Modelling of acid-base titration curves of mineral assemblages

The modelling of acid-base titration curves of mineral assemblages was studied with respect to basic parameters of their surface sites to be obtained. The known modelling approaches, component additivity (CA) and generalized composite (GC), and three types of different assemblages (fucoidic sandstones, sedimentary rock-clay and bentonite-magnetite samples) were used. In contrary to GC-approach, application of which was without difficulties, the problem of CA-one consisted in the credibility and accessibility of the parameters characterizing the individual mineralogical components

Thermodynamic parameters of Am(III), Cm(III) and Eu(III) extraction by CyMe4-BTPhen in cyclohexanone from HNO3 solutions

The thermodynamic parameters of the extraction system consisting of CyMe4-BTPhen dissolved in cyclohexanone and Am(III), Cm(III) and Eu(III) in HNO3 in the aqueous phase have been determined. Kinetic extraction experiments were carried out under various temperatures (15–45 °C) and the corresponding over-all mass transfer coefficients were used for the calculation of apparent activation energy and frequency factor values. The values of reaction enthalpy and entropy were also calculated using the distribution coefficients resulting from the experiments mentioned above. Based on the calculated data, the rate-controlling processes and the exothermic character of the studied extractions were determined

BTBPs versus BTPhens: some reasons for their differences in properties concerning the partitioning of minor actinides and the advantages of BTPhens

Two members of the tetradentate N-donor ligand families 6,6′-bis(1,2,4-triazin-3-yl)-2,2′-bipyridine (BTBP) and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) currently being developed for separating actinides from lanthanides have been studied. It has been confirmed that CyMe4-BTPhen 2 has faster complexation kinetics than CyMe4-BTBP 1. The values for the HOMO−LUMO gap of 2 are comparable with those of CyMe4-BTBP 1 for which the HOMO−LUMO gap was previously calculated to be 2.13 eV. The displacement of BTBP from its bis-lanthanum(III) complex by BTPhen was observed by NMR, and constitutes the only direct evidence for the greater thermodynamic stability of the complexes of BTPhen. NMR competition experiments suggest the following order of bis-complex stability: 1:2 bis-BTPhen complex ≥ heteroleptic BTBP/BTPhen 1:2 bis-complex > 1:2 bis-BTBP complex. Kinetics studies on some bis-triazine N-donor ligands using the stopped-flow technique showed a clear relationship between the rates of metal ion complexation and the degree to which the ligand is preorganized for metal binding. The BTBPs must overcome a significant (ca. 12 kcal mol−1) energy barrier to rotation about the central biaryl C−C axis in order to achieve the cis−cis conformation that is required to form a complex, whereas the cis−cis conformation is fixed in the BTPhens. Complexation thermodynamics and kinetics studies in acetonitrile show subtle differences between the thermodynamic stabilities of the complexes formed, with similar stability constants being found for both ligands. The first crystal structure of a 1:1 complex of CyMe4-BTPhen 2 with Y(NO3)3 is also reported. The metal ion is 10- coordinate being bonded to the tetradentate ligand 2 and three bidentate nitrate ions. The tetradentate ligand is nearly planar with angles between consecutive rings of 16.4(2)°, 6.4(2)°, 9.7(2)°, respectively

BTBPs versus BTPhens: Some Reasons for Their Differences in Properties Concerning the Partitioning of Minor Actinides and the Advantages of BTPhens

Two members of the tetradentate <i>N</i>-donor ligand families 6,6′-bis­(1,2,4-triazin-3-yl)-2,2′-bipyridine (BTBP) and 2,9-bis­(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) currently being developed for separating actinides from lanthanides have been studied. It has been confirmed that CyMe₄-BTPhen <b>2</b> has faster complexation kinetics than CyMe₄-BTBP <b>1</b>. The values for the HOMO–LUMO gap of <b>2</b> are comparable with those of CyMe₄-BTBP <b>1</b> for which the HOMO–LUMO gap was previously calculated to be 2.13 eV. The displacement of BTBP from its bis-lanthanum­(III) complex by BTPhen was observed by NMR, and constitutes the only direct evidence for the greater thermodynamic stability of the complexes of BTPhen. NMR competition experiments suggest the following order of bis-complex stability: 1:2 bis-BTPhen complex ≥ heteroleptic BTBP/BTPhen 1:2 bis-complex > 1:2 bis-BTBP complex. Kinetics studies on some bis-triazine <i>N</i>-donor ligands using the stopped-flow technique showed a clear relationship between the rates of metal ion complexation and the degree to which the ligand is preorganized for metal binding. The BTBPs must overcome a significant (ca. 12 kcal mol^–1) energy barrier to rotation about the central biaryl C–C axis in order to achieve the <i>cis</i>–<i>cis</i> conformation that is required to form a complex, whereas the <i>cis</i>–<i>cis</i> conformation is fixed in the BTPhens. Complexation thermodynamics and kinetics studies in acetonitrile show subtle differences between the thermodynamic stabilities of the complexes formed, with similar stability constants being found for both ligands. The first crystal structure of a 1:1 complex of CyMe₄-BTPhen <b>2</b> with Y­(NO₃)₃ is also reported. The metal ion is 10-coordinate being bonded to the tetradentate ligand <b>2</b> and three bidentate nitrate ions. The tetradentate ligand is nearly planar with angles between consecutive rings of 16.4(2)°, 6.4(2)°, 9.7(2)°, respectively

BTBPs versus BTPhens: Some Reasons for Their Differences in Properties Concerning the Partitioning of Minor Actinides and the Advantages of BTPhens

Two members of the tetradentate <i>N</i>-donor ligand families 6,6′-bis­(1,2,4-triazin-3-yl)-2,2′-bipyridine (BTBP) and 2,9-bis­(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) currently being developed for separating actinides from lanthanides have been studied. It has been confirmed that CyMe₄-BTPhen <b>2</b> has faster complexation kinetics than CyMe₄-BTBP <b>1</b>. The values for the HOMO–LUMO gap of <b>2</b> are comparable with those of CyMe₄-BTBP <b>1</b> for which the HOMO–LUMO gap was previously calculated to be 2.13 eV. The displacement of BTBP from its bis-lanthanum­(III) complex by BTPhen was observed by NMR, and constitutes the only direct evidence for the greater thermodynamic stability of the complexes of BTPhen. NMR competition experiments suggest the following order of bis-complex stability: 1:2 bis-BTPhen complex ≥ heteroleptic BTBP/BTPhen 1:2 bis-complex > 1:2 bis-BTBP complex. Kinetics studies on some bis-triazine <i>N</i>-donor ligands using the stopped-flow technique showed a clear relationship between the rates of metal ion complexation and the degree to which the ligand is preorganized for metal binding. The BTBPs must overcome a significant (ca. 12 kcal mol^–1) energy barrier to rotation about the central biaryl C–C axis in order to achieve the <i>cis</i>–<i>cis</i> conformation that is required to form a complex, whereas the <i>cis</i>–<i>cis</i> conformation is fixed in the BTPhens. Complexation thermodynamics and kinetics studies in acetonitrile show subtle differences between the thermodynamic stabilities of the complexes formed, with similar stability constants being found for both ligands. The first crystal structure of a 1:1 complex of CyMe₄-BTPhen <b>2</b> with Y­(NO₃)₃ is also reported. The metal ion is 10-coordinate being bonded to the tetradentate ligand <b>2</b> and three bidentate nitrate ions. The tetradentate ligand is nearly planar with angles between consecutive rings of 16.4(2)°, 6.4(2)°, 9.7(2)°, respectively