Cesium extraction

Tsuda, T., Hussey, G. L., Luo, H. M., Dai, S., Recovery of cesium extracted from simulated tank waste with an ionic liquid Water and oxygen effects, /. Electrochem. Soc., 153, D171-D176, 2006. 

Engle, N.L., Bonnesen, P.V., Tomkins, B.A., Haverlock, T.J., Moyer, B.A. 2004. Synthesis and properties of calix[4]arene-bis[4-(2-ethylhexyl)benzo-crown-6], a cesium extractant with improved solubility. Solvent Extr. Ion Exch. 22 (4) 611-636. 

Chamberlin, R.M., Abney, K.D. 1999. Strontium and cesium extraction into hydrocarbons using alkyl cobalt dicarbollide and polyethylene glycols. J. Radioanal. Nucl. Chem. 240 (2) 547-553. 

Kaminski, M.D. Nunez, L. Cesium extraction from a novel chemical decontamination process solvent using magnetic microparticles, Sep. Sci. Technol. 37 (2002) 3703-3714. 

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... 

Sachleben et al. observed that for bis(alkoxy)calix[4]arene monocrown ethers, reducing the size of the alkoxy substituent from octyl to allyl increased the cesium extraction by 10%-30% and the cesium-to-potassium selectivity by 20%-40%, with little impact on cesium over sodium selectivity. A standard modeling approach was used to analyze the complementarity of the calix-crown cavity toward potassium and cesium. MM3 optimizations were performed by modifying the K+ and Cs+ complexes, replacing the 1,3-dioxybenzene-substituent with tert-butoxy, methoxy, or hydrogen groups. 

To investigate the effect of alcohol hydrogen-bond donor (HBD) strength in a systematic way, a series of modifiers possessing a common 4-teri-octylphenoxy ethanol core element were prepared, in which the properties of the substituent attached to the alcohol carbon atom were varied. These modifiers were evaluated with respect to both the cesium extraction strength they afforded when used in combination with BC6 and the HBD strength of the solvent as assessed using the solvatochromic parameter E. ... 

Some of the modifiers in this study (1-5) were also evaluated in the isoparaffinic diluent Isopar L for cesium extraction performance from a Savannah River waste simulant. The effect the modifiers have on the cesium distribution ratio in aliphatic diluents is more pronounced than it is in polar diluents, such as 1,2-DCE, previously used. The cesium distribution results are shown in Table 4.17 alongside those obtained from 1 M NaN03 in 1,2-DCE. 

Two systems based on crown-calixarenes, able to be used in liquid-liquid extraction process were chosen. Both systems use a modifier in the organic phase to avoid the occurrence of a third phase in the TPH (diluent used at the reprocessing plant of la Hague for the PUREX process) and ensure a sufficient cesium extraction. 

For cesium extraction, Couette columns have been used. The operations in such a contactor can be easily extrapolated to a pulsed column, and the quantity of implemented solvent is less important. The hydrodynamic behavior is satisfactory for the two calixarene systems studied in spite of a more emulsion-prone behavior with system 2. The selectivity obtained compared to other elements is excellent. 

The developed cesium and potassium extraction model, based on extraction data obtained from simple aqueous media, was tested to ensure the validity of the prediction for the cesium extraction from actual waste.112 The predicted values agreed with the measured values for the simulants predicted values also agreed, with some exceptions, with measured values for the tank wastes. Discrepancies were attributed, in part, to the uncertainty in the cation/anion balance in the actual-waste composition, but likely more so to the uncertainty of the potassium concentration in the waste, given the demonstrated large competing effect of this metal on cesium extraction. It was demonstrated that the upper limit for the potassium concentration in the feed should not exceed 0.05 M, in order to maintain suitable cesium distribution ratios. 

Luo et al.90 have described yet another approach to reducing the impact of ion exchange in metal ion extraction by neutral extractants in ILs, one which relies on modifying neither the structure of the IL nor the properties of the extractant. Instead, a sacrificial species that transfers in preference to the IL cation upon metal ion extraction (thereby reducing loss of the IL) is added to the IL phase. Ideally, the sacrificial species should exhibit no affinity for the extractant (in order not to interfere with extraction of the metal ion of interest) and be more hydrophilic than the IL cation (in order to favor its loss to the aqueous phase upon metal ion transfer). Tests with sodium tetraphenylborate indicate that its addition to a solution of a calix-crown ether in [C4mim+][Tf2N ] reduces the loss of the IL induced by cesium extraction by nearly one-quarter with no adverse effect on the efficiency of cesium extraction. 

Duchemin, C. R., Engle, N. L., Bonnesen, P. V., Haverlock, T. J., Delmau, L. H., and Moyer, B. A Solvatochromic Solvent Polarity Measurements of Alcohol Solvent Modifiers and Correlation with Cesium Extraction Strength, Solvent Extr. Ion Exch. 19(2001), 1037-1058. 

CEA Cadarache and seven European universities were involved in a research programme to synthesize and test new macrocyclic extractants (crown-ethers and calixarenes). The main aim of this study was to selectively remove caesium, strontium and actinides from medium level liquid waste (MLLW) to decontaminate them to the extent that they can be disposed of in a near surface site. A new calixarene has been synthesized by the University of Parma, which has a cesium/sodium selectivity 100 times higher than that of the best current extractant for cesium. The large selectivity of this molecule has been explained theoretically. The results obtained for cesium extraction from simulated MLLW have been confirmed with real HLLW. Finally, new functionalized calixarenes have been also synthesized, which are more selective to actinides and lanthanides than the best extractant available on the market. 

The electronic, pauramagnetic susceptibility of cesium, extracted from measurements of XtotaU is plotted as a function of reduced density p/Pc) in Fig. 3.2. The volume susceptibility xv plotted here is related to the mass susceptibility Xm by the density, that is. 

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