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 diagrams of the ternary liquid systems [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2] and [Ce(NO3)3(TBP)3]-C10H22-[Th(NO3)4(TBP)2] and of the quaternary liquid system [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2]-[Th(NO3)4(TBP)2]

The phase diagrams of the ternary liquid systems [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂] and [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] and of the quaternary liquid system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂]-[Th(NO₃)₄(TBP)₂] at T = 298.15 K are constructed. The phase diagrams are characterized by areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one phase (I) enriched in [Ce(NO₃)₃(TBP)₃], [Th(NO₃)₄(TBP)₂], and [UO₂(NO₃)₂(TBP)₂], and the other phase (II), in C₁₀H₂₂. Using the data on the mutual solubility of the components in the systems under consideration and equations of the NRTL model, the parameters of intermolecular interactions and the excess Gibbs energies (G ^ex) were calculated for the binary, ternary, and quaternary systems. Passing from the ternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] to the quaternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂ (TBP)₂]-[Th(NO₃)₄(TBP)₂] does not appreciably affect the distribution of C₁₀H₂₂ between phases I and II, but leads to the redistribution of [Ce(NO₃)₃(TBP)₃] into phase II and of [Th(NO₃)₄(TBP)₂] into phase I.     

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.     

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.     

On-line time-resolved laser-induced fluorescence of UO2(NO3)2.2TBP in supercritical fluid CO2

Time-resolved laser-induced fluorescence has been shown to be effective for on-line measurement of uranyl chelates in supercritical carbon dioxide. Quenching and other factors affecting the method's accuracy were identified and quantified to allow for accurate measurements under variable supercritical fluid conditions. The method was applied to the kinetic analysis of uranium extraction from acidic solutions with tributyl phosphate modified supercritical carbon dioxide.     

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.     

Americium and plutonium in trigonal phosphates (NZP type) Am1/3[Zr2(PO4)3] and Pu1/4[Zr2(PO4)3]

Phosphates Am_1/3[Zr₂(PO₄)₃] and Pu_1/4[Zr₂(PO₄)₃] were synthesized and studied by X-ray diffraction. The X-ray patterns were indexed in trigonal crystal system, and the unit cell parameters were evaluated. The possibility of accommodation of actinides in the framework cavities of the structure of sodium zirconium phosphate was demonstrated for the first time. It was suggested that incorporation of highly charged Pu and Am cations in the framework cavities decreases the symmetry of the crystal structure to simple trigonal. The rates of Pu leaching from a ceramic material based on phosphate Pu_1/4[Zr₂(PO₄)₃] were measured.     

Calculation of Phase Equilibria in the Th(NO3)4-HNO3-H2O System at 25°C

Pitzer's binary parameters of thorium nitrate were calculated from critically selected published data on the water vapor pressure in the Th(NO₃)₄-H₂O system at 25°C. From data on the water vapor pressure in the Th(NO₃)₄-HNO₃-H₂O ternary system, the Pitzer's ternary parameters were calculated at 25°C. The branch of thorium nitrate hexahydrate crystallization in the ternary system was calculated in the region from 0 to 15 m HNO₃ using complete set of Pitzer's binary and ternary parameters. The calculation results coincide with the experimental data on the solubility.     

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.     

Tetramethylammonium Neptunium(IV) Isothiocyanate [N(CH3)4]4[Np(NCS)8]

A new Np(IV) complex, [N(CH₃)₄]₄[Np(NCS)₈], was prepared. Its crystal structure was determined, and the absorption spectra in the IR and near IR ranges were measured. Crystal data: a = 27.280(6), b = 12.288(3), c = 13.493(3) Å, space group Pna2₁, Z = 4, V = 4523(2) A³, R = 0.044, wR(F ²) = 0.091. The crystal structure of the compound consists of [Np(NCS)₈]^{4 -} anions and N(CH₃)₄ ⁺ cations. The coordination polyhedron of the Np atom is a distorted tetragonal antiprism formed by the nitrogen atoms of eight NCS^- ions.     

