.78E+03 5.17E-04 Salt Cake 53.8 2.78E+03 5.17E-04 0.0305 0.20.0305 0.2
Overall waste 129.1 3.098E+04 2.40E-03 0.141 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 Question to be studied : Which components absorb Tc with Kd higher than 3 and are resistant to leaching?resistant to leaching?
Sludge components as Sludge components as carriers for Tc(VII) and carriers for Tc(VII) and
Tc(IV)Tc(IV)
. SO D IU M O XALAT E .N a 2C 2O 4
. C R YO LIT E .N a 3AlF6
ALU MIN O SILIC AT ESC AN C R IN IT E
SO D ALIT E
W H IT E SO LID S
. PLAT IN U M G R O U P .MET ALS
R h, R u, Pd
MET AL H YD R O XID ES(Fe, C r, Mn)(O )(O H )
B R O W N SO LID S
SOLID SLUDGE COM PONENTS
TiO2 was also tested
Experimental conditions Experimental conditions for precipitation and for precipitation and
leaching tests:leaching tests:
Precipitation tests: Precipitation tests: Wastes are alkalineWastes are alkaline Tc is redox sensitiveTc is redox sensitive Sharp differences in the Sharp differences in the
redox potential within the redox potential within the tanks are observed, tanks are observed,
So, both:So, both: oxidizing [Tc(VII)]oxidizing [Tc(VII)] and reducing [Tc(IV)] and reducing [Tc(IV)] conditions were tested in conditions were tested in
0.1- 5 N NaOH + 0-5 N NaOH.0.1- 5 N NaOH + 0-5 N NaOH.
Leaching modes: Leaching modes: Surface leaching. Surface leaching. Complete dissolution.Complete dissolution.
Leaching agentsLeaching agents all precipitates : 0.1N NaOH all precipitates : 0.1N NaOH aluminosilicates - NaHFaluminosilicates - NaHF22
Na oxalate - 0.1N NaOH, NaNONa oxalate - 0.1N NaOH, NaNO22
FeOOH - 0.1N NaOH, HFeOOH - 0.1N NaOH, H22OO22
MnOOH - 0.1N NaOH, HMnOOH - 0.1N NaOH, H22OO22
TiOTiO22 - 0.1- 3N NaOH - 0.1- 3N NaOHMethods: Liquid scintillation counting (LSC) of solutions, XRD, NMR, IR
Study of Tc uptake with Study of Tc uptake with AluminosilicatesAluminosilicates under oxidizing under oxidizing
conditions at 70-130conditions at 70-130ooCC
TcOTcO44-- is too large is too large
and therefore it is and therefore it is excludedexcluded from the from the
aluminosilicate aluminosilicate structure in both structure in both
cancrinite and cancrinite and sodalitesodalite
Solution Formed solid Kd
10-3-10-5M Tc0.2-5M NaOH
0.5-5 M NaNO3Cancrinite less 1
10-3-10-5M Tc0.2-5M NaOHNaNO3 free
Sodalite less 1
Literature data have demonstrated the possibility of Literature data have demonstrated the possibility of ClOClO44
-- and MnO and MnO44-- co-crystallisaton with aluminosilicates : co-crystallisaton with aluminosilicates :
purple Na8[AlSiO4]6(MnO4)2 (Weller,1999 etc.)
