Tremendous impact of substituent group on the extraction and selectivity to Am(III) over Eu(III) by diaryldithiophosphinic acids: experimental and DFT analysis
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Comparative extraction of Am3+ over Eu3+ from nitric acid media by three dithiophosphinic acids (L) bearing different substituent aryl groups was studied. Within the experimental pH range, the distribution ratio of Am3+ and Eu3+ increases with the increase of pH due to deprotonation of the acidic extractant. Both the extraction and separation ability toward Am3+/Eu3+ by these extractants were affected drastically by the substituent aryl groups. The bis-phenyl substituted extractant shows almost no ability to extract and separate Am3+ from Eu3+, while bis(ortho-trifluoromethylphenyl) dithiophosphinic acid has the optimum extraction and separation capabilities. To help reveal the complexation and extraction behavior, the structure and bonding characters of neutral ML3 (M = Am or Eu) complexes as well as the biphasic extraction reaction were studied by density functional theory (DFT). The conduct-like screening model implicit solvation model was used to simulate the extraction reaction in the aqueous-toluene biphasic system. The calculated sequence of the Gibbs free energy difference of extraction (ΔΔG ext Am/Eu ) is consistent with the experimental results.
KeywordsDithiophosphinic acids Actinide Extraction DFT
We acknowledge the financial support from National Natural Science Foundation of China (Grant Nos. 51425403, 21822606, 91426302). The calculations were performed using Tsinghua HPC Platform.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
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