Tributyl Phosphate In Dodecane Research Articles

Experimental Studies on Two-Phase Flow with a Novel Slotted Plate Internal in an Air Pulsed Column

ABSTRACT A novel air pulsed column plate internal featuring plates having concentric circular slots of fixed width (3 mm) is conceptualized, tested, and compared against standard sieve plate internal for counter-current two-phase flow. This new plate design (slotted plates) offers significant intensification in terms of specific interfacial area by as much as ~ 50% vis-à-vis standard sieve plates. The studies are carried out in a 3 inch diameter air pulsed column with tap water as the continuous phase and 30% (v/v) tributyl phosphate in dodecane as the dispersed phase. A high-speed imaging system is used to quantify the state of dispersion and obtain drop size distribution along with Sauter mean drop diameter. The effects of pulsing velocity, dispersed phase velocity and continuous phase velocity on dispersed phase holdup, drop size and consequentially specific interfacial area have been systematically studied for both internals. In all cases, slotted plates are characterized by generation of smaller drops and a higher holdup leading to significant improvement in specific interfacial area. Previously reported correlations for estimating dispersed phase holdup and Sauter mean diameter in pulsed sieve plate columns are found to be inadequate for slotted plate internals. Therefore, new correlations for prediction of holdup and drop diameter have been proposed for the new plate design.

A non-destructive dielectric based approach for the rapid determination of tributyl phosphate in dodecane.

Reliable determination of tributyl phosphate (TBP) in suitable diluents is indispensable in studies related to nuclear fuel reprocessing. Herein, we present a rapid and non-destructive dielectric based approach to determine TBP in mixtures of TBP and n-dodecane in the quality control as well as research laboratories associated with nuclear fuel reprocessing. The measurement is based on an in-house developed new class of sensors called pulsating sensors. The heart of the instrument consists of a three gate oscillator circuit that generates the first electronic response directly in the digital domain. With a single capacitive type probe and using a standalone embedded unit, two different ranges of measurement are covered. A detailed investigation on the various factors affecting the probe output is carried out to achieve maximum sensitivity and precision in analysis. It takes less than a minute to take a measurement. The precision in analysis in the reported range of measurement (0.7-35% v/v TBP) lies between 0.15% and 11.4% relative standard deviation, while the absolute error in measurement lies between ±0.02 and ±0.43% (v/v). The response time and limit of quantification are 4.5s and 0.1% (v/v), respectively. The measurements made with the proposed technique are compared with the well-established gas chromatographic technique.

Molecular Insights into Water Clusters Formed in Tributylphosphate-Di-(2-ethylhexyl)phosphoric Acid Extractant Systems from Experiments and Molecular Dynamics Simulations.

Di-(2-ethylhexyl)phosphoric acid (D2EHPA) and tributylphosphate (TBP) are two of the most studied and researched organophosphorous extractants. D2EHPA is an acidic extractant, offering both hydrogen bond donor and acceptor sites while TBP, a neutral extractant, only offers a single acceptor site per molecule. In spite of this, it is observed that 1 M D2EHPA in dodecane is a poorer extractant for water than 1 M TBP in dodecane. The objective of present work is to look into the molecular interactions that cause such behavior. Experiments were carried out with varying molar ratios of TBP and D2EHPA in the organic dodecane phase. Total extractant concentration was kept constant at 1 M with dodecane as diluent. Water extraction was quantified by measuring the moisture content of the organic phase after equilibration. 1H and 31P NMR spectra of the organic phase samples were recorded to study the change in the chemical environment upon extraction. Small angle X-ray scattering data of water saturated extractant phases were analyzed for the possibility of a reverse micellar aggregate formation. Molecular dynamics simulations could calculate free energies in quantitative agreement with experiments. Experimental and simulation studies showed that aggregation in the organic phase was promoted by the presence of water. This combined approach, of experiments and simulation, has shown that water is indispensable for the formation of ordered aggregates of extractants in nonpolar organic solvents. It is seen that, in the organic phase, around 80% of water's hydrogen bonds are with extractant molecules rather than with itself. The analysis clearly indicates that, rather than forming an aqueous core surrounded by extractant, water acts as a bridge between extractant molecules.