OUR EXPERIMENTS on TcOOUR EXPERIMENTS on TcO44- - (reaction: NaAlO2+Na2SiO3+NaOH)
Case of Aluminosilicates Case of Aluminosilicates formed in concentrated formed in concentrated
Tc(VII) solutionTc(VII) solution [Tc] = 0.2 M[Tc] = 0.2 M in NaNO3 solutions - cancrinite in NaNO3 solutions - cancrinite in NaNO3-free solutions - in NaNO3-free solutions -
sodalitesodalite Although NMR spectrum Although NMR spectrum
presented shift typical for presented shift typical for coordinated Tc(VII) its coordinated Tc(VII) its concentration is very lowconcentration is very low
Dissolution in NaHFDissolution in NaHF22 and LSC and LSC has shown : [Tc] in solid has shown : [Tc] in solid cancrinite was 57 mg/kg ~ 100 cancrinite was 57 mg/kg ~ 100 times less than in initial solution times less than in initial solution
Tc is excluded from the Tc is excluded from the aluminosilicate structurealuminosilicate structure
Fig. 1. NMR-99Tc spectrum of the aluminosilicate containing
57 mg-Tc/kg. Tc spectrum presents evidence for -30 ppm shift
characteristic of coordinated pertechnetate
Study of Tc uptake with Study of Tc uptake with AluminosilicatesAluminosilicates under under reducing reducing conditionsconditions
( (0.2M N0.2M N22HH55Cl, 1M NaNOCl, 1M NaNO33, , T T = 80= 8000С, t = 3 С, t = 3
d)d)
Precipitation ofcancrinite
Leaching conditions:
NaOHM
Tc yield, %
Leaching agent:
T, oC
Leaching yield , Tc, %
3 hour
1 day 10 days
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 + 0.25 M H2O2
60 25 26.9 27
2.0 18.9 0.1M NaOH + 0.5 H2O2
18 4 6.9 7
4.0 32 0.1M NaOH + 0.5 H2O2
18 6.5 6.9 11
Under reducing conditions Tc uptake is important Under reducing conditions Tc uptake is important
Tc(IV) in aluminosilicates is resistant to leachingTc(IV) in aluminosilicates is resistant to leaching
Study of Tc(VII) sorption Study of Tc(VII) sorption by crystalline TiOby crystalline TiO22
under oxidizing conditionsunder oxidizing conditions
Tc(VII) was sorbed by Tc(VII) was sorbed by TiOTiO22 from neutral from neutral solution with Ksolution with Kdd = 30 = 30 ml/g. ml/g.
However, the KHowever, the Kdd at at pH=10 was only 3.3 pH=10 was only 3.3 ml/gml/g
No affinity to Tc(VII) No affinity to Tc(VII) was noted for was noted for TiOTiO2 2 at at pH=12 and higherpH=12 and higher ..
Among the minerals tested
for Tc(VII) uptake, high-
density TiO2 was the most efficient
MST and Silicotitanates yet not tested ..?
Study of Tc uptake withStudy of Tc uptake with Na oxalateNa oxalate under under
oxidizing and reducing conditionsoxidizing and reducing conditions
Tc(VII) is excluded from the Na oxalate structure Tc(VII) is excluded from the Na oxalate structure under oxidizing conditions (Kd = 1-2)under oxidizing conditions (Kd = 1-2)
Under reducing conditions Tc(IV) forms a separate Under reducing conditions Tc(IV) forms a separate TcOTcO22*1.6H*1.6H22O phase - no interaction between Tc O phase - no interaction between Tc hydroxide and Na oxalate were detectedhydroxide and Na oxalate were detected
Tc precipitate is not resistant to leaching with 0.1 N Tc precipitate is not resistant to leaching with 0.1 N NaNONaNO22
NaOH + H2C2O4 = Na2C2O4
X-ray diffraction tests : the precipitate is
sodium oxalate Na2C2O4
(PDF#20-1149)
Study of Tc uptake withStudy of Tc uptake with Cryolite NaCryolite Na33AlFAlF66 under under
oxidizing and reducing conditionsoxidizing and reducing conditions
Reduced Tc Reduced Tc ::
17-35% of Tc(IV) as 17-35% of Tc(IV) as TcClTcCl662-2- is co- is co-precipitated with precipitated with cryolite cryolite
NN22HH55NONO33 inhibits co- inhibits co-precipitationprecipitation
Oxidizing conditionsOxidizing conditions: :
Kd is less 1Kd is less 1
Tc(VII) is excluded Tc(VII) is excluded from cryolite from cryolite structurestructure
6F6F--+NaAlO+NaAlO22+Na+Na22COCO33
X-ray diffraction tests : the precipitate is cryolite Na3AlF6
Study of Tc(IV) uptake Study of Tc(IV) uptake with with Cryolite NaCryolite Na33AlFAlF66
under under rreducing conditionseducing conditions
No [NH4F]
initial,M
[Na2CO3] in
final solution, M
[N2H5NO3], in
final solution, M
Tc(IV) uptake,
%
1234589
10
2,02.53.04,06,02,02,02,0
0,60.60,60.60,60,40,80,6
-------
0,1
202326283525170
• Tc(IV) is added as NaTc(IV) is added as Na22TcClTcCl66 to ( to (NHNH44F+NaAlOF+NaAlO22) solution) solution
• No additional reducing agent in exp. No 1-9No additional reducing agent in exp. No 1-9• Leaching test were impossible to quantify relative to real Leaching test were impossible to quantify relative to real cryolite in tanks as complete peptization occurred.cryolite in tanks as complete peptization occurred.
