Tri-n-butyl Phosphate Solutions Research Articles

Influence of Di-n-butyl Phosphoric Acid on Cerium Redox and Speciation in Tri-n-butyl Phosphate.

The effects of simulated radiolytic degradation of tri-n-butyl phosphate (TBP) on the chemical speciation of cerium were studied by spectrophotometry and electrochemistry of TBP solutions containing increasing amounts of di-n-butyl phosphoric acid (HDBP), a common degradation product of TBP. Tetravalent cerium was found to exchange coordinated nitrate for the dibutyl phosphate anion, forming dinuclear complexes of the formula (CeOCe)(NO3)(6-d)(DBP)d·3TBP (d = 0-3). Compared to Ce(IV), Ce(III) was complexed less strongly by HDBP in TBP, but HDBP displaced both nitrate and TBP to form the series of mononuclear complexes Ce(NO3)(3-d)(HDBP·DBP)d·(3-d)TBP (d = 0-3). Dibutyl phosphate coordination caused large negative shifts in the Ce(IV/III) reduction potential in TBP, indicating a strong stabilization of the tetravalent state. Electrochemical investigation of the reduction of Ce(IV) in TBP revealed it to be a two-electron process in accordance with the dinuclear nature of the organic-phase Ce(IV) complexes. The diffusion coefficients of the d = 0 dinuclear Ce(IV)-nitrate-TBP complex and mononuclear Ce(III)-nitrate-TBP complex in TBP equilibrated with 7 M HNO3 were determined to be (1.16 ± 0.06) × 10-7 cm2/s and (1.9 ± 0.4) × 10-7 cm2/s, respectively, which also is consistent with the larger molecular volume of the dinuclear Ce(IV) complexes.

A comparison of the extraction behaviour of tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates for the separation of metal ions for U–Zr and U–Pu–Zr systems by cross-current mode

Abstract Even though, pyroprocessing is considered as a suitable technique for metal fuel processing, attempts are being made in our laboratory to develop a solvent extraction based process as an interim method. Since, the metallic fuels contain considerable amount of Pu(IV) and Zr(IV), the use of conventional extractant tri-n-butyl phosphate (TBP) for reprocessing may pose problems due to third phase formation. In the exploration for the identification of an alternate extractant in the organophosphate family, tris(2-methylbutyl) phosphate (T2MBP), a branched isomer of tri-n-amyl phosphate (TAP) was found to be a potential extractant for nuclear fuel reprocessing. In this context, batch wise extraction and stripping studies with a feed solution containing U(VI) and 6 wt% Zr(IV) were carried out with unirradiated and irradiated 1.1 M solution of T2MBP in n-dodecane (n-DD) and the results were compared with corresponding solutions of TBP and TAP in n-DD. Among all these systems under identical conditions, third phase formation was observed only in the case of irradiated TBP system which makes U–Zr fuel reprocessing difficult using TBP as the extractant. Furthermore, studies have also been carried out with U–Pu–Zr feed solution to understand the extraction and stripping behaviour of these extractants. The stage wise and cumulative percentage of extraction and stripping for each metal ion of these systems were evaluated. Overall, these batch studies indicated that, T2MBP system has comparable extraction and stripping behaviour with U–Zr and U–Pu–Zr feed solutions and T2MBP exhibits better separation factor than TBP.

Dynamics of gas release during thermal oxidation of TBP solutions in Isopar-M in two-phase system

ABSTRACTThe dynamics of the gas release at thermal oxidation of the two-phase systems of 30% solution of tri-n-butyl phosphate (TBP) in isoparaffinic diluent Isopar M – aqueous solution of 4.3, 8.2 and 12 mol/L of HNO3 has been investigated within the temperature range from 70°C to 110°C. The effect of pre-irradiation of the system TBP–Isopar-M–HNO3 on the kinetics of its thermolysis has been determined. All of the samples were irradiated with an electron accelerator at a dose rate of 10 kGy/h up to integrated doses of 0.5, 1 and 2 MGy. The parameters of heat and gas emission during thermolysis of the tested extraction system in an open apparatus have been determined experimentally. It has been demonstrated, that there are no conditions for extension of autocatalytic oxidation under heat treatment of two-phase extraction systems in open vessels.

