共查询到20条相似文献,搜索用时 31 毫秒
1.
A. S. Kanekar P. N. Pathak P. K. Mohapatra V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(3):789-796
Extraction of uranium from tissue paper, synthetic soil, and from its oxides (UO2, UO3 and U3O8) was carried out using supercritical carbon dioxide modified with methanol solutions of extractants such as tri-n-butyl phosphate (TBP) or N,N-dihexyl octanamide (DHOA). The effects of temperature, pressure, extractant/nitric acid (nitrate) concentration, and of hydrogen
peroxide on uranium extraction were investigated. The dissolution and extraction of uranium in supercritical CO2 modified with TBP, from oxide samples followed the order: UO3 ≫ UO2 > U3O8. Addition of hydrogen peroxide in the modifier solution enhanced the dissolution/extraction of uranium in dynamic mode. DHOA
appeared better than TBP for recovery of uranium from different oxide samples. Similar enhancement in uranium extraction was
observed in static mode experiments in the presence of hydrogen peroxide. Uranium estimation in the extracted fraction was
carried out by spectrophotometry employing 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) as the chromophore. 相似文献
2.
S. Biswas P. N. Pathak D. K. Singh S. B. Roy V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):13-19
The extraction of uranium(VI) from nitric acid medium is investigated using 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl
ester (PC88A in dimeric form, H2A2) as extractant either alone or in combination with neutral extractants such as tri-n-butyl phosphate (TBP), trioctyl phosphine oxide (TOPO), and dioctyl sulfoxide (DOSO). The effects of different experimental
parameters such as aqueous phase acidity (up to 10 M HNO3), nature of diluent [xylene, carbon tetrachloride (CCl4), n-dodecane and methyl iso-butyl ketone (MIBK)] and of temperature (303–333 K) on the extraction behavior of uranium were investigated. Synergistic
extraction of uranium was observed between 0.5 and 6 M HNO3. Use of MIBK as diluent was also studied. Temperature variation studies using PC88A as extractant showed exothermic nature
of extraction process. Studies were carried out to optimize the conditions for the recovery of uranium from the raffinate
generated during the purification of uranium from nitric acid medium. Inductively Couple Plasma Atomic Emission Spectroscopy
(ICP-AES) and Energy Dispersive X-Ray Fluorescence (EDXRF) techniques were employed for analysis of uranium in equilibrated
samples. 相似文献
3.
R. K. Singhal P. K. Sharma M. K. T. Bassan H. Basu A. V. R. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(1):149-156
During this work selective separation of uranium from rock phosphate and columbite mineral was done before its quantitative
estimation by using Inductively Coupled Plasma Optical Emission Spectrometery (ICP-OES). Uranium from the rock phosphate and
columubite was extracted by sodium peroxide fusion followed by leaching in 2 M HNO3. To avoid spectral interference in the estimation of uranium by ICP-OES, the selective separation of uranium from the leachate
was carried out by using two different extractants, 30% Tributyl Phophates (TBP) in CCl4 and a equi-volume mixture of Di(2-ethylhexyl) phosphoric acid (D2EHPA) & TBP in petrofin. Uranium was stripped from the organic
phase by using 1 M ammonium carbonate solution. Determination of uranium by ICP-OES was done after dissolving the residue
left after evaporation of ammonium carbonate solution in 4% HNO3. The concentration of the uranium observed in the rock phosphates samples was 40–200 μg g−1 whereas in columbite samples the concentration range was 100–600 μg g−1. Uranium concentration evaluated by ICP-OES was complimented by gamma & alpha spectrometry. Concentration of uranium evaluated
by gamma spectrometry in case of rock phosphate and coulmbite was in close agreement with the uranium content obtained by
ICP-OES. Uranium determination by alpha spectrometry showed only minor deviation (1–2%) from the results obtained by ICP-OES
in case of rock phosphates whereas in case of coulmbites results are off by 20–30%. 相似文献
4.
