Technetium coprecipitation

Technetium has been determined in seawater by inductively coupled plasma mass spectrometry after preconcentration by coprecipitation with iron hydroxide [33]. 

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. 

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 above-cited reactions are used to separate Tc for measurement. Rhenium is a common nonisotopic carrier for precipitation or yield measurement. The shorter-lived Tc (60 days) has been used as isotopic tracer for yield measurement (Anders 1960). Technetium can be separated from rhenium by coprecipitating the +4 state with ferric hydroxide while rhenium remains in solution. Technetium is separated from the fission-produced radionuclides ° Ru and ° Ruby distillation with Re207 from sulfuric acid while ruthenium remains behind because it is volatile only in its... 

Preparative strategies have been a key factor in the development of new procedures for radionuclide determination by ICP-MS. Momoshima et al. [80] used ferric hydroxide coprecipitation to scavenge Tc from seawater after technetium had been reduced to its tetravalent oxidation state. Solvent extraction and ion exchange decrease the interferences caused by spectral overlap and the sample matrix. Hollenbach et al. [81] determined Tc, and in soil by using a combination of flow injection and extraction... 

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