Physicochemcial analysis of the phase diagram of the ternary liquid system [Y(NO3)3(TBP)3]-tetradecane-[UO2(NO3)2(TBP)2]

The phase diagram of the ternary liquid system (TLS) [Y(NO₃)₃(TBP)₃]-tetradecane-[UO₂ · (NO₃)₂(TBP)₂] (TBP is tri-n-butyl phosphate) at 298.15 K is constructed. The TLS is characterized by an area of homogeneous solutions and an area of two-phase liquid systems with one of the phases (I) enriched in [Y(NO₃)₃(TBP)₃] and [UO₂(NO₃)₂(TBP)₂] and the other phase (II), in tetradecane. The inter-molecular interaction parameters and excess Gibbs energies (g ^E ) for the binary systems and TLS along the binodal curve were calculated from data on the mutual solubility in the binary system [Y(NO₃)₃(TBP)₃]-tetradecane and the ternary liquid system, using equations of the NRTL theory. For the binary system [Y(NO₃)₃(TBP)₃]-[UO₂(NO₃)₂(TBP)₂], g ^E < 0, and for the other binary systems, g ^E > 0. An algorithm is given for computer calculation of the binodal curve and nodes for the TLS within the framework of NRTL equations using the intermolecular interaction parameters.     

Phase equilibria in the liquid ternary system [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-Isooctane at different temperatures

The phase diagrams of the ternary systems [Th(NO₃)₄(TBP)₂]-[UO₂(NO₃)₂(TBP)₂]-isooctane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in isooctane. With increasing temperature from 298.25 to 333.15 K, the mutual solubility of Th(NO₃)₄(TBP)₂ and isooctane does not change noticeably, but the two-phase fields somewhat contract. In the two-phase systems [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂]-isooctane is single-phase over the entire temperature range examined. The preferential accumulation of [UO₂(NO₃)₂(TBP)₂] in phase I causes the redistribution of [Th(NO₃)₄(TBP)₂] and isooctane into phases II and I, respectively. The compositions of the ternary systems in the critical points at different temperatures were determined. The electronic absorption spectra of uranyl nitrate solvate with TBP in the homogeneous and two-phase systems were recorded and analyzed. Original Russian Text ? A.K. Pyartman, V.A. Keskinov, V.V. Lishchuk, Ya.A. Reshetko, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 420–422.     

Phase Separation in the Ternary Liquid System [Th(NO3)4(TBP)2]— [UO2(NO3)2(TBP)2]—Decane at Various Temperatures

The phase diagram of the ternary liquid system [Th(NO₃)₄(TBP)₂]— [UO₂(NO₃)₂(TBP)₂]—decane was studied within the 298.15–333.15 K range. The system has the area of homogeneous solutions and area of binary liquid subsystems (with separation); one phase (I) is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂·(TBP)₂] and the other phase (II), in decane. The temperature does not substantially affect the area of phase separation. In two-phase systems, [UO₂(NO₃)₂(TBP)₂] is mainly concentrated in phase I, in spite of the fact that the binary system [UO₂(NO₃)₂(TBP)₂]—decane is single-phase in the entire temperature range studied. Concentration of [UO₂(NO₃)₂(TBP)₂] in phase I results in redistribution of [Th(NO₃)₄(TBP)₂] into phase II. The points of the critical composition of the ternary system are compositions with similar content of the solvates [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂] at all the temperatures studied. __________ Translated from Radiokhimiya, Vol. 47, No. 6, 2005, pp. 520–522. Original Russian Text Copyright ? 2005 by Keskinov, Mishina, Pyartman.     

Phase equilibria in the liquid ternary system [Y(NO3)3(TBP)3]-[UO2(NO3)2(TBP)2]-C14H30 at different temperatures

The phase diagrams of the ternary system [Y(NO₃)₃(TBP)₃]-[UO₂(NO₃)₂(TBP)₂]-tetradecane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Y(NO₃)₃(TBP)₃] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in tetradecane. With increasing temperature, the two-phase fields contract. The critical points of the ternary liquid systems depend on temperature. In the two-phase systems, [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂] tetradecane is homogeneous over the entire temperature range. Original Russian Text ? V.A. Keskinov, V.V. Lishchuk, A.K. Pyartman, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 417–419.     

