Decontamination of uranium oxides from solid wastes by supercritical CO2 fluid leaching method using HNO3–TBP complex as a reactant

Jung

2015

Metals

An environmentally friendly decontamination process for uranium-contaminated soil sand is proposed. The process uses supercritical CO2 as the cleaning solvent and a TBP-HNO3 complex as the reagent. Four types of samples (sea sand and coarse, medium, and fine soil sand) were artificially contaminated with uranium. The effects of the amount of the reagent, sand type, and elapsed time after the preparation of the samples on decontamination were examined. The extraction ratios of uranium in all of the four types of sand samples were very high when the time that elapsed after preparation was less than a few days. The extraction ratio of uranium decreased in the soil sand with a higher surface area as the elapsed time increased, indicating the possible formation of chemisorbed uranium on the surface of the samples. The solvent of supercritical CO2 seemed to be very effective in the decontamination of soil sand. However, the extraction of chemisorbed uranium in soil sand may need additional processes, such as the application of mechanical vibration and the addition of bond-breaking reagents.

Section: Preparation Of the Reagent For Extraction And The Extractionmentioning

confidence: 99%

Decontamination of Uranium-Contaminated Soil Sand Using Supercritical CO2 with a TBP–HNO3 Complex

Jung

2015

Metals

“…Cette méthode présente de nombreux avantages : -diminution des déchets secondaires par la non-utilisation de solvants organiques, -les complexes de métaux extraits sont rapidement et complètement séparés du milieu par gazéification du CO 2, Cependant des études, dans le domaine du nucléaires, sur la décontamination de déchets solides par un fluide supercritique (Meguro et al, 2004 ;Shamsipur et al, 2001 ;Tomioka et al, 2000) ont montrées que, dans la plupart des cas, pour augmenter l'efficacité de cette technique, il fallait ajouter des agents de chélation phosphate de tri-n-butyle (TBP), oxyde de trioctyl phosphine (TOPO)… qui doivent être stables, avec une cinétique rapide, une forte solubilité… Shamsipur et al (2001) augmente la solubilité avec l'augmentation du pouvoir de solvatation par addition de différents solvants organiques polaires appelés modificateurs. L'ajout de ces modificateurs et de ses agents de chélation n'est pas en adéquation avec nos critères puisqu'il y a utilisation de solvants organiques qui devront être retraités.…”

Section: Fluides Supercritiquesunclassified

Comparaison de l’efficacité de quelques procédés de décontamination surfacique

2009

Comparison of the efficiency of several methods of surface decontamination.The study of surface decontamination of radioactive waste packages is an important project for EDF in the context of decommissioning. This study has two objectives: firstly, to reduce dosimetry due to the control of non-contaminated area of radioactive waste packages and secondly to ensure the non-contamination of surface parcels as they are sent to their final destination (treatment site and/or storage). This serves to avoid the suspension and the filling of labile activity in the transport of packages that could lead to locally exceeding the regulatory surface contamination threshold. For that purpose, a bibliographical study of the methods of decontaminations proposed in the literature was made. This study allowed seeing if techniques could answer the chosen criteria. Techniques seeming to be able to answer the requirements were then tested to estimate their efficiency. The bibliographical study and the tries of qualification showed that a method seemed more adapted than the others to our problem.

“…Previously, an opposite pressure effect, which was a decrease of the extraction percentage with an increase of pressure, was observed in the extraction of uranium from UO2 powder 19 and from a sea sand sample contaminated with UO2. 12 The negative-pressure effect resulted from a decrease of activity of the HNO3-TBP complex along with an increase of solvation of the CO2 molecules to the HNO3-TBP complex in the supercritical CO2 phase of higher pressure or higher density. 19 The pressure effect on the uranium extraction consists of that on the reaction of the extractant with the uranium compound and that on the dissolution of a uranium-TBP complex formed by the reaction into the supercritical CO2.…”

Section: Extraction Of Uranium From Uranyl Phosphate Compoundsmentioning

confidence: 99%

“…[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%

“…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 autunite, pitchblende, uraninite, saleeite, zeunerite, torbernite, uranocircite, metazeunerite, and abernathyite, and uranium is formed as a compound like oxide, metal uranyl phosphate, or metal uranyl arsenate in the ores. In the present study, we investigated the extraction behavior of uranium into supercritical CO2 from uranium compounds, prior to developing a SFE method using CO2 of uranium from these uranium ores.…”

mentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2006

Self Cite

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...