Technetium behavior

Paquette, J. Reid, J. A. K. Rosinger, E. L. J., "Review of Technetium Behavior in Relation to Nuclear Waste Disposal," TR-25, Whiteshell Nuclear Research Establishment, Pinawa, Monitoba, Canada, 1980. 

As a general rule, elements in the second and third transition series have similar chemical properties. In contrast, the properties of the first member of the series are often different. This pattern of behavior is seen in Group 7 (VIIB). The properties of rhenium and technetium differ considerably from those of manganese. 

From the limited data on the kinetics and distribution of liposomes in man (Zonneveld and Crommelin, 1988) it can be concluded that the overall behavior of liposomes in man is similar to that observed in animals. Studies in cancer patients showed predominant lirer and spleen uptake of technetium-labeled liposomes (Richardson et al.,... 

Durand JP, Milcent MC, Goudard F, et al. 1994. Chemical behavior of three radionuclides (cesium, americium and technetium) and their uptake at the cystosolic level in aquatic organisms. Biochem Mol Biol Int 33(3) 521-534. 

Bearing this situation in mind we wished to describe the present status of studies on chemistry and its applications of technetium and rhenium. A part of this book was planned before the "Topical Symposium on the Behavior and Utilization of Technetium 93" was held in Sendai, Japan in March 1993, but the planning of the book in this style was accelerated after the symposium by suggestions from our friends. The editors are grateful for the cooperation from the contributes and the publisher. 

Yoshihara K (1991) Workshop on Current Topics in the Behavior of Technetium (KURRI-TR-362) Research Reactor Institute Kyoto University, Kumatori, Osaka, Japan, p 42... 

The behavior of technetium in soils is important from an ecological viewpoint, but is quite complicated and depends on many factors. Stalmans et al. [27] stated that it is ruled by a combination of chemical, physicochemical and biological factors and understanding of it is needed on two main accounts bioavailability and geochemical mobility . They also noticed that organic matter in soils and sediments play a significant role as a geochemical sink for technetium. 

There has been considerable interest recently in the migration of long-lived nuclides involving technetium. The behavior of technetium in groundwater, sorption and permeation under subterranean conditions needs to be studied for the purpose of assessing environmental safety in connection with the disposal of spent nuclear fuel. Chemical and physicochemical data on technetium under such conditions are necessary. 

Antipov VN, Kryutchkov SV, Gerasimov VN, Grigoriev MS, Kazin PE, Kharitonov W, Maksimov VG, Moisa VS, Sergeev VV, Yurik TK (1993) in Abstracts of Reports of Topical Symposium on the Behavior and Utilisation of Technetium 93, 18-20 March 1993, Tohoku University, Sendai, Japan, report No l-P-24, p 56... 

The kinetic behavior of the base hydrolysis of TcCl2(acac)2 is described as an example [26], A plot of the logarithm of the concentration of the technetium complex in the organic phase against time gives a straight line. Thus, the reaction rate of the base hydrolysis of TcCl2(acac)2 is expressed as... 

Crystals of [Tc(tu)6]Cl3 or [TcCl(tu)5]Cl2 are often employed for the synthesis of technetium(III) complexes. However, since the direct reduction of pertechnetate with excess thiourea in a hydrochloric acid solution yields [Tc(tu)6]3+ in high yield [37], direct use of the aqueous solution of the thiourea complex would be preferable for the synthesis of the technetium(III) complex without isolation of the crystals of the thiourea complex. In fact, technetium could be extracted from the aqueous solution of the Tc-thiourea complex with acetylacetone-benzene solution in two steps [38]. More than 95% extraction of technetium was attained using the following procedure [39] First a pertechnetate solution was added to a 0.5 M thiourea solution in 1 M hydrochloric acid. The solution turned red-orange as the Tc(III)-thiourea complex formed. Next, a benzene solution containing a suitable concentration of acetylacetone was added. After the mixture was shaken for a sufficient time (preliminary extraction), the pH of the aqueous phase was adjusted to 4.3 and the aqueous solution was shaken with a freshly prepared acetylacetonebenzene solution (main extraction). The extraction behavior of the technetium complex is shown in Fig. 6. The chemical species extracted into the organic phase seemed to differ from tris(acetylacetonato)technetium(III). Kinetic analysis of the two step extraction mechanism showed that the formation of 4,6-dimethylpyrimidine-... 

The periodic trends that distinguish the chemical behavior of rhenium and technetium are manifested in differences between the biological behavior between analogous rhenium and technetium compounds. The comparison can shed light on the mechanism of accumulation in target... 

TCISOTOPE "mTc isotope, uses for, 27 319. See also Technetium (Tc) T-curve behavior ceramics, 5 620... 

The different behavior of technetium and rhenium may arise because Re (VII) is not reduced by xanthic acid to the same oxidation state as Tc (VII). Other suitable extracting solvents are chloroform, 1.1.1-trichloroethane and isopropyl ether. 

Co-precipitation of Re S with platinum sulfide from cone, hydrochloric acid solutions of microamounts of technetium and rhenium is suitable for the separation of technetium from rhenium , since technetium is only slightly co-precipitat-ed under these conditions (Fig. 7). At concentrations of 9 M HCl and above, virtually no technetium is co-precipitated with platinum sulfide at 90 °C, whereas rhenium is removed quantitatively even up to 10 M HCl. The reduction of pertechnetate at high chloride concentration may be the reason for this different behavior, because complete co-precipitation of technetiiun from sulfuric acid solutions up to 12 M has been observed. However, the separation of weighable amounts of technetium from rhenium by precipitation with hydrogen sulfide in a medium of 9-10 M HCl is not quantitative, since several percent of technetiiun coprecipitate with rhenium and measurable amounts of rhenium remain in solu-tion . Multiple reprecipitation of Re S is therefore necessary. 

The redox behavior of the [Tc04] ion is important in terms of understanding its chemistry. The Latimer diagram of important oxidation states and standard redox potentials is given in Scheme 4. The electrochemistry of technetium has been reviewed on several occasions. " ... 

In broad terms the coordination chemistries of technetium and rhenium are similar, and isomorph-ous compounds are frequently found. One important exception is the behavior with phosphanes. Since Tc is a stronger oxidant than Re, the reaction with phosphanes very often leads to reduction to Tc° and lower oxidation states. This is particularly the case with compounds derived from the... 

The utility of [TcOCU] in Tc chemistry is demonstrated by the first synthesis of 8-hydroxy-quinoline (8-Hox, (126)) complexes of technetium in 1984. Ligand (126) is usually one of the first choices to explore the coordination chemistry of an element, but it was as late as 1984 when the first complex with Tc was prepared. It was known that the reaction of [ Tc04] with 8-Hox leads to complexes with high brain uptake, and it was therefore important to define the structure of the active species. This sequence of events is very typical for technetium chemistry. Nuclear medicinal experiments indentify a Tc species with useful biological behavior, which prompts investigations into the basic coordination chemistry to identify the structure of the Tc... 

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