Phase Separation in the Ternary Liquid System [Nd(NO3)3(TBP)3]-[UO2(NO3)2(TBP)2]-Tetradecane at Different Temperatures

Phase diagram of the ternary liquid system [Nd(NO₃)₃(TBP)₃]-[UO₂(NO₃)₂(TBP)₂]-tetradecane at 288.15–345.15 K is studied. There are homogeneous and two-phase regions in the diagram. One of the phases (I) is enriched with [Nd(NO₃)₃(TBP)₃] and [UO₂(NO₃)₂(TBP)₂], and the second phase (II), with tetradecane. The two-phase region decreases with increasing temperature. The upper critical temperature of solution (mixing) of the binary and ternary systems is T _cr = 344.85±0.5 K. The critical compositions of the ternary liquid system depend on the temperature. The two-phase systems demonstrate preferential concentration of [UO₂(NO₃)₂(TBP)₂] in phase I, despite the fact that the binary system [UO₂(NO₃)₂(TBP)₂]-tetradecane is homogeneous over the entire temperature range studied. __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 154–157. Original Russian Text Copyright ? 2005 by Pyartman, Keskinov, Mishina, Kudrova.     

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.     

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

The phase diagrams of ternary systems [Th(NO₃)₄(TBP)₂]-decane-third organic component (n-butanol, n-octanol, isobutanol, dimethylhexanol, chloroform, carbon tetrachloride, o-dichlorobenzene, tri-n-butyl phosphate, o-xylene, toluene, and linear carboxylic acids) were studied in the temperature range 288.15–333.15 K. These diagrams contain the fields of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in Th(NO₃)₄(TBP)₂ and third component and phase II is enriched in decane. The phase separation is not appreciably influenced by temperature. In phase separation, the third component is predominantly concentrated in phase I, in spite of the fact that the third component and decane have infinite mutual solubility at all the temperatures. The composition of the ternary systems in the critical point is dependent on the kind of the third component.     

Crystal Structure of K[UO2(NO3)3] and Some Features of Compounds M[UO2(NO3)3] (M = K,Rb, and Cs)

Greenish-yellow transparent crystals of K[UO₂(NO₃)₃] were prepared from aqueous solutions as by-product in synthesis of potassium chromatouranylates. The crystal structure was solved by the direct methods and refined to R ₁ = 0.037 (wR ₂ = 0.070) for 1452 reflections with |F _hkl| 4|F _hkl|. Mono- clinic system, space group C2/c, a = 13.4877(10), b = 9.5843(7), c = 7.9564(6) Å, = 116.124(2)°, V = 923.45(12) ų. The structure of K[UO₂(NO₃)₃] contains isolated complex ions [UO₂(NO₃)₃]^- whose uranyl groups are aligned parallel to the [-101] plane. The K⁺ cations, coordinated by twelve oxygen atoms, are located between the complex anions. Comparison of the structure with known data on M[UO₂(NO₃)₃] compounds (M = K, Rb, Cs) suggests the possibility of phase transitions due to relatively small displacements of [UO₂(NO₃)₃]^- anions and K⁺ cations, retaining the general structural motif.     

Physicochemical analysis of the phase diagrams of ternary liquid systems hydrocarbon diluents-[Th(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>(TBP)<Subscript>2</Subscript>]-Tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate

The phase diagrams of the ternary liquid systems (TLSs) saturated hydrocarbon (decane, dodecane, tetradecane, pentadecane) (1)-[Th(NO₃)₄(TBP)₂] (2)-tri-n-butyl phosphate (TBP) (3) at T = 298.15 K are presented in the mole fraction scale. The TLSs are characterized by the areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one of the phases (I) enriched in [Th(NO₃)₄·(TBP)₂] and TBP and the other phase (II), in the hydrocarbon diluent. Using the data on the mutual solubility in the binary systems [Th(NO₃)₄(TBP)₂]-saturated hydrocarbon and in TLSs and the equations of the NRTL model, the intermolecular interaction parameters and the excess Gibbs energies (G ^ex) for the binary and ternary liquid systems along the binodal curve were calculated. For the examined systems, G ^ex > 0 and decreases in the order of binary systems 1–2, 1–3, 2–3. For the binary systems [Th(NO₃)₄(TBP)₂]-CnH_2n+2, G ^ex decreases in the order pentadecane, tetradecane, dodecane, decane and for the binary systems TBP-CnH_2n+2 it only slightly depends on particular hydrocarbon. The behavior of the activity coefficients of the system components for the extraction isotherms of thorium(IV) nitrate with 30–100% solutions of TBP in pentadecane was considered.     

