Further study of extraction equilibrium of uranium(VI) with dicyclohexano-18-crown-6 and its application to separating uranium and thorium

International Nuclear Information System (INIS)

Wang Wenji; Sun Qing; Chen Bozhong

1987-01-01

The extraction equilibrium of uranium(VI) from aqueous hydrochloric acid solution with dicyclohexano-18-crown-6 isomer A (Ia) and isomer B (Ib) in 1,2-dichloroethane is presented. The extracted species are found to be 1:2 (metal/crown) for Ia and 2:3 for Ib from slope analysis and direct determination of extracted complexes. The extraction equilibrium constants (Kex) were determined at 25 deg C, and were equal to 29.5 for the former and 0.208 for the latter. It is concluded that Ia has stronger coordinate ability for uranium than Ib. The method is effective and selective. The results can be used for the separation of uranium and thorium. (author)

Investigation of uranium (VI) extraction mechanisms from phosphoric and sulfuric media by {sup 31}P-NMR

Energy Technology Data Exchange (ETDEWEB)

Fries, B.; Marie, C.; Pacary, V.; Berthon, C.; Miguirditchian, M.; Charbonnel, M.C. [CEA, Centre de Marcoule, Nuclear Energy Divison, RadioChemistry and Processes Department - DRCP, F-30207 Bagnols-sur-Ceze (France); Mokhtari, H. [AREVA Mines, Process and Analysis Department - SEPA, F-87250 Bessines-sur-Gartempe (France)

2016-07-01

Phosphate rocks contain uranium (∼1000 ppm on average) and are considered as a secondary source for uranium production. Uranium extraction using DEHCNPB (butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid, a bifunctional cationic extractant) has been studied to better understand mechanism differences depending on the original acidic solution (phosphoric or sulfuric). Solvent extraction batch experiments were carried out and the organic phases were probed using {sup 31}P-NMR. This technique enabled to demonstrate that phosphoric acid is poorly extracted by DEHCNPB ([H{sub 3}PO{sub 4}]{sub org} < 2 mM), using direct quantification in the organic phase by {sup 31}P-NMR spectra integration. Moreover, in the presence of uranium in the initial phosphoric acid solution, uranyl extraction by DEHCNPB competes with H{sub 3}PO{sub 4} extraction. Average stoichiometries of U(VI)-DEHCNPB complexes in organic phases were also determined using slope analysis on uranium distribution data. Uranium seems to be extracted from a phosphoric medium by two extractant molecules, whereas more than three DEHCNPB on average would be necessary to extract uranium from a sulfuric medium. Thus, uranium is extracted according to different mechanisms depending on the nature of the initial solution. (authors)

Extraction of uranium(VI) by emulsion liquid membrane containing 5,8-diethyl-7-hydroxy-6-dodecanone oxime

International Nuclear Information System (INIS)

Akiba, Kenichi; Takahashi, Toshihiko; Kanno, Takuji

1984-01-01

Extraction of uranium(VI) by a liquid surfactant membrane has been studied. The stability of water-in-oil (w/o) emulsion dispersed in the continuous aqueous phase increased with an increase in surfactant concentrations and in the fraction of the organic phase in emulsion globules. Uranium(VI) in dilute acid solutions was extracted into (w/o) emulsions containing 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63) as a mobile carrier and its concentration decreased according to [U]sub(t)=[U]sub(o)exp(-ksub(obsd)t). The apparent rate constants (ksub(obsd)) increased with an increase in carrier concentrations and in external pH values, while they were slightly dependent on the stripping acid concentrations. Uranium was transported and concentrated into the internal aqueous droplets. The final concentration of uranium in the external aqueous phase dropped to about 10 -3 of its initial value. (author)

Oxidation-extraction of uranium from wet-process phosphoric acid

International Nuclear Information System (INIS)

Lawes, B.C.

1985-01-01

The invention involves an improvement to the reductive stripping process for recovering uranium values from wet-process phosphoric acid solution, where uranium in the solution is oxidized to uranium (VI) oxidation state and then extracted from the solution by contact with a water immiscible organic solvent, by adding sufficient oxidant, hydrogen peroxide, to obtain greater than 90 percent conversion of the uranium to the uranium (VI) oxidation state to the phosphoric acid solution and simultaneously extracting the uranium (VI)

Impact of the uranium (VI) speciation in mineralised urines on its extraction by calix[6]arene bearing hydroxamic groups used in chromatography columns.

Science.gov (United States)

Baghdadi, S; Bouvier-Capely, C; Ritt, A; Peroux, A; Fevrier, L; Rebiere, F; Agarande, M; Cote, G

2015-11-01

Actinides determination in urine samples is part of the analyses performed to monitor internal contamination in case of an accident or a terrorist attack involving nuclear matter. Mineralisation is the first step of any of these analyses. It aims at reducing the sample volume and at destroying all organic compounds present. The mineralisation protocol is usually based on a wet ashing step, followed by actinides co-precipitation and a furnace ashing step, before redissolution and the quantification of the actinides by the appropriate techniques. Amongst the existing methods to perform the actinides co-precipitation, alkali-earth (typically calcium) precipitation is widely used. In the present work, the extraction of uranium(VI), plutonium(IV) and americium(III) from the redissolution solutions (called "mineralised urines") on calix[6]arene columns bearing hydroxamic groups was investigated as such an extraction is a necessary step before their determination by ICP-MS or alpha spectrometry. Difficulties were encountered in the transfer of uranium(VI) from raw to mineralised urines, with yield of transfer ranging between 0% and 85%, compared to about 90% for Pu and Am, depending on the starting raw urines. To understand the origin of such a difficulty, the speciation of uranium (VI) in mineralised urines was investigated by computer simulation using the MEDUSA software and the associated HYDRA database, compiled with recently published data. These calculations showed that the presence of phosphates in the "mineralised urines" leads to the formation of strong uranyl-phosphate complexes (such as UO2HPO4) which compete with the uranium (VI) extraction by the calix[6]arene bearing hydroxamic groups. The extraction constant of uranium (VI) by calix[6]arene bearing hydroxamic groups was determined in a 0.04 mol L(-1) sodium nitrate solution (logK=4.86±0.03) and implemented in an extraction model taking into account the speciation in the aqueous phase. This model allowed to

A study of the direct spectrophotometric determination of uranium (VI) in trialkylamine extracts with 2-(5-bromo- 2-pyridylazo)-5-diethylaminophenol

International Nuclear Information System (INIS)

Lyle, S.J.; Tamizi, M.

1979-01-01

A straightforward spectrophotometric method is described for the determination of uranium (VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to back extraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors. (Auth.)

Preparation of 1-(2-pyridylazo)-2-naphthol functionalized benzophenone/naphthalene and their uses in solid phase extractive preconcentration/separation of uranium(VI)

International Nuclear Information System (INIS)

Preetha, C.R.; Prasada Rao, T.

2003-01-01

The preparation of solid reagent 1-(2-pyridylazo)-2-naphthol functionalized benzophenone/naphthalene for preconcentration/separation of uranium(VI) is described. These reagents enriches uranium(VI) quantitatively from dilute aqueous solutions in the pH range 10.5-11.0. The solid mixture consisting of the enriched metal ion along with solid phase extractant were dissolved in 2 ml of acetone and uranium(VI) content was established spectrophotometrically by using Arsenazo III procedure. Calibration graphs were rectilinear over the uranium(VI) concentration in the range 0.002-0.1 μg cm -3 . Five replicate determinations of 40 μg of uranium present in 1 dm 3 of sample solution gave a mean absorbance of 0.185 with a relative standard deviation of 1.4%. The detection limit (corresponding to 3 times the standard deviation of the blank) and the enrichment factor were found to be 2 μg dm -3 and 500 respectively. Further the possible separation of uranium(VI) from several bivalent, trivalent and tetravalent elements was also established. In addition to validating the developed method by successfully analysing marine sediment reference material (MESS-3), uranium content was established in soil, river and marine sediment samples by the developed method and compared with standard inductively coupled plasma mass spectrometry (ICP-MS) values. (orig.)

Extraction of uranium (VI) sulphate complexes by Adogen amines

Energy Technology Data Exchange (ETDEWEB)

Elyamani, I S; Abd Elmessieh, E N [Nuclear chemistry department, hot laboratories center, atomic energy authority, Cairo, (Egypt)

1995-10-01

The distribution of U(VI) between aqueous H{sub 2} So{sub 4} solutions and organic phases of adogen-368 has been described. The dependence of extraction on acidity, diluent type, metal and extractant concentrations was investigated. The possible extraction mechanism is discussed in the light of results obtained. The separation of U(VI) from rare earths is suggested. 5 figs., 1 tab.

Determination of small amounts of nitric acid in the presence of large amounts of uranium (VI) and extraction of nitric acid into TBP solutions highly loaded with uranyl nitrate

International Nuclear Information System (INIS)

Kolarik, Z.; Schuler, R.

1982-10-01

A new method for the determination of small amounts of nitric acid in the presence of large amounts of uranium(VI) was elaborated. The method is based on the precipitation of uranium(VI) as iodate and subsequent alkalimetric titration of the acid in the supernatant. The extraction of nitric acid and uranium(VI) with 30% TBP in dodecane was studied at high loading of the organic phase with uranyl nitrate and at 25, 40 and 60 0 C. The results are compared with available published data on the extraction of nitric acid under similar conditions. (orig.) [de

Uranium(VI) adsorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety

International Nuclear Information System (INIS)

Matsuda, Masaaki; Akiyoshi, Yoshirou

1991-01-01

Uranium(VI) adsorption and desorption properties of a chelating resin containing polyamine-substituted methylphosphonic acid moiety of 2.29 mmol/g-resin (APA) were examined. Uranium(VI) adsorption properties of several ion exchange resins and extractant agents which were known as excellent adsorbents for uranium(VI), were examined together for a comparison with those of APA. Uranium(VI) adsorption capacity of APA at the concentration of 100 mg·dm -3 -uranium(VI) in 100 g·dm -3 -H 2 SO 4 aq. soln., 190 g·dm -3 -H 3 PO 4 aq. soln. and uranium enriched sea water, was 0.2, 0.05 and 0.05 mmol·g -1 respectively. The adsorption capacity of APA for uranium(VI) in these solutions was larger than that of another adsorbents, except the adsorption of uranium(VI) in enriched sea water on ion exchange resin containing phosphoric acid moiety (adsorption capacity ; 0.2 mmol·g -1 ). Uranium(VI) adsorption rate on APA was high and the relation between treatment time (t : min) and uranium(VI) concentration (y : mg·dm -3 ) in 100 g·dm -3 H 2 SO 4 aq. soln. after treatment, was shown as following equation, y=20 0.048t+1.90 (0≤t≤30). The adsorbed uranium(VI) on APA was able to be eluted with a mixed aq. soln. of hydrogen peroxide and sodium hydroxide and also was able to be eluted with an aq. alkaline soln. dissolved reduction agents such as sodium sulfite and hydrazine. From these results, it was thought that uranium(VI) adsorbed on APA was eluted due to the reduction to uranium(VI) by these eluents. (author)

Uranium(VI) speciation by spectroscopy

International Nuclear Information System (INIS)

Meinrath, G.

1997-01-01

The application of UV-Vis and time-resolved laser-induced fluorescence (TRLF) spectroscopies to direct of uranium(VI) in environmental samples offers various prospects that have, however, serious limitations. While UV-Vis spectroscopy is probably not sensitive enough to detect uranium(VI) species in the majority of environmental samples, TRLFS is principially able to speciate uranium(VI) at very low concentration levels in the nanomol range. Speciation by TRLFS can be based on three parameters: excitation spectrum, emission spectrum and lifetime of the fluorescence emission process. Due to quenching effects, the lifetime may not be expected to be as characteristics as, e.g., the emission spectrum. Quenching of U(VI) fluorescence by reaction with organic substances, inorganic ions and formation of carbonate radicals is one important limiting factor in the application of U(VI) fluorescence spectroscopy. Fundamental photophysical criteria are illustrated using UV-Vis and fluorescence spectra of U(VI) hydrolysis and carbonato species as examples. (author)

Liquid-solid extraction of uranium (VI) with TOPO - molten naphthalene and determination by laser fluorimetry in geological samples

International Nuclear Information System (INIS)

Kumar, Sanjay; Krishnakumar, M.; Patwardhan, A.A.

