Studies on the sorption of Pu(IV) on alumina microspheres from nitric acid-oxalic acid solutions

Sorption of Pu(IV) on alumina microspheres prepared by the sol-gel procedure has been investigated for the recovery of plutonium from nitric acid-oxalic acid solutions. Distribution ratio for Pu(IV) between alumina microspheres and nitric acid-oxalic acid have been determined. The influence of the mode of preparation and heat treatment of these microspheres, on the sorption of Pu(IV) have been investigated. Pu(IV) breakthrough capacities have been determined using a 5 ml bed of alumina with solutions of Pu(IV) in 1M HNO₃+0.05M H₂C₂O₄ and 0.5M HNO₃+0.05M H₂C₂O₄. The elution behavior of Pu(IV) loaded on these microspheres were studied using nitric acid solutions containing different oxidising and reducing agents. Investigations were also carried out to fix the activity in the alumina matrix by heat treatment.     

Ion exchange extraction of platinum(IV) and palladium(II) from hydrochloric acid solutions

Sorption concentration of platinum(II, IV) and palladium(II) from freshly prepared and aged two-yearold hydrochloric acid solutions by a series of anion exchangers with different functional groups and of different physical structure of Purolite and CYBBER grades was studied. The high sorption ability of the ion exchangers in relation to the extracted chlorocomplexes of noble metals is shown. It was demonstrated that palladium(II) from all tested ion exchangers can be completely desorbed with thiourea solutions acidified with hydrochloric acid, while complete desorption of platinum is achieved only from Purolite S 985 anion exchanger of the complexforming type and Purolite A 111 weak base anion exchanger.     

Iridium(IV) extraction with petroleum sulfoxides from hydrochloric acid solutions

Iridium(IV) extraction with petroleum sulfoxides (PSO) from hydrochloric acid solutions is studied. Optimum conditions of extraction are chosen. It is shown that in the investigated extraction systems for a phase contact time of 30 min, iridium(IV) is extracted by the ion-associative mechanism. Electronic, ¹H NMR, and IR-spectroscopy, and elemental analysis are used to establish the structure of the extracted compound.     

Extraction of iridium(IV) by dihexyl sulfoxide from hydrochloric acid solutions

The extraction of iridium(IV) by dihexyl sulfoxide from hydrochloric acid solutions was studied. Optimum conditions for the extraction of iridium(IV) were determined. It was found that an ion-association mechanism of iridium(IV) extraction took place in the test extraction systems at a phase contact time of 10 min. As the phase contact time was increased, the extraction took place by a mixed mechanism. One extractant molecule was incorporated into the inner coordination sphere of the iridium(IV) ion. This decreased the charge of the extracted complex to unity.     

Adsorption of some elements from hydrochloric acid by anion exchange

Anion exchange behavior of 20 anionic chemical species was studied focusing on hydrochloric acid solutions. Elution characteristics for some of these anions were followed by using a basic anion exchange resin. Estimates of distribution coefficients in 10⁻³-9 mol/l acid were obtained by analytical determinations of these elements in column effluent solutions. The adsorption data observed in this medium suggests many applications in analytical separations.     

Reducing Pu(IV) to Pu(III) with hydroxylamine in nitric acid solutions

Los Alamos National Laboratory (LANL) has evaluated different techniques to concentrate and remove plutonium from solutions stored at the Rocky Flats Environmental Technology Site (RFETS). Pu(III) oxalate precipitation was chosen to treat nitric acid solutions because it is a simple and efficient technique for removing plutonium. Reducing Pu(IV) to Pu(III) is a key process step which affects the rest of the processing sequence. Because of differences in the literature¹ over the kinetics of the reaction, additional data was obtained and compared with existing data to examine the kinetic relationship, and determine an appropriate relationship for future engineering evaluations. The results and conclusions of this work, along with new experimental data, are presented.     