Phase equilibria at various temperatures in ternary liquid systems consisting of thorium(IV) and lanthanide(III) nitrate solvates with tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate and of isooctane

The phase diagrams of ternary liquid systems (TLSs) [Th(NO₃)₄(TBP)₂]-[Ln(NO₃)₃(TBP)₃] (Ln = Nd, Gd, Ho; TBP = tri-n-butyl phosphate)-isooctane at 298.15–333.15 K were studied. The TLSs are characterized by the fields of homogeneous solutions and of two-phase liquid systems (systems with phase separation) in which one of the phases (I) is enriched in [Th(NO₃)₄(TBP)₂] and [Ln(NO₃)₃(TBP)₃], and the other phase (II), in isooctane. The temperature (298.15–333.15 K) does not noticeably affect the mutual solubility of [Th(NO₃)₄(TBP)₂] and isooctane but decreases the field of phase separation in ternary systems. In two-phase systems, [Ln(NO₃)₃(TBP)₃] is predominantly distributed into phase I, despite the fact that binary systems [Ln(NO₃)₃(TBP)₃]-isooctane are single-phase at all the examined temperatures. The distribution of [Ln(NO₃)₃(TBP)₃] into phase I results in the redistribution of [Th(NO₃)₄(TBP)₂] into phase II and of isooctane into phase I. The critical composition points of the TLSs at various temperatures were determined; they depend on particular lanthanide(III).     

Phase diagram of the liquid ternary system hexane-dimethylformamide-solvate of thorium(IV) nitrate with tri-n-butyl phosphate at various temperatures

The phase diagram of the ternary liquid system hexane-dimethylformamide-[Th(NO₃)₄(TBP)₂] was studied at various temperatures. The system consists of two pairs of partially miscible liquids: hexane-dimethylformamide and [Th(NO₃)₄(TBP)₂]-hexane. The area of separation into two liquid phases in the system [Th(NO₃)₄(TBP)₂]-hexane is narrowed with heating; the upper critical temperature T _cr is 337.85±0.25 K. The influence of temperature on the area of separation into layers of the system hexane-dimethylformamide is insignificant. The ternary liquid system is characterized by two homogeneous and one two-phase area of liquid solutions at T < 338 K. One of the phases contains variable amounts of [Th(NO₃)₄(TBP)₂] and hexane, and also small amounts of dimethylformamide; the other phase contains variable amounts of dimethylformamide and [Th(NO₃)₄(TBP)₂] and also small amounts of hexane. With increasing temperature, the two-phase area is narrowed and deformed and the homogeneous areas are extended. At T > 338 K, the system transforms into a ternary liquid system with one pair of partially miscible liquids (hexane-dimethylformamide).     

Kinetics of thorium(IV) nitrate extraction at various temperatures from aqueous salt solutions with a composite material based on a polymeric support and trialkylmethylammonium nitrate

The phase diagrams of the ternary liquid systems (TLSs) saturated hydrocarbon (decane, dodecane, tetradecane, pentadecane) (1)-[Th(NO₃)₄(TBP)₂] (2)-tri-n-butyl phosphate (TBP) (3) at T = 298.15 K are presented in the mole fraction scale. The TLSs are characterized by the areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one of the phases (I) enriched in [Th(NO₃)₄·(TBP)₂] and TBP and the other phase (II), in the hydrocarbon diluent. Using the data on the mutual solubility in the binary systems [Th(NO₃)₄(TBP)₂]-saturated hydrocarbon and in TLSs and the equations of the NRTL model, the intermolecular interaction parameters and the excess Gibbs energies (G ^ex) for the binary and ternary liquid systems along the binodal curve were calculated. For the examined systems, G ^ex > 0 and decreases in the order of binary systems 1–2, 1–3, 2–3. For the binary systems [Th(NO₃)₄(TBP)₂]-CnH_2n+2, G ^ex decreases in the order pentadecane, tetradecane, dodecane, decane and for the binary systems TBP-CnH_2n+2 it only slightly depends on particular hydrocarbon. The behavior of the activity coefficients of the system components for the extraction isotherms of thorium(IV) nitrate with 30–100% solutions of TBP in pentadecane was considered.     