Sujoy Biswas D. K. Singh K. N. Hareendran J. N. Sharma S. B. Roy 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):201-205
Solvent extraction of U(VI) with di-isodecyl phosphoric acid (DIDPA)/dodecane from nitric acid medium has been investigated
for a wide range of experimental conditions. Effect of various parameters including nitric acid concentration, DIDPA concentration,
temperature, stripping agents, and other impurities like rear earths, transition metal ion, boron, aluminum ion on U(VI) extraction
has been studied. The species extracted in the organic phase is found to be UO2(NO3)(HA2)·H2A2 at lower acidity (<3.0 M HNO3). Increase in temperature lead to the decrease in extraction with the enthalpy change by ∆H = −16.27 kJ/mol. Enhancement in extraction of U(VI) from nitric acid medium was observed with the mixture of DIDPA and tri
butyl phosphate (TBP). The stripping of U(VI) from organic phase (DIDPA–U(VI)/dodecane) with various reagents followed the
order: 4 M H2SO4 > 5% (NH4)2CO3 > 8 M HCl > 8 M HNO3 > Water. High separation factors between U(VI) and impurities suggested that the use of DIDPA for purification of uranium
from multi elements bearing solution. 相似文献
5.
Pai S. A. Shukla J. P. Subramanian M. S. 《Journal of Radioanalytical and Nuclear Chemistry》1982,74(1-2):31-38
The extraction, scrubbing and stripping behaviour of uranium, zirconium and ruthenium with di-n-hexyl and di-n-octyl sulfoxides
in Solvesso-100 and tri-n-butyl phosphate (TBP) in shell Sol-T irradiated by various gamma doses (0–169 Mrads) have been investigated.
2M HNO3 was used for extraction and scrubbing and 0.01M HNO3 for stripping purposes. Results indicate that the extraction of uranium with TBP increases and that with sulfoxide decreases
with dose. This is reflected in their corresponding scrubbing percentages too. The stripping percentage of uranium with TBP
decreases with dose while the reverse is the case with sulfoxide. The extraction of zirconium with TBP increases sharply with
dose as compared to sulfoxides. The extraction scrubbing and stripping of ruthenium remain almost unaffected by dose both
in the case of TBP and sulfoxides. These results lead to much higher overall decontamination factors for uranium with respect
to zirconium as well as ruthenium with irradiated sulfoxides as compared to those with irradiated TBP. 相似文献
6.
A. Aziz S. Jan F. Waqar B. Mohammad M. Hakim W. Yawar 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):117-121
An ion exchange method has been developed for the separation of uranium from trace level metallic impurities prior to their
determination by inductively coupled plasma optical emission spectrometry (ICP-OES) in uranium materials. Selective separation
of uranium from trace level metallic impurities consisting Cr, Co, Cu, Fe, Mn, Cd, Gd, Dy, Ni, and Ca was achieved on anion
exchange resin Dowex 1 × 8 in sulphate medium. The resin (100–200 mesh, in chloride form) was packed in a small Teflon column
(7.8 cm × 0.8 cm I.D.) and brought into sulphate form by passing 0.2 N ammonium sulphate solution. Optimum experimental conditions
including pH and concentration of sulphate in the liquid phase were investigated for the effective uptake of uranium by the
column. Uranium was selectively retained on the column as anionic complex with sulphate, while impurities were passed through
the column. Post column solution was collected and analyzed by ICP-OES for the determination of metallic impurities. Up to
2,500 μg/mL of uranium was retained with >99% efficiency after passing 25 mL sample through the column at pH 3. Percentage
recoveries obtained for most of the metallic impurities were >95% with relative standard deviations <5%. The method established
was applied for the determination of gadolinium in urania–gadolinia (UO2–Gd2O3) ceramic nuclear fuel and excellent results were achieved. Solvent extraction method using tributylphosphate (TBP) as extractant
was also applied for the separation of uranium in urania–gadolinia nuclear fuel samples prior to the determination of gadolinium
by ICP-OES. The results obtained with the present method were found very comparable with those of the solvent extraction method. 相似文献
7.
