Molybdenum-technetium oxide

Litinskii et al. investigated the contact between the fluoropolymer SKF 32 (fluorine-containing rubber) and three oxide surfaces molybdenum oxide and solid solutions of molybdenum-niobium oxides and molybdenum-technetium oxide [115], Contact appeared when a bond was created between a metal atom and a carbon that lost its fluorine atom. Molecular orbitals on clusters simulating the contact between the fluoropolymer and the oxide surfaces have been computed using the DFT B3LYP/3-21g. Nine contacts between the three available metal atoms (molybdenum, niobium, and technetium) and the three carbon atoms of the fluoropolymer have been studied. Electronic spectra revealed that the molybdenum atom leads to the most favorable contact with the SKF 32 fluoropolymer. A similar analysis has been carried out with ferric and nickel oxides [116]. 

Fission products that are compatible with the uraninite crystal stmcture—the REE, yttrium, neodymium, and zirconium—were largely retained in the uraninite core, the reactor clays, minor phosphate phases, and uranium and zirconium silicate phases (Gauthier-Lafaye et ai, 1996). Lighter REE—lanthanum, cerium, and praseodymium—were partially lost from the reactor. Einally, molybdenum, technetium, mthe-nium, rhodium, and other metallic elements were retained in the metal/metal oxide inclusions and arsenide/sulfide inclusions in the core, and in the reactor clays (Hidaka et ai, 1993 Jensen and Ewing, 2001). 

Tucker et al. have separated " Tc from the fission product Mo using chromatographic aluminum oxide washed by dilute nitric acid at pH 1.5. Mo dissolved in the same dilute HNO3 of pH 1.5 is passed through the column which is then eluted with 0.1 M HNO3. Tc is only slightly adsorbed and can easily be eluted while molybdenum is retained on the column. The purity of technetium is 99.99%. 

Among the metals which have achieved prominence only recently, molybdenum must certainly occupy first place. It has attracted interest chiefly because of its role in biological processes and also because it shows a great variety of oxidation states and coordination numbers. Steifel s extensive review of molybdenum complexes covers their chemistry up to 1977.3 Because of their use in nuclear medicine, the complexes of technetium have received recent interest.4... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

This is similar for mercury [15], caesium, technetium and uranium [16], as well as for molybdenum, which can be bound to iron oxides even in the form of the molybdate anion [17]. In some soils, hydrous oxides represent dominant substrates of copper [18] and cadmium [19]. The highly toxic, hexavalent chromium is by far more mobile than the trivalent, which makes its reduction in the environment especially important [20], although it also sorbs onto hydrous oxides [21]. 

As mentioned above, the classical polyoxoanion forming metals are molybdenum and tungsten in the oxidation state VI. It is assiuned that for these metal cations the combination of ion-radius and -charge and the availability of empty d-orbitals for the formation of metal-oxygen-rx-bonds is especially favorable. However, other metals can act as polyoxoanion-builders as well. Vanadimn-, niobiiun- and tantalum-V, technetium-, rhenium-, ruthenium- and osmium-Vl, chromium-, molybdenum-, timgsten-, technetium- and rhenium-V and tita-niiun-, vanadium-, chromium-, molybdenum- and tungsten-IV can build poly-oxometallate-clusters. 

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