COEXTRACTION OF URANIUM AND TECHNETIUM IN TBP-SYSTEMS

Abstract

The coextraction of technetium with uranium in TBP/HNO systems has been studied. The extraction mechanism,

has been found to agree well with experimental data at 5 M HNO,.The extraction constant, K_TC,e for this reaction Is given by

where T is temperature (K) and C_T total TBP concentration (%). This equation is valid for 5 M HNO, DSFS–30% TBP, and from 20 to 60°C, with an average error of 2·8% in log K_TC,e     

Application of Vapor Pressure Osmometry to the Study of Uranyl Nitrate and Thorium Nitrate Complexes with Tributyl Phosphate

Molecular weights of uranyl nitrate and thorium nitrate solutions in TBP were determined using vapor pressure osmometry. The results seem to show that in carbon tetrachloride uranyl nitrate forms a di-solvate only, whereas in acetone solution this complex is partly dissociated. Thorium nitrate results have been explained assuming a mixture of two complexes with TBP-a di-solvate and a tri-solvate. The equilibrium constant for the reaction Th(NO₃)₄ · 2TBP + TBP ? Th(NO₃)₄ · 3TBP was found to be K_x = 30 at 25°C.     

A TBP/BTBP-based GANEX Separation Process. Part 1: Feasibility

Abstract

A GANEX (Group ActiNide EXtraction) separation system for transmutation has been developed. In this separation process the actinides should be extracted as a group from the lanthanides and the fission and corrosion/activation products. This can be achieved by combining BTBP (bis-triazine-bipyridine) with TBP (tri-butyl phosphate) in cyclohexanone. From 4M nitric acid this organic system extracts the actinides (log(D_Am) = 2.19, log(D_Pu) = 2.31, log(D_U) = 1.03, log(D_Np) = 0.53) and also separates them from the lanthanides (log(D_La) = ?2.0, log(D_Ce) = ?1.72, log(D_Nd) = ?1.05, log(D_Sm) = ?0.18, log(D_Eu) = ?0.02). One problem encountered is that some of the fission and corrosion products are also extracted. The new system however still looks feasible.     

Thorium Ions Transport across Tri-n-butyl Phosphate—Benzene Based Supported Liquid Membranes

Abstract

Transport of Th(IV) ions across tri-n-butyl phosphate (TBP) benzene based liquid membranes supported in microporous hydrophobic polypropylene film (MHPF) has been studied. Various parameters such as variation of nitric acid concentration in the feed, TBP concentration in the membrane, and temperature on the given metal ions transport have been investigated. The effects of nitric acid and TBP concentrations on the distribution coefficient were also studied, and the data obtained were used to determine the Th ions—TBP complex diffusion coefficient in the membrane. Permeability coefficients of Th(IV) ions were also determined as a function of the TBP and nitric acid concentrations. The optimal conditions for the transport of Th(IV) ions across the membrane are 6 mol·dm^?3 HNO₃ concentration, 2.188 mol·dm^?3 TBP concentration, and 25°C. The stoichiometry of the chemical species involved in chemical reaction during the transport of Th(IV) ions has also been studied.     

DISTRIBUTION BEHAVIOUR OF U(VI), Th(IV) AND Pa(V) FROM NITRIC ACID MEDIUM USING LINEAR AND BRANCHED CHAIN EXTRACTANTS

ABSTRACT

The extraction behaviour of 1M solutions of tri-2-ethylhexyl phosphate (TEHP), di-2-ethyl hexyl isobutyramide (D2EHIBA), tri-n-butyl phosphate (TBP) and di-n-hexyl hexanamide (DHHA) in n-dodecane towards U(VI), Th(IV) and Pa(V) in the presence of 220 g/L of Th from nitric acid medium has been studied. The limiting organic concentrations (LOC) of thorium (g/L) for 1 M TBP and 1 M DHHA are evaluated as 31, 20 ( at 1 M HNO₃) and 25,13 (at 4 M HNO₃) respectively. The distribution ratio (D) values of U(VI), Th(IV) and Pa(V) in the presence of thorium (220 g/L) at. 1 M HNO₃ suggest that branching in the alky group of amides suppresses the extraction considerably. In view of the selective extraction of U over Th by 5 % TBP in THOREX process at 4 M HNO₃, distribution behaviour is also studied employing a lower concenfration (0·18 M) of extractant for comparison purpose, Separation factor (S. F.) values for U(VI) over Th(IV) under different experimental conditions consistently varied in the order: D2EHIBA > DHHA > TEHP > TBP. The quantitative extraction of ²³³U from a synthetic mixture containing ²³³U (10^?5 M). ²³³Pa (10^?11 M) and thorium (220 g/L) at 1 M HNO₃ using 1 M solution of D2EHIBA in n-dodecane is achieved in three stages, Stripping and reusability studies of D2EHIBA have also been carried out.     

