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The exchange extraction constants corresponding to the general equilibria M+(aq) + NaL+(org) ⇌ ML+(org) + Na+(aq) and the respective M+(aq) + CsL+(org) ⇌ ML+(org) + Cs+(aq), taking place in the two-phase water–nitrobenzene and water–phenyltrifluoromethyl sulfone (abbrev. FS 13) systems (M+ = Li+, H3O+, Ag+, K+, $${\text{NH}}_{4}^{ + }$$ , Tl+, Rb+; L = calix[4]arene-bis(t-octylbenzo-18-crown-6), 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6 and 1,3-alternate-25,27-bis(3,7-dimethyloctyl-1-oxy)calix[4]arene-benzocrown-6; aq = aqueous phase, org = organic phase) were evaluated. Stability constants of NaL+ and CsL+ were determined from the extraction of picrates and iodides by the solutions of L. Further, the stability constants of the ML+ complexes in nitrobenzene and FS 13 saturated with water were calculated. Enormously high selectivities were found in the systems under study.

On the basis of extraction experiments and $$\gamma$$ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq) + CsL+(nb) ⇌ ML+(nb) + Cs+(aq) occurring in the two-phase water–nitrobenzene system (M+ = K+, Rb+, Ag+, Tl+; L = bis(crown-6) ether derivatives of calix[4]arene, where aq = aqueous phase and nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the proven ML+ complexes in water-saturated nitrobenzene were calculated and are discussed.

Solvent extraction of microamounts of Eu3+ and Am3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate and 3,3′-bis(diisopropoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea (L) was studied. The equilibrium data were explained by assuming that the species HL+, $$ {\text{ML}}_{2}^{3 + } $$ , and $$ {\text{ML}}_{3}^{3 + } $$ {M3+ = Eu3+, Am3+; L = 3,3′-bis(diisopropoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea} are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and discussed. From the experimental results it is apparent that this very effective receptor for the Eu3+ and Am3+ cations could be considered as a potential extraction agent for nuclear waste treatment.

Solvent extraction of microamounts of Eu3+ and Am3+ from water into nitrobenzene by means of a mixture of hydrogen dicarbollylcobaltate (H+B−) and N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide (L) was studied. The equilibrium data were explained assuming that the species HL+, $$ \text{HL}_{\text{2}}^{ + } $$ , $$ \text{ML}_{2}^{3 + } $$ , and $$ \text{ML}_{\text{3}}^{{\text{3} + }} $$ (M3+ = Eu3+, Am3+; L = N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide) are extracted into the organic phase. Extraction and stability constants of the cationic complex species in nitrobenzene saturated with water were determined and are discussed. The reached separation factors SFAm/Eu in this two-phase system are in the range of 19–99. From the experimental results it is apparent that this very effective N,N′-diethyl-N,N′-bis(4-ethylphenyl)-1,10-phenanthroline-2,9-dicarboxamide receptor for the Eu3+ and Am3+ cations could be considered as a potential extraction agent for nuclear waste treatment.

On the basis of extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+(aq) + 1·Na+(nb) $$ \rightleftharpoons $$ 1·M+(nb) + Na+(aq) taking place in the two–phase water–nitrobenzene system (M+ = Li+, H3O+, $$ \text{NH}_{\text{4}}^{ + } $$ , Ag+, K+, Rb+, Tl+, Cs+; 1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1·M+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the cation series Cs+

Solvent extraction of micro amounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea (L) was investigated. The equilibrium data were explained assuming that the species HL+, ML3+, and $$ {\text{ML}}_{2}^{3 + } $$ (M3+ = Eu3+, Am3+; L = 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species were determined in nitrobenzene saturated with water. It was found that the values of the stability constants of the corresponding complexes $$ \text{EuL}_{n}^{{\text{3} + }} $$ and $$ \text{AmL}_{n}^{{\text{3} + }} $$ , where n = 1, 2 and L is 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea, in water-saturated nitrobenzene are comparable. Finally, it was proven experimentally that in the nitrobenzene medium, the 3,3′-bis(diphenoxyphosphoryl)-1,1′-(heptane-1,7-diyl)diurea ligand is a very effective receptor for the Eu3+ and Am3+ cations.

Solvent extraction of micro amounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of Sodium ionophore III (L) was investigated. The equilibrium data were explained assuming that the species HL+, $$ \text{HL}_{2}^{ + } $$ , ML3+, $$ \text{ML}_{\text{2}}^{{\text{3} + }} $$ , and $$ \text{ML}_{\text{3}}^{{\text{3} + }} $$ (M3+ = Eu3+, Am3+; L = Sodium ionophore III) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species were determined in nitrobenzene saturated with water. It was found that the values of the stability constants of the corresponding complexes $$ {\text{EuL}}_{n}^{ 3+ } $$ and $$ {\text{AmL}}_{n}^{ 3+ } $$ , where n = 1, 2, 3 and L is Sodium ionophore III, in water-saturated nitrobenzene are comparable. Finally, it was proven experimentally that in the considered nitrobenzene medium, the investigated Sodium ionophore III ligand is a very effective receptor for the Eu3+ and Am3+ cations. It means that this receptor can be considered as a potential extraction agent for nuclear waste treatment.

From extraction experiments and γ-activity measurements, the exchange extraction constant corresponding to the equilibrium Ag+(aq) + 1⋅Cs+(nb) ⇆ 1⋅Ag+(nb) + Cs+(aq) taking part in the two-phase water–nitrobenzene system (where 1 = hexaarylbenzene-based receptor; aq = aqueous phase, nb = nitrobenzene phase) was evaluated to be log 10Kex(Ag+, 1⋅Cs+) = −1.0±0.1. Further, the stability constant of the hexaarylbenzene-based receptor⋅Ag+ complex (abbreviation 1⋅Ag+) in nitrobenzene saturated with water, was calculated at a temperature of 25 °C: log 10βnb(1⋅Ag+) = 5.5±0.2. By using quantum mechanical DFT calculations, the most probable structure of the 1⋅Ag+ complex species was solved. In this complex having C3 symmetry, the cation Ag+ synergistically interacts with the polar ethereal oxygen fence and with the central hydrophobic benzene ring via cation–π interaction.

The extraction of micro amounts of cesium by nitrobenzene solutions of sodium, potassium and rubidium dicarbollylcobaltates (M+B−;M+=Na+,K+,Rb+) has been investigated in the presence of 2,3-naphtho-15-crown-5 (N15C5, L). The equilibrium data were explained by assuming that ML+ and ML 2 + complexes (M+=Na+,K+,Rb+, Cs+; L=N15C5) were present in the organic phase. The stability constants of the complex species ML+ and ML 2 + have been determined in nitrobenzene saturated with water. It was found that the stability of the complex cation ML+ (where M+=Na+,K+,Rb+, Cs+; L=N15C5) in water-saturated nitrobenzene solutions increases along the series Cs+