K. M. Michael G. H. Rizvi J. N. Mathur A. Ramanujam 《Journal of Radioanalytical and Nuclear Chemistry》2000,244(2):355-359
The separation of uranium and plutonium from oxalate supernatant, obtained after precipitating plutonium oxalate, containing ~10 g/l uranium and 30–100 mg/l plutonium in 3M HNO3 and 0.10–0.18M oxalic acid solution has been carried out. In one extraction step with 30% TBP in dodecane: ~92% of uranium and ~7% of Pu is extracted. The raffinate containing the remaining U and Pu is extracted with 0.2M CMPO+1.2 M TBP in dodecane and near complete extraction of both the metal ions is achieved. The metal ions are back extracted from organic phases using suitable stripping agents. The recovery of both the metal ions separately is >99%. The uranium species extracted into the TBP phase from the HNO3+oxalic acid medium was identified as UO2(NO3)2·2TBP. 相似文献
8.
K. V. Chetty P. M. Mapara Rajendra Swarup S. K. Patil 《Journal of Radioanalytical and Nuclear Chemistry》1988,121(1):149-159
The extraction of U(VI) by mixtures of HTTA and TBP from aqueous thiocyanate medium has been studied. From the data obtained it was observed that the predominant uranium species extracted, causing synergic enhancement in the extraction of U(VI), is UO2(SCN)TTA · 2TBP when benzene and cyclohexane are used as diluents, and that at a very low concentration of TBP the contribution of additional species, viz. UO2(TTA)2 · TBP becomes significant. With chloroform as diluent, however, both of these species are contributing to the synergic enhancement. The extraction of a quaternary uranium species, UO2(SCN)TTA · 2TBP, involving the participation of the aqueous anion is thus established. Equilibrium constants for the various extraction equilibria involved are calculated. 相似文献
9.
A. Senol 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(2):361-372
Liquid-liquid extraction of uranium(VI) (UO2
2+) from aqueous acidic (HCl and HNO3) solutions into a co-existing organic phase containing Alamine 308 (triisooctyl amine), TBP (tri-n-butyl phosphate) or CYANEX 302 (bis(2,4,4-trimethylpentyl) monothiophosphinic acid) and diluent (toluene) was studied at isothermal conditions (298.2 K) at aqueous phase acidity varying in the range 0.5-6 mol/dm3. All solvent systems exhibit a maximum distribution ratio restricted in the acidity range 3-4 mol/dm3. An obvious difference in extraction behavior through amine system has been observed for two acids, HCl and HNO3, distinguishing the divergent interactions attributed to the different mechanism of complexation depending on the acidic medium. The high degree of separation of UO2
2+ from HNO3 solution is feasible through a complex formation with extractants ranging in the order CYANEX 302 > TBP > Alamine 308. The results were correlated using various versions of the mass action law, i.e., a chemodel approach and a modified version of the Langmuir equilibrium model comprising the formation of one or at least two U(VI)-extractant aggregated structures. 相似文献
10.
Li Lin Yang Yan-Zhao Zeng Shan Zhu Tao Sun Si-Xiu 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(2):355-359
Summary The synergistic extraction of uranium(VI) from aqueous nitric acid solution with a mixture of tri-n-butyl phosphate (TBP)
and i-butyldodecylsulfoxide (BDSO) in toluene was investigated. The effects of the concentrations of extractant, nitric acid,
sodium nitrate and sodium oxalate on the distribution ratios of uranium(VI) have been studied. The values of enthalpy change
for the extraction reactions with BDSO, TBP and a mixture of TBP and BDSO in toluene were -23.2±0.8 kJ/mol, -29.2±1.4 kJ/mol
and -30.6±0.6 kJ/mol, respectively. It has been found that the maximum synergistic extraction effect occurs when the molar
ratio of TBP to BDSO is close to 1. The composition of the complex of the synergistic extraction is UO2(NO3)2 . BDSO . TBP. 相似文献
11.
