Actinides separation from lanthanides

Americium and other actinide elements may be separated from lanthanides by solvent extraction. Lithium chloride solution and an eight to nine carbon tertiary amine are used in the process. Americium is then separated from curium by the above methods. 

Nilsson, M., Ekberg, C., Foreman, M. et al. 2006. Separation of actinides(III) from lanthanides(III) in simulated nuclear waste streams using 6,6 -bis-(5,6-dipentyl-[l,2,4] triazin-3-yl)-[2,2 ]bipyridinyl (C5-BTBP) in cyclohexanone. Solvent Extr. Ion Exch. 

Arisaka, M., Watanabe, M., Kimura, T. 2007. Separation of actinides(EH) from lanthanides(III) by extraction chromatography using new N,N -dialkyl-N,N -diphenylpyridine-2,6-dicarboxyamides. Global 2007 Advanced Nuclear Fuel Cycles and Systems, September, Boise, ID. 

The selectivity factor is not sufficient to allow actinides to be separated from lanthanides. However, this process, easy to implement, can be used to remove actinides at low concentration from acidic waste containing even large amounts of sodium.180... 

G. Modolo and S. Nabet. Thermodynamic study on the synergistic mixture of bis(chlorophenyl) dithiophosphinic acid and tris(2-ethylhexyl) phosphate for separation of actinides(iii) from lanthanides(iii). Solvent Extr. IonExch., 23(3) 359-373, 2005. 

The redox reaction has been utilized in the separation of light actinide elements (U, Np, and Pu) with both ion-exchange process and solvent extraction process. For trivalent heavy actinides with Z> 94 (except No), separation of these actinide ions from lanthanide ions is required for safe storage of long-lived nuclear waste and transmutation of these nuclides. Fundamental researches have widely been carried out by several groups for the purpose of quantitative separation of transuranium elements. Recent topics on the development and application of solvent extraction for the separation of transuranium elements are briefly summarized below. 

Po and Bi as possibly interfering contaminants were also investigated under the same experimental conditions and, as shown in Fig. 20, were found to be similarly volatile as Re03. In conclusion, an on-line isolation of very volatile group-7 oxide hydroxides was not accomplished. The isolation of less volatile trioxides appeared not to be promising due to the interference of Po and Bi by-products hampering the unambiguous identihcation of Bh nuclides after chemical isolation. Nevertheless, the oxide system provided an excellent separation from lanthanides [62] and actinides [59, 60], separation factors of >10 were deduced. Preseparation with a recoil separator (see e.g. an application in one of the FI experiments in Sect. 8) may provide a path to much cleaner samples and a variety of Bh experiments in the gas phase. 

The formation of thiocyanate complexes of actinide(iii) ions (Section 21.4.6) has also been successfully utilized for the separation of actinides from lanthanides by means of anion exchange [188,201]. From a 5 m ammonium thiocyanate solution, americium (iii) is strongly sorbed on an anion-exchange column while the lanthanides pass through [201]. In this way, americium (iii) can be almost completely separated from lanthanides present even in very large amounts. 

Further discussion on the extraction of lanthanides, especially concerning their separation from actinides, can be found in Chapter 12. 

Americium may be separated from other elements, particularly from the lanthanides or other actinide elements, by techniques involving oxidation, ion exchange and solvent extraction. One oxidation method involves precipitation of the metal in its trivalent state as oxalate (controlled precipitation). Alternatively, it may be separated by precipitating out lanthanide elements as fluorosilicates leaving americium in the solution. Americium may also he oxidized from trivalent to pentavalent state by hypochlorite in potassium carbonate solution. The product potassium americium (V) carbonate precipitates out. Curium and rare earth metals remain in the solution. An alternative approach is to oxidize Am3+ to Am022+ in dilute acid using peroxydisulfate. Am02 is soluble in fluoride solution, while trivalent curium and lanthanides are insoluble. 

Periods (rows) 6 and 7 have an added wrinkle. Elements with atomic numbers 58 through 71 and 90 through 103 are lifted out of the regular order and placed below the rest of the table. These two series are the lanthanides and the actinides, respectively. These elements are separated from the table for two main reasons ... 

