Selective extraction of cesium

McDowell, W. J., Case, G. N., McDonough, J. A., Bartsch, R. A., Selective extraction of cesium from acidic nitrate solutions with didodecylnaphthalene-sulfonic acid synergized with bis(tert-butylbenszo)-21-crown-7 Anal. Chem., 64, 3013-3017, 1992. 

Delmau et al. (129) studied the self-association of fluorinated alcohols used as diluent modifiers for the selective extraction of cesium from caustic media by calixarene-crown ethers. They found that the salt distribution ratio is enhanced by the modifiers and explained this by a solubilization effect of the modifier due to its amphiphilic properties. 

Lamare, V., Bressot, C., Dozol, J. F., Vicens, J., Asfari, Z., Ungaro, R., and Casnati, A. Selective Extraction of Cesium at Tracer Level Concentration from a Sodium Nitrate Solution With Calixcrowns. Molecular Modeling Study of the Cs+/Na+ Selectivity, Sep. Sci. Technol. 32 (1997), 175-191. 

J.K. Kim, J.S. Kim, Y.G. Shul, K.W. Lee, and W.Z. Oh. Selective extraction of cesium ion with calix[4]arene crown ether through thin sheet supported liquid membranes. Journal of Membrane Science 187 3-11, 2001. 

Most of the studies carried out on cesium extraction conclude that the most efficient crown ethers for extraction of this cation are benzo-21-crown-7 derivatives. Like dicarbollides, these compounds need a synergistic agent or polar diluent modifier to allow cesium to be extracted from very acidic solutions. The resulting selectivity for cesium over sodium is low. Only dialkoxy-calix[4]arene-crown-6 and calix[4]arene bis(crown-6) compounds allow objectives to be fulfilled extraction of cesium at low-level concentration from acidic media.19... 

Extraction of Cesium and Sodium Cs/Na Selectivity and Competitive Extraction of Cesium in the Presence of an Excess of Sodium... 

In conclusion, calix[4]arene-bis(crown-6) and dialkoxy calix[4]arene crown-6, and especially their dibenzo derivatives, which display an important hydrophobic-ity, seem best suited for the extraction of cesium from very acidic media or media containing large amounts of sodium. In 2006, Mohapatra confirmed the high efficiency and selectivity of BC5 and BC10 for the extraction of cesium from simulated acidic high-activity level waste. The Cs distribution ratio follows the trend of diluent... 

Calix-crowns extract cesium from acidic and alkaline solutions with extremely high Cs/Na selectivity.66 71 Because their selectivity is higher, it seems promising to use the calix-crown instead of DB21C7 for extraction of cesium in mixtures with the... 

A unique assembly of a crystalline hybrid supramolecular salt was achieved by reaction of 2,4-bis (3-pyridylmethyl)oxy -(l,3)-p-bu -calix[4]-crown-6 (33), hexadecafluoro-l,8-diidooctane and Csl (2(X) 4951). In its solid state, the cesium ion of the supercation was encapsulated inside the cavity created by the crown ether loop, the picolyl and inverted phenyl moieties, whereas the two iodide ions of the superanion, formed a discrete five component aggregate held together by hydrogen and halogen bonds. Similar adduct existed in solution. A combination of this calix-crown 33 and octafluoro-l,4-diiodobutane acted as an effective binary host for the selective extraction of Csl from aqueous to fluonous phase. 

Removal of cesium from medium-level radioactive wastes involves extraction of cesium from aqueous solutions which are 1 M in HNO3 and 4 M in NaNOa (8). In a preliminary study, extraction experiments with ligands 1-7 were performed by mixing equal volumes (5 to 7 mL) of aqueous and organic solutions (calixarene 10 M in 2-nitrophenyl hexyl ether or 2-NPHE) in sealed polypropylene tubes for one hour at room temperal re (25 1 C). The aqueous solutions contained either NaNO or CSNO3 (5.0x10 M) in HNO3 (1 M) to assess the selectivity toward cesium in the hypothetical presence of sodium. A measure for the selectivity was assumed to be the ratio of the distribution coefBcients obtained separately for both cations ... 