Both single stage and multi-stages experiments on stripping plutonium with N,N-dimethylhydroxylamine (DMHAN) as reductant with methylhydrozine (MMH) as supporting reductant were carried out. The effect
of contact time, temperature, acidity, concentration of DMHAN on back-extraction rate of plutonium was investigated in the
single stage experiment. The results demonstrated that the reaction of stripping Pu(IV) in the organic phase (30% TBP–kerosene)
1BF solutions by DMHAN exhibits excellent stripping efficiency. Under the given conditions, the back-extraction rate of plutonium
reaches 90% within 2 min. Higher temperature, lower acidity and the increased concentration of DMHAN benifit the stripping
reaction. The concentration profile of HNO3, uranium and plutonium were determined in a multi-stages mixer-settler after the steady state of the back-extraction, and
the multi-stages results show that the plutonium can be separated effectively from uranium. The recovery of plutonium and
uranium reach 99.995% or over 99.99% respectively. The separation factor of U from Pu (SFPu/U) is about 2 × 104. 相似文献
12.
Yang Yan-Zhao Sun Si-Xiu Yang Yong-Hui Zhang Lei Yu Shao-Ning Bao Bo-Rong 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(1):231-234
The synergic extraction of uranium(VI) from nitric acid solution with petroleum sulfoxides (PSO) and tri-n-butyl phosphate (TBP) mixture has been studied. It has been found that maximum synergic extraction effect occurs if the molar
ratio of PSO to TBP is two to three. The composition of the complex of synergic extraction is UO2(NO3)2·TBP·PSO. The formation constant of the complex isK
PT=8.19. The effect of extractant concentration, nitric acid concentration, salting-out agent concentration and temperature
on the extraction equilibrium of uranium(VI) was also studied. 相似文献
13.
Trofim I. Trofimov Maxim D. Samsonov Yurri M. Kulyako Boris F. Myasoedov 《Comptes Rendus Chimie》2004,7(12):443
Dissolution of individual actinide oxides (Th, U, Pu, Np), or their mechanical mixtures, as well as of solid solutions U–Pu, U–Np, U–Am and U-Pu-Eu oxides in supercritical fluid carbon dioxide (SF-CO2) containing the complex of tri-n-butyl phosphate (TBP) with nitric acid (TBP–HNO3) has been investigated. The effect of the calcination temperature of solid solutions of dioxides on the separation of actinides during supercritical fluid extraction (SFE) has been studied as well. It was shown for the first time that milligram amounts of uranium dioxide could be quantitatively dissolved in (SF-CO2) containing the TBP–HNO3 complex and efficiently separated from Pu, Np, and Th during SFE of mechanical mixture of these oxides. On the contrary, both U and Pu are quantitatively dissolved in SF-CO2–TBP–HNO3 during SFE from solid solutions of U–Pu dioxide. An increase of the calcination temperature of the mixed U(IV)–Pu(IV) dioxide from 850 to 1200 °C has no influence on the relative extraction yield of these actinides during SFE. To cite this article: T. Trofimov et al., C. R. Chimie 7 (2004).
Résumé
Dissolution d’oxides d'actinides et extraction d’éléments dans le dioxide de carbone supercritique contenant le complexe tri-n-butylphosphate–acide nitrique. La dissolution d’oxydes de Th, U, Pu et Np, de leurs mélanges et de solutions solides U–Pu, U–Np, U–Am et U–Pu–Eu dans le dioxyde de carbone supercritique (CO2-SC) contenant le complexe tri-n-butyl phosphate–acide nitrique (TBP–HNO3) a été étudiée, et notamment l’effet de la température de calcination des solutions solides. On montre que quelques milligrammes de UO2 peuvent être dissous dans le système CO2-SC–TBP–HNO3 et être séparés de Pu, Np et Th en traitant un mélange d’oxydes. En revanche, U et Pu sont dissous dans la phase CO2-SC–TBP–HNO3 durant le traitement des solutions solides U(IV)–Pu(IV). Une augmentation de la température de calcination de 850 à 1200 °C de ces solutions solides n’a pas d’effet sur le rendement d’extraction des actinides. Pour citer cet article : T. Trofimov et al., C. R. Chimie 7 (2004). 相似文献14.