Fission products and actinides in spent nuclear fuels have also been analyzed using cation-exchange LC [98]. Chromatography was essential in order to separate fission Cs from Ba for the analysis of the lanthanides and to eliminate isobaric interferences in the separation of the actinides. Separation of fission... 

Modolo, G., Odoj, R. 1998. Influence of the purity and irradiation stability of Cyanex 301 on the separation of trivalent actinides from lanthanides by solvent extraction. J. Radioanal. Nucl. Chem. 228 (1-2) 83-89. 

Modolo, G., Odoj, R. 1999. Actinides(IH)-lanthanides group separation from nitric acid using new aromatic diorganyldithiophosphinic acids. 5th OECD/NEA IEM on An and FP P T. SCK-CEN, Mol, Belgium, November 25-27, 1998. 

Svantesson, I. 1984. A reversed TALSPEAK process for the separation of actinides from lanthanides. Thesis. Chalmers University of Technology, Goteborg. 

Schmidt, C., Saadioui, M., Bohmer, V. et al. 2003. Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides. Org. Biomol. Chem. 1 4089 4096. 

Shaibu, B.S. Reddy, M.L.P. Bhattacharyya, A. Manchanda, V.K. Evaluation of Cyanex 923-coated magnetic particles for the extraction and separation of lanthanides and actinides from nuclear waste streams, J. Magn. Magn. Mater. 301 (2006) 312-318. 

Lanthanides are coextracted with actinides and then separated from actinides, which are forecasted to be sent to a repository. The lanthanide elements comprise a unique series of metals in the periodic table. These metals are distinctive in terms of size, valence orbitals, electrophilicity, and magnetic and electronic properties, such that some members of the series are currently the best metals for certain applications. Increased use of the lanthanides in the future is likely, because their unusual combination of physical properties can be exploited to accomplish new types of chemical transformations. These elements coextracted with actinides and then separated from the latter, could in the future be recovered and used (among the lanthanides, only 151Sm is a long-lived isotope (half-life 90 years)).4... 

A mixture of well-known extractants, di-(2-ethylhexyl)phosphoric acid (HDEHP) and CMPO, in n-paraffin was used for the study of combined extraction of different actinides (americium, plutonium, and uranium) and lanthanides (cerium and europium) and their separation from fission products (cesium, strontium, ruthenium, and zirconium).54 Combined extraction of MAs and lanthanides was studied together with group separation of MAs from lanthanides by selective stripping with a solution of diethylenetriaminepentaacetic acid (DTPA), formic acid, and hydrazine hydrate. This solution strips only MAs, leaving lanthanides in the organic phase. Subsequently, the lanthanides are stripped using a mixture of DTPA and sodium carbonate. 

Calixarenes are potential platforms on which specific binding arms can be grafted. The extractive properties of these molecules for metallic ions depend on the cavity size, the conformation, and the nature of the ligating groups. Different calix[4] arene-crown-6 derivatives in the 1,3-alternate conformation have been studied for Cs recovery from both basic and acidic solutions (257-262). Calixarene-based picol-inamide ligands have been proposed as candidates for separating actinides from lanthanides (263, 264). 

The radioly tic behavior of a substituted picolinamide calix[6]arene, studied for the separation of actinides from lanthanides, was recently investigated by Mariani (263). For doses ranging from 0.014 to 0.055 MGy, the distribution ratios of both Am(III) and Ln(III) strongly increased, whereas after absorbed doses higher than 0.10 MGy, they decreased to values lower than those measured for nonirradiated samples. The selectivity for Am/Eu remained constant. Comparable experiments under a nitrogen atmosphere indicated the role of oxygen in the radiolysis, because the distribution ratios decreased by factors of 10 and 1.5-5 for Am-Eu and other lanthanides, respectively. The increase for lower doses was then explained by the formation of oxidized radiolytic products. No evidence of new products was obtained with the ESI-MS technique. 

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