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  • Author or Editor: M. Subramanian x
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Abstract  

The present paper describes a novel type of extractant for actinides called bis (dioctylcarbamoylmethyl) sulfoxide which neither contains phosphorus nor entails the addition of tributyl phosphate as phase modifier for extraction. This extractant, abbreviated as CMSO, has been found to be freely soluble in dodecane and to form no third phase even with concentrations of nitric acid as high as 10M. The distribution ratios for the extraction of Am(III), Pu(IV) and U(VI) at trace levels have been found to be 13, 220 and 11, respectively, from 5M nitric acid using 0.2M CMSO in dodecane and those for back-extraction have been found to be 2×10–4, 8×10–3 and 5×10–2 using 0.01M nitric acid, 0.1M oxalic acid and 0.35M sodium carbonate, respectively. Similar distribution ratios were obtained with the recycled extractant. Extraction was found to be very rapid. Eu(III) and Sr(II) were found to be moderately extracted with distribution ratios of 2 and 0.77, respectively, while the extraction of Cs(I) was negligible (KD=0.005).

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Abstract  

A rapid extractive photometric method using Aliquat-336 and xylenol organe for the determination of plutonium(IV) at μg levels has been developed. Quantitative extraction is obtained from ∼4M aqueous HNO3 medium, affording estimation in the presence of several commonly occurring impurities, viz. iron, uranium, fission products and cladding materials. Effects of acidity, reagent concentration and diverse ions on the estimation have also been invetigated. Unlike the well-known absorptiometric method for determining plutonium(IV) employing Arsenazo III, the procedure presented here tolerates manyfold excesses of uranium(VI) as well as chromium(III), iron(III) and zirconium(IV), which are some of the major contaminants of plutonium during reprocessing.

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Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and oxo donors with widely varying basicity, viz. diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octylphosphine-oxide (TOPO) has been studied at various fixed temperatures. Results indicate that the equilibrium constants in the organic phase for addition reactions (KS) with these donors follow their order of basicity (KH) viz. DPSO (0.033)<TBP (0.16)TOPO (8.9) with log KS values of 3.70, 4.28 and 6.45, respectively. The thermodynamic parameters associated with the formation of these systems have been evaluted by the temperature coefficient method. The results indicate that the complex in the organic phase for DPSO and TBP is stabilized only by enthalpy, whereas both enthalpy and entropy contribute to the stabilization of the TOPO complex. Also, enthalpy contribution is more prominent as compared with the UO 2 2+ /HTTA/TOPO system, where both enthalpy and entropy contribute almost equally.

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Abstract  

Extraction behaviour of plutonium (IV) from nitric acid media by two long-chain aliphatic sulphoxides, namely, di-n-hexylsulphoxide and di-n-octylsulphoxide has been investigated in the presence of several water-miscible organic solvents to study their possible synergistic effect on metal ion extraction. Methanol, ethanol, n-and iso-propanol, dioxane, acetone as well as as acetonitrile were used as the organic component of the mixed (polar) phase. These additives affected the extraction to varying degrees. Thus, extractability of Pu increases 2–3 fold with increasing concentration (upto 20%) of acetonitrile, acetone, methanol and ethanol while it decreases with increasing concentration of n-and isopropanol. At high concentration of the former, synergism changes into antagonism. Possible reasons for such behaviour are briefly discussed. Among these organic additives, maximum enhancement in the extraction of Pu(IV) was observed in the presence of acetonitrile. The relative increase in extraction was found to be more at lower sulphoxide concentrations.

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Abstract  

A radiometric method based on substoichiometric isotope dilution analysis has been developed for the determination of mercury using cetyltrimethylammonium bromide (CTAB) as the substoichiometric reagent. The method is based on the extraction of mercury as an ionassociation complex of tetraiodomercurate(II) ion with a substoichiometric amount of CTAB in benzene. The calibration graph was found to be linear in the range 0–10 μg Hg (II) in the aqueous phase of 10 ml volume. A detection limit of 0.06 μg·ml−1 could be achieved by the proposed method. The relative standard deviation of the method was found to be 3.0% and the method has been successfully applied to study the determination of mercury in various synthetic mixtures.

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Abstract  

The colour reaction of Am(III) with Arsenazo III in several hydroorganic media has been examined systematically on the addition of certain polar water-miscible organic solvents in the course of a search for improved and simple spectrophotometric methods for the estimation of americium. Addition of these substances resulted in the stabilization of colour and brought about a drastic enhancement in the absorbance values. The organic additives studied include acetone, acetonitrile, dimethylformamide, dioxane and ethanol. Among the many solvents tested, alcohol and dioxane proved to be the most effective; highest sensitivity is obtained by using a 60% dioxane-ethanol (11) mixture. The apparent molar absorptivity based on Am content is 184616±9931 mol–1 cm–1 at 655 nm which is about 3 times that attained for the reaction in aqueous medium (65178±1243). Strikingly, this is the highest value reported as yet for its determination. Beer's law is obeyed both in mixed as well as aqueous media. The effects of some experimental variables on colour development have also been studied to optimize the conditions for the assay of Am.

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Abstract  

A simple solvent extraction procedure is reported for the sequential separation of mercury(II), cadmium(II) and zinc(II). Mercury is separated first using 1,3-diphenyl-2-thiourea in chloroform at an overall acidity of 0.3M HCl. Then cadmium separated using the same reagent at pH 10 into dichloromethane. The zinc which is remaining in the aqueous phase is then quantitatively extracted into toluene-cyclohexanol mixture using 2-mercaptobenzoxazole. Suitable stripping solutions have been proposed for the re-extraction of these metal ions for their subsequent estimations. The method has been made highly selective by the use of appropriate masking agents and has been applied in conjunction with estimation procedures for the determination of these metal ions in city waste incineration ash (CRM 176), mercuric chloride (A. R. grade) and in magnesium alloy samples.

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Abstract  

A method has been developed for the determination of trace amounts of palladium using radioactive mercury dithizonate as the reagent. Experimental conditions for the quantitative displacement of mercury from the reagent, calibration graph and the interfering effects of various ions have been studied. The method is sensitive down to 2 g of palladium present in 10 ml of the aqueous solution.

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Abstract  

A rapid method based on the extraction of neptunium(IV) by Aliquat-336 followed by its direct photometric determination in the organic phase employing xylenol orange is reported. Optinum conditions have been established for the extraction and determination of as little as 0.4 ppm of Np. The molar absorptivity of the red-coloured neptunium complex at 535 nm is 49535±361 1·mol−1·cm−1. Unlike the well-known absorptimetric method for estimating NP(IV) with Arsenazo III, this method tolerates many-fold excesses of fluoride, nitrite, nitrate, phosphote, oxalate as well as UO 2 2+ , Pu4+, Zr4+, etc., which are some of the major contaminants associated with neptunium during its reprocessing.

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Abstract  

A radioreagent method for the analysis of traces of palladium using radioactive zinc dithizonate as the reagent has been developed. The method is rapid, highly selective and palladium concentration down to 2 g present in 10 ml solution can be measured.

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