S. Perevalov E. Toropchenova 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1613-1618
Microwave-assisted dissolution of ceramic uranium dioxide in tri-n-butyl phosphate (TBP)–HNO3 complex was investigated. The research on dissolution of ceramic uranium dioxide in TBP–HNO3 inclusion complex under microwave heating showed the efficiency of the use of this method. Nitric acid present in the inclusion complex participates both dissolution of UO2, and oxidation of U(IV)–U(VI), the resulting UO2(NO3)2 extracted with tri-n-butyl phosphate. Dissolution rate depends on both temperature of microwave dissolution process, and concentration of nitric acid present in the inclusion complex. The most intensive dissolution process is when the concentration of nitric acid ≥2 mol/L and the temperature of 120 °C. From the experimental data obtained by two kinetic models activation energies were calculated. At the average activation energy of UO2 dissolution in TBP–HNO3 complex equal 70 kJ/mol, and reaction order is close to one, i.e. the reaction takes place in an area close to kinetic. 相似文献
15.
Extraction behavior of 1 × 10−2–0.1 M U(VI) from aqueous phases containing 0.86 M Th(IV) at 4 M HNO3 in 1.1 M tributyl phosphate (TBP) and 1.1 M N,N-dihexyl octanamide (DHOA) solutions in different diluents viz. n-dodecane, 10% 1-octanol + n-dodecane, and decahydronaphthalene (decalin) was studied. Third-phase formation was observed in both the extractants using
n-dodecane as diluent. There was a gradual decrease in Th(IV) concentration in the third-phase (heavy organic phase, HOP) with
increased aqueous U(VI) concentration [0.71 M (no U(VI))–0.61 M (0.1 M U(VI)) for TBP; 0.27 M (no U(VI))–0.22 M (0.1 M U(VI))
for DHOA]. The HOP volume in case of DHOA was ~2.2 times of that of TBP. Uranium concentration in HOP increased with its initial
concentration in the aqueous phase [from 1.8 × 10−2 M (0.01 M U(VI))–0.162 M (0.1 M U(VI)) for TBP; from 1.4 × 10−2 M (0.01 M U(VI))–0.14 M (0.1 M U(VI)) for DHOA] suggesting that Th(IV) was being replaced by U(VI). An empirical correlation
was developed for predicting the concentrations of uranium and thorium in HOP for both the extractants. No third-phase appeared
during the extraction of uranium and thorium from the aqueous phases employing 10% 1-octanol + n-dodecane, or decalin as diluents, and therefore, were better choices as diluent for alleviating the third-phase formation
during the reprocessing of spent thorium based fuels, and for the recovery of thorium from high-level waste solutions. 相似文献
16.
Jyothi Rajesh Kumar Joon-Soo Kim Jin-Young Lee Ho-Sung Yoon 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):301-308
The present scientific study on uranium(VI) solvent extraction and vanadium(V) separation from sulfate solutions using Alamine
336 as an extractant diluted in kerosene was established. The preliminary experiments indicating the uranium extraction process
will follow the solvation as well as ion-exchange mechanisms. In the present acid region (0.1–1.0 mol dm−3 H2SO4) it showing the ion-exchange type mechanism. Time (1–120 min) and temperature (25–55 °C) not influencing the present extraction
system. Other experimental parameters like loading capacity of Alamine 336, stripping of uranium from loaded organic phase,
recycling of Alamine 336 and separation of uranium(VI)/vanadium(V) was studied. 相似文献
17.