The effect of irradiation on the thermal stability of TBP solutions in Isopar-M

The dynamics of gas evolution during the thermal oxidation of 30% solutions of tri-n-butyl phosphate (TBP) in Isopar-M saturated with 4.3, 8.2 and 12.0 mol/L nitric acid was investigated in open vessels in the temperature range of 70oC to 150oC. The volume of the released gases has been measured. The influence of the pre-irradiation by accelerated electrons has been determined for the thermolysis and accumulation of liquid products of TBP degradation in the system TBP-Isopar-M-HNO3. The temperature borders of oxidation processes transition to autocatalytic regime have been estimated. It has been shown, that the conditions resulting in growth of autocata-lytic oxidation do not exist under heating of single-phase systems in open vessels.

Thermodynamic Properties and Phase Equilibria in the Water–Tri-n-butyl Phosphate System

Tri-n-butyl phosphate (TBP) is widely used as an extractant in many technological processes. A thermodynamic model of the base extraction system water–tributyl phosphate is of great importance for industry. In this work a three-dimensional shape of the liquid phase Gibbs energy surface was modeled for the entire concentration range from pure water to pure TBP at temperatures from 273.15 K to more than 400 K and a pressure of 101325 Pa. Volumetric properties of the water–TBP solutions were measured at 288.15, 298.15, and 323.15 K. To obtain a thermodynamic description of the system of interest a new model of the excess Gibbs energy, the generalized local composition model (GLCM), was developed. Density of solutions, activity of components, enthalpy of mixing, and liquid–liquid equilibria in the water–TBP system were described by the GLCM expression.

Kinetics of oxidation of 30% TBP solutions in С13 diluent with nitric acid: Effect of temperature and γ-irradiation

The behavior of the two-phase system consisting of a 30% solution of tri-n-butyl phosphate (TBP) in a paraffin diluent (C13) and a 12 M aqueous HNO3 solution was studied in the temperature interval from 70 to 110°С. The parameters of thermolysis of TBP solutions in C13 in the reaction with HNO3 in open vessels were determined with the aim of evaluating the explosion hazard of the system in the course of extraction reprocessing of high-level radioactive materials. Solutions of TBP in C13 in the two-phase systems are characterized in the examined temperature interval by more intense gas evolution compared to that from the singlephase systems.

Effect of γ-irradiation on the thermal decomposition of nitric acid saturated solutions of TBP in С13 diluent

The dynamics of gas evolution in the course of thermal oxidation of 30% solutions of tri-n-butyl phosphate (TBP) in C13 diluent, equilibrated with 12.9 M HNO3, was studied in open vessels in the temperature interval from 70 to 150°С. The total volumes of the released gases were measured, and the effect of the preliminary γ-irradiation of the TBP–С13–HNO3 system on the thermolysis of nitric acid and accumulation of liquid products of TBP decomposition was studied. The boundary temperature parameters for the development of the oxidation process in the autocatalytic mode were estimated. On heating of the single-phase systems in open vessels, the conditions for the development of the autocatalytic oxidation are not created.

Calculation of the equilibrium in the extraction of nitric acid with 30 and 12% Tri-n-butylphosphate solutions in dodecane

The concentrations of nitric acid and tri-n-butylphosphate (TBP) have been calculated for 30 and 12% TBP solutions in dodecane from the experimental data for the H2O-HNO3-TBP–dodecane system. The used model implies the formation of the HNO3 · TBP monosolvate, the HNO3 · 2TBP disolvate, and the 2HNO3 · TBP semisolvate. The mean-square relative deviations of the calculated data from experimental results have been determined and used to optimize the calculated formation constants of the solvates and their hydrate numbers. The calculated 2HNO3 · TBP semisolvate concentrations in the studied data array are small and can be neglected. It has been established that the extraction of nitric acid with 30 and 12% TBP solutions in dodecane can be described by the same equation.

