Technetium minerals

The discovery of the elements 43 and 75 was reported by Noddack et al. in 1925, just seventy years ago. Although the presence of the element 75, rhenium, was confirmed later, the element 43, masurium, as they named it, could not be extracted from naturally occurring minerals. However, in the cyclotron-irradiated molybdenum deflector, Perrier and Segre found radioactivity ascribed to the element 43. This discovery in 1937 was established firmly on the basis of its chemical properties which were expected from the position between manganese and rhenium in the periodic table. However, ten years later in 1937, the new element was named technetium as the first artificially made element. 

Strickert, R., Friedman, A. M., and Fried, S., "The Sorption of Technetium and Iodine Radioisotopes by Various Minerals," Nuclear Technology, in press (1978). 

FIGURE 21.2 Primary mineral sources of metals. The s-block metals occur as chlorides, silicates, and carbonates. The d- and p-block metals are found as oxides and sulfides, except for the group 3B metals, which occur as phosphates, and the platinum-group metals and gold, which occur in uncombined form. There is no mineral source of technetium (Tc in group 7B), a radioactive element that is made in nuclear reactors. 

Reactions Between Technetium in Solution and Iron-Containing Minerals Under Oxic and Anoxic Conditions... 

Figure 2 is a combined E -pH diagram for technetium and iron and shows that, under certain conditions, technetium can be reduced by ferrous iron. To study the role of ferrous iron in the removal of technetium from solution, experiments were carried out with crystalline rock and ferrous minerals and TcO -containing solutions, under both anoxic and oxic conditions. 

Experimental Details and Results. A series of experiments was carried out to study the behaviour of TcO, in various solutions in contact with a number of rocks and minerals, under both oxic and anoxic conditions, to determine the conditions that lead to removal of technetium from solution and the role played by the various minerals in this process. 

Table V. Ferrous-Iron-Containing Minerals used in Technetium Sorption Studies...

FIGURE 7. Decrease in technetium concentration as a function of time for solutions in contact with iron metal and iron minerals under (a) oxic and (b) anoxic conditions. 

Thus, while fresh, unaltered granite matrix rock has little or no iron in the form of iron oxides, alteration zones around fractures do, and technetium sorption may occur there. It should also be noted that sorption of technetium is limited to specific mineral surfaces. Thus, it appears that the reduction of TcO, to a lower oxidation state occurs at or near the surface of the iron oxide and not in the bulk of the solution, by dissolved ferrous ions. 

The authors would like to acknowledge the assistance of J. Paquette and N. Garisto in providing the Eft-pH diagrams for technetium and iron and of D.C. Kamineni, who performed the petrographic analyses. The minerals from the GSC were obtained through its curator, H.R. Steacy. R.F. Hamon, B.L. Sanipelli and K. Ross performed the various chemical analyses reported in this paper. 

Palmer, D. A. Meyer, R. E., "Adsorption of Technetium on Selected Inorganic Ion-Exchange Materials and on a Range of Naturally Occurring Minerals under Oxic Conditions," J. Inorg. Nucl, Chem. 1981, 43, 2979. 

The congeners of manganese are very rare. The middle element of the group, technetium (Z = 43), has not been isolated from mineral sources, and there is good reason to suppose that detectable quantities do not occur naturally (Chap. 27, Exercise 7). Weighable amounts of this element and its compounds have been made from molybdenum by nuclear displacement and from uranium by nuclear fission (p. 474). Rhenium (Z =5 75) occurs naturally but in only tiny amounts. It has been estimated that there is one atom of rhenium present in the earth s crust for each two billion (2 X 109) atoms of silicon. Rhenium was discovered in 1925, technetium in 1937. 

Huie Z., Zishu Z., and Lanying Z. (1988) Sorption of radionuclides technetium and iodine on minerals. Radiochim. Acta 44/45, 143-145. 

Strickert R., Friedman A. M., and Fried S. (1980) The sorption of technetium and iodine radioisotopes by various minerals. Nuclear Technol. 49, 253-266. 

Vandergraaf T. T., Tichnor K. V., and George I. M. (1984) Reactions between technetium in solution and iron-containing minerals under oxic and anoxic conditions. In Geochemical Behaviour of Disposed Radioactive Waste. ACS Symposium Series 246 (eds. G. S. Barney, J. D. Navratil, and W. W. Schultz). American Chemical Society, Washington, DC, pp. 25-44. 

Winkler A., Bmhl H., Trapp C., and Bock W. D. (1988) Mobility of technetium in various rock and defined combinations of natural minerals. Radiochim. Acta 44/45, 183-186. 

The radioactive isotope most widely used in nuclear medicine is tech-netium-99, which has a short half-life and emits low-energy gamma rays. This radioactive isotope is used in bone scans. Bone repairs occur when there is a fracture, infection, arthritis, or an invading cancer. Bones that are repairing themselves take in minerals and absorb the technetium at the same time. If an area of bone has an unusual amount of repair, the technetium will gather there. Cameras detect the gamma rays that result from its decay. 

It is no surprise that the majority of the noble gases, krypton and xenon, have been lost, nor that there are still traces trapped in some of the core minerals. The relatively soluble alkali and alkaline earth elements have also been lost to a large extent, as have molybdenum, cadmium and iodine. The elements zirconium, technetium, lead, and to some extent ruthenium have at least been redistributed in the core. The rare earth elements, cerium, neodymium, samarium, and gadolinium as well as the actinides, thorium, uranium, neptunium, and plutonium show little evidence of migration, except possibly near the periphery of the core. By analogy to the rare earth elements it is probable that the transplutonium actinides, americium, curium, etc. would not migrate in this same environment. 

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