Study of extracted complexes in TRUEX process by nuclear magnetic resonance

The coordination properties of extracted HNO3 and lanthanide (Ln) complexes in TRUEX process were studied by NMR (nuclear magnetic resonance) measurements. The main results are shown as follows; (1) In the HNO3 extraction with TRUEX solvent, coordination manner of CMPO to HNO3 changes with the HNO3 concentration in the aqueous phase. (2) The mole ratio of coordinated ligands (TBP and CMPO) to free ligands in the heavy organic phase (third phase), which was generated from the TRUEX solvents after extracting HNO3, is larger than that in the light organic phase. (3) In the Ln extraction with TRUEX solvents, only CMPO coordinates to the lanthanide ion, and TBP doesn't exist within the first coordination sphere. (4) The contribution of CMPO carbonyl to the Ln extraction will become larger with the extraction of HNO3. (5) The CMPO coordinates to Ln in the bidentate manner, which is independent of Ln elements and the phase separation. (6) As for CMPO exchange reaction in the extracted Ln complexes, the activation parameters (exchange rate constants, activation enthalpy and activation entropy) decrease with the increase of atomic number of extracted Ln, which may be caused by the interaction with TBP in the outer sphere and the exchange rate constants in the heavy organic phase are larger than that in the light organic phase. (author)