Synergistic Extraction of Np(IV) by Mixtures of HTTA and TBP in Chloroform

Abstract

Extraction of Np(IV) from perchloric acid medium by chloroform solutions of HTTA and TBP was studied. The species Np(TTA)₄TBP was found to be mainly responsible for the observed synergism. Equilibrium constants for the extraction equilibria involved were obtained.     

Extraction Theory and Form of the Extraction Complex for the Metals Dysprosium,Holmium, Thulium,and Curium in the Synergistic System Kerosene/HTTA/TBP/Dilute HNO3

Abstract

Data were taken for the distribution of HTTA and the metals Dy, Ho, Tm, and Cm in the system kerosene/thenoyltrifluoroacetone (HTTA)/tributylphosphate (TBP)/dilute HNO₃. The theory first proposed by Tournier (1) and Tournier and Davis (2) for the HTTA distribution was modified and new values of the equilibrium constants resulting from the theory were determined by a least squares fit of the HTTA distribution data. The new values are K ₁ = 14 and K ₂ = 3.45.

An analysis of the HTTA distribution data indicates that one molecule of TBP associates with one molecule of (HTTA·H₂O) to form a complex. Analysis of distribution data for the metals, Dy, Ho, Tm. and Cm using the modified theory indicates that the form of the metal complex is M⁺³(TTA)₃(TBP)₂ reported by most investigators.

A log-log plot of q o/a as a function of [H⁺] under conditions of constant free TBP and HTTA and constant ionic strength indicates an inverse squared effect of [H⁺] on the metal distribution ration, q o/a. This in turn supports the indications that two (TTA) molecules are associated with the metal complex. No experimental data to verify the presence of (NO₃ ^?) in the complex have as yet been obtained.     

SOLVENT EXTRACTION OF SOME TERVALENT LANTHAN01DS WITH 5-BR0M0-, 3,5-DIBROMO- AND 5-NITROSALICYLALDEHYDE ACETOHYDRAZONES

ABSTRACT

5-Bromo-, 3,5-dibromo- and 5-nitrosalicylaldehyde acetohydrazones (BSAH, DBSAH and NSAH, respectively, or H₂L) were synthesized. The extraction of lanthanoid ions (Ln3+) including praseodymium, europium and ytterbium ions into 1,2-dichloroethane with the synthesized hydrazones in the presence of both tri-n-butylphos-phate (TBP) and perchlorate has been investigated. The extracted species were (Ln³⁺)(HLP^?)₂(TBP)₃(CI₄ ^?) for all the hydrazones. The acid dissociation constants, Ka, and the partition coefficients, K_o, of the hydrazones and the extraction constants, K_ex, of the lanthanoid complexes were determined. The introduction of electron-withdrawing bromo or nitro groups to the 3- and/or 5-position of the benzene ring in salicylaldehyde acetohydrazone (SAH), the mother compound of the synthesized hydrazones, was very effective for increasing not only the K_ex value of SAH but also its K_D value and the K_ex values of its lanthanoid complexes. Taking into consideration the above-mentioned three constants, of the synthesized hydrazones DBSAH was the most balanced and recommend-able extractant for the lanthanoids.     

DISTRIBUTION DATA FOR THE SYSTEM Th(NO3)4:UO2(NO3)2:HNO3/30 % TBP IN DODECANE

Abstract

Distribution data for the systems Th(NO₃)₄:HNO₃/30 % TBP in dodecane and Th(NO₃)₄:UO₂(NO₃)₂:HNO₃/30 % TBP in dodecane have been evaluated experimentally. By means of these data a caleulationa1 model has been derived which makes it possible to determine data in the investigated range. A method is also described for the evaluation of distribution data at very low thorium concentrations.     