Extraction of cadmium by TODGA–dodecane and TBP–dodecane: A comparative study by MD simulation

ABSTRACTMolecular dynamics (MD) simulation of [Cd(II)] along with nitrate ions and water in dodecane was carried out for different nitric acid concentrations. The extraction process using N,N,N’,N’-tetraoctyldiglycolamide (TODGA) and tributyl phosphate (TBP), in biphasic systems, is also simulated at three nitric acid concentrations. In the TBP-based system, the formation of a third phase was observed at 3 M nitric acid concentration. Cd(II) ions form reverse micelles-like clusters with TODGA as an extractant in dodecane. The mass percentage of TODGA in these clusters decreases with increase in the acid concentration while increasing the size of the aggregates at the same time.

Description of partition equilibria for uranyl nitrate, nitric acid and water extracted by tributyl phosphate in dodecane

Experiments were carried out on the partitioning of uranyl nitrate in nitric acid solution extracted by 30 vol.% of tributyl phosphate (TBP) in dodecane at 25 °C. The model proposed by Naganawa and Tachimori ( Bull. Chem. Soc. Jap. 70, 809, (1997)) for the case of aqueous solutions of nitric acid was used to additionally describe the extraction equilibria of uranyl nitrate. The treatment is based on the assumption of thermodynamic ideality for the organic solution composed of the diluent, the free extractant and the complexes. The stoichiometries of the metal complexes were determined one by one by a suitable procedure. The formation of 6 different complexes involving uranyl nitrate was found capable of representing the partition equilibria for the three extracted compounds: nitric acid, water and uranyl nitrate. This approach suggests the formation of 2:1 and 3:1 complexes for TBP and uranyl nitrate, respectively.

Tributylphosphate Extraction Behavior of Bismuthate-Oxidized Americium

Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am (3+) in acidic solution. Room-temperature oxidation produced AmO 2 (2+) quantitatively, whereas oxidation at 80 degrees C produced AmO 2 (+) quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am (3+) at 503 nm, AmO 2 (+) at 514 nm, and AmO 2 (2+) at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO 2 (2+) over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions.

Extraction Equilibrium of Monocarboxylic Acids in Aqueous Solution by Using Tributyl Phosphate in Dodecane

Extraction Equilibrium of Monocarboxylic Acids in Aqueous Solution by Using Tributyl Phosphate in Dodecane

Uranyl coordination environment in hydrophobic ionic liquids: an in situ investigation.

Different inner-sphere coordination environments are observed for the uranyl nitrate complexes formed with octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and tributyl phosphate in dodecane and in the hydrophobic ionic liquids (ILs) [C(4)mim][PF(6)] and [C(8)mim][N(SO(2)CF(3))(2)]. Qualitative differences in the coordination environment of the extracted uranyl species are implied by changes in peak intensity patterns and locations for uranyl UV-visible spectral bands when the solvent is changed. EXAFS data for uranyl complexes in dodecane solutions is consistent with hexagonal bipyramidal coordination and the existence of UO(2)(NO(3))(2)(CMPO)(2). In contrast, the complexes formed when uranyl is transferred from aqueous nitric acid solutions into the ILs exhibit an average equatorial coordination number of approximately 4.5. Liquid/liquid extraction results for uranyl in both ILs indicate a net stoichiometry of UO(2)(NO(3))(CMPO)(+). The concentration of the IL cation in the aqueous phase increases in proportion to the amount of UO(2)(NO(3))(CMPO)(+) in the IL phase, supporting a predominantly cation exchange mechanism for partitioning in the IL systems.

