Technetium separation

Procedure The irradiated molybdenum is dissolved in cone, sulfuric acid and technetium is distilled with the acid. The distillate obtained is diluted to 4 M H2SO4, heated to boiling and treated with bromic water. A platinum salt (1 mg of Pt/200 ml solution) is added to the solution as collector, and technetiiun is coprecipitated with the platinum sulfide. The precipitate is dissolved in NH OH/ HjOj mixture and the solution evaporated to dryness. The residue is dissolved in cone. HjSO or HCIO4 and technetium separated from platimun by distillation. The solution is diluted and the sulfide precipitated. 

Jarvinen, G. D. Technology Needs for Actinide and Technetium Separations Based on Solvent Extraction, Ion Exchange, and Other Processes. In Chemical Separation Technologies and Related Methods of Nuclear Waste Management, Choppin, G. R., Khankhasayev, M. K., Ed., Kluwer Academic Dordrecht, The Netherlands, 1999, pp 53-70. 

Analysis of technetium is usually made after chemical separation of the element and it requires a chemical yield tracer (99mTc or 95mTc). These sometimes make... 

Chemical separation of technetium in soils is not easy, but it is fairly well-known that under aerobic conditions pertechnetate Tc(YII) is readily transferred to plants while under anaerobic conditions insoluble TcCh (or its hydrate) is not transferred to them. Even under aerobic conditions, however, the transfer rate decreases with time [28], indicating that soluble pertechnetate changes to insoluble forms by the action of microorganisms which produce a local anaerobic condition around themselves [29,30]. Insoluble technetium species may be TcOz, sulfide or complexes of organic material such as humic acid. 

In closing, recovery of technetium from waste solution should be touched upon. Studies of the base hydrolysis of technetium P-diketone complexes revealed that all of the complexes studied decompose in an alkaline solution even at room temperature, until technetium is finally oxidized to pertechnetate. These phenomena are very important for the management of technetium in waste solutions. Since most metal ions precipitate in alkaline solution, only technetium and some amphoteric metal ions can be present in the filtrate [29]. A further favorable property of pertechnetate is its high distribution coefficient to anion exchangers. Consequently, it is possible to concentrate and separate technetium with anion exchangers from a large volume of waste solution this is especially effective using an alkaline solution [54],... 

Hall, N. F and D. H. Johns The separation of Technetium from Molyb-... 

Keith-Roach et al. [114] has described a radiochemical separation and ICPS protocol for determining "technetium in seawater. 

Technetium, a fission product, also, can be separated by distillation of the oxide in its purification (91). 

Other elements often separated from pile or cyclotron targets by distillation or volatilisation are tritium (3), germanium as the bromide (23), arsenic as the trichloride (67), technetium (23), (91), rhenium (24), (25) and osmium (25) as oxides. 

Separation of Technetium from Uranium Fission Products.114... 

Subsequently, solvent extraction was applied to recover the fission product technetium from the residue remaining after the fluorination of irradiated uranium fuel elements . The residue was leached with concentrated aluminum nitrate solution, which was extracted by 0.3 M trilaurylamine in a hydrocarbon diluent. After separation of uranium, neptunium, and aluminum nitrate, technetium was back extracted into a 4 N sodium hydroxide solution. 

Campbell has studied the separation of technetium by extraction with tributyl phosphate from a mixture of fission products cooled for 200 days. Nearly complete separation of pertechnetate is achieved by extraction from 2 N sulfuric acid using a 45 % solution of tributyl phosphate in kerosene. Ruthenium interferes with the separation and is difficult to remove without loss of technetium other radioisotopes can be removed by a cation-exchange process. However, this separation procedure has not been widely applied because of the adverse influence of nitrate. 

Goishi and Libby have investigated the extraction of pertechnetate from alkali solutions with pyridine. Later work showed that a better extraction is obtained using a mixture of sodium hydroxide and sodium carbonate as the aqueous phase. Since the uranyl carbonate complex is not extracted into pyridine, this system may be used for the separation of technetium from uranium. Distribution coefficients of fission products in pyridine are given in Table 4. Substituted pyridine such as 2,4-dimethylpyridine or 4-(5-nonyl)pyridine ) are useful for separating technetium from solutions containing appreciable amounts of aluminum nitrate. 

The solvent extraction of pertechnetate with cyclohexanone has proved to be an efficient and selective method which can be applied to the separation of Tc from long-lived fission products in the bum-up analysis . The recovery of technetium from the fission products is about 93 %. 

The known process of distillation of technetium heptoxide from sulfuric acid has been successfully applied to the separation of microgram amounts of technetium from fission elements . 

Chromatographic methods for the separation of technetium from fission products are based on the strong sorption of pertechnetate from weakly acidic, neutral, and... 

A selective separation of fission technetium induced by fission of can be performed by stopping the speed of the Tc nuclides in solid KCl and SrClj catchers. At temperatures of 300 to 750 °C, 30% to 85% of Tc is selectively released. Purified nitrogen is used for the transportation of the nuclides from the target to the detector. The release is accelerated by increasing the temperature and adding ZrCl as a carrier. 

However, a more detailed study of the co-distillation with sulfuric acid has revealed that technetium can be distilled quantitatively with HjS04 provided the acid and the distillation apparatus are free from contaminations. Reducing agents only inhibit distillation but display no effect on the complete separation of technetium. If, for example, bromide ions are present, distillation begins at 155 °C instead of 110 °C thus resulting in a rapid and quantitative distillation of technetium. 

The property of pertechnetate to be easily reduced by hydrochloric acid is utilized in its separation from rhenium by distillation. Perrier and Segre separated both elements by distillation from a mixture of sulfuric and hydrochloric acid at 180-200 °C. Under these conditions about 90% of rhenium is said to pass into the distillate, but almost all the technetium which is reduced to Tc (IV) remains in solution. The separation factor was found to be 50. 

Another distillation method involves reduction of pertechnetate by hydroxyl-amine . Rhenium is distilled from sulfuric acid. This method can be used for the separation of about 10 mg of rhenium from microamounts of technetium. 

Partial separation of technetium and rhenium is possible by distillation from perchloric acid since the first fraction is enriched by technetium. However, ruthenium is oxidized by perchloric acid to RuO and volatilized together with technetium. 

In consequences of the great differences in vapor pressures of the heptoxides and acids at low temperatures, technetium may be partially separated from rhenium by repeated alternating evaporation with nitric acid and hydrochloric acid ]... 

Distillation methods using sulfuric acid are the most efficient for isolating technetium produced by neutron irradiation of kilogram amounts of molybdenum. Boyd et al. have used this method to separate technetium from pure molybdenum which had been irradiated for one year. In this case for each gram of molybdenum 6 ml of concentrated surfuric acid are added and about 75 % of technetium is passed into the distillate. When double the amount of acid is added, nearly 90 % of technetium are found in the distillate. More than 98 % of technetium are extracted after two distillations. 

The extraction of technetiiun by different organic solvents is used in numerous separation and concentration procedures. Technetium is extracted as pertechnetate or, in lower oxidation states, as a complex compound. TcO can be extracted by the following main types of reactions ... 

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