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  • Author: P. R. Vasudeva Rao x
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Summary

N-octanoyl-N-phenylhydroxamic acid (OHA) has been prepared by partial reduction of nitrobenzene with Zn dust/NH4Cl, followed by acylation with n-octanoyl chloride. Structure of OHA was confirmed by 1H NMR, IR spectra and CHNS microanalysis. The extraction of uranium by OHA has been studied as a function of pH, temperature and concentration of OHA. The extraction of uranium was found to increase with increase in pH. Uranium forms a 1:2 complex with OHA. IR Spectra & NMR Spectra of the uranium-OHA complex and slope analysis obtained from extraction studies indicated that the extraction of uranium was due to the formation of a chelate. The enthalpy change accompanied by the extraction of uranium by OHA has been obtained by temperature variation method. The extraction process was found to be endothermic at pH 2 and exothermic at pH 6.

Abstract

A procedure has been developed for the decontamination of radioruthenium from the lean organic phase composed of a solution 0.2 M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylyphosphineoxide (CMPO) and 1.2 M tri-n-butylphosphate (TBP) in n-dodecane (n-DD), which was used for the partitioning of minor actinides from actual high active waste solution (155 GWd/Te). For this purpose, the stripping behavior of radioruthenium from 0.2 M CMPO–1.2 M TBP in n-DD was studied at 298 K by using various aqueous reagents and adsorbents. Among the different reagents investigated, the aqueous solution of sodium hydroxide and sodium carbonate and adsorbents such as neutral alumina and anion exchange resin (OH- form) were identified as the promising candidates. Nearly 90–95% of radioruthenium was removed from the lean organic phase in seven contacts using sodium carbonate or sodium hydroxide solution. The residual radioactivity in the organic phase was removed by treatment with neutral alumina or anion exchange resin. The quality of the organic phase was ascertained by 241Am(III) retention test.

Summary

Room temperature molten salts for possible application of recovery of fission palladium from irradiated nuclear fuel/wastes have been investigated. The redox behavior of a solution of palladium(II) chloride and 1-butyl-3-methylimidazolium chloride (bmimCl) at glassy carbon working electrode has been studied at various temperatures using cyclic voltammetry. The voltammogram of bmimCl-PdCl2 consists of a single reduction and two oxidation waves indicating that Pd2+ undergoes a single step two-electron quasi-reversible reduction process at the working electrode. Controlled potential deposition of palladium on platinum electrode gave a black deposit, which was characterized to be metallic palladium. Extraction of palladium by Aliquat-336 has been studied as a function of nitric acid concentration and the redox behavior of palladium in Aliquat-336 phase has been investigated by cyclic voltammetry. The results suggest that some aqueous insoluble room temperature ionic liquids can act both as extractant and electrolytic medium and also have the potential of recovering of palladium from nuclear wastes.

Summary

Alkali metal uranyl chloride (M2UO2Cl4 (M = Na or Cs)) was dissolved in 1-butyl-3-methylimidazolium chloride (bmimCl) and the redox behavior of uranyl ion present in the resultant solution was investigated by cyclic voltammetry at 343 K. The cyclic voltammogram consisted of a reduction wave occurring at the peak potential of −0.85 V, due to the reduction of U(VI) and two oxidation waves occurring at the peak potentials of −0.6 V and +0.2 V. Controlled potential electrolysis of uranium(VI) loaded bmimCl gave a black deposit, which was characterized as uranium oxide by EDXRF and XRD analysis. Extraction of uranium(VI) from nitric acid medium by 0.05 M tri-n-octylmethylammonium chloride (TOMAC) in chloroform was studied and the cyclic voltammogram of uranyl ion present in the extracted phase exhibited a single reduction (−0.8 V) and an oxidation wave (0.06 V) at 298 K. Controlled potential electrolysis of uranium(VI) loaded TOMAC at −1.0 V also gave a black uranium oxide deposit similar to that observed in the previous case. The results indicated that uranyl ion in organic phase undergoes a single step two electron quasi-reversible reduction at the working electrode, which can be conveniently exploited for the direct recovery of uranium from the spent fuel or from high level liquid wastes.

Abstract

The retention behaviour of uranium, thorium, americium and lanthanides has been investigated, using a reverse phase C18 column modified with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (n-Pr-BTP) with the aim of investigating rapid lanthanide-actinide separations by HPLC technique. Nitric acid and α-hydroxy isobutyric acid (α-HIBA) have been employed as the mobile phase. The influence of mobile phase pH and concentration on the retention of metal ions has been studied. The aim of this study is to investigate the use of BTP coated reverse phase columns as analytical columns for the fast separation of the minor actinides from the lanthanides in the high-level waste (HLW), and to explore whether such columns can be used on a preparative scale for the purification and the recovery of minor actinides from the high-level waste (HLW). It was observed that reverse phase columns modified with BTP showed greater affinity for actinides but exhibited no retention for lanthanides and the lanthanide-actinide separations could be achieved in nitric acid mobile phase, without the need for complexing agents. Americium was separated from the lanthanides with good peak profile and baseline resolution in both nitric acid as well as α-HIBA as the mobile phase. Based on this, the separation of americium from the lanthanides in the HLW was also demonstrated. The retention of a significant amount of thorium by the column in breakthrough studies also indicated that these columns can be used for preparative scale purification of the actinides.

Abstract

The extractants, bis(2-ethylhexyl)diglycolamicacid (HDEHDGA) and bis(2-ethylhexy)thiodiglycolamic acid (HDEHSDGA) were synthesized and characterized by 1H and 13C NMR, mass and IR spectroscopy. The extraction behaviour of (152+154)Eu(III) and 241Am(III) from nitric acid medium by a solution of HDEHDGA (or HDEHSDGA) in n-dodecane (n-DD) was studied for the mutual separation of actinides and lanthanides. The effect of various parameters such as the pH, concentrations of HDEHDGA, HDEHSDGA, sodium nitrate, N,N,,-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and diethylenetriaminepentaacetic acid (DTPA) on the separation factor (SF) of americium(III) over europium(III) and vice versa was studied, and the conditions needed for the preferential separation were optimised. The results show that HDEHDGA exhibits higher extraction for (152+154)Eu(III) and HDEHSDGA shows the superior selectivity for 241Am(III).

Abstract

A solution of 0.1 M N,N-di-2-ethylhexyl-N´,N´-di-octyl-3-oxa-1,5-diamide (DEHDODGA)-0.5 M N,N-dihexyloctanamide (DHOA) in n-dodecane has been evaluated for the separation of trivalent actinides from high-level liquid waste (HLLW). The extraction and stripping behaviour of Am(III) and other metal ions present in HLLW was studied. The distribution ratio of various metal ions was measured as a function of concentration of nitric acid and interfering ion. The extraction of metal ions decreased in the order M4+ ≥ M3+ ≫ M2+ ∼ MO2 2+ ≫ M+. The extraction of Am(III), Eu(III), Y(III), and Zr(IV) was quantitative. However, the distribution ratio of unwanted metal ions such as Fe(III), Co(II), Sb(III), Mn(II), and Cs(I) was negligible. The distribution ratios of Cd(II), Ru(III), Pd(II), Mo(VI), Cr(VI), Ba(II), Ni(II), and Sr(II) were not insignificant, but were quite low. The conditions needed for the quantitative recovery of trivalents from the loaded organic phase were optimized with the use of diethylenetriaminepentaacetic acid (DTPA)-citric acid at pH 3 to facilitate the mutual separation of lanthanides-actinides in the subsequent step.