Effect of pore characteristics on carrier-facilitated transport of Am(III) across track-etched membranes

Track-etched membranes (TEMs) with well-defined pore characteristics were prepared by bombarding polycarbonate plastics with 161 Dy ions of 13.0 MeV per nucleon energy and by bombarding polycarbonate plastics with fission fragments from a 252 Cf source. In order to optimise the properties of TEMs for their applications as model supports in supported liquid membrane (SLM) studies, the transport of Am(III) across the SLM with TRUEX extractants (0.2 M n-octylphenyl ( N, N-diisobutyl carbamoyl methyl) phosphine oxide (CMPO)+1.2 M tributyl phosphate (TBP) in dodecane) as carrier has been examined. The latent tracks formed by heavy-ions in the plastics were enlarged into well-defined pores by chemical etching. The geometry of the pores formed in the plastics was obtained by the track-etched model, based on the dynamics of pore etching. The TEMs were converted as supports for SLM studies by impregnating them with the carrier (0.2 M CMPO+1.2 M TBP in dodecane). The SLMs with different supports were used for studying the facilitated transport of Am(III). The permeation across the SLM formed by using TEM with 17% porosity was found to be comparable to those SLMs formed by using commercial membranes with much higher porosities. The comparison of permeability coefficients ( P) obtained by using TEMs with 29–30 μm and 10 μm thickness indicated that P decreases linearly with thickness and hence transport of Am(III) is diffusion controlled, and reaction kinetics of extraction and stripping steps are fast. The variation of P as a function of porosity of the TEM support indicated that P decreased with increase in porosity upto 10% and thereafter it remained constant. The data on variation of P as a function of porosity were used to obtain the thickness of the aqueous diffusion layer and the membrane diffusion coefficient of the SLM system studied in the present work. The TEMs with very small pore size (0.07 μm) and very large pore size (3 μm) were found to deviate from the expected trend and gave anomalously low P values. Such low P values were also reported elsewhere with membranes of small pore size. The low P values with small pore size support may be due to hindered diffusion due to aggregation of the permeant (Am–CMPO complex in this case), but no satisfactory explanation was found for low P values in the case of supports with large pore size.

Complex Formation between Tributyl Phosphate and Nitric Acid and the Hydration of the Complexes in Dodecane

Abstract Complex-formation of nitric acid with tributyl phosphate (TBP) and the hydration of the complexes in dodecane were examined from the acid and water distribution data between the aqueous and organic phases at 298 K. The equilibrium constants were determined by analyzing the acid and water distribution data as functions of the TBP concentration in the organic phase, the aqueous acid activity, and the water activity. Three complexes (TBP·HNO3, (TBP)2·HNO3, and (TBP)3·HNO3) were found in the organic phase when the aqueous nitric acid concentration was not higher than 3 mol dm−3. The hydration numbers for these complexes were also obtained. The TBP·HNO3 was chiefly anhydrous, but partially a monohydrate. In contrast, the (TBP)2·HNO3 was only a monohydrate and (TBP)3·HNO3 was only a tetrahydrate. The TBP–HNO3–H2O stoichiometry, by taking account of these complexes in addition to the TBP hydrates and free nitric acid in the organic phase, applied very well, up to 2 mol dm−3 (54.6 vol%) TBP in dodecane without any activity correction.

Highly Hydrated Associate of Tributyl Phosphate in Dodecane

The hydration and association of tributyl phosphate (TBP) in dodecane were investigated on the basis of the water distribution between aqueous solutions and TBP-dodecane solutions at 298 K. The water distribution data were analyzed as functions of the TBP concentration in the organic phase and the water activity in the aqueous phase. A highly hydrated TBP trimer was found in the organic phase at high TBP concentrations by the data analysis. At [TBP]org,total≤0.02 mol dm-3, no TBP association occurred and only TBP•H2O formed as a unique hydrate. In the range of 0.02 mol dm−3<[TBP]org,totla≤0.3 mol dm-3, a part of the monohydrate dimerized to form (TBP)2(H2O)2. At [TBP]org,total>0.3 mol dm-3, trimerization also occurred at high water activities. The trimer was found to be hydrated with six water molecules, (TBP)3(H2O)6.

