The extraction coefficients for the actinyl ions extracted with tri-n-butyl phosphate (TBP) from 2.0M CH3 COOH, CH2 ClCOOH and CCl3 COOH in various temperatures have been measured. Distinct discontinuities of the lnD vs. 1/T plots were interpreted as a proof for the extraction mechanism changes. Results obtained were used to calculate the thermodynamic functions of the actinyl complexation in the aqueous phase and of the partition process. It is proposed that the inner-sphere complex formation increases in the order acetates < chloroacetates < trichloroacetates.
Extraction coefficients and separation factors of all lanthanides in the diluted aqueous HDBP—HNO3 system were determined in the temperature range 10–50 °C. Essential differences were noticed between the results obtained
for light (La—Gd) and heavy (Gd—Lu) lanthanides. It was found that the selectivity of the investigated system, in the case
of heavy lanthanides, is as high as that observed for the best organophosphorous extractants: HEHϕP and HDEHP. The sequence
of the separation factors shows the pattern of regularities (the double-double effect) within the whole series of lanthanides
and within the whole investigated temperature range.
The paper concerns the extraction of lanthanides by TBP from dilute solutions of nitric acid. The results show that the relative
free energy associated with the investigated process decreases from La to Sm and the increases up to Lu. The occurrence of
a minimum in the free energy changes is explained by the change of coordination number in the first hydration sphere of lanthanide
aqua ions between Pm and Gd. The results are discussed in terms of the most probable structures of the extracted species.
Outer sphere complexa tion seems to be realized by the Ln3+ ions transferring into the organic phase. The estimation of the trends in the enthalpy and entropy terms is under preparation.
Stability constants of chloride complexes of U(VI), Np(VI) and Pu(VI) have been determined by the method of extraction chromatography
at an ionic strength of 2.0 and [H+]=2.0M. Dilute HDEHP has been used as the stationary phase.
Extraction coefficients of actinyl ions have been determined by the method of extraction chromatography. Two systems have
been studied and compared with the third one investigated earlier. Trends in extractability are interpreted as to be correlated
with the properties of the inorganic ligand.
The complex formation of U(VI), Np(VI) and Pu(VI) with chloride ions was studied in HClO4−HCl solutions at ionic strength of 2.0 and [H+]=2.0M by the method of extraction chromatography using dilute HDEHP as the stationary phase.
Extraction coefficients and separation factors of all lanthanides were determined in the system: dibutylphosphoric acid /HDBP/ - 3M NH4NCS, in the temperature range of 15–50 °C. The values for the separation factors for such pairs as: Gd–Tb and Er–Tm, are higher than 4, those for the pair of Tb–Dy are higher than 3, and those for the La–Ce, Pm–Sm, Dy–Ho, Ho–Er and Tm–Yb pairs are higher than 2. The influence of temperature on the separation factors of light /La–Gd/ and heavy /Gd–Lu/ lanthanides is discussed and compared with that observed for the extraction from the nitric acid solutions. The results are also discussed in the light of the double-double effect and outer-, vs. inner-sphere complexation in the lanthanide series.
The changes of the free energy, enthalpy and entropy accompanying the extraction of the U/VI/, Np/VI/ and Pu/VI/ by TBP have been determined by the method of extraction chromatography. The results obtained indicate outer-sphere complexation.
Extraction coefficients for all lanthanides have been determined in two systems: 0.2M TBP-3M NaNCS, and 3.6M TBP-0.2M NaNCS. The data have been used for the calculation of relative changes in thermodynamic functions accompanying the investigated extraction process. The compensation of enthalpy and entropy changes is found as a result of dehydration of the lanthanide aquaions.