Thorium separate elution

Strongly acid cation-exchangers have been used for the separation of Th from rare-earth elements and other metals [8,9]. From the metal cations retained on the column 3-5 A/ HCl elutes rare-earth- and most other metals except thorium. Thorium is eluted with 10 M HCI or 3 M H2SO4, as well as with 5 MHNO3 [10], ammonium oxalate [11], ammonium carbonate [1] or ammonium sulphate solutions. Cation-exchange chromatography has also been used to separate thorium with the use of media such as HBr [12], formic acid -I- dimethyl sulphoxide [13], and nitric acid -1- methanol -i-TOPO [14]. 

Separation of thorium and uranium from ore samples using anion-exchange column (Dowex 1-X8) has been investigated [1]. Thorium was eluted with 6 M HCl. 

The most important minerals of the lanthanide elements are monazite (phosphates of La, Ce, Pr, Nd and Sm, as well as thorium oxide) plus cerite and gadolinite (silicates of these elements). Separation is difficult because of the chemical similarity of the lanthanides. Fractional crystallization, complex formation, and selective adsorption and elution using an ion exchange resin (chromatography) are the most successful methods. 

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

The other metal ions that exhibited an appreciable reaction with Arsenazo(III) at 650nm under the separation and detection conditions used, were iron(III), zirconium(IV), thorium(IV) and the lanthanides. The lanthanides, iron(III) and zirconium(IV) were eluted at or near the solvent front before uranium(VI) and thorium(IV) was eluted after uranium(VI). 

In third separation, thorium is retained on a cation-exchange resin while uranium is eluted from the resin column. Thorium is then eluted as an oxalate complex and evaporated on a planchet for counting. The planchet is flamed to volatilize the oxalic acid and then counted. 

Cerium is separated from the other rare earths based on differences in adsorption and selective elution. In a typical process, thorium free rare-earth solutions are run... 

Plutonium Purification. The same purification approach is used for plutonium separated from sediments or seawater. In case reduction may have occurred, the plutonium is oxidized to the quadrivalent state with either hydrogen peroxide or sodium nitrite and adsorbed on an anion exchange resin from 8M nitric acid as the nitrate complex. Americium, curium, transcurium elements, and lanthanides pass through this column unadsorbed and are collected for subsequent radiochemical purification. Thorium is also adsorbed on this column and is eluted with 12M hydrochloric acid. Plutonium is then eluted from the column with 12M hydrochloric acid containing ammonium iodide to reduce plutonium to the non-adsorbed tervalent state. For seawater samples, adequate cleanup from natural-series isotopes is obtained with this single column step so the plutonium fraction is electroplated on a stainless steel plate and stored for a-spectrometry measurement. Further purification, especially from thorium, is usually needed for sediment samples. Two additional column cycles of this type using fresh resin are usually required to reduce the thorium content of the separated plutonium fraction to insignificant levels. 

The thorium is removed from the column with 12N HCl, since it does not form a chloride complex, to separate it from neptunium and plutonium. The plutonium is removed by reduction to Pu(III) with 12N HCl-O.lM NH4I solution. The neptunium is then removed by dilute acid. The neptunium and plutonium can also be eluted together with dilute acid and the various nuclides determined by alpha spectrometry. 

Anion-exchange separation of thorium from uranium in nitrate solutions is possible but the application is almost solely in the field of chemical analysis. Absorption of uranium and thorium takes place from 6N nitric acid as a narrow band at the top of a column. Uranium is eluted first with boiled 4N nitric acid, followed by thorium elution with water. 

Publications on the analysis of soil samples by Smith et al. [78] and Crain et al. [79] summarized two possible routes for the analysis of aqueous samples in chromatography extraction columns, with detection by conventional radiometric techniques such as ICP-MS. In this procedure, TRU-Spec SPS columns were used for group separation of actinides and TEVA-Spec columns were used to isolate the trivalent actinides from the lanthanide elements. A reduced solution (with ascorbic acid) was passed through a 1 mL TRU-Spec column equilibrated with 2 M nitric acid and 0.5 M aluminum nitrate. The trivalent actinides including americium and the lanthanide elements were eluted from the column with 12 mL of 4 M HCl. Plutonium and thorium were removed with 30 mL of... 

O. 1 M tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA). The trivalent actinides were separated by using TEVA-Spec resin. The lanthanide elements were removed by washing the column with 10 mL of 1 M NH4SCN in 0.1 M formic acid. The trivalent actinides were eluted from the column with 15 mL of 2 M HCl. The THFTCA fraction containing plutonium (239,240py thorium (230,232 1 can be analyzed directly by ICP-MS. 

Determination of Thorium Isotopes in Soil. Thorium was separated exactly as uranium except that the samples were spiked with Th radiotracer (instead of U), and 8 M and IM HNO3 were used in loading and eluting thorium (instead of lOM and 0. IM HCl in case of uranium), respectively. Thorium source was also prepared as that of uranium except that there is no need for the addition of TiCL solution. ... 

Neither Pa(lV) nor Th(lV) le adsorbed from 6m - 12.6m The elution of Fu(lll) by 12H HCl from strong base anion exchange resin has already been mentioned. Wish and Rowell have effected the separation of Th, Pu, Zr, and Np from U by elution with hydrochlorlo acid In a sequence of concentrations. The elements are 2ulsorbed on the resin (Dowex-2) from ISH HCl. Thorium does not adsorb. Plutonium Is eluted In the trlvalent state with 12N HCl saturated with hydroxyl-amine hydrochloride and amnonlum Iodide Zirconium Is eluted with 7.5M HCl neptunium (JV) with a % HCl - 5 NH OH HCl solution. Thranlum Is finally eluted with O.IM HCl. 

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