2007-01-01

A simple, rapid, sensitive, cost-effective and efficient method for separation of uranium using tri-n-octylphosphine oxide (TOPO)-molten naphthalene as solid phase extractant and its determination by laser fluorimetry in geological samples (rock, soil, sediment) was developed. Under optimum conditions, using 50 mg TOPO and 100 mg naphthalene, 50 - 5000 ng of uranium in 10 ml sample solution (3% (v/v) HNO 3 ) could be extracted quantitatively. The extracted uranium was stripped using tetra sodium pyrophosphate (5% (v/v) solution, pH adjusted to 7.0 with H 3 PO 4 ) and determined by laser fluorimetry. The influence of different acid concentrations, the amount of solid phase extractant, sample volumes, different stripping reagents, their volumes and effect of foreign ions on the extraction and determination of uranium (VI) were investigated. Synthetic samples of varying concentration as regards uranium were prepared and analysed. Recoveries ranging from 90% to 105% were obtained. The method was validated by analyzing four certified reference materials namely, BL-5, DH-1a, SY-2, SY-3 and the values obtained for uranium agreed well with the certified values. The method was also applied to the determination of uranium in geological samples (rock, soil and sediment) by laser fluorimetry and the results obtained compared favorably with those obtained from the pellet fluorimetry method. Following the proposed method, determination limit for uranium was found to be 1 μg/g with RSD ± 10%. (author)

Solid phase extraction of uranium from phosphoric acid. Kinetic and thermodynamic study

Energy Technology Data Exchange (ETDEWEB)

Abdel-Magied, Ahmed Fawzy [Nuclear Materials Authority, Cairo (Egypt); Stockholm Univ. (Sweden). Dept. of Organic Chemistry

2017-07-01

There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPA-TOPO rate at MCM-41 (mass ratio 2:1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg{sup -1} min{sup -1} calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H{sub 3}PO{sub 4} is an exothermic and spontaneous process.

Solvent extraction of uranium(VI) and thorium(IV) from nitrate media by carboxylic acid amides

International Nuclear Information System (INIS)

Preston, J.S.; Preez, A.C. du

1995-01-01

A series of nineteen N-alkyl carboxylic acid amides (R.CO.NHR') has been prepared, in which the alkyl groups R and R' have been varied in order to introduce different degrees of steric complexity into the compounds. A smaller number of N,N-dialkyl amides (R.CO.NR 2 ') and non-substituted amides (R.CO.NH 2 ) has also been prepared for comparison purposes. These amides were characterized by measurement of their boiling points, melting points, refractive indices and densities. The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate media by solutions of the amides in toluene was studied. Increasing steric bulk of the alkyl groups R and R' was found to cause a marked decrease in the extraction of thorium, with a much smaller effect on the extraction of uranium, thus considerably enhancing the separation between these metals. Vapour pressure osmometry studies indicate that the N-alkyl amides are self-associated in toluene solution, with aggregation numbers up to about 2.5 for 0.6 M solutions at 35 degree C. In contrast, the N,N-dialkyl amides behave as monomers under these conditions. The distribution ratios for the extraction of uranium and thorium show second- and third-order dependences, respectively, on the extractant concentration for both the N-alkyl and N,N-dialkyl amides. 15 refs., 8 figs., 8 tabs

The Effect of pH and Time on the Extractability and Speciation of Uranium(VI) Sorbed to SiO2

International Nuclear Information System (INIS)

Ilton, Eugene S.; Wang, Zheming; Boily, Jean F.; Qafoku, Odeta; Rosso, Kevin M.; Smith, Steven C.

2012-01-01

The effect of pH and contact time on uranium extractability from quartz surfaces was investigated using either acidic or carbonate (CARB) extraction solutions, time-delayed spikes of different U isotopes (i.e., 238U and 233U), and liquid helium temperature time-resolved laser-induced fluorescence spectroscopy (LHeT TRLFS). Quartz powders were reacted with 238U(VI) bearing solutions that were equilibrated with atmospheric CO2 at pH 6, 7, and 8. After a 42 day equilibration period with 238U(VI), the suspensions were spiked with 233U(VI) and reacted for an additional 7 days. Sorbed U was then extracted with either dilute nitric acid or CARB. For the CARB extraction there was a systematic decrease in extraction efficiency for both isotopes from pH 6 to 8. This was mimicked by less desorption of 238U, after the 233U spike, from pH 6 to 8. Further, the efficiency of 233U extraction was consistently greater than that of 238U, indicating a strong temporal component to the strength of U association with the surface that was accentuated with increasing pH. LHeT TRLFS revealed a strong correlation between carbonate extraction efficiency and differences in sorbed U speciation as a function of pH. In contrast, the acid extraction was consistently more efficient than the CARB extraction, with a smaller dependence on both pH and aging time. Collectively, the observations show that aging and pH are critical factors in determining the form and strength of uranium-silica interactions.

Uranium(VI) and ruthenium extraction by dialkyldithio-phosphoric acids

International Nuclear Information System (INIS)

Fitoussi, R.; Musikas, C.

1980-01-01

Oxygen donors like dialkylphosphoric acids are good extractants for actinide ions, but little is known about their sulfur homologs. Investigations of U(VI) and Ru extraction from various aqueous media are reported. This includes extraction of U(VI) from nitric, perchloric, and phosphoric acids by solutions of dialkyldithiophosphoric acids in dodecane or benzene. Extraction of U(VI) by synergistic mixtures, of which at least one of the components is a sulfur donor, has been investigated. The extracted species have been identified, and a comparison with the complexes obtained by extraction with the homologous oxygen donors is made. The sulfur-actinide bond is weaker than the oxygen-actinide one, but in some synergistic extractions the dialkyldithiophosphonates are more efficient than the oxygen donors. In addition to size effects, this behavior could be attributed to the weakness of the hydrogen bonds of the SH groups, which allows a greater variety of the ligands to enter the coordination sphere of the metal. Ruthenium, like the d-transition elements, gives strong bonds with the sulfur donors. However, its extraction from nitric acid is slow. We investigated the influence of several parameters on the distribution coefficients and found that the presence of a reagent which destroys nitrous ions is necessary to achieve quantitative extraction. The role of RuNO groups is also discussed

Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

International Nuclear Information System (INIS)

Martins, Monica; Faleiro, Maria Leonor; Chaves, Sandra; Tenreiro, Rogerio; Santos, Erika; Costa, Maria Clara

2010-01-01

Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L -1 U(VI) and 99% of 13 mg L -1 Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

Anaerobic bio-removal of uranium (VI) and chromium (VI): Comparison of microbial community structure

Energy Technology Data Exchange (ETDEWEB)

Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande 1749-016 Lisboa (Portugal); Santos, Erika [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

2010-04-15

Several microbial communities, obtained from uranium contaminated and non-contaminated samples, were investigated for their ability to remove uranium (VI) and the cultures capable for this removal were further assessed on their efficiency for chromium (VI) removal. The highest efficiency for removal of both metals was observed on a consortium from a non-contaminated soil collected in Monchique thermal place, which was capable to remove 91% of 22 mg L{sup -1} U(VI) and 99% of 13 mg L{sup -1} Cr(VI). This study revealed that uranium (VI) removing communities have also ability to remove chromium (VI), but when uranium (VI) was replaced by chromium (VI) several differences in the structure of all bacterial communities were observed. TGGE and phylogenetic analysis of 16S rRNA gene showed that the uranium (VI) removing bacterial consortia are mainly composed by members of Rhodocyclaceae family and Clostridium genus. On the other hand, bacteria from Enterobacteriaceae family were detected in the community with ability for chromium (VI) removal. The existence of members of Enterobacteriaceae and Rhodocyclaceae families never reported as chromium or uranium removing bacteria, respectively, is also a relevant finding, encouraging the exploitation of microorganisms with new abilities that can be useful for bioremediation.

Antagonism in the extraction of uranium(VI) by the binary mixture of PC88A and benzimidazole

International Nuclear Information System (INIS)

Mukherjee, A.; Kamila, S.; Chakravortty, V.

1999-01-01

Extraction studies of uranium(VI) by the binary mixture of PC88A and benzimidazole show an antagonistic behavior in the concentration range 10 -5 -10 -6 M of PC88A and 0.005M of benzimidazole. Antagonism is observed due to the deprotonation of PC88A by benzimidazole forming an adduct resulting in the virtual removal of PC88A from the system. (author)

Application of Calixarenes as Macrocyclic Ligands for Uranium(VI: A Review

Directory of Open Access Journals (Sweden)

Katarzyna Kiegiel

2013-01-01

Full Text Available Calixarenes represent a well-known family of macrocyclic molecules with broad range of potential applications in chemical, analytical, and engineering materials fields. This paper covers the use of calixarenes as complexing agents for uranium(VI. The high effectiveness of calix[6]arenes in comparison to other calixarenes in uranium(VI separation process is also presented. Processes such as liquid-liquid extraction (LLE, liquid membrane (LM separation, and ion exchange are considered as potential fields for application of calixarenes as useful agents for binding UO22+ for effective separation from aqueous solutions containing other metal components.

Polarographic behaviour of uranium (VI) in tributyl phosphate organic solutions

International Nuclear Information System (INIS)

Degueldre, C.A.; Meklati, M.

1984-01-01

U(VI) determination by D.C. and differential pulse polarography was studied in the organic solutions derived from tributyl phosphate - diluent extracts (after separation from nitric acid media) along with a selected aprotic solvent (i.e.: propylene carbonate and N,N-dimethylacetamide). Miscibility of the TBP-diluent (e.g. cyclohexane, n-hexane, kerosene, n-dodecane) phase with nitric acid as supporting electrolyte, either by addition or already present in the extract was larger in DMA than in PC. In the DMA organic mixture, U(VI) exhibited a DPP peak due to a one electron step, with Esub(p)=-0.4 V (position connected with H 2 O and HNO 3 concentrations). This peak which was proportionnel to the U(VI) concentration from 5x10 -6 to 10 -3 M can be used to determinate directly hexavalent uranium in the industrial organic extraction phases TBP-diluent. (orig.)

The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains

Energy Technology Data Exchange (ETDEWEB)

Pan, Xiaohong; Chen, Zhi [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China); Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen, Fanbing [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China); Cheng, Yangjian [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Lin, Zhang, E-mail: zlin@fjirsm.ac.cn [Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); School of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Guan, Xiong, E-mail: guanxfafu@126.com [Key Lab of Biopesticide and Chemical Biology, Fujian Agriculture and Forestry University, Ministry of Education & Fujian–Taiwan Joint Center for Ecological Control of Crop Pests, Fuzhou, Fujian 350002 (China)

2015-10-30

Highlights: • Indigenous B. thuringiensis exhibited highly accumulation ability to U(VI) in the absence of additional nutrients. • The amorphous uranium compound would transformed into crystalline nano-uramphite by B. thuringiensis. • The chemical nature of formed U-species were monitored. • The cell-free extracts of B. thuringiensis had better uranium-immobilization ability than its cell debris. • Provided the understanding of the uranium transformation mechanism. - Abstract: The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains was investigated in the present work. Our data showed that the bacteria isolated from uranium mine possessed highly accumulation ability to U(VI), and the maximum accumulation capacity was around 400 mg U/g biomass (dry weight). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyzes indicated that the U(VI) was adsorbed on the bacterial surface firstly through coordinating with phosphate, −CH{sub 2} and amide groups, and then needle-like amorphous uranium compounds were formed. With the extension of time, the extracellular crystalline substances were disappeared, but some particles were appeared in the intracellular region, and these particles were characterized as tetragonal-uramphite. Moreover, the disrupted experiment indicated that the cell-free extracts had better uranium-immobilization ability than cell debris. Our findings provided the understanding of the uranium transformation process from amorphous uranium to crystalline uramphite, which would be useful in the regulation of uranium immobilization process.