Isolation of an oxychloroniobium(IV) complex from hydrochloric acid solution

Summary An oxychloroniobium(IV) complex was isolated for the first time by zinc reduction of NbCl₅ in concentrated HCl solution. The product, an extremely moisture- and air-sensitive, intense blue solid was assigned a dimeric structure (H₃O)₂[Nb₂O₂Cl₆] based on elemental analysis, i.r. and u.v.-vis spectroscopy as well as magnetic and conductometric measurements.     

Polymerization of Pu(IV) in aqueous nitric acid solutions

The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to determine the effects of large UO₂(NO₃)₂ concentrations on the polymerization rates and, more generally, to review the influence of other major parameters on the polymer reaction. Typically, experiments have been performed at 50°C and at 0.05M Pu in aqueous solutions of HNO₃ at concentrations ranging from 0.07 to 0.4M. An induction period usually precedes the polymer growth stage, during which time it is believed that primary hydrolysis products form and begin to aggregate. Uranyl nitrate retards the polymerization reaction by approximately 35% despite the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation at 50°C has been shown to be third order in Pu(IV) concentration.     

Radiochemical investigation of the electron exchange reaction between tin(II) and tin(IV) in hydrochloric acid solutions

This paper is concerned with the study of isotope exchange reaction between Sn(II) and Sn(IV) in hydrochloric acid solutions. The kinetics of the exchange reaction of tin in these solutions were studied by extraction of Sn(IV)-hydroxyquinolate into chloroform.¹¹³Sn tracer, initially in the Sn(IV) state, was used. The rate of exchange reaction was determined at 22°C in a wide range of hydrochloric acid concentrations (2.8–12M). The dependence of the exchange rate on the concentration of chloride and hydrogen ions in these solutions (ionic strength: I∼8 and I∼12) are given. The activation energy dependence on chloride ion concentration at I∼12 was determined. The possible mechanism of the exchange reaction between tin(II) and tin(IV) is discussed on the basis of these data.     

The extraction of vanadium(IV) from hydrochloric acid solutions by di-(2-ethylhexyl)-phosphoric acid

The distribution of vanadium(IV) between hydrochloric acid solutions and solutions of di-(2-ethylhexyl)-phosphoric acid (DEHPA; HX) in organic solvent has been investigated under different conditions. Both the aqueous and organic phases have been examined spectrophotometrically. IR and electron spin resonance spectroscopies have been applied to the organic extracts. The mechanism of extraction is discussed on the basis of the results obtained.     

Electrochemical and spectroscopic studies of Pu(IV) and Pu(III) in nitric acid solutions

Electrochemical and absorption spectroscopic properties of Pu(IV) and Pu(III) in nitric acid have been investigated by using cyclic voltammetry (CV) and UV–Visible spectroscopy. CV using a glassy carbon electrode suggested that the electrochemical reaction of Pu(IV) nitrate complexes were found to be a quasi-reversible reduction to Pu(III) species. The formal redox potentials (E ⁰) for Pu(IV)/Pu(III) couples were +0.721, +0.712, +0.706, +0.705, +0.704, 0.694, and +0.696 V (vs. Ag/AgCl) when nitric acid concentrations are 1–7 M nitric acid solutions, respectively. These results indicate that the reduction product of Pu(IV) is only Pu(III). Further details for reaction mechanism of Pu(IV) were discussed on the basis of digital simulation of the experimental cyclic voltammograms. The absorption spectroscopic properties of Pu(III) and Pu(IV) in nitric acid solutions were investigated with UV–Visible spectrophotometry. As a result, it was founds that the intensities of the characteristic absorption peaks of Pu(III) and Pu(IV) tend to decrease with increasing nitric acid concentration for 1–8 M, and the peaks positions shifted longer or shorter wavelengths depending on the complex-forming abilities of Pu(III) and Pu(IV) with an increase in the nitric acid concentration.     

Extraction of zirconium(IV) from hydrochloric acid solutions by tri-octylamine and neutral donors

Solvent extraction of Zr(IV) from aqueous HCl solutions by mixtures of TOA and different organophosphorous bases in carbontetrachloride solvent have been found to be always higher than that by any single extractant. Synergism has been observed in the range of 2.4–9.6M HCl. Although the species extracted with neutral donor alone seems to be ZrCl₄·TOPO etc, with a mixture of extractants, however, the extracted species appears to be Q₂ZrCl₆·TOPO where Q is R₃NH. The extraction has also been found to increase with increase in the concentration of amines and neutral donors. Enhancement of extraction has been explained by the formation of a complex adduct in organic phase. Synergistic coefficients and apparent formation constants of the complex adducts have also been calculated.     

Electrodialytic recovery of chromium(VI) from hydrochloric acid solutions with liquid membranes based on tri-n-octylamine

A study of the process of electrodialytic recovery of chromium(VI) from a solution of 0.01 M K₂Cr₂O₇ in 0.1 M HCl with liquid membranes containing tri-n-octylamine with addition of di(2-ethyl hexyl)phosphoric acid in1,2-dichloroetrhane to dilute solutions of various acids determined the optimal process conditions: electrodialysis current density and the composition of the starting and receiving aqueous solutions and liquid membranes. It was found that all the liquid membranes studied provide a complete recovery of chromium(VI) anions from the starting solution.     

Studies on extraction of beryllium by di-(2-ethyl hexyl)-phosphoric acid from hydrochloric acid solutions

The distribution of Be between aqueous HCl solutions and organic phases of di-(2-ethyl hexyl)-phosphoric acid, has been described. The dependence of extraction on aqueous acidity, metal and extractant concentration as also on the diluent type, was thoroughly examined. The possible mechanism of extraction has been discussed in the light of results obtained.     

Ion exchange equilibria in simultaneous extraction of platinum(II,IV) and rhodium(III) from hydrochloric solutions

Regularities of sorption extraction of platinum(II, IV) and rhodium(III) by anion exchangers of various physical and chemical structure in the presence of hydrochloric media were studied. It is established that AM-2B, Purolite A 500, and Purolite S 985 ionites adsorb complex anions of platinum metals employing mixed mechanism. A high affinity of the studied anionites for the studied complex anions of platinum and rhodium is established.     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.     

Extraction recovery of vanadium(IV) from acid sulfate solutions with di-(2-ethylhexyl)phosphoric acid

Extraction of vanadium(IV) with di-(2-ethylhexyl)phosphoric acid from acid sulfate solutions in the presence of sodium sulfate was studied. The composition of the complex being extracted was found, and the equation of the extraction reaction was determined. The equilibrium constant of the reaction by which vanadium(IV) is extracted with di-(2-ethylhexyl)phosphoric acid was found by taking into account the complexation of vanadium(IV) in acid sulfate solutions.     

Ion exchange of uranium(IV) in hydrochloric acid—Organic solvent mixed media

In this paper, the distribution of U(IV) between a solution and a strong basic anion exchange resin 201×7 in mixed media HCl-methanol, HCl-ethanol, HCl-n-propanol and HCl-acetone has been investigated. The distribution ratio of U(IV) D in various conditions has been determined, the species of U(IV) sorbed on resin has been studied by visible and infrared spectroscopy and in mixed media by visible spectroscopy. The results show that the distribution ratio of U(IV) obviously increases in the presence of organic solvents, but the species of U(IV) sorbed on the resin are not influenced.     

Solvent extraction studies on the recovery of plutonium(IV) from phosphoric acid solution using monooctylphenylphosphoric acid

Extraction of plutonium from analytical waste solutions containing phosphoric acid using a solution of monooctylphenylphosphoric acid (MOPPA) is described. Effect of reagent concentration, presence of uranium, plutonium loading and back extraction of plutonium from the organic phase are described. Using a solution of 0.05 F MOPPA in xylene, more than 90% plutonium could be extracted in one cycle.