Hydration and Dimerization of Tributyl Phosphate in Dodecane

Hydration of tributyl phosphate (TBP) at concentrations up to 0.3 mol dm−3 in dodecane (8.1 vol% TBP) was examined at 298 K. Water extraction into TBP-dodecane solutions was measured and the data were analyzed as a function of TBP concentration in the organic phase and of water activity in the aqueous phase. The data analyses showed the presence of two TBP-water complexes in the organic phase. When the TBP concentration in the organic phase is low enough, only a TBP hydrate of TBP • H2O is formed. However, at high TBP concentrations, this hydrate dimerizes to form (TBP)2(H2O)2. The TBP-water stoichiometry taking account of these two complexes well explained the experimental data in the TBP concentration range examined.

EXTRACTION OF GALLIUM(III) AND ACCOMPANYING ELEMENTS WITH TRIBUTYL PHOSPHATE FROM CHLORIDE MEDIA

ABSTRACT The distribution of Ga(lll), Fe(lll), Fe(ll), Zn(ll), Mo(VI) and V(V) between solutions of tributyl phosphate in dodecane and aqueous HCi solutions was investigated. To determine the composition of the extracted complexes, the results were treated in terms of thermodynamic activities in the aqueous phase. Possibilities of separating gallium from potentially accompanying elements were assesed.

Carrier-mediated transport of uranyl ions across tributyl phosphate—dodecane liquid membranes

Carrier-facilitated transport of uranium(VI) against its concentration gradient from aqueous nitrate acidic solutions across an organic bulk liquid membrane (BLM) and flat-sheet supported liquid membranes (SLM) containing tributyl phosphate (TBP) as the mobile carrier and dodecane as the membrane solvent has been investigated. Extremely dilute to moderately concentrated uranyl nitrate solutions (ca. 10 −4 M) in 2 M HNO 3 generally constituted the source phase. With increasing carrier concentration in the organic membrane, both the amount of uranium that could be extracted into the membrane and the viscosity of the organic solution increased. These opposing effects resulted in maximum uranium permeation at ca.30% TBP in dodecane, while enhanced acidity of the strip side adversely affected the partitioning of the cation into the receiving phase. Among the several aqueous reagents tested, dilute ammonium carbonate (ca. 1 M) solution was the most efficient strippant. The stoichiometry of the urnium—TPB complex in this liquid membrane system was established to be UO 2(NO 3) 2·2TBP, which is in accord with that deduced on the basis of liquid—liquid distribution measurements.

EXTRACTION OF NEPTUNIUM AND PLUTONIUM NITRATES WITH n-OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE∗

ABSTRACT Distribution equilibria of Np and Pu in various valence states and stripping of Np(V) were studied in a system involving 0.20 M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide + 1.2 M tributyl phosphate in dodecane as a solvent. Np(V) is weakly extractable at 3 M nitric acid, due to the disproportionation of Np(V) to Np(IV) and Np(VI). Addition of nitrous acid to solutions containing Np(V) increases the over-all extractabllity of Np, due to its partial oxidation to Np(VI). This is also the case In the presence of oxalic acid, both at room temperature and at 40°C. Both Np(IV) and Np(VI) are highly extractable, but the reduction of Np(V,VI) to Np(IV) is slow even with a reductant as strong as sodium formaldehyde sulfoxylate. Pu(IV) is highly extractable and its reduction to Pu(III) with sulfoxylate Is incomplete in the two-phase system if the aqueous phase contains >0.5 M nitric acid. Extracted Np(VI) can be stripped by reduction to...

EXTRACTION WITH TRIBUTYL PHOSPHATE (TBP) FROM FERRIC NITRATE SOLUTIONS

ABSTRACT Ferric nitrate acts as a strong salting-out agent in the extraction of thorium(IV), uranyl, europium(III), samarium(III) and zirconium(IV) nitrates as well as of nitric acid with tributyl phosphate in dodecane. Nitric acid, if present in the extraction system together with large amounts of ferric nitrate, markedly suppresses the extraction of thorium(IV) and lanthanides(III) but significantly supports the extraction of zirconium(IV). Separation factors of different metal pairs are presented as functions of the concentrations of ferric nitrate and nitric acid.