The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains

International Nuclear Information System (INIS)

Pan, Xiaohong; Chen, Zhi; Chen, Fanbing; Cheng, Yangjian; Lin, Zhang; Guan, Xiong

2015-01-01

Highlights: • Indigenous B. thuringiensis exhibited highly accumulation ability to U(VI) in the absence of additional nutrients. • The amorphous uranium compound would transformed into crystalline nano-uramphite by B. thuringiensis. • The chemical nature of formed U-species were monitored. • The cell-free extracts of B. thuringiensis had better uranium-immobilization ability than its cell debris. • Provided the understanding of the uranium transformation mechanism. - Abstract: The mechanism of uranium transformation from U(VI) into nano-uramphite by two indigenous Bacillus thuringiensis strains was investigated in the present work. Our data showed that the bacteria isolated from uranium mine possessed highly accumulation ability to U(VI), and the maximum accumulation capacity was around 400 mg U/g biomass (dry weight). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyzes indicated that the U(VI) was adsorbed on the bacterial surface firstly through coordinating with phosphate, −CH 2 and amide groups, and then needle-like amorphous uranium compounds were formed. With the extension of time, the extracellular crystalline substances were disappeared, but some particles were appeared in the intracellular region, and these particles were characterized as tetragonal-uramphite. Moreover, the disrupted experiment indicated that the cell-free extracts had better uranium-immobilization ability than cell debris. Our findings provided the understanding of the uranium transformation process from amorphous uranium to crystalline uramphite, which would be useful in the regulation of uranium immobilization process

Extractive separation of uranium(VI) as perchlorate/chloroacetate complexes with 1-phenyl-2,3 dimethyl-5-pyrazolone and its applications

International Nuclear Information System (INIS)

Bose, R.; Murty, D.S.R.

2003-01-01

The extraction of U(VI) with 1-phenyl 2,3 dimethyl-5-pyrazolone, at a pH of 2.5, in the presence of common anions, like perchlorate and tri-, di-, and monochloroacetates has been investigated. The optimum experimental conditions have been evaluated by studying various parameters such as pH, equilibration period, reagent concentration, metal concentration, and solvents. Effect of diverse anions and cations on the extraction has also been studied. The extracted species, determined by log D - log R plots are represented as, [UO 2 (Apy) 4 (ClO 4 ) 2 ], [UO 2 (Apy) 2 (TCA) 2 ], [UO 2 (Apy) 2 (DCA) 2 ], [UO 2 (Apy)(H 2 O)(MCA) 2 ]. The conditional stability constants of the quantitatively extracted complexes are calculated. The proposed method allows the selective separation of uranium(VI) from multicomponent mixtures and geological matrices and is also applied for the separation and chemical characterization of impurities at trace and ultratrace levels. (author)

Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

International Nuclear Information System (INIS)

Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P.

2005-01-01

A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm 3 of 1.0 mol dm -3 HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 μg dm -3 with a relative standard deviation of 2.15% (for 25 μg of uranium(VI) present in 1.0 dm 3 of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

Solvent-extraction and purification of uranium(VI) and molybdenum(VI) by tertiary amines from acid leach solutions

International Nuclear Information System (INIS)

La Gamma, Ana M.G.; Becquart, Elena T.; Chocron, Mauricio

2008-01-01

Considering international interest in the yellow-cake price, Argentina is seeking to exploit new uranium ore bodies and processing plants. A study of similar plants would suggest that solvent- extraction with Alamine 336 is considered the best method for the purification and concentration of uranium present in leaching solutions. In order to study the purification of these leach liquors, solvent-extraction tests under different conditions were performed with simulated solutions which containing molybdenum and molybdenum-uranium mixtures. Preliminary extraction tests carried out on mill acid-leaching liquors are also presented. (authors)

Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

Energy Technology Data Exchange (ETDEWEB)

Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P. [Regional Research Lab. (CSIR), Trivandrum (India)

2005-07-01

A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm{sup 3} of 1.0 mol dm{sup -3} HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 {mu}g dm{sup -3} with a relative standard deviation of 2.15% (for 25 {mu}g of uranium(VI) present in 1.0 dm{sup 3} of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

Extraction and separation studies of uranium(VI) with tris-(2-ethyl hexyl) phosphate

International Nuclear Information System (INIS)

Sundaramurthi, N.M.; Desai, G.S.; Shinde, V.M.

1990-01-01

A solvent extraction method is proposed for the extraction and separation of uranium from salicylate media using tris-(2-ethyl hexyl) phosphate dissolved in xylene as an extractant. The optimum conditions were evaluated from a critical study of pH, salicylate concentration, extractant concentration, period of equilibration and diluent. The method permits the separation of uranium from thorium, cerium, titanium, zirconium, hafnium, copper, vanadium and chromium from binary mixtures and is applicable to the analysis of uranium in synthetic samples. The method is precise, accurate, fast and selective. (author) 5 refs.; 2 tabs

Analytical method of uranium (IV) and uranium (VI) in uranium ores and uranium-bearing rocks

International Nuclear Information System (INIS)

Shen Zhuqin; Zheng Yongfeng; Li Qingzhen; Zhong Miaolan; Gu Dingxiang

1995-11-01

The best conditions for keeping the original valences of uranium during the dissolution and separation procedure of geological samples (especially those micro uranium-bearing rock) were studied. With the exist of high concentration protectants, the sample was decomposed with concentration HF at 40 +- 5 degree C. The U(VI) was dissolved completely and formed stable complex UO 2 F 2 , the U(IV) was precipitated rapidly and carried by carrier. Quantitative separation was carried out immediately with suction. The decomposition of sample and separation of solid/liquid phases was completed within two minutes. After separation, the U(IV) and U(VI) were determined quantitatively with laser fluorescence or voltametry respectively according to the uranium content. The limit of detection for this method is 0.7 μg/g, RSD is 10.5%, the determinate range of uranium is 2 x 10 -6 ∼10 -1 g/g. The uranium contents and their valence state ratio were measured for more than one hundred samples of sand stone and granite, the accuracy and precision of these results are satisfactory for uranium geological research. (12 tabs.; 11 refs.)

MODELING OF THE SOLVENT EXTRACTION EQUILIBRIUM OF URANIUM (VI SULFATE WITH ALAMINE 336

Directory of Open Access Journals (Sweden)

É. C. Avelar

Full Text Available Abstract The present study investigated the solvent extraction of uranium from sulfate acid solutions using Alamine 336 as an extractant dissolved in commercial kerosene Exxsol D-100 and 5% v/v of tridecanol as a modifying agent at room temperature (25±2 ºC and an aqueous/organic volumetric ratio of unity. Experiments were carried out at typical concentration levels like those used at the uranium plant of INB (Indústrias Nucleares do Brasil, Brazil. Data fitting using the slope analysis method revealed that uranium is extracted by Alamine 336 as UO2SO4 and UO2(SO422- species, forming (R3NH+2UO2(SO422- in the organic phase; the extraction of the species UO2(SO434- seems improbable for the operating conditions investigated. The extraction of uranium is significantly reduced when the concentrations of sulfate and chloride ions in the aqueous phase are increased.

Highly efficient extraction and selective separation of uranium (VI) from transition metals using new class of undiluted ionic liquids based on H-phosphonate anions.

Science.gov (United States)

Zarrougui, Ramzi; Mdimagh, Raouf; Raouafi, Nourreddine

2018-01-15

In this paper, we report the development of an environmental friendly process to decontaminate uranium-containing ores and nuclear wastes by using non-fluorinated ionic liquids (ILs). The main advantages of this extraction process are the absence of any organic diluent and extra extraction agents added to the organic phase. Moreover, the process is cost-effective and maybe applied as a sustainable hydrometallurgical method to recover uranium. The distribution ratio (D U ) and the extraction efficiency (%E) of uranium(VI) (UO 2 2+ ) were found to be dependent on the acidity of the aqueous phase, the extraction time, the alkyl chain length in the ILs, the concentration of the aqueous feed and molar quantity of ILs. The D U value is higher than 600 and the %E is equal to 98.6% when [HNO 3 ]=7M. The extraction reactions follows a neutral partition or ionic exchange mechanism depending on nitric acid concentration. The nature of bonding in the extracted complexes was investigated by spectroscopic techniques. The potential use of Mor 1-8 -OP for the separation of UO 2 2+ from a mixture containing transition metal ions M n+ was also examined. The UO 2 2+ ions were separated and extracted efficiently. These ILs are promising candidates for the recovery and separation of uranium. Copyright © 2017 Elsevier B.V. All rights reserved.

Uranium(VI) transport modeling: geochemical data and submodels

International Nuclear Information System (INIS)

Tripathi, V.S.

1984-01-01

Understanding the geochemical mobility of U(VI) and modeling its transport is important in several contexts including ore genesis, uranium exploration, nuclear and mill-tailings waste management, and solution mining of uranium ores. Adsorption is a major control on partitioning of solutes at the mineral/solution interface. The effect of carbonate, fluoride, and phosphate complexing on adsorption of uranium was investigated. A critical compilation of stability constants of inorganic complexes and solid compounds of U(VI) necessary for proper design of experiment and for modeling transport of uranium was prepared. The general features of U(VI) adsorption in ligand-free systems are similar to those characteristic of other hydrolyzable metal ions. The adsorption processes studied were found to be reversible. The adsorption model developed in ligand-free systems, when solution complexing is taken into account, proved remarkably successful in describing adsorption of uranium in the presence of carbonate and fluoride. The presence of phosphate caused a much smaller decrease in the extent of adsorption than expected; however, a critical reassessment of the stability of UO 2 2+ .HPO 4 2- complexes, showed that phosphato complexes, if any, are extremely weak under experimental conditions. Removal of uranium may have occurred due to precipitation of sodium uranyl phosphates in addition to adsorption

Determination of U(VI) using novel reagent by extractive spectrophotometry

International Nuclear Information System (INIS)

Suvardhan, K.; Subrahmanyam, P.; Dilip Kumar, J.; Chiranjeevi, P.

2007-01-01

A simple and spectrophotometric method for the determination of U(VI) using a 5-(4-pyridyl azo)-8-quinolinol (PAQ) is developed the reagent was synthesized and used for extraction of uranium. At pH 7.0 ±0.2 uranium forms a yellowish orange colored complex with PAQ, which was then quantitatively extracted from chloroform showing maximum absorbance at wavelength of 485 nm. The proposed method obeys Beer's law in the range of 0.2-10.0 μg ml -1 . Molar absorptivity and Sandelson's sensitivity of extracted species was calculated to be 1.325x10 4 lmol -1 cm -1 and 0.421 x10 -4 μg cm -2 respectively. The method was applied for the determination of uranium in food and plant samples. It was found that the newly developed method is competent to those of standard methods. (author)

A spectroscopic study of uranium(VI) interaction with magnetite

International Nuclear Information System (INIS)

El Aamrani, S.; Gimenez, J.; Rovira, M.; Seco, F.; Grive, M.; Bruno, J.; Duro, L.; Pablo, J. de

2007-01-01

The uranium sorbed onto commercial magnetite has been characterized by using two different spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS). Magnetite samples have been put in contact with uranium(VI) solutions in conditions in which a high uranium uptake is expected. After several days, the magnetite surface has been analysed by XPS and EXAFS. The XPS results obtained are not conclusive regarding the uranium oxidation state in the magnetite surface. On the other hand, the results obtained with the EXAFS technique show that the uranium-magnetite sample spectrum has characteristics from both the UO 2 and schoepite spectra, e.g. a relatively high coordination number of equatorial oxygens and two axial oxygens, respectively. These results would indicate that the uranium sorbed onto magnetite would be a mixture of uranium(IV) and uranium(VI)

Extraction of uranium (VI) from sea water using hydrous metalic oxide binded with hydrophilic polymers

International Nuclear Information System (INIS)

Shigetomi, Yasumasa; Kojima, Takehiro; Kamba, Hideaki

1978-01-01

In the past five years, many researches have been made to extract U(VI) from sea water. This is a report of the extraction of U(VI) from sea water using hydrous titanium oxide binded with hydrophilic polymers, the apparatus for the adsorption and the separation of U(VI) by means of ion exchange. (author)

Isolation and characterization of a uranium(VI)-nitride triple bond

Science.gov (United States)

King, David M.; Tuna, Floriana; McInnes, Eric J. L.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T.

