Journal of Solution Chemistry

, Volume 44, Issue 3–4, pp 606–620 | Cite as

Determination of pK aIL Values of Three Chelating Extractants in ILs: Consequences for the Extraction of 4f Elements

  • Maria Atanassova
  • Isabelle BillardEmail author


Aqueous–ionic liquid biphasic systems have been examined in terms of water and acid solubilities in the IL-rich phase at ambient temperature. The biphasic mixtures were comprised of acids of various concentrations (H+; Cl, H+; \( {\text{NO}}_{3}^{ - } \), H+; \( {\text{ClO}}_{4}^{ - } \), mainly from 1 × 10−2 to 1 × 10−4 mol·dm−3) and four ionic liquids of the imidazolium family [C1C n im][Tf2N] (n = 4, 6, 8 and 10). The effects of ionic medium (μ = 0.1 mol·dm−3, by use of Na+; Cl, Na+; \( {\text{NO}}_{3}^{ - } \) or Na+; \( {\text{ClO}}_{4}^{ - } \), according to the acid investigated), the nature of the IL cation as well as the nature of the acid on the mutual solubilities of (H2O, H+, [C1C n im]+ and [Tf2N]) entities were determined. Then, three chelating compounds (HL), which belong to the β-diketone family (thenoyltrifluoroacetone (HTTA), 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) and 4-benzoyl-3-phenyl-5-isoxazolone (HPBI)), were added to [C1C4im][Tf2N] and subsequent determination of the H+ distribution between the two phases allowed the determination of their dissociation constants (pK aIL) in the water-saturated ionic liquid phase. A very strong effect of the IL cation on the HTTA pK aIL value was observed from n = 4 to n = 10. The influence of this phenomenon on the lanthanide extraction process is discussed.


Ionic liquids Imidazolium [Tf2N] β-Diketones pKa 



The authors are grateful to FP7-PEOPLE-Marie Curie Actions-IEF for the financial support of the project INNOVILLN (622906) 2014–2016. The authors would like also to acknowledge the contribution of the COST Action CM1206 (EXIL). I.B. is grateful to Guillaume Klein for valuable discussions on arctan function properties.

Supplementary material

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Supplementary material 1 (DOCX 574 kb)


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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Institut Pluridisciplinaire Hubert Curien, UMR7178, RadiochimieStrasbourg CedexFrance
  2. 2.Department of General and Inorganic ChemistryUniversity of Chemical Technology and MetallurgySofiaBulgaria
  3. 3.University Grenoble Alpes, LEPMIGrenobleFrance
  4. 4.LEPMISaint Martin d’HèresFrance
  5. 5.CNRS, LEPMIGrenobleFrance

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