Temperature dependence of microscopic structure formed by tri--butyl phosphate and zirconium ion in extracted solution

Motokawa, Ryuhei   ; Suzuki, Shinichi; Yaita, Tsuyoshi

In the solvent extraction of Zr(NO)-HNO/Octane-Tri--butyl phosphate (TBP), zirconic ions (Zr) in aqueous phase are extracted to organic phase with involving a complex formation among Zr, NO, and TBP, i.e., Zr(NO)(TBP). In this solvent extraction process the organic phase is separated into two organic phases: light organic phase and heavy organic phase, which is in particular called as the third phase, when the solution temperature deceases over a critical temperature. In this study, we investigated the temperature dependence of microscopic structure, formed by TBP, Zr, and NO, in diluent by employing small-angle neutron and X-ray scattering (SANS and SAXS) techniques. As a result, we found that the correlation length of the thermal concentration fluctuation of the organic phase strongly contributes to the third phase formation with varying temperature.