2013-06-01

The nature and extent of covalency in uranium bonding is still unclear compared with that of transition metals, and there is great interest in studying uranium-ligand multiple bonds. Although U=O and U=NR double bonds (where R is an alkyl group) are well-known analogues to transition-metal oxo and imido complexes, the uranium(VI)-nitride triple bond has long remained a synthetic target in actinide chemistry. Here, we report the preparation of a uranium(VI)-nitride triple bond. We highlight the importance of (1) ancillary ligand design, (2) employing mild redox reactions instead of harsh photochemical methods that decompose transiently formed uranium(VI) nitrides, (3) an electrostatically stabilizing sodium ion during nitride installation, (4) selecting the right sodium sequestering reagent, (5) inner versus outer sphere oxidation and (6) stability with respect to the uranium oxidation state. Computational analyses suggest covalent contributions to U≡N triple bonds that are surprisingly comparable to those of their group 6 transition-metal nitride counterparts.

Effect of pH and uranium concentration on interaction of uranium(VI) and uranium(IV) with organic ligands in aqueous solutions

International Nuclear Information System (INIS)

Li, W.C.; Victor, D.M.; Chakrabarti, C.L.

1980-01-01

The effect of pH and uranium concentration on the interactions of uranium(VI) and uranium(IV) with organic ligands was studied by employing dialysis and ultrafiltration techniques. The interactions of U(VI) and U(IV) with organic ligands in nitrate or chloride aqueous solution have been found to be pH-dependent. The stability constants of uranium-organic complexes decrease in the order: fulvic acid>humic acid>tannic acid for U(VI) and humic acid>tannic acid>fulvic acid for U(IV). Scatchard plots for the uranium-organic acid systems indicate two types of binding sites with a difference in stability constants of about 10 2 . Ultrafiltration of uranium-humic acid complexes indicates that U(VI) and U(IV) ions are concentrated in larger molecular size fractions (>5.1 nm) at pH less than or equal to 3 and in smaller molecular size fractions (in the range 5.1 to 3.1 nm and 2.4 to 1.9 nm) at pH greater than or equal to 5. 7 figures, 4 tables

Extractants for uranium recovery from wet phosphoric acid

International Nuclear Information System (INIS)

Musikas, C.; Benjelloun, N.; Lours, S.

1981-08-01

It must be pointed out that despite their lower affinity for uranyl, the dialkyldithiophosphates show higher extraction coefficients than dialkylphosphates. In addition, it is possible to back extract uranium with oxalate solutions at pH levels where the solvents remain in their acidic form. This last possibility seems to be correlated with the presence of a H 2 PO 4 - ion in the U(VI) organic complexes

Study on selective separation of uranium(VI) by new N,N-dialkyl carboxy-amides

International Nuclear Information System (INIS)

Suzuki, Shinichi; Sugo, Yumi; Kimura, Takaumi; Yaita, Tsuyoshi

2007-01-01

The Feasibility study (FS) on commercialized FR cycle systems has been carried out in Japan. In this Feasibility study, 'Advanced Aqueous' reprocessing was designed as a new reprocessing concept to enhance nuclear non-proliferation by recycling U, Pu and minor actinides (MA) with some fission products (FP). The crystallization and U(VI)/TRU(transuranics) co-extraction technique have been selected as candidate technique in the 'Advanced Aqueous' reprocessing. In JAEA, the result of Feasibility study was received and Fast Reactor Cycle Technology Development Project (FaCT) was started. In the nuclear spent fuel reprocessing, FBR spent fuels will coexist with LWR spent fuels for several decades until FBR cycle begins to operate. For the treatment of LWR spent fuels, high decontamination factor for FP was required for U(VI) storage, and solvent extraction technique was selected in the nuclear fuel treatment. In our laboratory, N,N-di-alkyl carboxy-amides have been developed as extractant based on solvent extraction technique for one of a back-up technology of 'Advanced Aqueous' reprocessing in FBR spent fuel treatments. N,N-di-alkyl carboxy-amides were noted as one of the alternative extractant of tri-butylphosphate (TBP) in the field of nuclear fuel reprocessing. Extraction behavior of U(VI) and Pu(IV) with N,N-di-alkyl carboxy-amides was almost similar to those with TBP. N,N-di-alkyl carboxy-amides have some advantages, namely, their complete incinerability (CHON principle) and high stability for hydrolysis and radiolysis. Their main degradation products are carboxylic acids and secondary amines which hardly affect the separation of U(VI) and Pu(IV) from fission products. Further, the synthesis of N,N-di-alkyl carboxy-amides was relatively easy with reaction of carboxylic chloride and secondary amine. The main purpose of this solvent extraction technique using N,N-di-alkyl carboxy-amides is selective separation of Uranium(VI) with branched N,N-di-alkyl carboxy

Ion-exchanger ultraviolet spectrophotometry for uranium(VI)

International Nuclear Information System (INIS)

Waki, H.; Korkisch, J.

1983-01-01

A sensitive method based on solid-phase spectrophotometry has been developed for the microdetermination of uranium(VI) in water samples. Uranium is sorbed on the anion-exchanger QAE-Sephadex from thiocyanate solution and the absorbance of the exchanger is measured at 300 nm. This method is about 30 times more sensitive than solution spectrophotometry. Absorption spectra of various metals in the anion-exchanger phase are presented and their interferences discussed. A procedure for the cation-exchange separation of uranium from accompanying elements before spectral measurement of uranium is proposed. (author)

Uranium extraction from gold-uranium ores

Energy Technology Data Exchange (ETDEWEB)

Laskorin, B.N.; Golynko, Z.Sh.

1981-01-01

The process of uranium extraction from gold-uranium ores in the South Africa is considered. Flowsheets of reprocessing gold-uranium conglomerates, pile processing and uranium extraction from the ores are presented. Continuous counter flow ion-exchange process of uranium extraction using strong-active or weak-active resins is noted to be the most perspective and economical one. The ion-exchange uranium separation with the succeeding extraction is also the perspective one.

Preconcentration of trace uranium from seawater with solid phase extraction followed by differential pulse polarographic determination in chloroform eluate

International Nuclear Information System (INIS)

Dojozan, Dj.; Pournaghi-Azar, M.H.; Toutounchi-Asr, J.

1998-01-01

In the present study, an effective method is presented for the separation and preconcentration of uranium (VI) by solid phase extraction (SPE). For this purpose, U(VI) oxinate is formed by the reaction of U(VI) with 8-hydroxyquinoline and adsorbed onto the octylsilane (C-8) SPE cartridge. The analyte is completely eluted with chloroform and determined by differential pulse polarography. The SPE conditions were optimized by evaluating the effective factors such as pH, oxine concentration, type and concentration of buffer and masking agent. By the proposed method a preconcentration factor of more than 100 was achieved. The average recovery of uranium (VI) oxinate (0.1 mg l -1 ) was 99.8%. The relative standard deviation was 1.6% for seven replicate determinations of uranyl ion in the solution with a concentration 20 μg l -1 . Some concomitant ions such as Ca +2 , Mg +2 and Fe +3 which interfere in extraction or determination process of uranium were masked with EDTA in aqueous phase during the extraction process. The proposed method was successfully used for the determination of uranium in Caspian Sea and Persian Gulf water samples

A contribution to the study of mass transfer: uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

Maher, A.

1985-12-01

Liquid-liquid extraction of uranium (VI) contained in phosphoric acid is examined. Synergism and thermodynamical equilibria are studied. Influence of drop size, extractant concentration and temperature on reaction kinetics are determined. The experimental study concerns extraction by HDEHP, TOPO and the mixture of both. Reaction mechanisms are interpreted [fr

Recovery of uranium (VI) from low level aqueous radioactive waste

International Nuclear Information System (INIS)

Kulshrestha, Mukul

1996-01-01

Investigation was undertaken to evaluate the uranium (VI) removal and recovery potential of a naturally occurring, nonviable macrofungus, Ganoderma Lucidum from the simulated low level aqueous nuclear waste. These low level waste waters discharged from nuclear mine tailings and nuclear power reactors have a typical U(VI) concentration of 10-100 mg/L. It is possible to recover this uranium economically with the advent of biosorption as a viable technology. Extensive laboratory studies have revealed Ganoderma Lucidum to be a potential biosorbent with a specific uptake of 2.75 mg/g at an equilibrium U(VI) concentration of 10 mg/L at pH 4.5. To recover the sorbed U(VI), the studies indicated 0.2N Na 2 CO 3 to be an effective elutant. The kinetics of U(VI) desorption from loaded Ganoderma Lucidum with 0.2N Na 2 CO 3 as elutant, was found to be rapid with more than 75% recovery occurring in the first five minutes, the specific metal release rate being 0.102 mg/g/min. The equilibrium data fitted to a linearised Freundlich plot and exhibited a near 100% recovery of sorbed U(VI), clearly revealing a cost-effective method of recovery of precious uranium from low level wastewater. (author). 7 refs., 3 figs., 1 tab

Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite

Science.gov (United States)

Bargar, John R.; Reitmeyer, Rebecca; Davis, James A.

1999-01-01

Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)−carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. We have used attenuated total reflectance Fourier transform infrared (ATR-FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of ≡FeOsurface−U(VI)−carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)−carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)−carbonato complexes, which are trace constituents at pH carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium.

Uranium(VI) speciation: modelling, uncertainty and relevance to bioavailability models. Application to uranium uptake by the gills of a freshwater bivalve

International Nuclear Information System (INIS)

Denison, F.H.

