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  • Author or Editor: R. Pathak x
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Abstract  

Thorium was extracted from a mixture of nitric acid and NaNO3 of 0.01M each at pH 2.2 on a column of silica gel coated with TOPO. Thorium was separated from alkalis, alkaline earths, chromium, iron, cobalt, nickel, zinc, cadmium, mercury, lead, trivalent rare earths, platinum group metals, chloride, phosphate and acetate in binary mixtures by selective extraction of thorium. Thorium was separated from cerium (IV), zirconium, uranium and molybdenum by selective elution of thorium with 0.01M H2SO4. The method was extended for the analysis of thorium in monozite ore.

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Summary  

The complexation behavior of Ni2+with ortho-silicic acid (o-SA) has been studied as a function of ionic strength (I) from 0.20 to 1.00M (NaClO4) at pcH 4.55±0.05 and 25 °C by a solvent extraction technique with bis(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stoichiometry of the extracted species was determined to be Ni(DEHP)2(HDEHP)2. Ni2+forms a 1:1 complex, Ni(OSi(OH)3)+, as the predominant species withconcentrations of 1.00. 10-3to 1.00. 10-2M o-SA. The stability constant (logb1) values for Ni(OSi(OH)3)+complex formation decrease with increased ionic strength. These values have been fitted with the extended Debye-Huckel expression to obtain the value of logb1=6.34±0.03 at I=0.00M. The data allowed the calculation of speciation of the Ni2+- silicate system as a function of ionic strength.

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Abstract  

The distribution behavior of uranium and thorium has been investigated in a biphasic system of different aqueous nitric acid concentrations and a solution of tris(2-ethylhexyl) phosphate (TEHP) inn-dodecane at 25°C. The effect of different uranium and thorium concentrations in the aqueous phase on the extraction of these metal ions is evaluated. These results indicate that TEHP is a better choice than tri-n-butyl phosphate (TBP) for the separation of233U from the irradiated thorium matrix.

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Summary  

Sorption of nickel, Ni2+, on SiO2 . xH2O (silica gel) has been studied as a function of time conditions: amount of silica gel: 0.10-1.00 g, nickel concentration: 5.00 . 10-5-1.20 . 10-3M, ionic strength: 0.20-1.40M NaClO4, pH 6.50 to 8.50, and temperature 273-318 K. From the kinetic data, the diffusion coefficient of Ni2+ ion was calculated to be 1.28(±0.07) . 10-11 m2 . s-1 under particle diffusion-controlled conditions. The sorption rate was determined as 3.79(±0.35) . 10-3 s-1 at 298 K, pH 8.40 in 0.20M (NaClO4). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Nickel sorption on 0.20 g silica gel decreased with ionic strength from 77.70±0.70% (0.20M NaClO4) to 16.12±0.37% (1.40M NaClO4) at intial pH of 8.50±0.05. A gradual decrease in pH with increasing ionic strength suggests an ion exchange mechanism and the sorption of Ni2+ on silica gel increasing with temperature indicates an endothermic enthalpy. The effect of different ligands such as fluoride, carbonate, phosphate and oxalate on Ni2+ sorption on silica gel was studied.

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Summary  

The complexation behavior of Co2+with ortho-silicic acid (o-SA) has been studied as a function of ionic strength (I) from 0.20 to 1.00M (NaClO4) at pH 4.96±0.03 and 25 °C by solvent extraction with bis(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stoichiometry of the extracted species was determined to be Co(DEHP)2(HDEHP)2. Co2+forms a 1:1 complex, CoOSi(OH)3 +, as the predominant species witho-SA concentrations of 3.00. 10-4to 4.00. 10-3M. The stability constant (logb1) values for CoOSi(OH)3 +complex decrease with the increase in ionic strength. These values were fitted with the extended Debye-Huckel expression to obtain the value of logb1at I=0.00M. The effect of aging time of the o-SA solution on logb1values for CoOSi(OH)3 +complex was investigated and compared with those of the UO2OSi(OH)3 +complex.

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Вводится продолжение функцио налов с пространства на , гдеc kb k. Такие функционалы ха рактеризуются в терм инах их роста на бесконечнос ти. Исследуется также пр одолжение функциона лов в пространстве мульти пликаторов. Накладываются разли чные условия роста го ломорфных функций в трубчатых областях и исследует ся рост соответствую щих специальных функций.

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Вводятся два простра нства тест-функцийH μ,M,a иH μ,b Ω. Изучаются их счетные объеди-нения — пространстваH μ,M иH μ Ω. Р ассматриваются топологические и алг ебраические свойства этих простр анств. Доказано, что преобразование Ганк еляH μ,μ≧−1/2, является изоморфизмом изH μ,H,a наH μ Ω,1/a и и изH μ,M наH μ Ω. Строится операционное исчисл ение, которое применяется для решения одной обо бщенной граничной задачи.

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Summary  

Sorption behavior of europium, Eu3+, on SiO2 . xH2O (silica gel) has been investigated as a function of time, the amount of silica gel, Eu3+ concentration, the ionic strength, and pH (in absence and in presence of carbonate). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity of silica gel was determined to be in the range of (2.62-8.00) . 10-7 mol/g at pH 5.30±0.05 and 0.20M NaClO4. The mean energy of sorption was calculated to be 13.50±0.05 kJ/mol from the D-R isotherm, suggesting the involvement of ion-exchange reactions in the sorption process. Sorption of Eu3+ decreased with increased ionic strength. A gradual decrease in pH with increased ionic strength supports the involvement of an ion-exchange mechanism in the sorption process. The diffusion coefficient of Eu3+ ion on silica gel was calculated as (3.98±0.12) . 10-13 m2 . s-1 under the particle diffusion-controlled conditions.

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Abstract  

Porous zirconia spherical particles have been prepared by internal gelation process. During preparation of these spherical particles, a cationic surfactant, cetrimide was added in the feed broth to increase the surface area and porosity of the particles. The sorption behavior of plutonium was investigated on this material from different complexing aqueous media from the recovery point of view. Distribution ratio studies have been carried out to investigate the effect of varying concentrations of oxalic acid, phosphoric acid, sulphuric acid, nitric acid, sodium carbonate and sodium bicarbonate to optimize the conditions of sorption of plutonium on this ion exchange material.

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Abstract  

The paper aims to investigate cytogenetic and apoptotic responses of γ-irradiation in a radio-resistant cell strain designated as M5. Induced micronuclei, chromosomal aberrations, nuclear fragmentation and nucleosomal ladders by γ-irradiation were less at equal doses in M5 cells in comparison with that obtained in the parental Chinese hamster V79 cells. However, at equal survival, there were no differences in the end points studied. Results indicate that the residual damages that lead to reproductive cell death also resulted in the cytogenetic and apoptotic responses. We speculate that the repair efficiency in M5 cells was more efficient and increased DNA repair could be the cause of radiation resistance observed in M5 cells.

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