Simultaneous recovery of plutonium and americium from assorted analytical waste solutions using extraction chromatography

A rapid extraction chromatography based methodology was developed for simultaneous recovery of plutonium and americium from various kinds of analytical waste obtained during chemical quality control of plutonium based nuclear materials using sulphonic acid based actinide? resin. Efforts were made to understand the effect of initial feed acidity, gamma radiation and the concentrations of Am³⁺ and Pu⁴⁺ on their k _d. values. Processing of assorted analytical waste solutions through this method revealed that more than 95 % of Am³⁺ and 90 % of Pu⁴⁺ were adsorbed on the resin while iso- propanol can be successfully employed for the quantitative recovery of both the actinides from the loaded resin phase.     

Extraction of actinides by quaternary amines from hydrochloric acid medium

The extraction of Np(IV), Pu(IV) and U(VI) from aqueous hydrochloric acid into quaternary amines has been studied. The dependence of the distribution coefficient on amine concentration suggests that the actinide ions extracted are NpCl ₆ ²⁻ PuCl ₆ ²⁻ and UO₂Cl ₄ ²⁻ . This is further supported by the absorption spectra of the amine extracts of these actinide ions. Based on the extraction data obtained, a simple method for the separation of typical metal ions such as Cs, lanthanides and Zr from U(VI) and Pu(IV) is suggested.     

Application of hollow fiber supported liquid membrane for the separation of americium from the analytical waste

Americium from analytical solid waste containing U and metallic impurities was separated using hollow fiber supported liquid membrane (HFSLM) technique impregnated with DHOA–TODGA from nitric acid medium. An aliquot of 5 g of the solid waste containing Am (19.95 mg) as minor actinide and of U (2,588 mg), Fe (1,360 mg), Ca (1,810 mg) and Na (3,130 mg) as major impurities was processed. The feed solution obtained after the dissolution of the residue in ~4 M HNO₃ was passed through HFSLM module. In the first stage using 1 M DHOA–dodecane U was recovered while Am and other impurities were left in the raffinate. In the second stage, 0.5 M DHOA + 0.1 M TODGA/dodecane was used for the separation of Am from other impurities. Though, majority of the elements were separated in this cycle, Ca was co extracted along with the americium. CMPO extraction chromatographic technique was used for further separation of americium from Ca. Significant decontamination factors were achieved in this three step separation process with respect to U, Fe, Na and Ca with ~77 % recovery of americium.     

Recovery of americium from analytical solid waste containing large amounts of uranium,plutonium and silver

Trace metallic impurity analysis by spectroscopic techniques is one of the important steps of chemical quality control of nuclear fuel materials. Depending on the burn-up and the storage time of the fuel, there is an accumulation of ²⁴¹Am in plutonium based fuel materials due to β decay of ²⁴¹Pu. In this paper, attempts were made to develop a method for separation of ²⁴¹Am from 1.2 kg of analytical solid waste containing 70% U, 23% Pu, 5% Ag and 1–2% C as major constituents along with other minor constituents generated during trace metal assay of plutonium based fuel samples by d. c. arc carrier distillation atomic emission spectrometry. A combination of ion exchange, solvent extraction and precipitation methods were carried out to separate ~45 mg of ²⁴¹Am as Am(NO₃)₃ from 15 L of the analytical waste solution. Dowex 1×4 ion exchange chromatographic method was used for separation of Pu whereas 30% TBP–kerosene was utilized for separation of U. Am was separated from other impurities by fluoride precipitation followed by conversion to nitrate. The recovery of Pu from ion exchange chromatographic separation step was ~93% while the cumulative recovery of Am after separation process was found to be ~90%.     

Protonation and solvent extraction of N-p-tolylbenzohydroxamic acid in hydrochloric acid medium

the protonation of N-p-tolylbenzohydroxamic acid (p-TBHA) in aqueous hydrochloric acid has been investigated by determination of its distribution between cyclohexane and hydrochloric acid. The pK(a) value found was - 2.30 +/- 0.02 at 30 degrees . The solubility of p-TBHA as a function of hydrochloric acid concentration has also been determined. At lower acid concentrations the solubility decreases owing to a salting-out effect, whereas at higher concentrations it increases because of formation of the more hydrophilic protonated species and a salting-in effect. Intramolecular hydrogen-bonding observed in p-TBHA provides evidence for protonation of the nitrogen atom.     

Ion-pair extraction of tetravalent plutonium from hydrochloric acid medium using crown ethers

Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL⁺].[HPu(Cl) ₆ ^– ] and [HL⁺]2·[Pu(Cl) ₆ ^2– ] as ion-pairs (where L represents the crown ether) is suggested.     

Extraction of platinum metals from hydrochloric acid medium with triphenylphosphine solution in 1,2-dichloroethane

Extraction of platinum metals with TPP in 1,2-dichloroethane from hydrochloric acid medium has been examined. At hydrochloric acid concentrations higher than 6M, palladium, platinum and osmium are extracted, whereas at low acidity only palladium is quantitatively extracted. Addition of stannous chloride as labilizing agent makes possible a group separation of platinum metals (except osmium). Possible extraction mechanisms are discussed.     

Separation of molybdenum (VI) by extraction withn-octylaniline from hydrochloric acid medium

n-Octylaniline in bezene was used for the extractive separation of molybdenum (VI) from hydrochloric acid medium. Molybdenum(VI) was extracted quantitatively from 10 ml aqueous solution 1.5M in hydrochloric acid and 10M in lithium chloride into 10 ml of 10%n-octylaninline in benzene. It was stripped from the organic phase with 5% aqueous ammonia solution and estimated spectrophotometrically with thiocyanate at 465 nm. The interference of various ions has been studied in detail and conditions have been established for the determination of molybdenum(VI) in synthetic mixtures and alloy samples.     

Fluorescence characteristics of inorganic complexes in hydrochloric acid medium at liquid-nitrogen temperature

A study of the low-temperature fluorescence characteristics of the ions of 55 elements in concentrated hydrochloric acid is reported. The spectral characteristics, effects of hydrochloric acid concentration and time, calibration linearity and sensitivity for Sb(III), Bi, Ce(III), Pb, Te(IV), Tl(I) and Sn(IV) have been investigated. Uranium(VI), copper(I) and antimony(V) also exhibit fluorescence under these conditions. The detection limits using a commercial spectrofluorimeter with modified sample cells are Sb(III), 10(-6)M; Bi(III), 10(-8)M; Ce(III), 10(-7)M; Pb, 10(-8)M; Te(IV), 10(-7)M; Tl(I), 10(-6)M; Sn(IV), 10(-4)M. The suitability of some inorganic acid solvents for clear glass formation at -196 degrees is also investigated.     

Kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium

The kinetics of oxidation of glycine and valine by chloramine-T in hydrochloric acid medium has been studied. The rate of disappearance of chloramine-T shows a first order dependence on both chloramine-T and the amino acid, and an inverse first order with respect to [H⁺]. The solvent isotope effect was studied using heavy water. The kinetic parameters,E _a ,Arrhenius factorA, H and S and G have been calculated. A rate law in agreement with experimental results has been derived. A mechanism is proposed.

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Über die Kinetik der Oxidation von Glycin und Valin mit Chloramin-T in salzsaurem Medium

Zusammenfassung Die Kinetik der Oxidation von Glycin und Valin mit Chloramin-T in Salzsäure wurde untersucht. Die Geschwindigkeitskonstante des Wegreagierens von Chloramin-T zeigt eine Abhängigkeit erster Ordnung sowohl von Chloramin-T als auch von der Aminosäure und ist invers erster Ordnung bezüglich [H⁺]. Der Lösungsmittel-Isotopeneffekt wurde mit D₂O untersucht. Es wurden die kinetischen Parameter,E _a , derArrhenius-FaktorA, H , S und G , bestimmt. Ein Mechanismus, der in Übereinstimmung mit den experimentenllen Daten ist, wird vorgeschlagen.

     

Purification of americium from bulk quantities of plutonium loading effluent using trilaurylamine

Four litres of Am solution containing 81.5 mg/l Am and 0.6 mg/l Pu could be purified by a two-step procedure involving solvent extraction and extraction chromatography with trilaurylamine. The final product contained a maximum concentration of 9 g/l Pu.     

Kinetics and mechanism of oxidation of arsenious acid by tetrachloroaurate(III) in hydrochloric acid medium

Kinetics of the oxidation of arsenious acid by tetrahcloroaurate(III) have been studied spectrophotometrically in hydrochloric acid medium. Initial complex formation between As(III) and Au(III) followed by the decomposition of the intermediate complex to give products of the reaction is suggested. The empirical rate law is

k and K are found to be 13.9 × 10^?4 s^?1 and 24.2 M^?1 respectively at 30°C and μ = 1.0 M. ΔH³ and ΔS³ for k are found to be 49.2 kJ mol^?1 and - 137.2 JK^?1 mol^?1 whereas ΔH and ΔS associated with K are - 6.75 kJ mol^?1 and 4.14 JK^?1 respectively.     

Corrosion inhibition investigations of 3-acetylpyridine semicarbazone on carbon steel in hydrochloric acid medium

The corrosion inhibition efficiency of 3-acetylpyridine-semicarbazide (3APSC) on carbon steel (CS) in 1.0 M HCl solution has been investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies. The results show that inhibition efficiency on metal increases with the inhibitor concentration. 3APSC exhibited marked inhibition towards carbon steel in HCl medium even at low concentrations. The adsorption of inhibitor on the surfaces of the corroding metal obeys the Langmiur isotherm and thermodynamic parameters (K _ads, ?G _ads ⁰ ) were calculated. Activation parameters of the corrosion process (E _a, ?H* and ?S*) were also calculated from the corrosion rates. Polarization studies revealed that 3APSC act as a mixed-type inhibitor. Surface analysis of the metal specimens was performed by scanning electron microscopy.     

Final purification and concentration of americium/curium separated from high-level reprocessing waste

A cation-exchange cycle has been developed for the recovery and concentration of the Am/Cm product from a DTPA/lactic acid solution used in an extraction process for the isolation and separation of the actinides from lanthanide fission products. The optimum pH region for the sorption of Am³⁺ from 0.05M DTPA/1M lactic acid solutions by strongly acidic cation-exchange resins is pH 0.9–1.0. Maximum usable capacities, heights of the exchange zone, and concentration factors for different resins, cross-linkages and temperatures have been determined. Decontamination factors are given for some fission products, as well as U, Np and Pu.     

Synergic extraction for recovery of americium from waste solution containing an excess of uranium

A method based on synergic extraction has been evolved for the recovery of tens of milligrams of americium from analytical wastes in 7-8M HNO₃ medium containing excess uranium as a two step procedure viz., (1) separation of uranium by contacting with TBP in dodecane and (2) recovery of americium by an extraction-cum-strip cycle using a synergic mixture of PMBP-TBP in dodecane after decreasing the acidity of the solution. Other transition metals such as iron found in significant proportion were separated from Am by using the difference in the kinetics of extraction of iron and americium into HPMBP-TBP-dodecane mixture by short duration contacts. About 99% of Am could be recovered into about 20% of its initial volume. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of oxidation of hypophosphite ion by Au(III) in hydrochloric acid medium

Hypophosphite ion is oxidised by Au(III) in aqueous hydrochloric acid to give phosphorus acid and Au(I). The kinetics of the reaction has been studied spectrophotometrically in the UV region at different temperatures. The oxidation of hypophosphorous acid is first order with respect to both Au(III) and substrate. Hydrogen ion has no effect on the rate in acid media (0.15–1.0)M. The energy and entropy of activations are 128 ± 3.0kJ mol^?1 and 135.8 ± 6.5 JK^?1 mol^?1 respectively. The results are interpreted in terms of the probable formation of intermediate Au(lI).     

The determination of U,Np and Pu in urine by sequential extraction with ALAMINE-336 from hydrochloric acid medium

A method has been developed for the extraction of uranium, neptunium and plutonium from human urine using the comparatively cheap technical amine ALAMINE-336. These elements are coprecipitated with a calcium phosphate carrier, which is then subjected to a wet-ashing procedure with NHO₃/H₂O₂ and HCl/H₂O₂. The residue is dissolved in 10M hydrochloric acid and U, Np and Pu are extracted with a 10% ALAMINE-336/xylene solution, followed by subsequent back-extraction with 10M HCl/NH₄I (Pu), 4M HCl/HF (Np) and 0.1M HCl (U), respectively. The average recoveries are around 95%.     

Separation of molybdenum(VI) from other elements by solvent extraction with dibenzo-18-crown-6 from hydrochloric acid medium

DB-18-C6 was used for the extractive separation analysis of molybdenum(VI) from a range of other elements. Molybdenum(VI) was quantitatively extracted from 8M hydrochloric acid with 0.01M DB-18-C6 in nitrobenzene. It was stripped from the organic phase with 2M nitric acid and determined spectrophotometrically with Tiron at 390 nm. Molybdenum was separated from a large number of elements in binary mixtures, the tolerance limit for most elements being very high. Selective extraction of molybdenum permits its separation from barium, thorium, cesium, rubidium, strontium, lanthanum, chromium(III) and cerium(III). The method was extended for the analysis of molybdenum in a soil sample.     

Reaction between U(IV) and H2O2 in hydrochloric acid medium

Kinetic investigations on the reaction between U(IV) and H₂O₂ have been carried out at different acidities in chloride medium at an ionic strength of 2M. The observed bimolecular rate constant has been found to be dependant on [H⁺]^?1.3. The activation energy of the overall reaction has been found to vary from 13.4 ± 0.7 to 18.0 ± 0.8 kcal/mol in the range of acidity from 0.3 to 1.5M. The results have been explained on the basis of three parallel rate-controlling reactions involving unhydrolyzed species of U(IV) and hydrolyzed species UCl(OH)²⁺ and UO²⁺. The values of the rate constants for these three reaction paths have been found to be of the order of 3.95, 5.59 × 10³, and 1.49 × 10⁵M^?1 min^?1, respectively.