The use of 13a in the extraction process or in the transport through supported liquid membranes (SLMs) allows to recover more than 98% of the cesium cation present in solution, making this derivative extremely attractive for declassification of nuclear wastes. Ligand 13a was dso used for the selective detection of cesium in ISEs and ISFETs with very high selectivity and low detection limit. Very recently, we anchored calix[4]arene-crown-5 and -crown-6 derivatives on silica-gel via hydrosilanization and we were able to separate by chromatography potassium or cesium fi"om other alkali metal ions with high efficiency. ... 

CSSX that hydrogen-bond donor modifiers were most effective for Cs extraction, TBP being a poor modifier by comparison (413). The results of preliminary tests showed that the process is effective at selectively extracting Cs and Sr from solutions of nitric acid concentration between 0.5 and 2.5 M. Cesium and Sr can be stripped from the solvent with 0.01 M HN03 solution. 

Tetraphenylborate (TPB) was used at Savannah River to recover cesium from alkaline solutions, but attempts to treat HLW tanks with TPB resulted in the production of benzene (a TPB decomposition product) at levels that did not permit the safe operation of the process.8 Crown ethers and dicarbollides were proposed as extractants to remove cesium from acidic HAW, but these compounds are not selective enough to allow cesium to be removed from solutions containing large amounts of nitric acid or sodium nitrate.9 Dicarbollides were used in Russia at industrial scale to recover cesium from HAW, but the removal of cesium was only possible after partial denitration of the liquid waste.10... 

Electrospray Ionization/Mass Spectrometry (ES/MS), a soft-ionization desorption technique using polar solvents such as water, methanol, or acetonitrile, was used for direct measurement of cations in solution. The first measurements carried out with mono or bis(crown-6) calix[4]arenes from an equimolar cation-extractant solution confirm that the calixarenes mono(crown-6) extract only one cesium cation. On the contrary, in the same conditions, bis(crown-6) calix[4]arenes can extract two cesium cations for a ratio Cs/BC6 equal to 2.5. The binuclear complex (composed of two cesium cations) is the major species. Cesium/sodium selectivity measurements implementing various mono or bis(crown-6) calix[4]arenes were in agreement with liquid/liquid results.42... 

Distribution ratios and transport were carried out on real HAW arising from dissolution of a mixed oxide of uranium and plutonium (MOX) fuel (burnup 34,650 MW d/tU), where uranium and plutonium have been previously extracted by TBP.86 The experiments were performed in the CARMEN hot cell of CEA Fontenay aux Roses with two dialkoxy-calix[4]arene-crown-6 derivatives (diisopropoxy and dini-trophenyl-octyloxy). High cesium distribution ratios were obtained (higher than 50) by contacting the HAW solution with diisopropoxy calix[4]arene-crown-6 (0.1 M in NPHE). Moreover, the high selectivity observed with the simulated waste was confirmed for most of the elements and radionuclides (actinides or fission products Eu, Sb, Ce, Mo, Zr, and Nd). The residual concentration or activity of elements, other than cesium, was less than 1% in the stripping solution, except for iron (2%) and ruthenium (8%) the extraction of these two cations, probably under a complexed... 

In the early 1990s, there existed several classes of extractants for actinides (CMPO), for cesium and more generally alkali cations, and for strontium and alkaline earth cations (crown ethers and cosan). The combination of these extractants and the grafting of these functions on calixarene platforms have led to new classes of extremely efficient and selective extractants, in particular calixarene-crown, which are presently applied in the United States to treat the huge amounts of waste at the SRS. Calixarenes/ CMPO, crown ethers/cosan, CMPO/cosan, and more recently calixarenes/CMPO/ cosan are promising compounds. It is desirable that these studies, conducted at the international level, continue in particular to obtain a better understanding of the complex mechanisms of extraction of these compounds.127187... 

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. 

PRINCIPLES OF SOLVENT EXTRACTION OF ALKALI METAL IONS UNDERSTANDING FACTORS LEADING TO CESIUM SELECTIVITY IN EXTRACTION BY SOLVATION Bruce A. Moyer and Yunfu Sun... 

Model Fitting to Mixing-Cell Data Multiple-site kinetic models have been used to describe pesticide and herbicide movement in soils (15,16,17), cesium migration in columns (18), and strontium migration in a sandy aquifer over a twenty-year time period (1L). The results of the selective extraction procedures in all experiments discussed here suggest that a multi-site model should provide a better fit of the data than a single-site model. This hypothesis is supported by the variances in Table I, with the possible exception of selenium. 

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