4th EucheMs chemistry congress

Poster Session 1
s923
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - Environmental Radiochemistry
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urAniuM SorPtion And AMS MeASureMentS
i. SPendLiKovA 1 , M. neMeC 1 , f. SeBeStA 1 ,
P. Steier 2 , G. wALLner 3
1 Czech Technical University in Prague, Department of Nuclear
Chemistry, Prague 1, Czech Republic
2 University of Vienna, Vera Laboratory, Vienna, Austria
3 University of Vienna, Department of Inorganic Chemistry,
Vienna, Austria
The uranium separation from natural waters was studied at
the Department of Nuclear Chemistry in late 80’s and early 90’s.
TiO-PAN sorbent (titanium dioxide embedded in
polyacrylonitrile) showed high sorption capacity for this element.
This composite sorbent is planned to be used for uranium
preconcentration for measuring environmental 236U/U ratios by
Acceleration Mass Spectrometry (AMS) in bilateral cooperation
with the University of Vienna. After the preliminary AMS results
showing anthropogenic contamination in TiO-PAN sorbent, the
preparation of titanium oxide was studied with a strong emphasis
on elimination of this contamination. Several samples of titanium
oxide were prepared from an organic uranium-free compound.
These samples were studied using X-Ray Diffraction for their
crystal structure and using selective sorption of nitrogen gas for
their specific surface area. Their sorption properties were also
evaluated.
Presently we are focusing on finding a water source which
is not anthropogenically contaminated in order to use this water
for further experiments and on the following separation and
concentration steps for AMS sample preparation.
Keywords: uranium; titanium oxide;
4 th EucheMs chemistry congress
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retention ProCeSSeS of SeLeniuM SPeCieS on
CzeCh GrAnitiC roCK
K. videnSKA 1 , v. hAvLovA 2
1 Institute of Chemical Technology, Analytical Chemistry,
Prague, Czech Republic
2 Nuclear Research Institute Rez, Waste Management & Fuel
Cycle Chemistry, Rez, Czech Republic
Selenium (Se-79, T = 6.5·10 1/2 4yrs) belongs among fission
products with long lifetime, high mobility and prevailing anionic
character. Retention of selenium depends on its oxidation state
therefore knowledge of migration behaviour under different
conditions can significantly improve input into performance and
safety assessment models.
Granite is considered as a potential host rock for deep
geological disposal of radioactive waste in several countries,
including Czech Republic. Considering that, retention processes
of selenium species on granitic rock were investigated using
sorption and diffusion experiments. Granitic rock from Melechov
massive (Centre Bohemian Massive, Czech Republic) was used
as a representative for crystalline rock material.
The sorption batch experiments were conducted on the
crushed granite, which was sieved into several fractions with
defined grain size. Mineral composition of each granitic fraction
was evaluated using X-ray diffraction. The through-diffusion
experiments were conducted on the granitic discs of the same
origin (Melechov Massive, average 50 mm, and length 10 mm).
Granitic discs were saturated with experimental tracer solution
Na SeO or Na SeO . Afterwards they were placed into diffusion
2 3 2 4
cells. Due the saturation we can directly observed steady state
diffusion processes.
The X-ray diffraction results showed differences in mineral
composition of granitic fractions (different content of quartz,
feldspar, plagioclase, mica, chlorite, kaolinite). The
enrichment/depletion, namely concerning Fe containing phases
(micas) can influence the extent of both sorption and diffusion of
observed tracers.
Sorption experiments revealed that retention of selenite was
higher then sorption of selenate. Granitic fractions enriched in
mica indicated increased affinity to selenite. However, presence
of mica did not influence sorption behaviour of selenate. The
diffusion experiments suggested similar trend: selenite exhibited
lower diffusion movement through rock samples in comparison
with selenate. Selenate was proved to be rather mobile, almost
non-sorbing specie.
Acknowledgement: This research was supported by project of
Ministry of Trade and Industry FR-TI1/362.
Keywords: selenium; granite; retention;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc