Investigation of foam properties in some extraction systems with TBP in kerosene and in carbon tetrachloride

Using the nephelometric sedimentation analytical method, the emulsions dispersity was investigated. These emulsions were formed in a centrifugal extractor mixing chamber with different extraction systems: TBP in kerosene—HNO₃ and TBP in CCl₄−HNO₃. The TBP and HNO₃ concentration, the speed of rotation and the supply of the mixing chamber with the phases stream influence on the histeresis loop of the emulsion type and the emulsion dispersity was described. The foaminess of extraction systems was investigated, and the stabilizing influence of w/o emulsions on the foaminess was confirmed.     

Extraction of Nitric Acid and Np(IV) by some aliphatic ketones and alcohols

The extraction behaviour of HNO₃ and Np(IV) from aqueous nitrate solutions with some aliphatic alcohols and ketones using hexane, carbon tetrachloride, benzene and chloroform as diluents was studied. The acid concentration in the aqueous phase varied from 0.25 to 10 M and that of the extractant in the organic phase varied from 0.5 M to the undiluted fraction. In the alcohol systems, solutions of the same alcohol in the diluents CCl₄ and CHCl₃ showed similar capacity for acid extraction, and also in the same diluents, solutions of diisopropyl and diisobutyl alcohol showed similar capacity for extraction. Extraction of Np(IV) with the different ketones and alcohols used follow the same pattern as HNO₃.     

Extraction chemistry of uranyl nitrate and nitric acid in high concentration systems

HNO₃ is extracted in significant quantities by uranyl nitrate solvates with different extractants: TBP (tributyl phosphate), TOPO (trioctyl phosphine oxide) and TDA (tetradecyl ammonium). The effect of diluent nature is not observed on extracting HNO₃ and TBP saturated by uranium at equilibrium with its salt using the diluents (CCl₄, C₆H₅Cl, C₁₂H₂₆, CHCl₃) which are less polar than UO₂(NO₃)₂(TBP)₂. HNO₃ occurs in organic phase as undissociated form and its state is similar to pure anhydrous HNO₃. Solvates of TBP and TDA with uranyl nitrate dissolve HNO₃ without displacement of uranium from organic phase.     

Extraction of pertechnetate anion as a ligand in metal complexes with tributylphosphate

The extraction of the pertechnetate anion has been investigated in the systems tributylphosphate (TBP)—solvent (carbon tetrachloride, n-heptane, chloroform)—metal salt (uranyl nitrate and chloride, thorium nitrate)—ammonium salt. In the absence of a metal, the solvates HTeO₄. iTBP (i=4) are extracted, while in the presence of uranium and thorium, the distribution of technetium corresponds to the formation of the mixed complexes: UO₂(NO₃)(TeO₄)·2TBP, UO₂Cl(TcO₄)·2TBP and Th(NO₃)₃ (TcO₁)·2TBP. The effective constants of the reactions H⁺+TcO ₄ ⁻ +i(TBP)_org←(HTcO₁·iTBP)_org, and (ML_n·2TBP)_org+TcO ₄ ⁻ ←(ML_n−1TcO₄·2TBP)_org+L were established in the above systems. The extraction of pertechnetate ion is more effective when it is coordinated to a cation solvated by TBP than the extraction in the form of pertechnetate acid solvated by TBP.     

Extraction of U(VI) with Cyanex 302

U(VI) was quantitatively extracted from 1·10⁻³M HNO₃ using 5·10⁻³M Cyanex 302 in xylene and was stripped from organic phase with 5M HCl. The optimum extraction conditions have been evaluated by studying parameters like acidity, effect of diluents, extractant concentration and period of equilibration. Based on this data, the separations of uranium from binary and complex metal mixtures and its recovery from uranmicrolite tailings (leachate) were successfully tested. Uranium can be determined with a relative standard deviation of 0.4%.     

Thermodynamics of solvent extraction of thorium by solutions of HHTA and mixtures of HHTA and TBP

The changes in free energy, enthalpy and entropy for the extraction of thorium by solutions of thenoyltrifluoroacetone (HTTA) and mixtures of solutions of HTTA and tri-n-butylphosphate (TBP), in three diluents, viz. cyclohexane, benzene and chloroform, were determined using the solvent extraction data obtained at different temperatures. From these data the thermodynamic parameters associated with the formation of Th(TTA)₄ · TBP in the respective organic diluents were evaluated. Trends in the enthalpy changes were attributed to different degrees of association of the diluents with themselves and with the solutes present in them.     