QSAR FOR CARCINOGENICITY IN METHYL BENZ[a]ANTHRACENES AND BENZ[c]ACRIDINES USING π-ELECTRONIC DATA IN A SELF-CONSISTENT FIELD MO THEORY

Quantitative structure-activity relationships were obtained for series of methyl benz[a]anthracene and benz[c]acridine molecules. Regression analysis was done on π-electronic indices associated with specified molecular regions of importance named “bay” (Q _AB ),“K” (Q _K ), “L”(QL), N-heteroatomic position (QN) and superdelocalizability index (SK associated with K-region) of these molecules to correlate with reported experimental carcinogenicity indices. The electronic indices calculated earlier for methyl benz[c]acridines by a self-consistent field molecular orbital theory named ‘two-parameter omega-technique’ are reported from unpublished data. ‘Two-parameter omega-technique’ used successfully for methyl derivatives earlier, was modified to incorporate the N-heteroatom present in benzacridines. Reported log (carcinogenicity indices) for a series of 14 methylbenz[a]anthracenes are found to be positively correlated with Q _AB having correlation coefficient (R = 0.65) which is increased to 0.82 by combining this correlation equation with that depending on QL which is negatively correlated (R = 0.7) with reported log (carcinogenicity indices). Highly significant positive correlations of QN (R = 0.92), Q _AB (R = 0.85) and SK (R = 0.90) and negative correlations of QL (R = 0.94) for a series of 9 methyl benz[c]acridines with reported cancer indices are obtained. Combining the negative correlation equation dependent on QL with the best positive correlation equation involving QN cannot improve the correlation coefficient, but still gives the best value of (R = 0.94) for methylbenz[c]acridines. The carcinogenicities of a series of methyl derivatives of benz[a]anthracene and benz[c]acridines are discussed in terms of the relationships with frontier electron density and superdelocalizability of specific regions of molecular periphery of these molecules. π-Electron density obtained by combination of electron-density of a low reactive L-region with a highly reactive region like bay-region, K-region or nitrogen-atom position of molecular periphery is found to be the best indicator of carcinogenicity in a series of methyl benz[a]anthracenes and benz[c]acridines.     

Compositional Characterization of Organic Phases after the Phase Splitting in the Extraction of Th(NO3)4 by 1.1 M Tri-n-butyl phosphate/n-Alkane

Third phase formation in the extraction of Th(IV) by 1.1 M solutions of tri-n-butyl phosphate (TBP) in n-decane and n-hexadecane from Th(NO₃)₄ solution in 1 M HNO₃ has been investigated as a function of equilibrium aqueous phase Th(IV) concentration ([Th(IV)]_aq,eq) to estimate the concentrations of Th(NO₃)₄, HNO₃, and TBP in the third phase (TP) and the diluent-rich phase (DP). In this connection, new methods for the estimation of TBP in the organic phases after the phase splitting have been developed by exploiting the linear relationships of the density and refractive index of the solvent, the limiting organic concentration (LOC) for the third phase formation in the extraction of Th(IV) from solution with near-zero free acidity with TBP concentration in the solvent. TBP concentrations estimated by the above-mentioned methods have been validated by nitric acid (8 M) equilibration method. Experimental values for the concentration of TBP in the TP and DP for 1.1 M TBP/n-alkane–Th(NO₃)₄/1 M HNO₃ systems have been compared with the values computed based on a model proposed earlier. In addition, the density of organic phases and the ratio of the volume of the DP to that of the TP have been measured for the above-mentioned systems as a function of [Th(IV)]_aq,eq at 303 K.     

Mercury Extraction By The TRUEX Process Solvent: III. Extractable Species And Stoichiometry†

ABSTRACT

Mercury extraction from acidic aqueous solutions by the TRUEX process solvent, 0.2 M n-octyl(phenyl)N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), 1.4 M tributylphosphate (TBP) in n-dodecane, has not been extensively examined, Research is currently in progress at the Idaho Chemical Processing Plant to evaluate the TRUEX process for actinide removal from several acidic waste streams, including liquid sodium-bearing waste (SBW), which contains significant quantities of mercury. Reactions for two mercury species, HgCl₂ and HgCl₄ ^?2, are reported. Classical slope analysis techniques were utilized to evaluate the stoichiometric coefficients of each Hg species independently for both CMPO and TBP. The slope analysis results indicate that even the HgCl₄ ^?2 species extracts as HgCl₂. The results also indicate that 1.9 to 2.2 moles of CMPO and 1.5 to 1.81 moles of TBP are required per mole of HgCl₂ extracted. A generic equation for mercury extraction into CMPO or TBP has been shown to be:

where x = 2 or 4, y = 0 or ?2, E = CMPO or TBP, a = the experimentally determined CMPO or TBP stoichiometry, and over lines indicate organic species. Equilibrium constants for HgCl₂ species were determined to be 295 when extracted by CMPO and 18.2 when extracted by TBP. Equilibrium constants for the HgCl₄ ^?2 species were found to range between 5.8 and 12.0 for the CMPO reaction and 0.13 to 0.27 with TBP.     