2004-07-01

The effects of varying solution composition on the interactions between uranium(VI) and excised gills of the freshwater bivalve Corbicula fluminea have been investigated in well defined solution media. A significant reduction in the uptake of uranium was observed on increasing the concentrations of the uranium complexing ligands citrate and carbonate. Saturation kinetics as a function of uranium concentration at a pH value of 5.0 were observed, indicating that the uptake of uranium is a facilitated process, probably involving one or several trans-membrane transport systems. A relatively small change in the uptake of uranium was found as a function of pH (factor of ca. 2), despite the extremely large changes to the solution speciation of uranium within the range of pH investigated (5.0 - 7.5). A comprehensive review of the thermodynamic data relevant to the solution composition domain employed for this study was performed. Estimates of the uncertainties for the formation constants of aqueous uranium(VI) species were integrated into a thermodynamic database. A computer program was written to predict the equilibrium distribution of uranium(VI) in simple aqueous systems, using thermodynamic parameter mean-values. The program was extended to perform Monte Carlo and Quasi Monte Carlo uncertainty analyses, incorporating the thermodynamic database uncertainty estimates, to quantitatively predict the uncertainties inherent in predicting the solution speciation of uranium. The use of thermodynamic equilibrium modelling as a tool for interpreting the bioavailability of uranium(VI) was investigated. Observed uranium(VI) uptake behaviour was interpreted as a function of the predicted changes to the solution speciation of uranium. Different steady-state or pre-equilibrium approaches to modelling uranium uptake were tested. Alternative modelling approaches were also tested, considering the potential changes to membrane transport system activity or sorption characteristics on

Thin film-XRF determination of uranium following thin-film solid phase extraction

Energy Technology Data Exchange (ETDEWEB)

Hassan, Jalal, E-mail: jalalhassan@ut.ac.ir [Department of Toxicology, Faculty of Veterinary Medicine, University of Tehran (Iran, Islamic Republic of); Hosseini, Seyed M.; Mozaffari, Shahla [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Jahanparast, Babak; Karbasi, Mohammad H. [Iranian Mineral Processing Research Center, Ministry of Industry and Mineral, Karaj (Iran, Islamic Republic of)

2014-07-01

A sensitive method based on the preconcentration of uranium on modified filter paper (thin film) has been developed to determinate this element in water and soil samples by wavelength dispersive X-ray fluorescence. Uranium (VI) extraction from nitric acid medium by trioctyl phosphine (TOPO) from 100 mL of sample was carried out. The effects of nitric acid concentration, TOPO concentration and sample breakthrough on uranium extraction were investigated in this study. The proposed method provided good linearity from 7 to 1000 μg and the limit of detection (LOD), based on a signal-to noise ratio (S/N) of 3, was 2.5 μg. (author)

Polarography of uranium(VI)-salicylic acid system

International Nuclear Information System (INIS)

Salah, El-Maraghy B.

1980-01-01

Uranium(VI)-salicylic acid system has been studied polarographically in perchloric acid medium. Varying concentrations of HClO 4 and salicylic acid have been used. The nature of the polarographic waves is irreversible. (author)

Polarography of uranium(VI)-salicylic acid system

Energy Technology Data Exchange (ETDEWEB)

Salah, E M.B. [Ain Shams Univ., Cairo (Egypt). Faculty of Education

1980-08-01

Uranium(VI)-salicylic acid system has been studied polarographically in perchloric acid medium. Varying concentrations of HClO/sub 4/ and salicylic acid have been used. The nature of the polarographic waves is irreversible.

Solvent extraction as a method of promoting uranium enrichment by chemical exchange

International Nuclear Information System (INIS)

Fathurrachman.

1995-01-01

This thesis examines a chemical exchange process for uranium enrichment using solvent extraction. The system selected is the isotope exchange for uranium species in the form of uranous and uranyl chloride complexes. Solvent extraction has been studied before by French workers for this application but little was published on this. Much of this present work is therefore novel. The equilibrium data for the extraction of U(IV) as U 4+ and U(VI) as UO 2 2+ from hydrochloric media into an organic phase containing tri-n-octylamine (TOA) in benzene is given. Benzene is used to prevent third phase formation. In 4 M HCl U(VI) was found to be very soluble in the organic phase but U(IV) was virtually insoluble. Most of the equilibrium data has been correlated by the Langmuir isotherm. This thesis also outlines the methodology that has to be used to design a plant based on this process. (author)

Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments

Science.gov (United States)

Stoliker, Deborah L.; Campbell, Kate M.; Fox, Patricia M.; Singer, David M.; Kaviani, Nazila; Carey, Minna; Peck, Nicole E.; Barger, John R.; Kent, Douglas B.; Davis, James A.

2013-01-01

Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

Study on the electrolytic reduction of Uranium-VI to Uranium-IV in a nitrate system

International Nuclear Information System (INIS)

Araujo, B.F. de; Almeida, S.G. de; Forbicini, S.; Matsuda, H.T.; Araujo, J.A. de.

1981-05-01

The determination of the best conditions to prepare hydrazine stabilized uranium (IV) nitrate solutions for utilization in Purex flowsheets is dealt with. Electrolytic reduction of U(VI) has been selected as the basic method, using an open electrolytic cell with titanum and platinum electrodes. The hydrazine concentration, the current density, acidity, U(VI) concentration and reduction time were the parameters studied and U(IV)/U(VI) ratio was used to evaluate the degree of reduction. From the results it could be concluded that the technique is reliable. The U(IV) solutions remains constant for at least two weeks and can be used in the chemical processing of irradiated uranium fuels. (Author) [pt

Extraction and separation of U(VI and Th(IV from hydrobromic acid media using Cyanex-923 extractant

Directory of Open Access Journals (Sweden)

Ghag Snehal M.

2010-01-01

Full Text Available A systematic study of the solvent extraction of uranium(VI and thorium(IV from hydrobromic acid media was performed using the neutral phosphine oxide extractant Cyanex-923 in toluene. These metal ions were found to be quantitatively extracted with Cyanex-923 in toluene in the acidity range 5x10-5-1x10-4 M and 5x10-5-5x10-3 M, respectively, and they are stripped from the organic phase with 7.0 M HClO4 and 2.0- 4.0 M HCl, respectively. The effect of the equilibrium period, diluents, diverse ions and stripping agent on the extraction of U(VI and Th(IV was studied. The stoichiometry of the extracted species of these metal ions was determined based on the slope analysis method. The extraction reactions proceed by solvation and their probable extracted species found in the organic phase were UO2Br2•2Cyanex-923 and ThBr4•2Cyanex-923. Based on these results, a sequential procedure for their separation from each other was developed.

Current extraction and separation of uranium, thorium and rare earths elements from monazite leach solution using organophosphorous extractants

International Nuclear Information System (INIS)

Biswas, Sujoy; Rupawate, V.H.; Hareendran, K.N.; Roy, S.B.

2014-01-01

A new process based on solvent extraction has been developed for separation of uranium, thorium and rare earths from monazite leach solution using organophosphorous extractants. The Thorium cake coming from monazite source was dissolved in HNO 3 medium in presence of trace amount of HF for feed preparation. The separation of U(VI) was carried out by liquid-liquid extraction using tris-2-ethyl hexyl phosphoric acid (TEHP) in dodecane leaving thorium and rare earths elements in the raffinate. The thorium from raffinate was selectively extracted using 1M tri iso amyl phosphate (TiAP) in dodecane in organic phase leaving all rare earths elements in aqueous solution. The uranium and thorium from organic medium was quantitatively stripped using 0.05 M HNO 3 counter current mode. Results indicate the quantitative separation of uranium, thorium and rare earths from thorium cake (monazite source) using organophosphorous extractant in counter current mode

The determination of uranium(VI) by flow-injection analysis

International Nuclear Information System (INIS)

Jones, E.A.

1985-01-01

A method is described for the direct determination of uranium(VI) in waste waters and acid leach liquors by use of a flow-injection procedure and spectrophotometric measurement with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (bromo-PADAP). The interference effects of several commonly occurring elements were studied. The calibration curve is linear over concentrations of uranium(VI) from 0,5 to 20 mg/1, and the precision obtained on a synthetic leach liquor was 0,019 (relative standard deviation). The procedure is rapid and convenient, and up to 40 samples can be analysed in an hour

Mechanism of uranium (VI) removal by two anaerobic bacterial communities

Energy Technology Data Exchange (ETDEWEB)

Martins, Monica [Centro de Ciencias do Mar, Universidade do Algarve, FCT-DQF (edificio 8), Campus de Gambelas, 8005-139 Faro (Portugal); Faleiro, Maria Leonor [IBB - Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, FCT, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, Ana M. Rosa da [Centro de Investigacao em Quimica do Algarve, Universidade do Algarve, FCT, DQF, Campus de Gambelas, 8005-139 Faro (Portugal); Chaves, Sandra; Tenreiro, Rogerio [Universidade de Lisboa, Faculdade de Ciencias, Centro de Biodiversidade, Genomica Integrativa e Funcional (BioFIG), Campus de FCUL, Campo Grande, 1749-016 Lisboa (Portugal); Matos, Antonio Pedro [Servico de Anatomia Patologica, Hospital Curry Cabral, Lisboa (Portugal); Costa, Maria Clara, E-mail: mcorada@ualg.pt [Centro de Ciencias do Mar, Universidade do Algarve, FCT-DQF (edificio 8), Campus de Gambelas, 8005-139 Faro (Portugal)

2010-12-15

The mechanism of uranium (VI) removal by two anaerobic bacterial consortia, recovered from an uncontaminated site (consortium A) and other from an uranium mine (consortium U), was investigated. The highest efficiency of U (VI) removal by both consortia (97%) occurred at room temperature and at pH 7.2. Furthermore, it was found that U (VI) removal by consortium A occurred by enzymatic reduction and bioaccumulation, while the enzymatic process was the only mechanism involved in metal removal by consortium U. FTIR analysis suggested that after U (VI) reduction, U (IV) could be bound to carboxyl, phosphate and amide groups of bacterial cells. Phylogenetic analysis of 16S rRNA showed that community A was mainly composed by bacteria closely related to Sporotalea genus and Rhodocyclaceae family, while community U was mainly composed by bacteria related to Clostridium genus and Rhodocyclaceae family.

Mechanism of uranium (VI) removal by two anaerobic bacterial communities

International Nuclear Information System (INIS)

Martins, Monica; Faleiro, Maria Leonor; Costa, Ana M. Rosa da; Chaves, Sandra; Tenreiro, Rogerio; Matos, Antonio Pedro; Costa, Maria Clara

2010-01-01

The mechanism of uranium (VI) removal by two anaerobic bacterial consortia, recovered from an uncontaminated site (consortium A) and other from an uranium mine (consortium U), was investigated. The highest efficiency of U (VI) removal by both consortia (97%) occurred at room temperature and at pH 7.2. Furthermore, it was found that U (VI) removal by consortium A occurred by enzymatic reduction and bioaccumulation, while the enzymatic process was the only mechanism involved in metal removal by consortium U. FTIR analysis suggested that after U (VI) reduction, U (IV) could be bound to carboxyl, phosphate and amide groups of bacterial cells. Phylogenetic analysis of 16S rRNA showed that community A was mainly composed by bacteria closely related to Sporotalea genus and Rhodocyclaceae family, while community U was mainly composed by bacteria related to Clostridium genus and Rhodocyclaceae family.

Polarographic behaviour and determination of uranium(VI) in alcoholic solutions from organic extraction phases

International Nuclear Information System (INIS)

Degueldre, C.; Taibi, K.

1996-01-01

The determination of U(VI) in organic extraction phases: hydrocarbon-diethyl-2-hexyl phosphoric acid-trioctylphosphine oxide and hydrocarbon-tri-n-octylamine, diluted by an alcohol has been studied by direct current polarography, as well as by differential pulse polarography (DPP). In order to optimise the analytical procedure, miscibility and conductivity studies of the mixtures hydrocarbon-alcohol (ethanol, n- and isopropanol and n- and isobutanol) were made after addition of sulphuric acid as a supporting electrolyte. In the solutions of sulphuric acid in the alcohol-extractant-hydrocarbon phases, U(VI) gives rise to well defined polarograms. Its electroreduction involves a single electron step in all cases. The DPP peak height is proportional to the U(VI) concentration between 2x10 -6 and 2x10 -3 M, and the 3σ detection limit is ca. 10 -6 M

Effect of uranium (VI) on two sulphate-reducing bacteria cultures from a uranium mine site

International Nuclear Information System (INIS)

Martins, Monica; Faleiro, Maria Leonor; Chaves, Sandra; Tenreiro, Rogerio; Costa, Maria Clara

2010-01-01

This work was conducted to assess the impact of uranium (VI) on sulphate-reducing bacteria (SRB) communities obtained from environmental samples collected on the Portuguese uranium mining area of Urgeirica. Culture U was obtained from a sediment, while culture W was obtained from sludge from the wetland of that mine. Temperature gradient gel electrophoresis (TGGE) was used to monitor community changes under uranium stress conditions. TGGE profiles of dsrB gene fragment demonstrated that the initial cultures were composed of SRB species affiliated with Desulfovibrio desulfuricans, Desulfovibrio vulgaris and Desulfomicrobium spp. (sample U), and by species related to D. desulfuricans (sample W). A drastic change in SRB communities was observed as a result of uranium (VI) exposure. Surprisingly, SRB were not detected in the uranium removal communities. Such findings emphasize the need of monitoring the dominant populations during bio-removal studies. TGGE and phylogenetic analysis of the 16S rRNA gene fragment revealed that the uranium removal consortia are composed by strains affiliated to Clostridium genus, Caulobacteraceae and Rhodocyclaceae families. Therefore, these communities can be attractive candidates for environmental biotechnological applications associated to uranium removal.