Model studies on TBP—diluent—aqueous HNO3 extraction systems were performed to establish the mechanism of emulsyfying during the reprocessing of spent reactor fuel
with mixtures of TBP solutions. The systems of interest were emulsified under fixed conditions. The rate of separation of
the primary emulsion as well as the turbidity of each phase were determined. The experiments were performed on mixtures of
pure components of the extraction systems. Emulsion stability was investigated in terms of the influence of such factors as
main products of TBP decay, the type of diluents, HNO3 concentration and concentration of TBP in different diluents. 相似文献
18.
Liu Wen-Tao Zeng Shan Yang Yan-Zhao Han Jian Zhu Tao Luo Chang-Hong 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(2):315-317
The i-butyldodecylsulfoxide (BDSO) was synthesized. The extraction of uranium(VI) has been carried out with BDSO in toluene from various HNO3 concentrations. It was found that the distribution ratio increases with increasing nitric acid concentration up to 3.0 mol/l and then decreases. The distribution ratios also increase with increasing extractant concentration. The extracted species appears to be UO2(NO3)2·2BDSO and the equilibrium constant value is 15.2. The influence of temperature, sodium nitrate and oxalate concentrations on the extraction was also investigated, and the thermodynamic functions of the extraction reaction were obtained.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
19.
E. S. Stoynov V. A. Mikhailov V. G. Torgov T. V. Us 《Journal of Structural Chemistry》1994,35(6):809-816
This paper reprots of31P NMR and IR studies of the interaction of tributyl phosphate (TBP) and di-n-octyl sulfoxide (DOSO) with polymer molecules
of uranyl di-2-ethylhexyl phosphate (UO2X2)p (I) in C6H6 sulutions. Detailed interpretations of the31P NMR spectra and the vas(POO) IR bands and determination of the fraction of nonequivalent phosphorus atoms of X− anions and uranium (VI) atoms as well as the concentration of U(VI)-bonded TBP in I have shown that only a single TBP or
DOSO molecule is coordinated to the uranium atoms of polymer I at CTBP=0.1–2 M or CDOSO=0.1–0.5 M. In the case of 100% TBP, two TBP molecules are coordinated to some U(VI) atoms. Distribution of TBP (DOSO) molecules
along the polymer chain agrees with the mean statistical value. The portion of terminal chalate POO-groups of X− anions is determined. The dependence of the degree of (UO2X2)p·nL (L=TBP, DOSO) polymerization on CL is obtained. Saturation of solutions with water only slightly affects the terminal POO-groups and has no effects on the distribution
of L along the polymer chain of I.
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 66–73, November–December, 1994.
Translated by K. Shaposhnikova 相似文献
20.
M. Eskandari Nasab 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1739-1747
The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272 or HA), and synergistic extractants (S) such as tri-butylphosphate (TBP), tri-octylphosphine oxide (TOPO) or bis(2,4,4-trimethylpentyl)thiophosphinic acid (Cyanex301). The results showed that these metallic ions are extracted into kerosene as Th(OH)2(NO3)A·HA and UO2(NO3)A·HA with Cyanex272 alone. In the presence of neutral organophosphorus ligands TBP and TOPO, they are found to be extracted as Th(OH)2(NO3)A·HA·S and UO2(NO3)A·HA·S. On the other hand, Th(IV), U(VI) are extracted as Th(OH)2(NO3)A·HA·2S and UO2(NO3)A·HA·S in the presence of Cyanex301. The addition of neutral extractants such as TOPO and TBP to the extraction system enhanced the extraction efficiency of both elements while Cyanex301 as an acidic extractant has improved the selectivity between uranium and thorium. The effect of TOPO on the extraction was higher than other extractants. The equilibrium constants of above species have been estimated by non-linear regression method. The extraction amounts were determined and the results were compared with those of TBP. Also, it was found that the binding to the neutral ligands by the thorium–Cyanex272 complexes follows the neutral ligand basicity sequence. 相似文献