AKUFVE STUDIES ON EXTRACTION BEHAVIOUR OF NEPTUNIUM FROM SIMULATED HLW SOLUTIONS BY 30% TBP

ABSTRACT

The extraction behaviour of neptunium from 3 M nitric acid as well as simulated pressurised heavy water reactor high level radioactive waste (PHWR-HLW) solution by 30% TBP/dodecane was studied using AKUFVE. Np(IV)/Np(V) was oxidised to Np(VI) using oxidising agents, such as K₂Cr₂O₇, VO₂ ⁺ and NaNO₂. Stripping of neptunium from the loaded TBP phase was studied using reducing agents like hydrogen peroxide, ascorbic acid, hydroxyl-amine hydrochloride and hydrazine sulphate. Results of these extraction and stripping studies have been discussed in this paper.     

Synergistic Extraction of Trivalent Actinides by Mixtures of 1-Phenyl-3-methyl-4-benzoyl-pyrazolone-5 and Neutral Oxo Donors

Abstract

The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and TBP or TOPO has been investigated in xylene at 30°C. With HPMBP alone, all four trivalent actinides form M(PMBP)₃· HPMBP-type self-adducts. Bk(III) shows an abnormally high extraction with HPMBP alone. With TBP or TOPO(S) as neutral donor, except in the Bk/HPMBP/TBP system where Bk(PMBP)₃· HPMBP·TBP was extracted, all metal ions were extracted as M(PMBP)₃·S and M(PMBP)₃·(S)₂ into the organic phase. The equilibrium constants (β₁, β₂, and K ₂ for the organic phase synergistic reactions have been calculated. The β₁, β₂ values for Bk(III)/HPMBP/TOPO system are much lower as compared to the corresponding values for other trivalent actinides. The reasons for this extraordinary behavior of Bk(III) have been discussed. The extraction behavior of the M(III)/HPMBP/S and the M(III)/HTTA/S systems has also been compared.     

Interpretation of Third Phase Formation in the Th(IV)–HNO3, TBP–n‐Octane System with Baxter's “Sticky Spheres” Model

Abstract

Small‐angle neutron scattering (SANS) data for the tri‐n‐butylphosphate (TBP)–n‐octane, HNO₃–Th(NO₃)₄ solvent extraction system, obtained under a variety of experimental conditions, have been interpreted using two different models. The particle growth model led to unrealistic results. The Baxter model for hard‐spheres with surface adhesion, on the other hand, was more successful. According to this model, the increase in scattering intensity in the low Q range observed when increasing amounts of Th(NO₃)₄ are extracted into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules. Upon extraction of Th(NO₃)₄, the micelles interact through attractive forces between their polar cores with a potential energy of up to about 2 k_BT. The intermicellar attraction, under suitable conditions, leads to third phase formation. Upon phase splitting, most of the solutes of the original organic phase separate in a continuous phase containing interspersed layers of n‐octane.     

EXTRACTION OF PLUTONIUM (III) BY TBP IN PRESENCE OF URANIUM

ABSTRACT

The distribution ratio (D) values for the extraction of plutonium (III) from nitric acid medium into 30% TBP in n-dodecane saturated with uranium(VI) (0% to 80%) were determined. For a fixed saturation of TBP with uranium, the D values for Pu(III) were found to increase with increase in nitric acid concentration (1M to 5M). At a fixed nitric acid concentration, the D values were found to decrease with increase in loading of TBP with uranium. The D values for the extraction of Pu(III) using 20% TBP in n-dodecane and 30% TBP in n-paraffin at 80% uranium saturation were also determined The distribution data was least squares analysed against concentration of HNO₃ as well as percentage saturation of TBP with uranium and the coefficients obtained are reported. For all these extraction systems, D values for U(VI) were also determined.     

