Complexation and Transport of Uranyl Nitrate in Supercritical Carbon Dioxide with Organophosphorus Reagents

Toews, Karen L.; Smart, Neil G.; Wai, Chien M.

doi:10.1524/ract.1996.75.4.179

Cited by 42 publications

(37 citation statements)

References 11 publications

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“…[1][2][3][4][5][6][7][8] Among these studies, a method has been studied in which decladded spent fuels are "directly" treated by the supercritical fluid, a single-phase mixture of HNO3, H2O and tri-n-butylphosphate (TBP) in supercritical carbon dioxide (SC-CO2). [9][10][11] Here, "directly" means "without a dissolution process".…”

Section: Introductionmentioning

confidence: 99%

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

et al. 2006

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Several studies have been performed to extract actinides from the spent nuclear fuels using supercritical fluids. [1][2][3][4][5][6][7][8] Among these studies, a method has been studied in which decladded spent fuels are "directly" treated by the supercritical fluid, a single-phase mixture of HNO3, H2O and tri-n-butylphosphate (TBP) in supercritical carbon dioxide (SC-CO2). [9][10][11] Here, "directly" means "without a dissolution process". For the decladding process, the spent fuel is treated thermally in air and is pulverized by the stress of the swelling through oxidation of UO2 to U3O8 during the cladding. Uranium and plutonium in the solid fuel can be directly extracted into the supercritical fluid. The single-phase mixture of HNO3, H2O and TBP in SC-CO2 is reactive with U3O8. 8,12,13 As a result of the reaction, the uranium oxide is converted into UO2(NO3)2 and extracted as UO2(NO3)2·2TBP in the supercritical fluid. The dissolution and extraction simultaneously proceed in this series of reactions. Because uranium and plutonium are extracted from the spent fuel into the supercritical fluid, the fission products in the spent fuel can remain as solids. Therefore, the direct extraction can decrease the amount of secondary radioactive wastes by omitting the acid dissolution processes, which usually generates a large amount of highly radioactive liquid waste. This technique investigated in these studies can be useful for analytical purposes, because the minimization of the waste solution in the chemical analyses for process management becomes very important in spent nuclear fuel reprocessing plants.In an extraction process for nuclear fuel reprocessing, a higher extraction capacity and higher decontamination ability are desirable. For the former, the contact time of the spent fuel and supercritical fluid is long enough, over 2 min, and an equivalent extraction capacity for the TBP complex is expected. 9 For the decontamination nature, which is more sensitive to the chemical conditions during the direct extraction, we performed some experiments to evaluate the decontamination nature of the direct extraction process using a single-phase mixture of HNO3, H2O and TBP in SC-CO2. Prior to the experiments under high pressure, we performed the experiments at ambient pressure without SC-CO2 in order to determine the effect of SC-CO2 on the decontamination. Experimental ChemicalsAs simulated materials for the spent fuel, we prepared a mixture of U3O8 and metal or metal oxides as the fission products. The composition of the simulated fuel used in our experiments is as follows: U3O8 (92.22), SrO (0.40), ZrO2 (0.85), MoO3 (1.15), RuO2 (0.99), Pd (0.85), CeO2 (1.38) and Nd2O3 (2.16). The values in parentheses indicate the weight fraction of each chemical. The fraction of each element was proportional to the calculated results based on the ORIGEN-II computer code for PWR fuel of 45000 MWd t -1 . Based on the condition of the elements in the spent nuclear fuel, SrO, ZrO2, MoO3, RuO2, Pd, CeO2 and Nd2O3 were selected; these were...

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Section: Introductionmentioning

confidence: 99%

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

et al. 2006

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“…[2][3][4][5][6][7][8][9] It is particularly worth noting that an alternative and more attractive method of supercritical CO2 technology is "direct leaching" of metals from solid samples by utilizing a large penetration force and high diffusivity of supercritical CO2 into the solids. [9][10][11][12][13][14][15][16][17][18] In order to extract uranium from radioactive wastes, the authors have developed a novel extraction method, 12 in which supercritical CO2 containing a reactant is used as a medium to dissolve metal compounds involved in a solid matrix. It was demonstrated that the method using a nitric acid-tri-n-butyl phosphate (HNO3-TBP) complex as an extractant was applicable to the extraction of uranium from simulated radioactive waste samples contaminated by uranium oxides.…”

Section: Introductionmentioning

confidence: 99%

Extraction of Uranium from Simulated Ore by the Supercritical Carbon Dioxide Fluid Extraction Method with Nitric Acid-TBP Complex

