| Abstract
| - This paper describes the results of the extraction of trivalent lanthanides Ln(III) by supercritical fluid CO2(SF-CO2) containing N,N,N‘,N‘-tetrabutyl-3-oxapentanediamide (TBODA), one of a group of neutral oxa-diamide ligands that have the potential to replace traditional organophosphorus extractants and make theSF-CO2 extraction process more environmentally benign. According to this study, TBODA dissolves in neatSF-CO2 easily, but the solubility of Ln(III)/TBODA complexes in neat SF-CO2 is low and little Ln(III) canbe extracted in the SF-CO2 phase. Addition of small amounts of acetone as a modifier in SF-CO2 cansignificantly improve the extraction of Ln(III) from either aqueous nitric acid solutions or oxide solids. Thelow solubility of Ln(III)/TBODA complexes in neat SF-CO2 and the improved solubility of Ln(III)/TBODAcomplexes in acetone-modified SF-CO2 are discussed in terms of the structure of Ln(III)/TBODA complexesand its effect on solute−solvent interactions.
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