Europium , distribution

Therefore, the preliminary investigation described herein examined several aspects of the behavior of the equilibrium distribution coefficients for the sorption of rubidium, cesium, strontium, barium, silver, cadmium, cerium, promethium, europium, and gadolinium from aqueous sodium chloride solutions. These solutions initially contained one and only one of the nuclides of interest. For the nuclides selected, values of Kp were then... 

The distribution coefficients for europium also appear to be strongly influenced by low values of the solution pH. Such behavior is similar to that of barium and silver and again suggests that the sorption of the lanthanides may be due to at least two separate mechanisms, which are also probably essentially the same as those discussed for barium. 

For the nuclides studied (rubidium, cesium, strontium, bariun silver, cadmium, cerium, promethium, europium, and gadolinium) the distribution coefficients generally vary from about 10 ml/gm at solution-phase concentrations on the order of 10 mg-atom/ml to 10 and greater at concentrations on the order of 10 and less. These results are encouraging with regard to the sediment being able to provide a barrier to migration of nuclides away from a waste form and also appear to be reasonably consistent with related data for similar oceanic sediments and related clay minerals found within the continental United States. 

Nash, K.L., Lavallette, C., Borkowski, M., Paine, R.T., Gan, X. 2002. Features of the thermodynamics of two-phase distribution reactions of americium(III) and europium (III) nitrates into solutions of 2,6-bis[(di-2-ethylhexylphosphino)methyl]pyridine-N,P,P-trioxide. Inorg. Chem. 41 (22) 5849-5858. 

These compounds, tested in NPHE at Cadarache, were used as reference compounds for the extraction of actinides by functionalized calixarenes (see below). The distribution ratios for neptunium mainly at the oxidation state (V), plutonium at the oxidation state (IV), and americium (III) are shown in Table 4.21 for OOCMPO. They were also used as references for the americium over europium selectivity (Table 4.22). 

To increase the distribution ratios, a solution of lithium nitrate 1M was used. This salt, which has a common anion with europium and americium to be extracted but a cation which is usually negligibly extracted by other calixarenes, should increase the distribution ratios according to the relation Du = A (JU "[N03- ". It seems that these calixarenes, as several nitrogen ligands do, present a certain affinity for this lithium cation. The lipophilic dicarbollide anion (BrCosan), which is known to facilitate cation extraction, was implemented and led to a strong increase of the extraction of cations from 10 3 M HN03 solutions. Under these conditions, only thiopicolinamide was not able to significantly extract trivalent actinides.187... 

Under the same conditions, in contrast to what is observed for calix[4]arene-bearing CMPO moieties, with CPil2, distribution ratios of lanthanides increase from the lightest lanthanide, lanthanum, to europium. Americium can be easily separated from the lightest lanthanides (separation factor DAm/La > 20, DAm/Ce =15, /lAlll,Nd = 10, UAi /si = 7.5, DAm/Eu = 6), which are the most abundant lanthanides in fission-product solution. Cavitands bearing picolinamide (Cv5) or thiopicolin-amide (Cv6) residues seems much less selective than their calixarene counterparts, giving SAm/Eu < 2.18... 

Energy dispersive X-ray (EDX) analyses (data in Tables l-lll) represent semiquantitative analyses of elemental distributions of vanadium, europium and elements of the zeolite and gel structure. EDX data arise from about 2 mm area and, therefore, are more indicative of bulk analyses than surface analyses such as the data obtained by X-ray photoelectron spectroscopy. 

NWA Oil is basaltic in composition, with enrichments in aluminum, calcium, and titanium relative to chondrites, and is ferroan, with an mg of 36. NWA 011 has a cumulate-eucrite-like REE pattern (Figure 6). However, Afanasiev et al. (2000) report that NWA Oil has a negative europium anomaly and samarium content of 13.3 X Cl, more like those expected for a mafic melt composition. Yamaguchi et al. (2002) suggest that the heterogeneous distribution of calcium phosphate is the likely explanation for this discrepancy. This is supported by their hafnium and tantalum analyses, which are at 12.8 X Cl and... 

The key features in a normalized REE distribution plot are (I) the absolute magnitude of the concentrations (2) the differentiation of the lighter REEs from each other in going from the radius of La " (1.14 A) to Sm (1.00 A) (3) the differentiation of the heavier REEs as the size decreases from Gd (0.97 A) to Lu " (0.85 A) and (4) the difference between the europium concentration measured and that predicted by a smooth variation in normalized concentrations between samarium and gadolinium. Because the REE distribution curves are... 

---