THE FORMATION OF A THIRD PHASE IN THE SIMULTANEOUS EXTRACTION OF ACTINIDE(IV) AND URANYL NITRATES BY TRIBUTYL PHOSPHATE IN DODECANE

ABSTRACT The loading of a 30 vol.%solution of tributyl phosphate in do-decane with large amounts of thorium(IV), uranium(IV) or pluto-nium(IV) nitrate in the presence of uranyl nitrate causes the formation of a second organic phase, which contains both the acti-nide(IV)and uranium(VI). The presence of uranium(VI) in the third phase is due to physical distribution of uranyl nitrate, solvated by tributyl phosphate, between the two organic phases. Equations are suggested which describe the distribution of some components between the organic phases, and the actinide(IV)to uranium(VI)ratio in the second organic phase. The maximum attainable concentration of actinides(IV)in the organic phase of a two-'liquid-phase system, at which a third phase is not yet formed, was measured and described by an empirical equation as a function of the concentration of uranium(VI) in the organic phase and of nitric acid in the aqueous phase.

Oxidation of U(IV) nitrate in liquid-liquid dispersions and separate phases containing tributyl phosphate and nitric acid

U(IV) is extremely slowly oxidized by nitric acid in the absence of air in a 30% solution of tributyl phosphate in dodecane, in dilute aqueous solutions of nitric acid containing hydrazinium nitrate and in liquid-liquid dispersions formed by the two solutions. The oxidation of U(IV) by air oxygen in the organic solution is a rather slow first order reaction with a rate constant independent of the nitric acid concentration; there is a pronounced tendency for the oxidation to be accelerated by autocatalysis. In the aqueous solutions and the dispersions the oxidation of U(IV) by atmospheric oxygen is faster and exhibits an apparent zero reaction order with respect to U(IV). Pu(III) and Fe(II) retard oxidation in the dispersions. The dependence of the apparent rate constant in the aqueous solutions and dispersions on the nitric acid concentration was mathematically described and shown to be altered in the presence of Pu(III). In the dispersions U(IV) appears to be oxidized by atmospheric oxygen predominantly in the aqueous phase.

Zirconium behavior in the system HNO 3-30% tributyl phosphate-dodecane in the presence of monobutyl phosphoric acid

Dibutyl and monobutyl phosphoric acids result from the radiolytic degradation of tributyl phosphate in the solvent extraction processing of spent nuclear fuel. Information is needed about the interaction between zirconium and monobutyl phosphoric acid to assess the relative importance of this degradation product in terms of zirconium extraction, retention and solids formation. Monobutylphosphoric acid (H 2MBP) extracts zirconium from nitric acid to a similar extent as dibutyl phosphoric acid (HDBP). Zirconium extracts containing H 2MBP aged at low acidity, ≤0.1 M H +, undergo a reaction to produce a species that is retained by the solvent. There is no retention in the presence of HDBP alone. Gelatinous solids are formed in zirconium solutions in nitric acid by the addition of H 2MBP. Analyses of these solids correspond to the empirical formula Zr(MBP) 2·H 2O. In addition to this compound, an intermediate solid with a MBP Zr molar ratio of one is formed in 0.2 M HNO 3. The addition of H 2MBP to zirconium extracts in 1.09 M TBP in dodecane containing HDBP leads to a solid having a formula corresponding to Zr(OH) x (NO 3) y (DBP)-(MBP) where x + y = 1. Addition of H 2MBP to a zirconium extract in the absence of HDBP leads to a solid with a MBP Zr molar ratio of two. Solubility estimates of these solids show that the MBP compounds are more insoluble, by at least two orders of magnitude, than the corresponding DBP complexes. Extraction of zirconium in the system is mostly determined by HDBP while H 2MBP determines zirconium retention and precipitation.