328
SELIVERSTOV et al.
Co2+ in the form of sulfate). After complete decompo-
sition of EDTA and its intermediate decomposition
products (60 min of ozonolysis), pH of the solution
was brought to 10. The cobalt hydroxide precipitated
in the process was separated by centrifugation. The
influence of the ozonolysis time on the decontamina-
tion factor of the EDTA solution from 60Co is shown in
Fig. 4. As can be seen, starting from 60 min, cobalt(III)
hydroxide starts to precipitate, with decontamination
Fig. 4. Variation with ozonation time of the decontamina-
60
tion factor of EDTA solution from 60Co. pH 9.9. Solution
contains 10 mg l–1 Co2+ in the form of sulfate.
of the solution from Co (increase in Kdec) as a result
of its coprecipitation with Co(OH)3. The decontamina-
tion factor was 106.
will decrease with the progress of oxidation, the in-
creasing amount of ozone will break through the solu-
tion, so that the efficiency of its utilization will de-
crease. Therefore, the process should be organized so
as to retain ozone in the solution to the maximum pos-
sible extent (e.g., by organizing countercurrent of
ozone and solution) and to return the unchanged ozone
to the head of the process.
ACKNOWLEDGMENTS
The study was financially supported by the Russian
Foundation for Basic Research (project no. 06-03-
32682).
REFERENCES
In the presence of cobalt, a part of EDTA in solu-
tion is bound in a complex (log Kst [Co(II)·EDTA] =
16.31). We found that addition of 10 mg l–1 Со2+ did
not noticeably affect the oxidative decomposition of
EDTA, i.e., the observed dependences were similar to
those shown in Figs. 1–3 for the cobalt-free solutions.
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To check the applicability of the procedure for
EDTA decomposition with ozone to the recovery of
radioactive cobalt, we performed experiments with
tracer amounts of 60Co (in the presence of 10 mg l–1
RADIOCHEMISTRY Vol. 51 No. 3 2009