Abstract
Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H+CCD-) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs+ is a straightforward (H+ for Cs+) cation exchange reaction. In contrast, the extraction of Sr2+ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr2+ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs+ and Sr2+ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr2+ is complex, including evidence for both the partitioning of Sr(NO3)+ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.
Original language | English |
---|---|
Pages (from-to) | 161-183 |
Number of pages | 23 |
Journal | Solvent Extraction and Ion Exchange |
Volume | 28 |
Issue number | 2 |
DOIs | |
State | Published - Mar 2010 |
Funding
Work by PRZ was supported under subcontract number 11W-2452-0742 with the Idaho National Laboratory, the Laboratory Director’s Research and Development program.
Keywords
- Calorimetry
- Cesium
- Chlorinated cobalt dicarbollide
- FS-13
- Polyethylene glycol
- Solvent extraction
- Strontium
- Thermochemistry