et al. 2006

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Uranium used for the uranium fuel of nuclear power plants is obtained from uranium ores having relatively high uranium content by extraction and separation. However, generally utilized ores, such as monazite, phosphate rock, and titanium ore, are not uranium ores, but include a small amount of uranium. In order to determine uranium content in these ores, uranium is first separated out by leaching ores with mineral acids, and then uranium in the leaching solution is determined by inductively coupled plasma mass spectrometry (ICP-MS). The accuracy of this method is not very high due to a large resultant leaching solution and various associated impurities. Therefore, it is very important to develop a novel and selective uranium separation method from the ores, in which separation processes are simple and wastes are less generated, for ensuring that the analysis of uranium in ores is of high accuracy.Supercritical fluid extraction (SFE) using CO2 as a medium has been widely and practically utilized for the extraction and separation of useful materials in many industries, such as food, medicine, and cosmetic. Recently, much attention has been paid to a separation technology of metals involving SFE using CO2. 1 Several methods of SFE using CO2 as a medium were developed for the separation of metal ions from an aqueous solution using supercritical CO2 instead of an organic solvent. [2][3][4][5][6][7][8][9] It is particularly worth noting that an alternative and more attractive method of supercritical CO2 technology is "direct leaching" of metals from solid samples by utilizing a large penetration force and high diffusivity of supercritical CO2 into the solids. [9][10][11][12][13][14][15][16][17][18] In order to extract uranium from radioactive wastes, the authors have developed a novel extraction method, 12 in which supercritical CO2 containing a reactant is used as a medium to dissolve metal compounds involved in a solid matrix. It was demonstrated that the method using a nitric acid-tri-n-butyl phosphate (HNO3-TBP) complex as an extractant was applicable to the extraction of uranium from simulated radioactive waste samples contaminated by uranium oxides. 12,18 This extraction method is for the direct separation and recovery of metals from a solid sample without using any acid leaching, and shows several attractive properties, as follows: (i) the extraction efficiency and rate are enhanced due to the large penetration force and rapid diffusion of supercritical CO2, (ii) rapid and complete recovery of the extracted substances from the CO2 medium is attained by the gasification of CO2, (iii) the extraction system is easily expanded based on substantial experiences of SFE in general industry, such as the food industry, (iv) the generation of wastes from the process is totally minimized and (v) a solid sample after the extraction treatment is in the form of a dried solid that does not contain an appreciable quantity of an organic reactant and acid.There are many ores that are known as uranium including ores, such as autun...

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“…Supercritical fluid extraction (SFE) using an extractant-supercritical CO 2 mixture instead of an extractant-organic solvent mixture has recently been recognised to be promising as an advanced method for separation of metals from liquid samples or even from solid samples for the purpose of analytical pretreatment or hydrometallurgy. Hence, an increasing number of studies on the development of SFE of metals (Laintz and Tachikawa, 1994;Furton et al, 1995;Iso et al, 1995;Lin et al, 1995;Meguro et al, 1996;Toews et al, 1996;Wang and Wai, 1996;Smart et al, 1997) are available. One of several important advantages of SFE is that extraction efficiency and extraction selectivity can be enhanced by tuning the pressure and/or temperature.…”

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confidence: 99%

A novel equation of state (EOS) for prediction of solute solubility in supercritical carbon dioxide: Experimental determination and correlation

et al. 2009

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Solubility data of organophosphorous metal extractants in supercritical fluids (SCF) are crucial for designing metal extraction processes. We have developed a new equation of state (EOS) based on virial equation including an untypical parameter as BP/RT, reduced temperature and pressure for prediction of solute solubility in supercritical carbon dioxide (SC CO 2 ). Solubility experimental data (solubility of tributylphosphate in SC CO 2 ) were correlated with the two cubic equations of state (EOS) models, namely the Peng-Robinson EOS (PR-EOS) and the Soave-Redlich-Kwong EOS (SRK-EOS), together with two adjustable parameter van der Waals mixing and combining rules and our proposed EOS. The AARD of our EOS is significantly lower than that obtained from the other EOS models. The proposed EOS presented more accurate correlation for solubility data in SC CO 2 . It can be employed to speed up the process of SCF applications in industry.Les données de solubilité d'extractants de métaux organo-phosphorés dans des fluides supercritiques (FSC) sont cruciales pour concevoir des processus d'extraction des métaux. Nous avons développé une nouvelleéquation d'état (ÉÉ) basée sur uneéquation d'état du viriel comprenant un paramètre atypique tel que la température et la pression réduite pour la prédiction de la solubilité du soluté dans du dioxyde de carbone supercritique. Les données expérimentales de solubilité (solubilité du phosphate de tributyle dans CO 2 SC) ontété corrélées avec les deux modèles d'équations d'état cubiques, soit l'ÉÉ Peng-Robinson (ÉÉ-PR) et l'ÉÉ Soave-Redlich-Kwong (ÉÉ-SRK), avec deux paramètres ajustables, les règles de mélange et de combinaison van der Waals et notreÉÉ proposée. L'AARD de notreÉÉ est significativement plus faible que celui obtenuà partir des autres modèles d'ÉÉ. L'ÉÉ proposée présentait une corrélation plus exacte pour les données de solubilité dans le CO 2 SC. Elle peutêtre employée pour accélérer les processus des applications de FSC dans l'industrie.

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Complexation and Transport of Uranyl Nitrate in Supercritical Carbon Dioxide with Organophosphorus Reagents

Cited by 42 publications

References 11 publications

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO3 and H2O in Supercritical CO2

Extraction of Uranium from Simulated Ore by the Supercritical Carbon Dioxide Fluid Extraction Method with Nitric Acid-TBP Complex

A novel equation of state (EOS) for prediction of solute solubility in supercritical carbon dioxide: Experimental determination and correlation

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