Synthesis, structure, and properties of [Be(H2O)4][UO2(CH3COO)3]2

Crystals of previously unknown compound [Be(H₂O)₄][UO₂(CH₃COO)₃]₂ were prepared and studied by X-ray diffraction analysis. The compound crystallizes in the tetragonal system, unit cell parameters (at 100 K): a = 10.3647(3), c = 23.4127(8) Å, V = 2515.16(13) ų, space group I4₁/a, Z = 4, R = 0.0194. The structure consists of mononuclear complexes [Be(H₂O)₄]²⁺ and [UO₂(CH₃COO)₃]^? linked with each other by electrostatic interactions and hydrogen bonds formed by water molecules and O atoms of acetate anions. The compound was also studied by methods of thermal analysis and IR spectroscopy.     

Crystal structure of Rb3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)]

The structure of Rb₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] was studied by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system with the unit cell parameters (at 100 K) a = 18.387(3), b = 16.398(3), c = 12.460(2) Å, β = 92.837(5)^°, V = 3752.4(11) ų, space group C2/c, Z = 4, R = 0.0390. The uranium-containing structural units of the crystals are isolated mononuclear groups [UO₂(CH₃COO)₃]^? and [UO₂(CH₃COO)(NCS)₂(H₂O)]^?, belonging to crystal-chemical groups AB ₃ ⁰¹ and AB⁰¹M ₃ ¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?, M¹ = NCS^? and H₂O) of uranyl complexes, respectively. The uranium-containing complexes are linked in a framework by hydrogen bonds and by electrostatic interactions with Rb⁺ cations.     

Synthesis and Crystal Structure of Cs4[UO2(CO3)3]

Light green transparent crystals of Cs₄[UO₂(CO₃)₃] were prepared by evaporation from aqueous solutions. The crystal structure was refined to R ₁ = 0.039 (wR ₂ = 0.081) for 2311 reflections with |Fhkl| 4|Fhkl|. Monoclinic system, space group C2/c, a = 11.5131(9), b = 9.6037(8), c = 12.9177(10) Å, = 93.767(2)°, V = 1425.2(2) ų. The structure of Cs4[UO2(CO3)3] consists of isolated complex ions [UO₂(CO₃)₃]^{4 -} formed by uranyl cation UO₂ ^{2 +} and three CO₃ ^{2 -} groups. The equatorial planes of the [UO₂(CO₃)₃]^{4 -} ions are approximately parallel to the (201) plane. The nine-coordinate Cs⁺ cations are located between the complex anions. The compound is isostructural with M4[UO2(CO3)3] with M = K, NH₄, and Tl, but not isostructural with Na₄[UO₂(CO₃)₃].     

Synthesis,Structure, and Physicochemical Properties of AI 4[UO2(CO3)3]·nH2O (AI = Li,Na, K,NH4)

Procedures for the synthesis of Li₄[UO₂(CO₃)₃]·1.5H₂O, Na₄[UO₂(CO₃)₃], K₄[UO₂(CO₃)₃], (NH₄)₄[UO₂(CO₃)₃], and K₃Na[UO₂(CO₃)₃] were optimized. The structures of these compounds and their thermolysis were studied by X-ray diffraction, precision IR spectroscopy, and thermal analysis. The standard enthalpies of formation of these compounds at 298.15 K were determined by reaction calorimetry.     

Crystal Structure of U(VI) Peroxo Complex with Triphenylphosphine Oxide {(UO2)2O2[OP(C6H5)3]6}(ClO4)2

The peroxo complex {(UO₂)₂O₂[OP(C₆H₅)₃]₆}(ClO₄)₂ was synthesized, and its crystal structure was determined [triclinic unit cell: a = 10.523(2), b = 16.242(3), c = 16.978(3) Å, = 65.79(3)°, = 85.06(3)°, = 77.14(3)°, space group P-1, Z = 1, V = 2580.1(9) ų, d _{c a l c} = 2.789 g cm^{- 3}; CAD4, MoK , graphite monochromator, direct method, R ₁ = 0.0368 for 3115 observed reflections, wR ₂ = 0.1107 for 4403 unique reflections, 622 refined parameters]. {(UO₂)₂O₂[OP(C₆H₅)₃]₆}(ClO₄)₂ has monomeric structure and consists of the complex cations {(UO₂)₂O₂[OP(C₆H₅)₃]₆}^{2 +} and ClO₄ ^- anions. The uranium atom has a pentagonal-bipyramidal oxygen surrounding (CN 7). Uranyl groups UO₂ ^{2 +} are linear and symmetrical, the U = O bond lengths are 1.780(8) and 1.787(8) Å, the O(1) = U = O(2) bond angles are 178.7(4) Å. The equatorial planes of bipyramids are formed by oxygen atoms of three TPPO molecules [U-O_{T P P O} 2.352(8)-2.368(7) Å, average 2.362 Å] and peroxo group O₂ ^{2 -} [U-O_{p e r} 2.285(8) and 2.323(8) Å, average 2.305 Å]. Two pentagonal bipyramids sharing the common edge O(3)-O(3)^(a) form the centrosymmetrical peroxo-bridged diuranyl complex {(UO₂)₂O₂[OP(C₆H₅)₃]₆}^{2 +} with the [UO₂O₂UO₂]^{2 +} core. The length of the O(3)-O(3)^{( 9a )} edge is 1.426(15) Å.     

