Separation of Tc(VII) from Tc(IV) by solvent extraction

The solvent extraction of Tc(IV) and Tc(VII) by isoamyl alcohol has been studied. The TcCl ₆ ²⁻ and TcO ₄ ⁻ ions are both extracted from 3M H₂SO₄ solution but hydrolyzed Tc(IV) species are not. This permits the separation of the two valence states of technetium. The air oxidation of carrier-free hydrolyzed^99mTc(IV) may be limited by the presence of⁹⁹Tc carrier in the same chemical form. Paper chromatography and electrophoresis were used to identify TcCl ₆ ²⁻ , TcO ₄ ⁻ and hydrolyzed species. It was also found that the hydrolyzed ReCl ₆ ²⁻ can reduce TcO ₄ ⁻ to Tc(IV).     

Rapid and efficient column separation of Re(VII) as a surrogate for Tc(VII) with benzimidazole-based cross-linked poly(ionic liquid)s

Journal of Radioanalytical and Nuclear Chemistry - In this study, the imidazole-based poly(ionic liquid)s (PILs) synthesized by one step method has been applied for the enrichment and recovery of...     

Extraction of Re(VII) by neutral and basic extractants

The mechanism of Re(VII) extraction from sulphate-containing solutions using primary amine Primene JMT, trioctylphosphine oxide (TOPO), tributyl phosphate (TBP), and their mixtures was investigated. It was found that the ratio of Re(VII) with Primene JMT and its sulphate in the organic phase was 1:1. The composition of Re(VII) complexes with TOPO depended on the acidity of solution ranging from about 1:1 to 2:1. When the extraction was carried out by TBP the mole ratio of TBP to Re was approximately 4. Primene JMT proved to be the most suitable agent for Re(VII) extraction with the exception of strongly acidic solutions, in which TOPO provided better results. The mixed solvents Primene JMT and TOPO as well as Primene JMT and TBP presented a slight synergism in weakly acidic solutions. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

Sorption of Tc(IV) and Tc(VII) on Soils: Influence of Humic Substances

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.     

Re(VII) complex of N-fused tetraphenylporphyrin

By treatment of N-fused tetraphenylporphyrin rhenium(I) tricarbonyl complex with trimethylamine N-oxide, oxidation of the metal center proceeded to afford N-fused tetraphenylporphyrin rhenium(VII) trioxo complex, which was quite stable against air, light and heat.     

Sorption of Tc(VII) and Am(III) by carbon materials: effect of oxidation

In this work we studied the effect of oxidation on the sorption properties of carbon materials, produced on the basic of activated carbons FAS and VSK in relation to radionuclides Am(III) and Tc(VII). It has been found that the oxidation increases the distribution coefficients for the extraction of radionuclides of sorption nitric acid raising agents. As to identify the mechanism of the oxidation influence on the sorption properties the physical and chemical properties of the synthesized samples (porous surface structure, IR-spectrums etc.) were studied. The possibility of removal of radionuclides from the real industrial solutions of complex composition using of the obtained carbon nanomaterials was investigated.     

Structural study on 2,2'-(methylimino)bis(N,N-dioctylacetamide) complex with Re(VII)O4- and Tc(VII)O4- by 1H NMR, EXAFS, and IR spectroscopy

The structures of the complex of 2,2'-(methylimino)bis(N,N-dioctylacetamide) (MIDOA) with M(VII)O(4)(-) (M = Re and Tc), which were prepared by liquid-liquid solvent extraction, were investigated by using (1)H nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS), and infrared (IR) spectroscopy. The (1)H NMR spectra of the complex of MIDOA with Re(VII)O(4)(-) prepared in the organic solution suggest the transfer of a proton from aqueous to organic solution and the formation of the H(+)MIDOA ion. The EXAFS spectra of the complexes of H(+)MIDOA with Re(VII)O(4)(-) and Tc(VII)O(4)(-) show only the M-O coordination of the aquo complexes, suggesting that the chemical state of M(VII)O(4)(-) was unchanged during the extraction process. The results from (1)H NMR and EXAFS, therefore, provide evidence of M(VII)O(4)(-)···H(+)MIDOA complex formation in the organic solution. The IR spectra of Re(VII)O(4)(-)···H(+)MIDOA and Tc(VII)O(4)(-)···H(+)MIDOA were analyzed based on the structures and the IR spectra that were calculated at the B3LYP/cc-pVDZ level. Comparison of the observed and calculated IR spectra demonstrates that an intramolecular hydrogen bond is formed in H(+)MIDOA, and the M(VII)O(4)(-) ion interacts with H(+)MIDOA through multiple C-H(n)···O hydrogen bonds.     