Extraction behaviour of uranium,zirconium and ruthenium with gamma-irradiated sulfoxides and tri-n-butyl phosphate

The extraction, scrubbing and stripping behaviour of uranium, zirconium and ruthenium with di-n-hexyl and di-n-octyl sulfoxides in Solvesso-100 and tri-n-butyl phosphate (TBP) in shell Sol-T irradiated by various gamma doses (0–169 Mrads) have been investigated. 2M HNO₃ was used for extraction and scrubbing and 0.01M HNO₃ for stripping purposes. Results indicate that the extraction of uranium with TBP increases and that with sulfoxide decreases with dose. This is reflected in their corresponding scrubbing percentages too. The stripping percentage of uranium with TBP decreases with dose while the reverse is the case with sulfoxide. The extraction of zirconium with TBP increases sharply with dose as compared to sulfoxides. The extraction scrubbing and stripping of ruthenium remain almost unaffected by dose both in the case of TBP and sulfoxides. These results lead to much higher overall decontamination factors for uranium with respect to zirconium as well as ruthenium with irradiated sulfoxides as compared to those with irradiated TBP.     

Some studies on synergic extraction of mixed ligand species of uranium(VI)

The extraction of U(VI) by mixtures of HTTA and TBP from aqueous thiocyanate medium has been studied. From the data obtained it was observed that the predominant uranium species extracted, causing synergic enhancement in the extraction of U(VI), is UO₂(SCN)TTA · 2TBP when benzene and cyclohexane are used as diluents, and that at a very low concentration of TBP the contribution of additional species, viz. UO₂(TTA)₂ · TBP becomes significant. With chloroform as diluent, however, both of these species are contributing to the synergic enhancement. The extraction of a quaternary uranium species, UO₂(SCN)TTA · 2TBP, involving the participation of the aqueous anion is thus established. Equilibrium constants for the various extraction equilibria involved are calculated.     

Extraction liquide-liquide par des esters alkylphosphoriques. II. Extraction des nitrates de béryllium et des autres alcalino-terreux par le tri-n-butylphosphate

The solvent extraction systems Be(NO₃)₂? HNO₃? H₂O? TBP/kerosene and M(NO₃)₂? H₂O? TBP/kerosene (TBP = tri-n-butylphosphate, M = Be, Mg, Ca and Sr) have been studied. The alkaline earths elements are poorly extracted. Only very high acidities allow better extraction of beryllium. The sequence of extraction of the alkaline earths elements by the TBP depends on the concentration of the cations and is Ca > Be > Sr > Mg if the metal concentration is lower than 2 M.     

Extraction of Am(III) by mixture of dihexyl N,N-diethylcarbamoylmethyl phosphonate and tributyl phosphate in benzene from nitric acid solutions

Extraction of Am(III) by dihexyl N,N-diethylcarbamoylmethyl phosphonate (CMP) in benzene from nitric acid solutions (pH 2.0 to 6.0M) has been studied. High extraction of Am(III) by CMP from 2–3M HNO₃ was observed. The species extracted was found to be Am(NO₃)₃·3CMP. The extraction was also done with mixtures of CMP+TBP and CMP+TOPO, where mixed species were extracted in the organic phase. The back-extraction experiments gave an efficient back-extraction of Am(III) by pH 2.0 (HNO₃) from the loaded CMP+TBP phase but a poor back-extraction from the loaded CMP+TOPO phase. The loading of Nd(III) by mixture of CMP and TBP was 50% of the CMP concentrations at a total Nd(III) concentration of 0.182M. The thermodynamic parameters of Am(III) extraction by a mixture of CMP and TBP were evaluated by temperature variation method, which suggests that the two-phase reaction is stabilized by enthalpy and opposed by entropy.     

Extraction of Zr(IV) by TBP-DMSO and TBP-Py from aqueous solutions containing monobasic acids

The distribution ratios for the extraction of Zr(IV) by TBP and its binary mixtures with DMSO or Py in n-dodecane in the presence of HNO₃, and HClO₄ have been determined. Based on stoichiometric and slope analysis methods a possible mechanism for the extraction has been proposed.     

