Speciation of Tc(IV) in chloride solutions by capillary electrophoresis

Browse Search My Profile Activate Help Home > List of Issues > Table of Contents > Abstract Speciation of Tc(IV) in chloride solutions by capillary electrophoresis Author(s): Xiaolan Liu | Frédéric Poineau | Massoud Fattahi | Bernd Grambow | L. Vichot doi: 10.1524/ract.93.5.305.64276 View PDF article (245 K) View table of contents Email this link Add to my alerts What is RSS? Trouble viewing articles as PDF? Radiochimica Acta Print ISSN: 0033-8230 Volume: 93 | Issue: 5/2005 Cover date: 20050501 Page(s): 305-309 Abstract text A method for speciation of Tc(IV) species (TcCl62− and TcCl5(H2O)−) in chloride solutions, using capillary electrophoresis (CE) technique was developed. The proposed method has overcome the difficulties of unstable oxidation states analysis by shortening their travel time in the capillary. TcCl62− and TcCl5(H2O)− were thus separated without being hydrolyzed and polymerized, and their UV/Vis spectra were recorded. With a 1 M HCl/NaCl buffer solution (pH=1), the electrophoretic mobilities were determined as 5.47×10−4 cm2/Vs for TcCl62− and 2.13×10−4 cm2/Vs for TcCl5(H2O)− at 25 °C. The total analysis time for one run is 12 minutes

Organically bound tritium (OBT) for various plants in the vicinity of a continuous atmospheric tritium release

International audienceIn order to quantify tritium impact on the environmental, we studied vegetation continuously exposed to a tritiated atmosphere. We chose lichens as bio-indicators, trees for determination of past tritium releases of the Valduc Centre, and lettuce as edible vegetables for dose calculation regarding neighbourhood. The Pasquill and Doury models from the literature were tested to estimate tritium concentration in the air around vegetable for distance from the release point less than 500 m. The results in tree rings show that organically bound tritium (OBT) concentration was strongly correlated with tritium releases. Using the GASCON model, the modelled variation of OBT concentration with distance was correlated with the measurements. Although lichens are recognized as bio-indicators, our experiments show that they were not convenient for environmental surveys because their age is not definitive. Thus, tritium integration time cannot be precisely determined. Furthermore, their biological metabolism is not well known and tritium concentration appears to be largely dependent on species. An average conversion rate of HTO to OBT was determined for lettuce of about 0.20–0.24% h1. Nevertheless, even if it is equivalent to values already published in the literature for other vegetation, we have shown that this conversion rate, established by weekly samples, varies by a factor of 10 during the different stages of lettuce development, and that its variation is linked to the biomass derivative

Speciation of technetium(IV) chloride under gamma irradiation

International audienceSpeciation of Tc in aqueous solution is a complex phenomenon because several parameters intervene simultaneously. We show under gamma radiations, it is completely modified. At pH 8.5 TcO$_2$ is oxidized to Tc(VII) with a yield of 1.38×10^^{−7} mol J${−1}$. At pH 1.5, it was demonstrated that Tc is present as hydroxylated species Tc$_nO_y^{(4n-2y)+}$ (L. Vichot, M. Fattahi, M. Musikas: Radiochim. Acta 91, 263 (2003)). Its oxidation leads also to Tc(VII) with an experimental yield of 1.45×10$^{−7}$ mol J$^{−1}. In more acidic solutions, results are consistent with hydrolysis and oxidation of Tc(IV) to Tc(V). As for colloidal solutions of Tc(IV) or TcO$_2$, they give Tc(VII) whereas solutions of TcCl$_6^{2-}$ at pH 0.5 and 1.5 do not lead directly to Tc(VII). Reduced states of Tc are very sensitive to radiation. Hydrolysis as well as polymerisation of Tc are accelerated. Furthermore the radiolytic processes are pH dependent

XAS study of technetium(IV) polymer formation in mixed sulphate/chloride media

X-ray absorption spectroscopy has been used to establish polymer formation of Tc(IV) in aqueous solutions of Na+SO42- and Na+Cl-/SO42-. As the molybdenum chemistry show similarities to that of technetium, we used MoO2 as a reference to model our technetium species. Fitting of TcO2·xH2O with this model led to a good correlation with the literature data: (Tc-Tc=2.53 Å, Tc-O=1.87-1.98 Å). In aqueous solution, some polymers are formed regardless to the nature of the media composition: Tc-Tc=2.50±0.02 Å. The general structure is in agreement with a first coordination shell containing 6 O. The modelling shows that, in the first coordination shell, there is no chloride ligand. The observed geometries are close to those found for TcO2·xH2O, hence the unknown aqueous species must be considered as a precursor of the solid technetium dioxide. Combination of these results with XANES led to attribute TcnIVOp(4n-2p)+(H2O)q with n>2 to the species

Evolution of Pb speciation in Portland cement during leaching

Heavy metals, coming from raw materials and combustibles, are present in trace amount in cement. This study aims at evaluating Pb long-term behaviour, linking the evolution of Pb speciation due to leaching, with changes in the structure of the bearing mineralogical phases of the cement. EXAFS experiments point out a Pb retention through calcium silicate phases, but also show changes in Pb atomic environment due to leaching. These changes would be due to evolution in calcium silicate hydrates (C-S-H) structure with alteration, as $^{29}$Si NMR shows lengthening of the chains of silicon tetrahedron in the C-S-H

Loss of kAE1 expression in collecting ducts of end-stage kidneys from a family with SLC4A1 G609R-associated distal renal tubular acidosis

Distal renal tubular acidosis caused by missense mutations in kidney isoform of anion exchanger 1 (kAE1/SLC4A1), the basolateral membrane Cl−/HCO3− exchanger of renal alpha-intercalated cells, has been extensively investigated in heterologous expression systems but rarely in human kidneys. The preferential apical localization of distal renal tubular acidosis (dRTA)-associated kAE1 mutants R901X, G609R and M909T in cultured epithelial monolayers has not been examined in human kidney. Here, we present kidney tissues from dRTA-affected siblings heterozygous for kAE1 G609R, characterized by predominant absence rather than mistargeting of kAE1 in intercalated cells. Thus, studies of heterologous recombinant expression of mutant proteins should be, whenever possible, interpreted in comparison to affected patient tissues

Tritium in plants: A review of current knowledge

International audienceThe aim of this paper is to provide an overview of the literature regarding the fate of tritium in plants. At first, some prerequisites about the sources, chemical and physical characteristics, biological effects and potential risks associated to tritium are presented. The general scheme of tritium transport and cycling in the environment, the different tritium fractions in biological organisms and the corresponding techniques for sampling and measurement are discussed. Then, the main processes of uptake, incorporation and conversion of tritium into plants are described, based on experimental data. As tritium incorporated into the organic fraction may be the major contributor to the dose of radiation received following its ingestion by man, the biological mechanisms and kinetics of organically bound tritium (OBT) production are a major focus. Some predictive models of short-term or chronic exposure are described. Finally, the pending questions, concerning the fate of tritium in plants, are tackled