The complexation of technetium with humic acid is usually done by a reduction of pertechnetate by Sn2+ ions. A Tc-HA complex can be scavenged in a Sn-HA complex, if tin is present as reductant. The main aim of the study was a preparation of the Tc-HA complex without impurities of Sn ions or other metal reductant, which was performed by a ligand exchange with hexakis(thiourea-S)technetium(III) under nitrogen atmosphere at pH 5.5. The [Tc(tu)6]3+ complex was prepared from TcO4- in acidic solution with thiourea as a reductant. Presence of the Tc-HA complex and other technetium species was determined by gel chromatography, paper chromatography and dialysis. Yield of Tc-HA complex was about 80% and reaction mixture contains about 20% of technetium dioxide, which is a side product of ligand-exchange.
The preparation of technetium-99m-humic complex without presence of any metal reductant was studied. For the preparation of Tc-HA complex by ligand substitution hexakis(thiourea-S)technetium(III) complex was used as a precursor. Ligand exchanging reaction was studied with two different humate/thiourea concentration ratios. After mixing of [99mTc(tu)6]3+ complex with natrium humate under a nitrogen atmosphere a formation of technetium humate wasobserved. The determination of reaction products was performed by combination of gel and paper chromatography. Reaction yields are dependent on humate/thiourea concentration ratio and reaction time. Tc-HA complex was obtained with the highest yield of 62%. Reaction mixture also contains a technetium dioxide as a side product of exchanging reaction and other technetium species, which are also discussed. Oxidation state of technetium in prepared Tc-HA complex is apparently unchanged.
Authors:P. Tkac, A. Paulenova, G. Vandegrift, and J. Krebs
There was a significant research progress achieved with the aim to modify conventional PUREX process by stripping of plutonium
from the tri-n-butyl phosphate (TBP) extraction product in the form of non-extractable complexes upon addition of back-hold
complexation agents. The present paper reports effects of such salt-free complexant, acetohydroxamic acid (HAHA), on distribution
ratio of Pu(IV) under wide concentration of nitric acid and additional nitrate. General formula of plutonium species present
in the organic phase can be described as Pu(OH)x(AHA)y(NO3)4−x−y·2TBP·wHNO3.
Authors:P. Tkáč, R. Kopunec, F. Macášek, and S. Skrašková
The technetium sorption behaviour in different samples of soils was studied under aerobic conditions. Tc(VII) was reduced to Tc(IV) by Sn2+ ions. About 99% of reduced technetium is absorbed by the soils under investigation. Sorption of TcO4– was studied in short-term (1-hour) and long-term (1-month) experiments. Sorption of TcO4– in presence of sodium humate (Aldrich) was generally lower than from pure water (from 99% to 12%) and depends on the depth of origin of the ground. Immobilisation of TcO4– after sorption on superficial sample of soils was studied by paper chromatography. Oxidation of Tc(IV) in presence of NO3– and NO2– (concentration range 10–1–10–5 mol·dm–3) ions was studied as a function of time and concentration of NO3– and NO2– ions. The content of Tc(IV) in NO3– and NO2– solutions decreases with time (46 hours) relatively slowly.
Authors:P. Tkac, B. Matteson, J. Bruso, and A. Paulenova
The advanced separation extraction process based on tri-n-butyl phosphate organic phase called UREX is being developed to
separate uranium from fission products and other actinides, and the acetohydroxamic acid (AHA) is employed to reduce and complex
plutonium and neptunium in order to decrease their distribution to the TBP-organic phase. In this study, the extraction of
uranium was performed from various aqueous matrices with different concentrations of HNO3, LiNO3, and AHA. Extraction of uranium increases with increasing both initial HNO3 and total nitrate concentration. UV-VIS spectrophotometry confirmed that AHA is involved in the complex of uranium with TBP.