Study on Properties of TBP-HNO3 Complex Used for Direct Dissolution of Lanthanide and Actinide Oxides in Supercritical Fluid CO2

The tri-n-butyl phosphate-nitric acid （TBP-HNO3） complex prepared by contacting the pure TBP with the concentrated HNO3 can be used for direct dissolution of lanthanide and actinide oxides in the supercritical fluid carbon dioxide （SCF-CO2）. Properties of the TBP-HNO3 complex have been studied. Experimental results showed that when the initial HNO3/TBP volume ratio was varied from 1 ： 7 to 5 ： 1, the concentration of HNO3 in the TBP-HNO3 complex changed from 1.95 to 5.89 mol/L, the [HNO3]/[TBP] ratio of the TBP-HNO3 complex changed from 0.61 to 2.22, and the content of H20 in the TBP-HNO3 complex changed from 2.02% to 4.19%. All of the density, viscosity and surface tension of the TBP-HNO3 complex changed with the concentration of HNO3 in the complex, and were higher than those of the pure TBE The protons of HNO3 and H2O in the complex underwent rapid exchange to exhibit a singlet resonance peak in nuclear magnetic resonance spectra. When the TBP-HNO3 complex was dissolved in a low dielectric constant solvent, small droplets of HNO3 were formed that can be detected by NMR.     

Calorimetric studies on the thermal decomposition of tri n-butyl phosphate-nitric acid systems

Thermal decomposition of neat TBP, acid-solvates (TBP·1.1HNO₃, TBP·2.4HNO₃) (prepared by equilibrating neat TBP with 8 and 15.6?M nitric acid) with and without the presence of additives such as uranyl nitrate, sodium nitrate and sodium nitrite, mixtures of neat TBP and nitric acid of different acidities, 1.1?M TBP solutions in diluents such as n-dodecane (n-DD), n-octane and isooctane has been studied using an adiabatic calorimeter. Enthalpy change and the activation energy for the decomposition reaction derived from the calorimetric data wherever possible are reported in this article. Neat TBP was found to be stable up to 255?°C, whereas the acid-solvates TBP·1.1HNO₃ and TBP·2.4HNO₃ decomposed at 120 and 111?°C, respectively, with a decomposition enthalpy of ?495.8?±?10.9 and ?1115.5?±?8.2?kJ?mol^?1 of TBP. Activation energy and pre exponential factor derived from the calorimetric data for the decomposition of these acid-solvates were found be 108.8?±?3.7, 103.5?±?1.4?kJ?mol^?1 of TBP and 6.1?×?10¹⁰ and 5.6?×?10⁹?S^?1, respectively. The thermochemical parameters such as, the onset temperature, enthalpy of decomposition, activation energy and the pre-exponential factor were found to strongly depend on acid-solvate stoichiometry. Heat capacity (C _p ), of neat TBP and the acid-solvates (TBP·1.1HNO₃ and TBP·2.4HNO₃) were measured at constant pressure using heat flux type differential scanning calorimeter (DSC) in the temperature range 32?C67?°C. The values obtained at 32?°C for neat TBP, acid-solvates TBP·1.1HNO₃ and TBP·2.4HNO₃ are 1.8, 1.76 and 1.63?J?g^?1?K^?1, respectively. C _p of neat TBP, 1.82?J?g^?1?K^?1, was also measured at 27?°C using ??hot disk?? method and was found to agree well with the values obtained by DSC method.     

Separation of uranium from different uranium oxide matrices employing supercritical carbon dioxide extraction

Uranium from different uranium oxide matrices was extracted with tri-n-butyl phosphate–nitric acid (TBP–HNO₃) adduct using supercritical carbon dioxide (SC CO₂). While 30 min dissolution time at 323 K was sufficient for U₃O₈ and UO₂ powder, UO₂ granule (at 333 K) and crushed green pellet (at 353 K) required 40 min. Crushed sintered pellet required 60 min at 353 K for complete dissolution. Influence of various experimental parameters such as temperature, pressure, volume of TBP–HNO₃ adduct, acidity of nitric acid used for preparing TBP–HNO₃ adduct and extraction time on uranium extraction efficiency was also investigated. For UO₂ powder, temperature of 323 K, pressure of 15.2 MPa, 1 mL TBP–HNO₃ adduct, 10 M nitric acid and 30 min extraction time was found to be optimum. ~70% uranium extraction efficiency was obtained on extraction with SC CO₂ alone which increased to 90% with the addition of 2.5% TBP in SC CO₂ stream. Extraction efficiency was found to vary linearly with TBP percentage and nearly complete uranium extraction (~99%) was observed with 20% TBP. Nearly complete extraction was also achieved with addition of 2.5% thenoyltrifluoroacetylacetone (TTA) in methanol. The optimized procedure was extended to remove uranium from simulated tissue paper waste matrix smeared with uranium oxide solids.     