Synthesis and crystal structure of a new uranyl selenite(IV)-selenate(VI), [C5H14N]4[(UO2)3(SeO4)4(HSeO3)(H2O)](H2SeO3)(HSeO4)

Crystals of a new uranyl selenite(IV)-selenate(VI), [C₅H₁₄N]₄[(UO₂)₃(SeO₄)₄(HSeO₃)(H₂O)]·(H₂SeO₃)(HSeO₄) were obtained by evaporation from aqueous solutions. The compound crystallizes in the triclinic system, space group $P\bar 1$ , a = 11.7068(9), b = 14.8165(12), c = 16.9766(15) Å, α = 73.899(6)°, β = 76.221(7)°, γ = 89.361(6)°, V = 2743.0(4) ų, Z = 2. The crystal structure was solved by direct methods and refined to R ₁ = 0.081 (wR ₂ = 0.150) for 6966 reflections with |F _hkl | ≥ 4σ(|F _hkl |). The structure is based on [(UO₂)₃(SeO₄)₄(HSeO₃)(H₂O)]^3? layers formed by joining uranyl pentagonal bipyramids, selenate tetrahedra, and selenite pyramids. The [HSe(VI)O₄]^? anions, [H₂Se(IV)O₃] molecules, and protonated methylbutylamine cations are arranged between the layers.     

Synthesis and structural study of new potassium uranyl selenates K2(H5O2)(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)4 and K3(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)5

Single crystals of new uranyl selenates K₂(H₅O₂)(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₄ (1) and K₃(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₅ (2) were prepared by isothermal evaporation at room temperature. The crystal structure of 1 was solved by the direct method [C2/c, a = 17.879(5), b = 8.152(5), c = 17.872(5) Å, β = 96.943(5)°, V = 2585.7(19) ų, Z = 4] and refined to R ₁ = 0.0449 (wR ₂ = 0.0952) for 2600 reflections with |F _o| ≥ 4σ _F . The structure of 2 was solved by the direct method [P2₁/c, a = 17.8377(5), b = 8.1478(5), c = 23.696(1) Å, β = 131.622(2)°, V = 2574.5(2) ų, Z = 4] and refined to R ₁ = 0.0516 (wR ₂ = 0.1233) for 4075 reflections with |F _o| ≥ 4σ _F . The structures of 1 and 2 are based on [(UO₂)₂(SeO₄)₄(H₂O)₂]^4? layers. The charge of the inorganic layer is compensated by potassium and oxonium ions arranged in the interlayer space. Each K ion is surrounded by seven O atoms belonging to uranyl selenate layers and water molecules, so that it binds with each other the adjacent uranyl selenate structural elements.     

A single crystal X-ray diffraction study of R[UO2(C2H5COO)3] (R = K or NH4)

A single crystal X-ray diffraction study of R[UO₂(C₂H₅COO)₃] [R = K (I) or NH₄ (II)] was performed. Both compounds crystallize in the cubic system, unit cell parameters for I: a = 11.4329(3) Å (at 100 K), space group P2₁3, Z = 4; for II: a = 11.60503(7) Å (at 123 K), space group P2₁3, Z = 4. The structures of crystals of I and II contain complex anions [UO₂(C₂H₅COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ of uranyl complexes (A = UO ₂ ²⁺ , B⁰¹ = C₂H₅COO^?). These anions are linked in a framework by electrostatic interactions with outer-sphere cations R and by hydrogen bonds (in case of II). The effect of the kind of carboxylate ion on structural features of R[UO₂L₃] (L is propionate or acetate ion) is discussed.