Solvent extraction of Tc(VII) by the mixture of TBP and 2-nitrophenyl octyl ether

The extraction of Tc(VII) by the mixture of tri-n-butyl phosphate (TBP) and 2-nitrophenyl octyl ether (NPOE) has been studied. 0.2M NPOE-TBP can extract Tc(VII) effectively from 1M HNO₃ and 1M NaOH solutions with distribution ratios of 57.1 and 12.3, respectively. The distribution ratio of Tc(VII) decreases with increasing (>0.5M) HNO₃ concentration but increases with the increase of NaOH concentration. A pH 9 NaOH solution has proven to be suitable for Tc(VII) stripping. A simple extraction-stripping cycle can remove Tc(VII) from a sodium hydroxide solution. A more sophisticated extraction process is proposed to remove Tc(VII) from nitric acid solution because the co-extracted HNO3 prevents the direct stripping of Tc(VII) by NaOH solution of pH 9.     

Re(VII) extraction and separation from Mo(VI) by levextrel resins containing trialkyl amine

A synthetic method of novel trialkyl amine (N235, R₃N, R = C₈–C₁₀) Levextrel resin was described in this paper. The extraction behavior of rhenium(VII) and molybdenum(VI) with this N235 Levextrel resin has been studied. The mechanism of extraction of Re(VII) with the N235 Levextrel resin has been discussed briefly through equi-molar series method and the conventional slope analysis method. The optimal conditions of extraction and separation Mo(VI) and Re(VII) with the N235 Levextrel resin were determined. Also, its excellent extraction characteristics for Re(VII) were confirmed by extraction and stripping tests in a analog liquid solution containing Mo(VI) and Re(VII).     

Mild and efficient Re(VII)-catalyzed synthesis of 1,1-dihydroperoxides

Re2O7 in CH3CN is a remarkably efficient and mild catalyst for the peroxyacetalization of ketones, aldehydes, or acetals by H2O2 to generate 1,1-dihydroperoxides. Me3SiOReO3 and methyl rhenium trioxide (MTO) are also effective catalysts under these reaction conditions.     

Evaluation of the gravimetric tetraphenylarsonium method for the determination of Tc(VII)

Solubility losses in the gravimetric tetraphenylarsonium method for determining pertechnetate have been evaluated. Liquid scintillation counting was used to measure the beta(-) activity of (99)Tc in the filtrate, and indicated solubility losses of about 1% in analyses yielding 40-50 mg of precipitate. The solubility product Of (C(6)H(5))(4)AsTcO(4) is estimated to be (8.6 +/- 0.2) x 10(-10) at room temperature (24-25 degrees ) and K(sp) for (C(6)H(5))(4)AsReO(4) at approximately 21-23 degrees is estimated at (2.6 +/- 0.3) x 10(-9). Both values are satisfactory for gravimetric purposes, but to keep solubility losses within 1% at least 40mg of (C(6)H(5))(4)AsTcO(4) or 80 mg of (C(6)H(5))(4)AsReO(4) should be obtained (assuming 20 ml of solution, 20-30% excess of precipitant and 6 or 7 washes with 5-ml portions of distilled water).     

Electrolytic reduction of Tc(VII) in nitric acid solution using glassy carbon electrode

Electroreduction of Tc(VII) was studied in nitric acid solution using glassy carbon electrode. The electroreduction was conducted at a constant potential –300 mV (vs. Ag/AgCl) with a potentiostat. It was found that the difference of the Tc concentration in the solutions before and after the electrolysis was negligibly small. This means that there were almost no TcO₂ or Tc deposited on the carbon fiber electrode during the electroreduction. Absorption spectra and distribution coefficients obtained by ion-exchange analysis indicated that Tc(VII) was reduced to Tc(IV).This work was financed by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the framework of The Development of Innovative Nuclear Technologies.     