Liquid−Liquid Extraction of Pertechnetic Acid (TcVII) by Tri-n-butyl Phosphate: Where Is the Proton? A Molecular Dynamics Investigation

We report a molecular dynamics study on pertechnetic acid (PTA) extraction from water to an oil phase containing either pure TBP (tri-n-butyl phosphate) or a TBP/n-hexane mixture, with the main aim to understand the state of the acid (associated TcO(4)H vs dissociated TcO(4)(-)H(+)) and its "complexation" by TBP. Experimentally, Tc(VII) is extracted from acidic water to TBP:alkane solutions in 1:3 or 1:4 Tc:TBP ratio, suggesting that three or four TBPs coordinate to TcO(4)H or TcO(4)(-). According to simulations in TBP solution, however, neither TcO(4)H nor TcO(4)(-) species displays specific coordination to TBP. We thus investigated several hypothetical states of the proton of the dissociated pertechnetic acid in organic phases and at their aqueous interfaces, comparing "pH neutral" to nitric acid containing systems. Proton hydrates are shown to coordinate 3-4 TBPs, in the form of H(3)O(+)(TBP)(3) and H(5)O(2)(+)(TBP)(4) hydrogen-bonded adducts, whereas TBPH(+) binds 1 TBP. The MD and PMF results complemented by those of QM investigations suggest that Tc(VII) is extracted as TcO(4)(-)(H(3)O)(+)(TBP)(3) or TcO(4)(-)(H(5)O(2))(+)(TBP)(4) contact ion pairs instead of the neutral form TcO(4)H of the acid. They explain why nitric acid promotes the Tc(VII) extraction. Comparison between nitric acid (mainly extracted via its neutral form NO(3)H) and pertechnetic acid is discussed.

Physicochemical analysis of the phase diagrams of ternary liquid systems hydrocarbon diluents-[Th(NO3)4(TBP)2]-Tri-n-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 (Gex) for the binary and ternary liquid systems along the binodal curve were calculated. For the examined systems, Gex > 0 and decreases in the order of binary systems 1–2, 1–3, 2–3. For the binary systems [Th(NO3)4(TBP)2]-CnH2n+2, Gex decreases in the order pentadecane, tetradecane, dodecane, decane and for the binary systems TBP-CnH2n+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.

Extraction of U(VI) by Tri-n-Amyl Phosphate Under High Solvent Loading Conditions

Tri-n-butyl phosphate (TBP) is being employed as the extractant for the processing of nuclear materials all over the world. However, some of its limitations such as third-phase formation, aqueous solubility, chemical and radiation degradation, etc., affect the performance of TBP-based extraction processes. Hence, there is a need to identify alternative extractants that do not possess the disadvantages of TBP but retain the desirable properties of TBP. In this connection, higher homologues of TBP such as tri-n-amyl phosphate (TAP) and some of its isomers are considered to be important for various solvent extraction processes. Batch extraction studies have been carried out on the extraction of U(VI) by 1.1 M solutions of TBP and TAP in n-dodecane as well as heavy normal paraffin (HNP), and the results are reported in this paper. Extraction of U(VI) by 1.1 M TAP/HNP under high solvent loading conditions and subsequent stripping of U(VI) by 0.01 M HNO3 from loaded 1.1 M TAP/HNP in a countercurrent mode were also carried out with an ejector mixer-settler. This paper describes the results of these mixer-settler runs. Results revealed the suitability of higher homologues of TBP for reprocessing applications.

Densities of Supercritical Fluids Containing CO2 and Tri-n-butylphosphate

The densities of supercritical fluids consisting of CO2 and 1) tri-n-butylphosphate (TBP), 2) a TBP solution containing HNO3, and 3) UO2(NO3)2·2TBP were experimentally measured using a variable-volume-type view cell at 313, 323 and 333 K. The densities of the fluids increased with an increase in pressure, and decreased with an increase in temperature. The densities were expressed as a function of pressure for each mole fraction of TBP in the supercritical fluids consisting of CO2 and the organic solution at 15–30 MPa. When the mole fraction of TBP in the fluid of CO2 and UO2(NO3)2·2TBP was less than 0.01, the molar volume of the fluid calculated from its densities was smaller than that of CO2 due to negative partial molar volume of the complex, which showed characteristics of a supercritical fluid dissolving solutes.