Effect of high ionic strength on the extraction of uranium(VI ions

Directory of Open Access Journals (Sweden)

M.K. Nazal

2014-01-01

Full Text Available Preparation and characterization of didodecylphosphoric acid (HDDPA as an extractant in toluene was carried. Mass spectroscopy showed that the monomer peak at 457.4 amu [M–Na+] is double that of the dimer at 891.9 amu [M–M–Na+] and the monomer molecules concentration dominate the dimer molecules in toluene. HDDPA was used as an extractant for the extraction of U(VI ion from perchlorate and nitrate media that have ionic strength (1.00, 3.00, 5.00, 7.00 M. The effect of HDDPA concentration, pcH, ionic strength of supporting electrolytes, and temperature in the range 15–45 °C on the extraction process have been studied. The stoichiometry of the extraction of U(VI ion, the free energy change (ΔG, the enthalpy change (ΔH, the entropy change (ΔS, and Kex at different ionic strength have been calculated. The formula of the complexes, which were formed has been established to be UO2(X(R2(HR2 at pcH equal 2.00 and UO2(X(R2(HR2 and UO2(X(R2 at pcH = 1.00, where (X isClO4- orNO3- and (HR2 is didodecylphosphoric acid monomer, (R2 is the deprotonated didodecylphosphoric acid, where R is the dodecyl group.

Investigation of uranium (VI) adsorption by polypyrrole

Energy Technology Data Exchange (ETDEWEB)

Abdi, S. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Nasiri, M., E-mail: mnasiri@semnan.ac.ir [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Mesbahi, A. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Khani, M.H. [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, 14395-836 (Iran, Islamic Republic of)

2017-06-15

Highlights: • The adsorbent (polypyrrole) was synthesized by a chemical method using PEG, DBSNa and CTAB as the surfactant. • The solution pH was one of the most important parameters affecting the adsorption of uranium. • The CTAB provided higher removal percentage compared with the other surfactants. • The maximum adsorption capacity obtained from Langmuir isotherm was 87.72 mg/g. • The pseudo second-order model fitted well with the adsorption kinetic of polypyrrole to uranium. - Abstract: The purpose of this study was to investigate the adsorption of uranium (VI) ions on the polypyrrole adsorbent. Polypyrrole was synthesized by a chemical method using polyethylene glycol, sodium dodecylbenzenesulfonate, and cetyltrimethylammonium bromide as the surfactant and iron (III) chloride as an oxidant in the aqueous solution. The effect of various surfactants on the synthesized polymers and their performance as the uranium adsorbent were investigated. Adsorbent properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of different parameters such as pH, contact time, initial metal ion concentrations, adsorbent dose, and the temperature was investigated in the batch system for uranium adsorption process. It has been illustrated that the adsorption equilibrium time is 7 min. The results showed that the Freundlich model had the best agreement and the maximum adsorption capacity of polypyrrole for uranium (VI) was determined 87.72 mg/g from Langmuir isotherm. In addition, the mentioned adsorption process was fast and the kinetic data were fitted to the Pseudo first and second order models. The adsorption kinetic data followed the pseudo-second-order kinetic model. Moreover, the thermodynamic parameters ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0} showed that the uranium adsorption process by polypyrrole was endothermic and spontaneous.

Spectroscopic Confirmation of Uranium (VI)-Carbonato Adsorption Complexes on Hematite

International Nuclear Information System (INIS)

Bargar, John R

1999-01-01

Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)-carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. We have used Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of FeO surface -U(VI)-carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)-carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)-carbonato complexes, which are trace constituents at pH < 6. This result indicates the inadequacy of the common modeling assumption that the compositions and predominance of adsorbed species can be inferred from aqueous species. By extension, adsorbed carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium

Study of electrolytic reduction of uranium VI to uranium IV in nitrate systems

Energy Technology Data Exchange (ETDEWEB)

Araujo, B.F. de; Almeida, S.G. de; Forbicini, S; Matsuda, H T; Araujo, J.A. de [Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo (Brazil). Centro de Engenharia Quimica

1980-01-01

Experimental parameters are optimized in order to obtain uranium (IV) nitrate solutions at maximum yield, using hydrazine as stabilizer. Uranium (VI) electrolytic reduction was chosen because: there is no increase in the volume of radioactive effluents; there are no secondary reactions; there is no need for further separations; all reagents used are not inflammable. The method is, therefore, efficient and of low cost.

Modification of zirconium diphosphate with salicylic acid and its effect on the uranium (Vi) sorption

International Nuclear Information System (INIS)

Almazan T, M. G.; Garcia G, N.; Simoni, E.

2014-10-01

The surface of zirconium diphosphate (ZrP 2 O 7 ) was modified with salicylic acid and its effect was evaluated on the uranium (Vi) sorption. The modified surface of the material was analyzed with different analytical techniques among which are included the atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. This analysis allowed showing that the salicylic acid is being held on the surface of the zirconium diphosphate. The reactivity of modified zirconium diphosphate compared with uranium (Vi) was investigated using the classical method of batch sorption. The analysis of sorption isotherms shows that the salicylic acid has an important effect in the uranium (Vi) sorption. According to the study conducted, the interaction among the uranium (Vi) and the surface of zirconium diphosphate modified with the salicylic acid most likely leads to the complexes formation of binary (U(Vi)/ZrP 2 O 7 ) and ternary (U(Vi)/salicylate/ZrP 2 O 7 ) surface. (Author)

Solvent extraction of uranium(VI), plutonium(VI) and americium(III) with HTTA/HPMBP using mono- and bi-functional neutral donors. Synergism and thermodynamics

International Nuclear Information System (INIS)

Pai, S.A.; Lohithakshan, K.V.; Mithapara, P.D.; Aggarwal, S.K.

2000-01-01

Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO 3 with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz. DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as diluent. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (ΔG 0 , ΔH 0 , ΔS 0 ) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log K s values of bi-functional donors were found to be very high and deviate from the linear plot (log K s vs. log K h ) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA) system studied. This was supported by high +ve ΔS 0 values obtained for this system. (author)

Thermochemistry of uranium(VI), arsenic, and alkali metal triple oxides

International Nuclear Information System (INIS)

Karyakin, N.V.; Chernorukov, G.N.

1994-01-01

The standard enthalpies of reactions of stoichiometric mixtures of potassium dyhydrogen orthoarsenate, uranium(VI) oxide, alkali metal nitrates, and of mixtures of triple oxides with the general formula M I AsUO 6 (M I =Li, Na, K, Rb, and Cs) and potassium nitrate with aqueous solution of hydrofluoric acid were determined an an adiabatic calorimeter at 298.15 K. The standard enthalpies of formation of uranium(VI), arsenic, and alkali metal triple oxides at 298.15 K were calculated form the data obtained. 8 refs., 1 tab

Preparation and properties of N-Phenylbutyrohydroxamic acid and N-p-Chlorophenylbutyrohydroxamic acid and their uses as extracting agents for Chromium (VI), Molybdenum (VI), Titanium (IV) and Uranium (VI)

Energy Technology Data Exchange (ETDEWEB)

Abu Elnour, Sawsan Hassan [Department of Chemistry, Faculty of Science, University of Khartoum, Khartoum (Sudan)

1993-05-01

Two lignads, N-phenylbutyrohydroxamic acid (1), N-p-chlorophenylbutyryl chloride with {beta} phenyl-hydroylamine and N-p-chlorophenylhydroxylamine, respectively. The acids prepared were identified and characterised through their reactions with Vanadiun (V) and iron (III), their melting points, infra-red spectra and nitrogen content. The extractive properties of these acids towards the metals Cr (VI), Mo (VI), Ti (IV) and U (VI) were examined at different PH values. The percentage of maximum extraction with the two acids was found to be as follows : for Cr (VI) at PH 1, (100%) for both acids, Mo (VI) at PH 2 (33.34%) with acid (I) and (16.67%) with acid (II) and U (VI) at PH 6 (72%) with acid (I) and (76%) with acid (II). The metal: Ligand complexes ratios were determined by using the continuous variation method, the ratio of the two ligands with four metals was found to be 1:2. Finally the suitability of the two acids for spectrophotometric determination of four metals was examined.(Author) 90 refs. , 24 tabs. , 24 figs

Preparation and properties of N-Phenylbutyrohydroxamic acid and N-p-Chlorophenylbutyrohydroxamic acid and their uses as extracting agents for Chromium (VI), Molybdenum (VI), Titanium (IV) and Uranium (VI)

International Nuclear Information System (INIS)

Abu Elnour, Sawsan Hassan

1993-05-01

Two lignads, N-phenylbutyrohydroxamic acid (1), N-p-chlorophenylbutyryl chloride with β phenyl-hydroylamine and N-p-chlorophenylhydroxylamine, respectively. The acids prepared were identified and characterised through their reactions with Vanadiun (V) and iron (III), their melting points, infra-red spectra and nitrogen content. The extractive properties of these acids towards the metals Cr (VI), Mo (VI), Ti (IV) and U (VI) were examined at different PH values. The percentage of maximum extraction with the two acids was found to be as follows : for Cr (VI) at PH 1, (100%) for both acids, Mo (VI) at PH 2 (33.34%) with acid (I) and (16.67%) with acid (II) and U (VI) at PH 6 (72%) with acid (I) and (76%) with acid (II). The metal: Ligand complexes ratios were determined by using the continuous variation method, the ratio of the two ligands with four metals was found to be 1:2. Finally the suitability of the two acids for spectrophotometric determination of four metals was examined.(Author)

Uranium(VI) retention on quartz and kaolinite. Experiments and modelling

International Nuclear Information System (INIS)

Mignot, G.

2001-01-01

The behaviour of uranium in the geosphere is an important issue for safety performance assessment of nuclear waste repositories, or in the context of contaminated sites due to mining activity related to nuclear field. Under aerobic conditions, the fate of uranium is mainly governed by the ability of minerals to sorb U(VI) aqueous species. Hence, a thorough understanding of U(VI) sorption processes on minerals is required to provide a valuable prediction of U(VI) migration in the environment. In this study, we performed sorption/desorption experiments of U(VI) on quartz and kaolinite, for systems favouring the formation in solution (i) of UO 2 2+ and monomeric hydrolysis products or (ii) of di-/tri-meric uranyl aqueous species, and / or U(VI)-colloids or UO 2 (OH) 2 precipitates, or (iii) of uranyl-carbonate complexes. Particular attention was paid to determine the surface characteristics of the solids and their modification due to dissolution/precipitation processes during experiments. A double layer surface complexation model was applied to our experimental data in order to derive surface complexation equilibria and intrinsic constants which allow a valuable description of U(VI) retention over a wide range of pH, ionic strength, initial concentration of uranium [0.1-10μM] and solid - solution equilibration time. U(VI) sorption on quartz was successfully modeled by using two sets of adsorption equilibria, assuming (i) the formation of the surface complexes SiOUO 2 + , SiOUO 2 OH and SiO(UO 2 ) 3 (OH) 5 , or (ii) the formation of the mono-dentate complex SiO(UO 2 ) 3 (OH) 5 and of the bidentate complex (SiO) 2 UO 2 . Assumptions on the density of each type of surface sites of kaolinite and on their acid-base properties were made from potentiometric titrations of kaolinite suspensions. We proposed on such a basis a set of surface complexation equilibria which accounts for U(VI) uptake on kaolinite over a wide range of chemical conditions, with aluminol edge sites as

Bioreduction of Uranium(VI) Complexed with Citric Acid by Clostridia Affects its Structure and Mobility

International Nuclear Information System (INIS)

Francis, A.; Dodge, C.