Electrolytic reduction of Tc(VII) in nitric acid solution using glassy carbon electrode

Electroreduction of Tc(VII) was studied in nitric acid solution using glassy carbon electrode. The electroreduction was conducted at a constant potential –300 mV (vs. Ag/AgCl) with a potentiostat. It was found that the difference of the Tc concentration in the solutions before and after the electrolysis was negligibly small. This means that there were almost no TcO₂ or Tc deposited on the carbon fiber electrode during the electroreduction. Absorption spectra and distribution coefficients obtained by ion-exchange analysis indicated that Tc(VII) was reduced to Tc(IV).This work was financed by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) under the framework of The Development of Innovative Nuclear Technologies.     

Diffusion of Re(VII), Se(IV) and Cr(VI) in compacted GMZ bentonite

Journal of Radioanalytical and Nuclear Chemistry - The diffusion of Re(VII), Se(IV) and Cr(VI) in compacted Gaomiaozi bentonite was conducted by an integrated diffusion setup. The effective...     

(Cp-R)M(CO)(3) ] (M=Re or (99m) Tc) Arylsulfonamide, Arylsulfamide, and Arylsulfamate Conjugates for Selective Targeting of Human Carbonic Anhydrase IX

Enhanced receptor selectivity: Carbonic anhydrase inhibitors are relevant for both cancer diagnosis and therapy. Combining non-radioactive Re compounds with their radioactive (99m) Tc homologs enables the use of identical molecules for therapy and imaging (theragnostic). The syntheses and in?vitro evaluation of [(Cp-R)M(CO)(3) ] (Cp=cyclopentadienyl, M=Re, (99m) Tc) with R being a highly potent carbonic-anhydrase-targeting vector is reported.     

Retention behaviour of Cs(I), Sr(II), Tc(VII) and Np(V) on smectite-rich clay

The smectite-rich natural clay is being considered as a backfill and buffer material for Indian repository programme. In the present study, batch sorption measurements have been performed at trace concentrations for one of the minor actinide elements [Np(V)] and for the long lived fission products, Cs(I), Sr(II), and Tc(VII) on purified and conditioned smectite-rich clay at varying conditions of pH and ionic strength. In case of Cs(I) and Sr(II) the sorption was found to increase with pH. At any pH the sorption was found to decrease with increasing ionic strength of the suspension maintained with NaCl. Further, at any pH the sorption of Sr(II) is less than the corresponding value for Cs(I). This is indicative of effect of size selectivity on the sorption by the clay. Tc(VII), on the other hand, is poorly retained by the clay, which can be explained in terms of the negative charge on the TcO₄ ^? ion, which has negligible interaction with the predominantly negatively charged clay surface. In the case of Np(V), the sorption was found to increase albeit, slowly compared to Cs(I) and Sr(II) with pH, and it with no effect of ionic strength on the sorption at all pH values. This suggests that Np(V) primarily interacts with the surface sites via inner sphere complexation mechanism.     

Thin-Layer Chromatography Method for the Investigations of Re(VII), Mo(VI)

Abstract

The benavicur of Re(VII), Mo(VI) and V(V) ions was studied chromatographically in aliphatic alcohol -HC1 systems on Al ₂O₃ as an adsorbent. Changes in the chromatographic process with the changes of the kind and composition of mobile phase were analysed.

It was also attempted to describe theoretically the results of chromatograpnic separation by using the thermodynamic theory of adsorption from multicomponent solutions.     

Separation studies of molybdenum(VI) and rhenium(VII) using TPPO as an extractant

A simple, rapid and reproducible method for the extractive separation of molybdenum(VI) and rhenium(VII) is proposed using triphenylphosphine oxide (TPPO) dissolved in toluene as an extractant. The extractions are carried out from the hydrochloric and hydrobromic acid medium. The extraction of molybdenum is quantitative from 2.54-3.10 M hydrochloric acid and from 3.76-3.98 M hydrobromic acid, and that of rhenium is from 6.78-7.91 M hydrochloric acid. The probable nature of the extractable species is established using log distribution ratio-log concentration plots. The method permits mutual separation of molybdenum(VI) and rhenium(VII) and is applicable for the analysis of alloys and pharmaceutical sample. The detection limits for molybdenum(VI) and rhenium(VII) are 0.8 ppm and 4 ppm respectively.