Complexation of Eu(III) with dibutyl phosphate and tributyl phosphate

The complexation of Ln(III) with tributyl phosphate (TBP) in the presence of dibutyl phosphate (HDBP) is of importance for the smooth operation of the plutonium uranium refining extraction (PUREX) process. The Lime resolved laser-induced fluorescence spectroscopy (TRLFS) and extraction experiments were employed to study the complexation of Eu(III) with TBP or HDBP and their mixture. The emphasis was on the inner-sphere hydration numbers and emission spectra of the Eu(III) extracted complexes. The results show that the HNO3 loading in the organic phase influences not only the distribution ratio but also the emission spectra, as well as the hydration numbers of the complexes. For the Eu-TBP complexes, one water molecule remained at low HNO3 loading in the organic phase, and it would be removed at enhanced HNO3 loading. For the Eu-HDBP complexes, one water molecule remained at low or high HNO3 loading. For the Eu-HDBP/TBP or Eu-HDBP/30%TBP, more than one species formed and third phase with different chemical form appeared at low HNO3 loading. The possible species of Eu(III) complexes formed under various conditions were proposed and discussed.