Sans Study Of Third Phase Formation In The U(vi)-hno3/tbp-n-dodecane System#

In spite of its technological importance, third phase formation in the extraction of hexavalent actinides from nitric acid solutions into alkane solutions of tri-n-butylphosphate (TBP) has received only limited attention. The focus of the few available literature works has been primarily centered on the composition of the third phase and on the stoichiometry of the metal complexes. Very little is known, on the other hand, about the structure and morphology of the third phase species of hexavalent actinides. In the present investigation, the formation of a third phase upon extraction of U(VI) by 20% TBP in deuterated n-dodecane from nitric acid solutions was studied. Chemical analyses have shown that U(VI) exists in the third phase as a species having the compositionUO2(NO3)2·(TBP)2·HNO3. Small-angle neutron scattering measurements on TBP solutions loaded with only HNO3 or with increasing amounts of U(VI) have revealed the presence, both before and after phase splitting, of relatively large ellipsoidal aggregates with the parallel and perpendicular axes having lengths up to about 64 and 15 Å, respectively. The formation of these aggregates is observed in all cases, that is, when only HNO3, only UO2(NO3)2, or both HNO3 and UO2(NO3)2 are extracted by the TBP solution. Upon third phase formation, the SANS data reveal the presence of smaller aggregates in both the heavy and light organic phase. #Work performed under the auspices of the U. S. Department of Energy, Office of Basic Energy Science, Division of Chemical Science (for the part performed at the Chemistry Division of ANL) and Division of Material Science (for the part performed at INPS), under contract No. W-31-109-ENG-38. Accordingly, the U.S. Government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

Third Phase Formation Revisited: The U(VI), HNO3–TBP, n‐Dodecane System# §

In this work, the system U(VI), HNO3–tri‐n‐butylphosphate (TBP), n‐dodecane has been revisited with the objective of gaining information on the coordination chemistry and structural evolution of the species formed in the organic phase before and after third phase formation. Chemical analyses, spectroscopic and EXAFS data indicate that U(VI) is extracted as the UO2(NO3)2·2TBP adduct, while the third phase species have the average composition UO2(NO3)2·2TBP·HNO3. Small‐angle neutron scattering (SANS) measurements on TBP solutions loaded with only HNO3 or with increasing amounts of U(VI) have revealed the presence, before phase splitting, of ellipsoidal aggregates with the major and minor axes up to about 64 and 15 Å, respectively. The formation of these aggregates, very likely of the reverse micelle‐type, is observed in all cases, that is, when only HNO3, only UO2(NO3)2, or both HNO3 and UO2(NO3)2 are extracted by the TBP solution. Upon third phase formation, the SANS data reveal the presence of smaller aggregates in the light organic phase, while the heavy organic phase contains pockets of diluent, each with an average of about two molecules of n‐dodecane. #Work performed under the auspices of the U. S. Department of Energy, Office of Basic Energy Science, Division of Chemical Science (for the part performed at the Chemistry Division of ANL) and Division of Material Science (for the part performed at INPS), under contract No. W‐31‐109‐ENG‐38. §The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W‐31‐109‐ENG‐38 with the US Department of Energy. The US Government retains for itself, and others acting on its behalf, a paid‐up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Extraction of Am(VI) from Nitric Acid Solution Containing Phosphate Anion by TBP

The extraction behavior of Am(VI) was studied for a nitric acid solution containing ammonium dihydrogenphosphate using tri-n-butylphosphate (TBP) and other extractants. TBP and HDEHP solutions diluted with n-dodecane do not reduce Am(VI) in the extraction procedure, whereas CMPO and TOA do. In TBP extraction, phosphate anion raises the separation factor of Am from Nd as high as 120 with 1 MTBP solvent from 3 M HNO3-1 M NH4H2PO4, although it suppresses the extraction of both. A distribution ratio value of 6.6 was obtained using undiluted TBP. Dissociated phosphate anion H2PO4- forms a complex that lowers the distribution ratio of Am even in highly concentrated nitrate solution at low acidity. Americium(VI) is extracted as AmO2(NO3)2.2 TBP. The stability constant, log β, for Am(VI)- H2PO4- complex was estimated as 1.2.