SYNERGIC EXTRACTIONS OF INDIUM(III) FROM CHLORIDE AND PERCHLORATE MEDIA WITH 1-PHENYL-3-METHYL-4-ACYLPYRAZOL-5-0NES AND TRI-n-OCTYLPHOSPHINE OXIDE MIXTURES IN TOLUENE

ABSTRACT

The synergic mixtures of extractants HL + TOPO where HL = l-phenyl-3-methyl-4-acylpyrazol-5-one, acyl = benzoyl (HPMBP), thenoyl (HPHTP), lauroyl (HPMLP) and with TOPO = tri-n-octylphos-phine oxide, are studied by IR, PMR and 31P NMR spectroscopies and by liquid-liquid distribution analysis. In toluene solutions, the “acylpyrazolones” are, in fact, chelated 4-acyl-5-hydroxy-pyrazoles ; addition of TOPO weakens this intramolecular H-bond by formation of H-bonded (TOPO.HL) complexes (log Kc -?, 1.1) ; the chelate ring may be broken (HPHTP) or subsist (HPMBP, HPMLP) in these complexes. Solid HPMBP exists either as chelated 4-acyl-5-hydroxypyrazole (yellow solid, F = 92°C) or as “open” 4-acyl-5-hydroxypyrazole with strong intermolecular H-bonds (white solid, F = 1150C).

Extraction of indium with the extraction solvents studied, from CI /C10₄aqueous solutions.takes place according to the four-equilibria (x = 0 to 3) :

The constants K_xare determined : K_O? K₁> K₂> K₃; HPMBP is the best extractant in all cases. The HL - TOPO association has no influence upon these extractions     

Extraction relationship of Li+ and H+ using tributyl phosphate in the presence of Fe(III)

ABSTRACT

During the extraction of lithium from high Mg-containing salt lake brines by tributyl phosphate (TBP) in the presence of Fe(III), H⁺ is used to stabilize Fe(III). However, the distribution ratio of H⁺ (D_H) is 4–6 times higher than that of Li⁺ (D_Li), which affects the extraction of Li⁺ significantly. In this study, the competition mechanism between H⁺ and Li⁺ was investigated by spectral analysis and thermodynamic equilibrium. The extracted species are determined as HFeCl₄ · 2TBP and LiFeCl₄ · 2TBP for H⁺ and Li⁺, respectively. The apparent equilibrium constants are K_H = 799.8 and K_Li = 120.6, respectively. Both equilibrium constants and the distribution ratios for H⁺ and Li⁺ extraction show that extraction of H⁺ is stronger than Li⁺.     

Hydrophobicity Parameter (log Kow) Estimation for Some Phenolic Compounds of Pharmaceutical Interest from Retention Studies with Mobile Phase Composition in Reversed‐Phase Liquid Chromatography

Abstract:

Chromatographic retention of some phenolic compounds (impurities of related pharmaceutical active substances) was studied for different organic modifier contents in mobile phase. Their capacity factors k′ versus organic modifier content (acetonitrile, or methanol) in mobile phase were measured and the corresponding dependences were studied by linear and polynomial regressions and then they were extrapolated to a mobile phase with no content in organic modifier in order to estimate their octanol/water partition coefficient (log K_ow). The values of log K_ow from retention data were compared to known shake‐flask experimental values and theoretical values predicted by fragment methodology. Linear dependences for methanol and second‐degree polynomial dependences for acetonitrile between organic modifier volume percentage and log k′ provided good estimation of log K_ow. The chromatographic method can be considered as a method of choice for estimating hydrophobicity parameter for different solutes. The linear dependence between extrapolated values of log k′ for 0% organic modifier and log K_ow estimated by means of fragment methodology for the model compounds can be used to predict chromatographic retention of other similar compounds.     

SOLVENT EXTRACTION OF METALS WITH 4-DINITROBENZOYL-2, 4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-ONE (DMPP)

ABSTRACT

The mechanism of the extraction of copper (II), nickel (II), cobalt (II) and thorium (IV) from aqueous buffer media with 4-dinitrobenzoyl1-2, 4-dihydro-5-methyl-2-phenyl-311-pyrazol-3-one (DMPP) in benzene has been investigated. The values of log K^*where K^*refers to the extraction equilibrium Mn⁺+-nHL ? MD_n+ nH⁺are Cu(II)& lpar; + 0.3), Co(II) (?6.65), Ni(II) (?5.04) and Th(IV) ( + 6.1). Solid complexes synthesized have the composition CuL₂· 2H₂O, NiL₂· 2H₂O and ThL₄respectively (L = anion of the ligand). DMPP seems to be superior to the corresponding 4-benzoyland 4-nitrobenzoyl derivatives of 2,4-dihydro-5-methyl-2-phenyl1-3 H-pyrazol1-3-one (MPP) and also better than thenoyltrifluoroacetone, the popularly employed fluorinated β-dike tone in the system investigated.