The Chemistry of Protactinium : X. A Study of the Effect of Chromium(II) on the Solvent Extraction of Protactinium(IV), Using N-Benzoyl-N-phenylhydroxylamine, Tri-n-octylamine and Thenoyltrifluoroacetone as the Extractants(Chemistry)

Cr(II) has been used for reducing protactinium in microquantities to the tetravalent state and for protecting it from re-oxidation. However, the effect of Cr(II) on the extraction behavior of Pa(IV) has not been taken into account by all of the previous investigators. On the basis of the above facts, the influence of Cr(II) on the extraction of Pa(IV) was studied by using such extractants as BPHA, TTA, and TOA. In every case, the distribution ratio of Pa(IV) decreased with an increase in the concentration of Cr(II) in the aqueous phase. One of the most reliable explanations for the phenomena is the possibility that a multi-nuclear complex between Pa(IV) and Cr(II) or Cr(III) is formed. However, the effect of Cr(II) on the absorption spectra of Pa(IV) could not be found, and many more experiments will be necessary to explain the effect of Cr(II) on the extraction behavior of Pa(IV).