V. A. Keskinov

Extraction kinetics of lanthanum(III), uranyl(VI), and thorium(IV) nitrates from water-salt solutions using a composite based on a polymeric support and tri-n-butyl phosphate at various temperatures

The extraction kinetics of lanthanum(III), uranyl(VI), and thorium(IV) nitrates from water-salt solutions using a composite based on a polymeric support and tri-n-butyl phosphate (TBP) were studied at 293.15–333.15 K. Interfacial diffusion (the film kinetics) is the rate-controlling stage of extraction. Mass transfer coefficients were determined, and their temperature dependence was used to estimate apparent activation energies Ea. The mass transfer coefficients increase in going from lanthanum(III), uranyl(VI), and thorium(IV) nitrate solutions to water-salt solutions containing 2 mol/L sodium nitrate or with rising temperature. Ea is independent of the metal ion and the supporting electrolyte concentration; Ea = 25 ± 1 kJ/mol. At a fixed temperature, the increasing order of the mass transfer coefficients is as follows: thorium(IV) < uranyl(VI) < lanthanum(III).

Kinetics of extraction and back extraction of Pr(III) and Nd(III) nitrates from aqueous electrolyte solutions with a composite material based on polymer-supported tri-n-butyl phosphate at various temperatures

Kinetics of extraction and back extraction of Pr(III) and Nd(III) nitrates from aqueous electrolyte solutions with a composite material (CM) based on polymer-supported tri-n-butyl phosphate (TBP) at 293.15–333.15 K is studied. The rate-determining stage of the processes is found to be the interfacial diffusion (film kinetics). The mass-transfer coefficients are determined, and, from their temperature dependences, the apparent activation energy Ea is estimated. In extraction, the mass-transfer coefficients increase in passing from aqueous solutions of Pr(III) and Nd(III) nitrates to those containing 2 M NaNO3 and with increasing temperature. For the extraction, Ea is found to be 25±1 kJ mol−1, and for back extraction, 15.5±1.0 kJ mol−1. The Ea values are independent of particular Ln(III).

Extraction of Th(IV), La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate (Aliquat-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R4N)2[Ln(NO3)5] and (R4N)2[Th(NO3)6], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.

Extraction of Thorium(IV), Lantanum(III), and Yttrium(III) Nitrates with a Composite Solid Extractant Based on a Polymeric Support Impregnated with Trialkylamine

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylamine (Alamine-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R3HN)3[Ln(NO3)5] and (R3HN)2[Th(NO3)6], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.

Phase equilibria in ternary liquid systems containing solvates of lutetium(III) and uranyl(VI) nitrates with tri-n-butyl phosphate and tetradecane at various temperatures

The phase diagram has been studied for the ternary liquid system (TLS) [Lu(NO3)3(TBP)3]-[UO2(NO3)2(TBP)2]-tetradecane at T = 298.15–333.15 K. There are fields of homogeneous and two-phase solutions in the system. One phase (phase I) is enriched in [Lu(NO3)3(TBP)3] and [UO2(NO3)2(TBP)2]; the other (phase II) is enriched in tetradecane. Critical compositions in the system depend on temperature. [UO2(NO3)2(TBP)2] tends to be distributed to phase I, despite the fact that the binary system [UO2(NO3)2(TBP)2[-tetradecane is a single phase at all temperatures studied.

Mutual solubility between hexane and tri-n-butyl phosphate solvates of lanthanide(III) and thorium(IV) nitrates at various temperatures

The phase diagrams of binary liquid systems consisting of hexane and a tri-n-butyl phosphate (TBP) solvate of an Ln(III) (Ln = Nd, Gd, Y, Yb, Lu) or Th(IV) nitrate at various temperatures are considered. The diagrams show a field of homogeneous solutions and a two-phase field in which phase I is hexane-rich and phase II is rich in [Ln(NO3)3(TBP)3] or [Th(NO3)4(TBP)2]. The miscibility gap in the binary systems narrows with increasing temperature.

Mutual solubility of the components in systems RED-1 diluent-tri-n-butyl phosphate solvates of rare-earth element(III) (Nd, Gd, Y, Yb, Lu) nitrates-Escaid 100 diluent

Phase diagrams of liquid binary systems RED-1 diluent-tri-n-butyl phosphate solvates of rare-earth element(III) (neodymium, gadolinium, yttrium, ytterbium, lutetium) nitrates were studied, and the binodal curves in the ternary systems [Ln(NO3)3(TBP)3] (Ln = Nd and Yb)-RED-1-Escaid 100 were determined at various temperatures.

Influence of temperature on phase separation in the ternary systems [Th(NO3)4(TBP)2]-isooctane-third organic component

The phase diagrams of ternary liquid systems (TLSs) [Th(NO3)4(TBP)2]-isooctane-third organic component [n-butanol, isobutanol, n-octanol, n-decanol, cyclohexanol, toluene, o-xylene, CCl4, CHCl3, o-dichlorobenzene, TBP, and higher isomeric carboxylic acids (HICAs)] were studied in the temperature range 298.15–333.15 K. These diagrams contain the fields of homogeneous solutions and the field of separation into two liquid phases (I, II). Phases I is enriched in [Th(NO3)4(TBP)2] and third component, and phase II is enriched in isooctane. With increasing temperature, the field of separation into two liquid phases contracts and the content of the third component in the critical points decreases. The compositions of ternary systems in the critical point depend on the kind of the third component. In phase separation, the third component is predominantly concentrated in phase I, in spite of the fact that the third component and isooctane have infinite mutual solubility at all the temperatures.

Phase Separation in the Systems Constituted by Tetradecane (Hexane, Decane), Tri-n-Butyl Phosphate, and Cerium(III) Nitrate Solvate with Tri-n-Butyl Phosphate

Phase diagrams of ternary liquid systems constituted by tetadecane (hexane, decane), tri-n-butyl phophate, and cerium(III) nitrate solvate with tri-n-butyl phosphate Ce(NO3)3(TBP)3 with phase separation into liquid phases I and II were studied at 298.15 K. Phase I is enriched in the hydrocarbon diluent, and phase II, in Ce(NO3)3(TBP)3. The distribution of components between phases I and II was considered.

Phase Separation in Ternary Liquid Systems Tetradecane-n-Octanol (or Cyclohexanone)-Lanthanide(III) Nitrate Solvates with Tri-n-Butyl Phosphate

The phase diagrams of ternary liquid systems tetradecane-n-octanol (or cyclohexanone)-lanthanide(III) nitrate solvates with tri-n-butyl phosphate [Ln(NO3)3(TBP)3, Ln = La, Ce, Pr, or Sm] at T = 298.15 K were studied. These diagrams contain areas of homogeneous solutions and an area of separation into two liquid phases (I, II). Phases I and II are enriched in tetradecane and Ln(NO3)3(TBP)3, respectively. n-Octanol and cyclohexanone mainly pass into phase II.