V. V. Ramakrishna

The effect of temperature on the extraction of plutonium(IV) from nitric acid by tri-n-butyl phosphate

Abstract The extraction of Pu(VI) from varying concentration of nitric acid into TBP in dodecane was studied at different temperatures in the range 20–60°C. From the distribution coefficient data, the enthalpy changes for the extraction of Pu(VI) under different conditions were determined. All the data obtained showed that the extraction of Pu(VI) from nitric acid into TBP is exothermic in nature. An attempt was made to evaluate the thermodynamic free energy and entropy changes.

The effect of temperature on the extraction of uranium(VI) from nitric acid by tri-n-butyl-phosphate

Abstract The extraction of Pu(VI) from varying concentration of nitric acid into TBP in dodecane was studied at different temperatures in the range 20–60°C. From the distribution coefficient data, the enthalpy changes for the extraction of Pu(VI) under different conditions were determined. All the data obtained showed that the extraction of Pu(VI) from nitric acid into TBP is exothermic in nature. An attempt was made to evaluate the thermodynamic free energy and entropy changes.

Complexing of tetravalent plutonium in aqueous solutions

Abstract Complex formation by tetravalent plutonium at I = 2 and [H + ] = 2 M, has been studied by solvent extraction methods using vanadium(V) to eliminate the possibility of a change in the oxidation state of Pu(IV) during the experiment or complexing of Pu(IV) by the holding oxidant itself. Sulphate complexing of Pu(IV) has been studied using three extractants, viz. thenoyltrifluoroacetone, dinoylnaphthalene sulphonic acid and tri- n -butylphosphate, and nitrate, chloride and fluoride complexing of Pu(IV) has been studied using the thenoyltrifluoroacetone extraction method.

Some studies on the TBP extraction of actinides

Abstract Distribution coefficient data for tetravalent Th, U, Np and Pu and hexavalent U, Np and Pu were obtained at different temperatures in the range 10°–60°C for 3·0M nitric acid and 30% TBP in xylene. From these data the enthalpy changes associated with the extraction of the ions were determined. An attempt was also made to estimate the corresponding free energy and entropy changes.

THE EFFECT OF TEMPERATURE ON THE EXTRACTION OF PLUTONIUM(IV) BY TRI‐N‐BUTYL PHOSPHATE

Abstract Distribution coefficient data for Pu(IV) were obtained at different temperatures in the range 10–60°C for varying concentrations of nitric acid and TBP in dodecane. From these data the enthalpy change for extraction of Pu(IV) was determined. An attempt was also made to calculate the free energy and entropy changes associated with the extraction of Pu(IV).

Studies on the HTTA extraction of tetravalent actinides

The data on the extraction of Np(IV) and Pu(IV) from aqueous perchloric and nitric acid into benzene solution of thenoyl-trifluoro-acetone (HTTA) have been obtained at different temperatures. From these data the equilibrium constant for their extraction and the values of enthalpy for the extraction of Np(IV) and Pu(IV) were calculated. The absorption spectra of HTTA extracts containing Th(IV), U(IV), Np(IV) and Pu(IV) have been recorded to explore their analytical applications.

Sulphate and fluoride complexing of U(VI), Np(VI) and Pu(VI)

Abstract The complex formation of U(VI), Np(VI) and Pu(VI) with sulphate and fluoride ions was studied in HClO4H2SO4 and HClO4HF solutions respectively at an ionic strength of 2·0 and [H+] = 2·0 M by the distribution method employing the liquid cation exchanger dinonyl naphthalene sulphonic acid as the extractant. An attempt was made to explain the order of the stability constant values obtained.

Aqueous TTA complexing of Np(IV) and Pu(IV)

Abstract The sulphate and fluoride complexing of Np(IV) and Pu(IV) were studied at an ionic strength of 2.0 and a hydrogen ion concentration of 2.0 M using the thenoyltrifluoroacetone (TTA) extraction method employing TTA dissolved in two different solvents viz. benzene and n-heptane. The data obtained were utilized for the calculation of the stability constants for the aqueous phase TTA complexing of Np(IV) and Pu(IV). The values of the first constant (K1) for aqueous TTA complexing were found to be 83 ± 5 for Pu(IV) and 48 ± 2 for Np(IV).

Synergistic Extraction of Neptunium (IV) by Mixtures of HTTA (Thenoyltrifluoroacetone) and TBP (Tri-n-butylphosphate)

Abstract The results obtained on the extraction of Np(IV) into mixtures of HTTA and TBP by solvent extraction and spectrophotometric methods are reported here. The predominant extractable species, when perchloric acid was employed for extraction, was found to be Np(TTA)4·TBP when benzene was used as the solvent and probably Np(TTA)3·3TBP+ClCO4 when nitrobenzene was used as the solvent. On the other hand, when nitric acid was employed for the extraction into a benzene solution of the mixture, a number of extractable species, Np(NO3)4-x (TTA) x ·yTBP (x = 0, 1, 2, 3, and 4, and y = 0, 1, and 2), appear to be involved. Values of some equilibrium constants are reported.

Recovery of americium from nitric acid solutions containing calcium by different co-precipitation methods

Recovery of americium from nitric acid solutions was studied by co-precipitation as hydroxide with various ions like calcium, ferric, nickel using sodium hydroxide and ammonium hydroxide. Studies were also carried out to recover americium using lanthanum fluoride and bismuth phosphate co-precipitation. All the methods are able to co-precipitate Am quantitatively. However, co-precipitation of Am with optimum concentration iron using ammonia is found to be better from nitric acid solutions containing large concentrations of calcium ions. Approximately 2 g of Am was recovered from 150 litres of solution batch wise using iron.