Selective recovery of neodymium from oxides by direct extraction method with supercritical Co2 containing TBP–HNO3 complex

A method for the direct extraction of a metal utilizing supercritical CO2 containing tri-n-butylphosphate (TBP)–HNO3 (TBP), which is the TBP solution of TBP–HNO3 complex, has been developed for the recovery of Nd from its oxide. This method was applied using a flow reactor to several oxides (Nd2O3, ZrO2, MoO3, and RuO2), and binary mixtures of the oxides (Nd2O3–ZrO2, Nd2O3–MoO3, and Nd2O3–RuO2). Neodymium (Nd) was extracted almost quantitatively from 0.01 mol Nd2O3 powder with supercritical CO2 containing TBP–HNO3 (TBP) at 313K and 12 MPa, while Zr, Mo, and Ru were hardly extracted from their oxides and remained in the reactor. Nd was extracted quantitatively and selectively also from the binary mixtures of the oxides. From these results, it is found that the supercritical CO2 extraction process using TBP–HNO3 (TBP) as reactant is feasible for the selective recovery of lanthanides directly from the various oxide mixtures.

Characteristics of Nonlinear Dynamics Dependent on TBP Concentration Change in the Extraction Process for Nuclear Fuel Reprocessing

The laser-induced thermal lens oscillation process, which can be generated in an organic solution by argon-ion laser irradiation is studied to investigate the possibility of its application for monitoring of tri-n-butyl phosphate (TBP) concentration in nuclear fuel reprocessing. The oscillation process is a nonlinear dynamical system whose states depend on three control parameters: laser beam power, depth from solution surface to a laser beam irradiation position, and concentration of solvent, i.e., TBP. From a series of experiments, it is found that a transition between different states is distinctly related to the concentration of TBP solution. From this result, a new on-line monitoring method of solvent concentration is proposed. This method indicates the technique’s potential as a viable on-line analytical instrument in solvent extraction processes of nuclear fuel reprocessing.

Extraction, Separation, and Determination of Nickel and Bismuth with 1-(2-Pyridylazo)-2-naphthol in Aqueous Thiocyanate Media

Abstract Nickel(II) and bismuth(III) are quantitatively extracted from aqueous thiocyanate solutions, adjusted to pH 4.0–9.0 and 3.5–5.0, respectively, using solutions of 1-(2-pyridylazo)-2-naphthol (PAN) in tri-n-butyl phosphate (TBP). The extracted species of nickel and bismuth have the formulas [Ni(PAN)SCN]·4TBP and [Bi(PAN)SCN]X·TBP, respectively. Polyurethane foam treated with TBP solution containing PAN is used successfully for the quantitative retention and recovery of nickel and bismuth from aqueous thiocyanate solutions in the column extraction mode. The preconcentration of small amounts (10 mg) of nickel and bismuth from dilute aqueous solutions (1 L) is also possible, with a recovery of 95–97%. The feasibility of using PAN-foam for selective detection and semiquantitative determination of nickel and bismuth in aqueous thiocyanate media is examined. The detection limits of nickel and bismuth by the foam batch method are 0.05 and 0.50 ppm, respectively. Lower concentrations of these metal ions ar...

Extraction-spectrophotometric determination of tungsten as tungsten blue

Tri-n-butyl phosphate (TBP) is used to extract tungsten(IV) from 0.5 M hydrochloric acid containing molybdenum(VI) and other metals. Tungsten(VI) in the TBP solution is reduced by tin(II) chloride and n-butyl acetate is used for dilution. The tungsten blue formed in the TBP/n-butyl acetate medium (1:1) is measured at 615 nm. The apparent molar absorptivity is about 1000 1 mol −1 cm −1; calibration graphs are linear in the range 0.1–1.5 mg of tungsten.

Vanadium(V) extraction by tri- n-butylphosphate from hydrochloric acid solutions

The extraction of vanadium(V) from HCl solutions into pure and CCl 4 solutions of TBP (tri- n-butylphosphate) has been studied as a function of acid and TBP concentrations. Results suggests that vanadium(V) is extracted as a cationic complex, by an independent mechanism of the extraction of HCl and H 2O. The most likely composition of the organic phase is VO 2Cl·(TBP) 2−3·2HCl·(H 2O) 2−3.