Study of Tc(IV) uptake with Study of Tc(IV) uptake with FeOOH FeOOH under under rreducing conditionseducing conditions
Precipitation test: Leaching test (t=18 oC, d = days):
Leaching yield ,Tc, %NaOH
M
Tc in solidphase, %
Leachingagent: 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
Reducing agent: 0.02M FeSO4, T = 60Reducing agent: 0.02M FeSO4, T = 6000СС, time = 3 h , time = 3 h Precipitate : FeOOH/FePrecipitate : FeOOH/Fe22OO33
ThoughThough TcTc adsorbed adsorbed betterbetter on iron hydroxides from 0.5–2.0 M NaOH on iron hydroxides from 0.5–2.0 M NaOH than from 3.0-4.0 M NaOH,than from 3.0-4.0 M NaOH, the precipitates formed the precipitates formed at lower NaOH at lower NaOH
concentration were more easily leached by the NaOH leachantconcentration were more easily leached by the NaOH leachantTc leaching with H2O2 was 20 % and with Na2S2O8 was70-100% in 100 days
Study of Tc(IV) uptake with Study of Tc(IV) uptake with MnOOH MnOOH under under rreducing conditionseducing conditions
Reaction NaOH + NaReaction NaOH + Na22MnOMnO44+ N+ N22HH55OH= MnOOHOH= MnOOHX-ray diffraction tests : the freshly precipitated solid X-ray diffraction tests : the freshly precipitated solid
was Mnwas Mn22OO3 3 , the aged precipitate was manganite , the aged precipitate was manganite MnOOH MnOOH (PDF#18-805)(PDF#18-805)
Manganese(III) oxides were effective Tc carriers and underwent chemical transformations on ageing that increased leaching resistance
to most agents.
0
2
4
6
8
10
12
0 2 4 6 8 10 12Time. d
Lea
ched
Tc,
%
1) Mn/Al=1/10
2) Mn/Al=1/40
3)Mn/Al=1/10
4) Mn/Al=1/40
MnOOH precipitation MnOOH leaching to 0.1 NaOH (1,3,4) and Na2S2O8(2)
0
15
30
45
60
75
90
0 5 10 15 20 25 30
Time,d
Tc u
ptak
e by
pre
cipi
tate
, %
Mn/Al=1/10
Mn/Al=1/40
What additional work is necessary to What additional work is necessary to clarify results obtained in the clarify results obtained in the
present workpresent work
It is still possible that some polymeric inorganics involving larger ions It is still possible that some polymeric inorganics involving larger ions (like titanium, forming hydroxides, complex titanates and Silicotitanates) (like titanium, forming hydroxides, complex titanates and Silicotitanates) could be better sorbents for TcOcould be better sorbents for TcO44
--, - additional tests of different (Ti?) , - additional tests of different (Ti?) compounds could explain some cases of Tc presence in sludge, and compounds could explain some cases of Tc presence in sludge, and possibly result in efficient inorganic Tc(VII)-sorbent for long-term storage.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 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 continued aiming to demonstrate the nature of the precipitate and its stability domain. EXAFS/XANES, Tc-NMR and stability domain. EXAFS/XANES, Tc-NMR and -resonance spectroscopy -resonance spectroscopy could be useful for Tc speciation under these conditions.could be useful for Tc speciation under these conditions.
Co-precipitation tests could be continued with the transition metal 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 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 provide higher affinity to reduced technetium, or even Tc(VII) and higher resistance to leaching. Tc speciation experiments in these cases are resistance to leaching. Tc speciation experiments in these cases are desirable.desirable.
Acknowledgements
• This work was supported by the U.S. Department of EnergyThis work was supported by the U.S. Department of Energy Under a contract to the Institute of Physical Chemistry RAS Under a contract to the Institute of Physical Chemistry RAS by the Office of Environmental Management, Efficient by the Office of Environmental Management, Efficient Separations and Processing Cross cutting Program. Separations and Processing Cross cutting Program.
• We recognize the organizational skill of Dr. M. We recognize the organizational skill of Dr. M. Khankhasaev in contract implementation, Liliya Khankhasaev in contract implementation, Liliya Petrachenkova (SAIC), Dr. V. Polyanichko, IPC financial Petrachenkova (SAIC), Dr. V. Polyanichko, IPC financial manager Edouard German and RAS corr.-member A.K. manager Edouard German and RAS corr.-member A.K. Pikaev for administrative assistancePikaev for administrative assistance. .
• We are thankful to Dr.D. Hobbs for his encouraging We are thankful to Dr.D. Hobbs for his encouraging attention to this work, useful discussions and elaboration attention to this work, useful discussions and elaboration of the experimental programof the experimental program