Studies on synergistic extraction of thorium by mixtures of HTTA and TBP

Synergistic extraction of Th(IV) from perchlorate medium by mixtures of HTTA and TBP was studied. These studies include the effect of the ionic strength, temperature and the diluents on the extraction. Ionic strength was found to influence the extraction of Th(TTA)₄ and Th(TTA)₄·TBP whereas the adduct formation in the organic phase was almost unaffected. Increase of temperature resulted in a decrease of the extraction of Th(IV). The stability of the adduct was found to decrease in the order, cyclohexane > benzene > chloroform.     

New extractants for reprocessing of spent Th-U fuel

A study on solvent extraction of U(VI), Th(IV) and HNO₃ from nitric acid media by DEHSO is described. Extraction coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous HNO₃ concentration, extractant concentration and temperature have been studied. From the data the compositions of extracted species, equilibrium constants and enthalpies of extraction reaction have been evaluated. Back-extraction of U(VI) and Th(IV) from the organic phase by dilute nitric acid has also been tested. All studies on DEHSO are compared with TBP.     

Kinetic studies on the extraction of U(IV) by TBP in kerosene from nitrate medium

The kinetics of extraction of U(IV) by TBP in kerosene was investigated using a stirred Lewis cell. The effect of the different parameters affecting the extraction rate as well as temperature were separately investigated. The rate equation deduced from the experimental results show that the extraction of U(IV) is first order dependent on TBP concentration while it is of zero order with respect to U(IV), H⁺, NO ₃ ^– and HNO₃ concentrations. The data obtained show that the extraction process is governed by chemical reactions taking place at teh interface.     

Complexation of uranium(VI) with acetohydroxamic acid

The advanced separation extraction process based on tri-n-butyl phosphate organic phase called UREX is being developed to separate uranium from fission products and other actinides, and the acetohydroxamic acid (AHA) is employed to reduce and complex plutonium and neptunium in order to decrease their distribution to the TBP-organic phase. In this study, the extraction of uranium was performed from various aqueous matrices with different concentrations of HNO₃, LiNO₃, and AHA. Extraction of uranium increases with increasing both initial HNO₃ and total nitrate concentration. UV-VIS spectrophotometry confirmed that AHA is involved in the complex of uranium with TBP.     

Solvent extraction of reduced technetium from mineral acid solutions

The extraction of reduced^99mTc with 5,7-dichloroxine, tributyl phosphate (TBP) and 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP) from HCl−LiCl mixtures has been studied. A mechanism of extraction is proposed and the stability of the chlorocomplexes of technetium (V) in a hydrochloric and—lithium chlorid—perchloric acid mixture has been established using extraction data of^99mTc and spectrophotometric measurements with⁹⁹Tc.     

Studies on extraction behaviour of molybdenum (VI) from acidic radioactive waste using 2(ethylhexyl) phosphonic acids,mono 2(ethylhexyl) ester (PC-88A)/<Emphasis Type="Italic">n</Emphasis>-dodecane

This paper describes the studies on the extraction of molybdenum (VI) from aqueous nitric acid medium by (2-ethylhexyl) phosphonic acid, mono (2-ethylhexyl) ester (PC-88A). The extraction affecting parameters such as concentration of HNO₃ in aqueous feed, effect of concentration of extractants, effect of diluents, and molybdenum concentration in the aqueous phase are investigated to optimize the extraction conditions for the quantitative separation of molybdenum from nitric acid medium. With increase of HNO₃ concentration in aqueous phase, percentage extraction was found to be decreased in all the cases. Percentage extraction of molybdenum increases with increase in PC-88A concentration till the 0.15 M of PC88A, and after that it becomes constant. Kerosene and n-dodecane was found to be most suitable diluents. Among the various strippants used 0.2 M (w/v) solution of Na₂CO₃ and 0.2 M (w/v) solution (NH₄)₂CO₃ are found to be the equally suitable for stripping of molybdenum from the loaded organic phase. The stripping of molybdenum from loaded organic layer by various reagents followed the order: (NH₄)₂CO₃ >Na₂CO₃ >0.1 M sodium salt of EDTA >2 M NaOH >8 M HNO₃. The optimized process conditions are employed to extract molybdenum (VI) from actual Davies–Gray waste as well as from diluted high level waste generated in the purex stream. More than 94% Mo(VI) was extracted from radioanalytical as well as from high level waste of purex process and quantitative recovery was achieved in both the cases when 0.2 M sodium carbonate was used as stripping agent.