A zinc phosphate, [NH3(CH2)3NH3][Zn4(PO4)2(HPO4)2], possessing alternate inorganic and organic layers

A new zinc phosphate of the formula, [NH₃(CH₂)₃NH₃][Zn₄(PO₄)₂(HPO₄)₂], has been synthesized hydrothermally starting from a zinc amine complex. It crystallizes in the monoclinic space group C2/c; a=17.279(1), b=5.193(1), c=20.115(1) Å, β=92.6(1)°; V=1803.1(2) ų; Z=4; D_calc=2.05 g cm⁻³; μ (MoKα)=5.62 mm⁻¹. The final R, and wR₂=0.037, 0.093 obtained for 136 observed data [I>2σ(I)]. The structure consists of macroanionic sheets of interconnected ZnO₄ and PO₄ tetrahedra in the ab plane. The sheets are held together by hydrogen bond interactions with the organic structure-directing amine, forming alternate inorganic–organic layers in this material. Hydrogen bond interactions between the inorganic layers, via the terminal –OH group, leads to the formation of pseudo one-dimensional channels.     

Flexible bilayer architectures in the coodination polymers [MII(NO3)2(1,2-BIS(4-pyridyl)ethane)1.5]n (MII = Co,Ni)

X-ray crystal structures of the coordination polymers [M^II(NO₃)₂(1,2-bis(4-pyridyl)ethane)_1.5]_n (M^II = Co, Ni) (1a–d) reveal that they can exist as flexible bilayer architectures. An open framework form of the bilayer enclathrates small organic molecules, compounds 1b–d. A close-packed bilayer architecture in which no guest molecules can be incorporated is also observed, as exemplified by compound 1a. The size and shape of the channels in the open framework structures appears to be related to the inherent conformational flexibility of the 1,2-bis(4-pyridyl)ethane spacer ligand.     

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 and crystal structure of K3[NpO4(OH)2]

Attempts were made to isolate anhydrous compounds of [NpO₄(OH)₂]^3? anions with heavy alkali metal cations (K, Rb, Cs) by crystallization at elevated temperatures, and the salt K₃[NpO₄(OH)₂] was isolated and studied. Crystals of K₃[NpO₄(OH)₂] consist of tetragonal bipyramidal [NpO₄(OH)₂]^3? anions and K⁺ cations. The [NpO₄(OH)₂]^3? anion occupies the position in the symmetry center. The Np-O distances in this anion are 1.8992(7) and 1.9100(7) Å in the equatorial plane of the bipyramid and 2.3231(8) Å with OH groups. The OH hydrogen atoms participate in weak H bonds [O?O 3.0250(11) Å] linking the anions in layers [NpO₄(OH)₂] _n ^3n? parallel to the (010) plane. In the interlayer space, there are two crystallographically different K atoms. Their coordination number (CN) can be considered to be equal to 7 and 8. Comparison with the structures of the known compounds Na₃[NpO₄(OH)₂] and K₃[NpO₄(OH)₂]·2H₂O was made. The structure of the latter compound was redetermined with higher accuracy. The failure of attempts to prepare the anhydrous rubidium and cesium compounds is probably due to large ionic radius of these cations, requiring high coordination number.     

Structure of medium temperature phase β-LaSc3(BO3)4 crystal

The compound β-LaSc₃(BO₃)₄ crystallizes in the rhombohedral with space group R32 and cell parameters a=9.819(3), c=7.987(1) Å, Z=3, V=666.5(3) Å³, Dc=3.80 g/cm³, λ(MoKα)=0.71067 Å, F(000)=708, final R=0.053. R_W=0.072 for 512 observed reflection with I≥3σ(I). The La atoms, Sc atoms and B atoms occupy trigonal prisms, octahedra and planar triangle of oxygen, respectively. The isolated LaO₆ trigonal prisms alternate along the c-axis with BO₃ triangle (B(1)) that are perpendicular to the c-axis. La³⁺ ions join by means of La-O-Sc(B)-O-La with the distance between La³⁺ ions being 6.263 Å. This structural characteristic will result in a weaker interaction between Nd³⁺ ions and a lower fluorescence concentration quenching effect.     

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.