Synergistic extraction of Ce(IV) and Th(IV) with mixtures of Cyanex 923 and organophosphorus acids in sulfuric acid media

Abstract

The synergistic effect of mixtures of Cyanex 923 and organophosphorus acids including P204, P507 and Cyanex 272 in extraction of Ce(IV) and Th(IV) from sulfuric acid solutions has been investigated. Under the experimental conditions, the extraction of Ce(IV) presented an significant synergistic effect with the mixed extraction systems of Cyanex 923–P204, Cyanex 923–P507 and Cyanex 923–Cyanex 272. On the contrary, the extraction of Th(IV) showed significant antagonistic effects in the mixed systems. The separation factor for Ce(IV)/Th(IV) reached as 36.8 at a mole fraction of 70% Cyanex 923 in the Cyanex 923–P507 system. It is shown that the mixed extraction systems not only enhance the extraction efficiency of Ce(IV) but also improve the selectivity of Ce(IV) over Th(IV). Furthermore, a fractional extraction process (including 4 stages of extraction, 2 stages of scrubbing and 2 stages of stripping) with the mixed Cyanex 923–P507 to separate Ce(IV) from the bastnasite leach solution has been designed. Cerium solution of Ce2(SO4)3 and CeF3 nanoparticle were obtained with 99.8% and 99.9% purity, respectively.