2008-01-01

Uranium contamination of the environment from mining and milling operations, nuclear-waste disposal, and ammunition use is a widespread global problem. Natural attenuation processes such as bacterial reductive precipitation and immobilization of soluble uranium is gaining much attention. However, the presence of naturally occurring organic ligands can affect the precipitation of uranium. Here, we report that the anaerobic spore-forming bacteria Clostridia, ubiquitous in soils, sediments, and wastes, capable of reduction of Fe(III) to Fe(II), Mn(IV) to Mn(II), U(VI) to U(IV), Pu(IV) to Pu(III), and Tc(VI) to Tc(IV); reduced U(VI) associated with citric acid in a dinuclear 2:2 U(VI):citric acid complex to a biligand mononuclear 1:2 U(IV):citric acid complex, which remained in solution, in contrast to reduction and precipitation of uranium. Our findings show that U(VI) complexed with citric acid is readily accessible as an electron acceptor despite the inability of the bacterium to metabolize the complexed organic ligand. Furthermore, it suggests that the presence of organic ligands at uranium-contaminated sites can affect the mobility of the actinide under both oxic and anoxic conditions by forming such soluble complexes.

Sorption of Uranium(VI and Thorium(IV by Jordanian Bentonite

Directory of Open Access Journals (Sweden)

Fawwaz I. Khalili

2013-01-01

Full Text Available Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0∘C and . The highest rate of metal ions uptake was observed after 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at . Bentonite has shown high metal ion uptake capacity toward uranium(VI than thorium(IV. Sorption data were evaluated according to the pseudo- second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0∘C, 35.0∘C, and 45.0∘C. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI and thorium(IV. Recovery of uranium(VI and thorium(IV ions after sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. The best percent recovery for uranium(VI and thorium(IV was obtained when 1.0 M HNO3 was used.

Method of purifying uranium tetrafluoride hydrate and preparing uranium (VI) peroxide hydrate using a fluoride complexing agent

International Nuclear Information System (INIS)

Barreiro, A.J.; Lowe, C.M.T.; Lefever, J.A.; Pyman, R.L.

1983-01-01

The annual production of phosphate rock, on the order of about 30-40 million tons yearly, represents several million pounds of uranium. The present invention provides a process of purifying uranium tetrafluoride hydrate to produce a uranium (VI) peroxide product meeting 'yellow cake' standards using a double precipitation procedure. A fluoride complexing agent is used in the precipitation

Complexation study of a tert-butyl-calix[4]arene-based 2-hydroxynaphthalene ligand with uranium(VI) in non-aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Bauer, Anne; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

The actinide uranium, well known from nuclear power cycle, plays also a role in rare earth production as it is an undesired constituent of the respective ores. To facilitate the production of rare earth elements, uranium has to be removed. Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of actinides and lanthanides. The mechanism of uranium(VI) interaction with a tert-butyl-calix[4]arene-based 2-hydroxynaphthalene ligand (L1) was studied by TRLFS, UV-vis spectroscopy and isothermal calorimetry.

Empirical modeling of solvent extraction of uranium from sulphuric acid medium using PC-88A and TOPO as extractants

International Nuclear Information System (INIS)

Biswas, S.; Roy, S.B.; Pathak, P.N.; Manchanda, V.K.; Singh, D.K.

2011-01-01

Extraction behavior of uranium (VI) from sulphuric acid medium using PC-88A (H 2 A 2 , dimer form) and a mixture of PC-88A + TOPO in n-dodecane has been investigated. The extraction data have been used to develop a mathematical model correlating percentage extraction (%E) with PC-88A and TOPO concentration. It can be used to predict the steady-state concentrations of metal ion under the conditions of the present work. (author)

Selective extraction of metals from acidic uranium(VI) solutions using neo-tridecano-hydroxamic acid

International Nuclear Information System (INIS)

Bardoncelli, F.; Grossi, G.

1975-01-01

According to this invention neo-alkyl-hydroxamic acids are employed as ion-exchanging agents in processes for liquid-liquid extraction with the aim of separating, purifying dissolved metals and of converting a metal salt solution into a solution of a salt of the same metal but with different anion. In particular it is an objective of this invention to provide a method whereby a molecular pure uranium solution is obtained by selective extraction from a uranium solution delivered by irradiated fuel reprocessing plants and containing plutonium, fission products and other unwanted metals, in which method neo-tridecane-hydroxamic acid is employed as ion exchanger. (Official Gazette)

Extraction of plutonium and uranium from oxalate bearing solutions using phosphonic acid

International Nuclear Information System (INIS)

Godbole, A.G.; Mapara, P.M.; Swarup, Rajendra

1995-01-01

A feasibility study on the solvent extraction of plutonium and uranium from solutions containing oxalic and nitric acids using a phosphonic acid extractant (PC88A) was made to explore the possibility of recovering Pu from these solutions. Batch experiments on the extraction of Pu(IV) and U(VI) under different parameters were carried out using PC88A in dodecane. The results indicated that Pu could be extracted quantitatively by PC88A from these solutions. A good separation of Pu from U could be achieved at higher temperatures. (author). 6 refs., 3 tabs

Peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV) and thorium(IV) ions containing tridentate Schiff bases derived from salicylaldehyde and amino acids

International Nuclear Information System (INIS)

Tarafder, M.T.H.; Khan, A.R.

1997-01-01

The synthesis of peroxo complexes of molybdenum(VI), tungsten(VI), uranium(VI), zirconium(IV), thorium(IV) and their possible oxygen transfer reactions is presented. An attempt has also been made to study the size of the metal ions and the electronic effect derived from the tridentate Schiff bases on the v 1 (O-O) mode of the complexes in their IR spectra

Influence of radiolytic products on the chemistry of uranium VI in brines

International Nuclear Information System (INIS)

Lucchini, J-F.; Reed, D.T.; Borkowski, M.; Rafalski, A.; Conca, J.

2004-01-01

In the near field of a salt repository of nuclear waste, ionizing radiations can strongly affect the chemistry of concentrated saline solutions. Radiolysis can locally modify the redox conditions, speciation, solubility and mobility of the actinide compounds. In the case of uranium VI, radiolytic products can not only reduce U(VI), but also react with uranium species. The net effect on the speciation of uranyl depends on the relative kinetics of the reactions and the buildup of molecular products in brine solutions. The most important molecular products in brines are expected to be hypochlorite ion, hypochlorous acid and hydrogen peroxide. Although U(VI) is expected not to be significantly affected by radiolysis, the combined effects of the major molecular radiolytic products on the chemistry of U(VI) in brines have not been experimentally established previously. (authors)

Separation and concentration of uranium by extraction chromatography : U(VI) - H3PO4 system

International Nuclear Information System (INIS)

Nobre, J.S.M.

1981-01-01

The feasibility of using the extraction chromatographic technique as a way to recover uranium from phosphatic rocks evaluated. The behaviour of uranium from raw phsophoric acid solutions in chromatographic systems using the mixture di(2-ethylhexyl) orthophosphoric acid (D2EHPA) - tributyl phosphate (TBP) as the stationary phase was studied. Materials as alumina, activated carbon and the macroporous resins XAD-4 and XAD-7 were used as supports for organic stationary phase. The best results were obtained with poliacrilic polymer XAD-7, due to its excellent chromatographic properties and efficient organic phase retention. Uranium was quantitatively retained by D2EHPA-TBP-XAD-7 columns from synthetic phosphoric acid solutions with typical composition of phosphatic acid liquors. The elution of uranium from this system was also studied, and the best results were obtained with phosphoric acid solutions. This chromatographic column presented a high stability, not changing their properties even after more than twenty cycles, including the conditioning, sorption, wasking and elution steps. Uranium determinations were perfpormed by indirect titration with potassium dichromate and by molecular absorption spectrophotometry with hydrogen peroxide- carbonate. A new and more sensitive method for uranium determination in phosphoric medium, which might be applied to acid liquors of phosphatic ores, was developed. An extraction-photometric method was used, with Arsenazo III (1,8-dihydroxynaphtalene-3,6-disulphonic acid-2,7-bis(azo-2)-phenylarsonic acid) as the reagent for uranium. (Author) [pt

Coordination and solvent extraction behaviour of oxozirconium(IV), thorium(IV) and dioxouranium(VI)

International Nuclear Information System (INIS)

Dash, K.C.

1989-01-01

The systematic liquid-liquid extraction behaviour of oxozirconium (IV), thorium(IV) and dioxouranium(VI) have been investigated using a number of synthesised and commercial chelating extractants. The synergism or antagonism for these processes in presence of neutral donor ligands have also been identified and the conditions for separation and isolation of pure individual metal ions have been established. The coordination behaviour of oxozirconium(IV), thorium(IV) and dioxouranium(VI) with a large number of mono- and polydentate ligands have been studied. With oxozirconium(IV), invariably always a cyclic, tetranuclear species is obtained, derived from the tetrameric structure of the parent ZrOCl 2 .8H 2 O which is actually (Zr 4 (OH) 8 (H 2 O) 16 )Cl 8 .12H 2 O. No simple, monomeric oxozirconium(IV) complex was obtained. Uranium(VI) and thorium(IV) form a wide variety of complexes of higher coordination numbers and several bi- and trinuclear complexes were also characterised where the two adjacent metal centres are joined to each other by a double hydroxo-bridge. (author). 69 refs., 3 figs., 4 tabs

Uranium (Vi) sorption onto zirconium diphosphate chemically modified

International Nuclear Information System (INIS)

Garcia G, N.; Ordonez R, E.

2010-10-01

This work deals with the uranium (Vi) speciation after sorption onto zirconium diphosphate (ZrP 2 O 7 ) surface, hydrated and in a surface modified with organic acids. Oxalic and citric acids were chosen to modify the ZrP 2 O 7 surface because they have poly carboxylic groups and they mimic the organic matter in nature. Thus the interest of this work is to evaluate the uranium (Vi) sorption edge at different s ph values in natural and modified surfaces. The luminescence technique (fluorescence and phosphorescence, respectively) was used for the quantification and speciation of uranyl sorbed at the zirconium diphosphate interface. The fluorescence experiment, showed that adsorption of uranyl on surface of zirconium diphosphate tends to 100%. The speciation shows that there are different complexes in surface which were formed between zirconium diphosphate and uranyl, since it is produced a displacement of wavelength in fluorescence spectra of each system. (Author)

Preparation, characterization, uranium (VI) biosorption models, and conditions optimization by response surface methodology (RSM) for amidoxime-functionalized marine fungus materials

Energy Technology Data Exchange (ETDEWEB)

Yang, Xuechun; Gao, Yang; Jiang, Min; He, Dianxiong; Liao, Sen; Hou, Dan; Yan, Xueming; Long, Wei; Wu, Yaxin; Tan, Ni [Univ. of South China, Hengyang (China). School of Chemistry and Chemical Engineering

2017-08-01

Amidoxime-functionalized marine fungus Fusarium sp. ZZF51 (ZGDA) was synthesized and studied to adsorb uranium (VI) from the aqueous solution. Different instrumental techniques such as FTIR, SEM, and TGA were employed for the characterization of the manufactured materials, and theirs ability of removal uranium (VI) was optimized using RSM. The experimental results showed the maximum adsorption capacity for the synthesized materials was 230.78 mg g{sup -1} at the following optimization conditions: S-L ratio 150 mg L{sup -1}, pH 5.13, uranium (VI) initial concentration 40 mg L{sup -1}, and equilibrium time 122.40 min. More than 85% of the absorbed uranium (VI) could be desorbed by 0.5 or 1.0 mol L{sup -1} HCl, and the modified mycelium could be reused at least five times. The thermodynamic experimental data of adsorption uranium (VI) could fit better with Langmuir and Freundlich isotherms models, and the pseudo-second-order model was better to interpret the kinetics process. The modified fungus materials exhibited the better sorption capacity for uranium (VI) in comparison with raw biomass should be attributed to the strong chelation of amidoxime to uranium (VI) ions.

Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange

International Nuclear Information System (INIS)

Billon, A.

1968-04-01

The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO 2 (CO 3 ) 3 4+ ] S + 2 [CO 3 2- ] R ↔ [UO 2 (CO 3 ) 3 4- ] R + 2[CO 3 2- ] S is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [fr

In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen

International Nuclear Information System (INIS)

Wu, Weimin; Carley, Jack M.; Luo, Jian; Ginder-Vogel, Matthew A.; Cardenas, Erick; Leigh, Mary Beth; Hwang, Chaichi; Kelly, Shelly D.; Ruan, Chuanmin; Wu, Liyou; Van Nostrand, Joy; Gentry, Terry J.; Lowe, Kenneth Alan; Mehlhorn, Tonia L.; Carroll, Sue L.; Luo, Wensui; Fields, Matthew Wayne; Gu, Baohua; Watson, David B.; Kemner, Kenneth M.; Marsh, Terence; Tiedje, James; Zhou, Jizhong; Fendorf, Scott; Kitanidis, Peter K.; Jardine, Philip M.; Criddle, Craig

2007-01-01

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 (micro)M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water ( -1 or 0.126 (micro)M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L -1 ) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 (micro)M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 (micro)M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp

Investigation of the synergic effect of some neutral organophosphoric compounds on the extraction of uranium from phosphoric acid solutions by D1-(2-Ethyl Hexyl) phosphoric acid

International Nuclear Information System (INIS)

Stas, J.; Khorfan, S.; Koudsi, Y.

1998-05-01

The extraction of uranium (VI) from pure phosphoric acid media by D2EHPA/Kerosene has been studied. The mechanism of the extraction was found as follows: The logarithm of the equilibrium constant of the extraction (LogKex) was found (3.06), (3.32), (3.24), (3.3) for the following phosphoric acid concentrations respectively (1), (2), (3), (4) Mol/1, and the enthalpy change DELTA H was found (-100.68 kj/mol). (-76 kj/mol) for (1), (2) mol/1 phosphoric acid concentrations. The synergic effect of TOPO, TBP, and TBPI with DEHPA have been studied during the extraction of uranium from pure phosphoric acid and Syrian commercial phosphoric acid. The synergic effect increases as follows: TBP< TBPI<< TOPO (In pure phosphoric acid), TBPI approx TBP<< TOPO (In Syrian commercial phosphoric acid). The difficulty of extracting uranium (VI) from Syrian commercial phosphoric acid in comparison with pure phosphoric acid is due to the presence of several impurities capable of complexing uranium, and a small amounts of solid and organic matters, all these are factors which reduce the distribution coefficient of uranium. (Author)

Uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

Araujo Figueiredo, C. de

1984-01-01

The recovery of uranium from phosphoric liquor by two extraction process is studied. First, uranium is reduced to tetravalent condition and is extracted by dioctypyrophosphoric acid. The re-extraction is made by concentrated phosphoric acid with an oxidizing agent. The re-extract is submitted to the second process and uranium is extracted by di-ethylhexilphosphoric acid and trioctylphosphine oxide. (M.A.C.) [pt

Recovery of uranium from uranium bearing black shale

International Nuclear Information System (INIS)

Das, Amrita; Yadav, Manoj; Singh, Ajay K.

2016-01-01

Black shale is the unconventional resource of uranium. Recovery of uranium from black shale has been carried out by the following steps: i) size reduction, ii) leaching of uranium in the aqueous medium, iii) fluoride ion removal, iv) solvent extraction of uranium from the aqueous leach solution, v) scrubbing of the loaded solvent after extraction to remove impurities as much as possible and vi) stripping of uranium from the loaded organic into the aqueous phase. Leaching of black shale has been carried out in hydrochloric acid. Free acidity of the leach solution has been determined by potentiometric titration method. Removal of fluoride ions has been done using sodium chloride. Solvent extraction has been carried out by both tributyl phosphate and alamine-336 as extractants. Scrubbing has been tried with oxalic acid and sulphuric acid. Stripping with sodium carbonate solution has been carried out. Overall recovery of uranium is 95%. (author)

Adsorption of uranium(VI) to manganese oxides: X-ray absorption spectroscopy and surface complexation modeling.

Science.gov (United States)

Wang, Zimeng; Lee, Sung-Woo; Catalano, Jeffrey G; Lezama-Pacheco, Juan S; Bargar, John R; Tebo, Bradley M; Giammar, Daniel E

2013-01-15

The mobility of hexavalent uranium in soil and groundwater is strongly governed by adsorption to mineral surfaces. As strong naturally occurring adsorbents, manganese oxides may significantly influence the fate and transport of uranium. Models for U(VI) adsorption over a broad range of chemical conditions can improve predictive capabilities for uranium transport in the subsurface. This study integrated batch experiments of U(VI) adsorption to synthetic and biogenic MnO(2), surface complexation modeling, ζ-potential analysis, and molecular-scale characterization of adsorbed U(VI) with extended X-ray absorption fine structure (EXAFS) spectroscopy. The surface complexation model included inner-sphere monodentate and bidentate surface complexes and a ternary uranyl-carbonato surface complex, which was consistent with the EXAFS analysis. The model could successfully simulate adsorption results over a broad range of pH and dissolved inorganic carbon concentrations. U(VI) adsorption to synthetic δ-MnO(2) appears to be stronger than to biogenic MnO(2), and the differences in adsorption affinity and capacity are not associated with any substantial difference in U(VI) coordination.

Synthesis and evaluation of complexing and extracting properties of diamides for the U(VI)/Pu(IV) partitioning

International Nuclear Information System (INIS)

Wahu, S.

2012-01-01

This work concerns the synthesis and evaluation of new diamides for co-extraction of U(VI) and Pu(IV) from spent nuclear fuels in concentrated nitric acid medium and the subsequent selective back-extraction of Pu(IV) at lower nitric acidity. Thus, three diamides series, namely R 2 NOC(CH 2 ) n CONR 2 , RR'NOC(CH 2 ) n CONRR' and R 2 NOC(CH 2 CHR')CONR 2 (series 1, 2 and 3, respectively) were synthesized and studied in the expectation to establish a structure-activity relationship regarding the extraction properties of such compounds towards actinides. Extraction tests showed that these diamides can effectively and selectively extract U(VI) and Pu(IV) from Am(III) at high acidity. In addition, it was found that the selective back-extraction of Pu(IV) from U(VI) can be achieved, as expected, merely by changing the acidity, when the nitrogen atoms of these diamides are substituted by branched alkyl chains. The mode of coordination of actinides by the above diamides has also been studied through the use of short chain diamides model compounds, allowing the crystallization of the actinide complexes and, thus, their characterization by X-ray diffraction. EXAFS investigation suggested that the uranium coordination sphere in the complexes formed with long chain diamides and extracted into the organic phase is identical to the one observed in U(VI) complexes obtained with short chain diamides model compounds. However, the stoichiometry of model complexes is 1:1, UO 2 (NO 3 ) 2 TEDA, whereas extracted U(VI) complexes exhibit 1:2 stoichiometry, UO 2 (NO 3 ) 2 (TEHDA) 2 . Finally, Th (IV) complexes were also prepared and characterized and further compared to U(VI) complexes. (author) [fr

Extractive and spectrophotometric determination of U (VI) using 5-(3-phenolyl azo)-2-hydroxy-4-ethoxy propiophenone oxime (PHEPO)

International Nuclear Information System (INIS)

Subrahmanyam, P.; Krishnapriya, B.; Rekha, D.; Reddy Prasad, P.; Chiranjeevi, P.

2007-01-01

A simple spectrophotometric method for the determination of U (VI) using 5-(3-phenolyl azo)-2-hydroxy-4-ethoxy propiophenone oxime (PHEPO) is developed. The reagent PHEPO was synthesized and used for extraction of uranium. At pH 8.5-10.0 uranium forms a purple colored complex with PHEPO which was then quantitatively extracted in chloroform showing maximum absorbance at wavelength of 380nm. The proposed method obeys Beer's law in the range of 1.2-19.0ppm. molar absorptivity and Sandelson's sensitivity of extracted species were calculated to be 1.750 x 104 lmol-1 cm-1 and 8.5 x 10-5 mg cm-2 respectively. The method was applied for the determination of uranium in synthetic and plant samples. It was found that the newly developed method is competent to those of standard methods. (author)

Microbial reduction of uranium(VI) in sediments of different lithologies collected from Sellafield

International Nuclear Information System (INIS)

Newsome, Laura; Morris, Katherine; Trivedi, Divyesh; Atherton, Nick; Lloyd, Jonathan R.

2014-01-01

Highlights: • U(VI) (aq) mobility can be controlled by stimulating biogeochemical interactions. • Indigenous microbes in varied sediments reduced U(VI) to insoluble U(IV). • Sediment cell numbers and amount of bioavailable Fe(III) could limit this process. - Abstract: The presence of uranium in groundwater at nuclear sites can be controlled by microbial processes. Here we describe the results from stimulating microbial reduction of U(VI) in sediment samples obtained from a nuclear-licensed site in the UK. A variety of different lithology sediments were selected to represent the heterogeneity of the subsurface at a site underlain by glacial outwash deposits and sandstone. The natural sediment microbial communities were stimulated via the addition of an acetate/lactate electron donor mix and were monitored for changes in geochemistry and molecular ecology. Most sediments facilitated the removal of 12 ppm U(VI) during the onset of Fe(III)-reducing conditions; this was reflected by an increase in the proportion of known Fe(III)- and U(VI)-reducing species. However U(VI) remained in solution in two sediments and Fe(III)-reducing conditions did not develop. Sequential extractions, addition of an Fe(III)-enrichment culture and most probable number enumerations revealed that a lack of bioavailable iron or low cell numbers of Fe(III)-reducing bacteria may be responsible. These results highlight the potential for stimulation of microbial U(VI)-reduction to be used as a bioremediation strategy at UK nuclear sites, and they emphasise the importance of both site-specific and borehole-specific investigations to be completed prior to implementation

Kinetic and equilibrium study of uranium(VI) adsorption by Bacillus licheniformis

International Nuclear Information System (INIS)

Zheng-ji Yi; University of Science and Technology Beijing, Beijing; Jun Yao

2012-01-01

Uranium pollution is a severe problem worldwide. Biosorption has been proposed as one of the most promising technologies for the removal of uranyl cations. Here we report on the adsorption behavior of uranium(VI) [U(VI)] on Bacillus licheniformis biomass to explore the potentiality of its application in uranium contamination control. The adsorption equilibrium, adsorption kinetics, and effects of temperature, pH and initial biosorbent dosage on the adsorption equilibrium were investigated in detail through batch experiments. The adsorption process is pronouncedly affected by the solution pH and the optimum pH range should be 4.5-5.0.Temperature range from 25 to 45 deg C has a certain effect on the rate of biosorption, but little effect on the equilibrium adsorption capacity. The U(VI) percentage removal increased concurrently with increasing biomass dosage, whereas the adsorption capacity decreased. The process follows the Langmuir isotherm model. The adsorption kinetics data were fitted very well by the pseudo-first-order rate model. Finally, the calculation results of thermodynamic constant (ΔG a = 9.98 kJ/mol) reveal that the adsorption process can be identified as a spontaneous chemical process. The present results suggest that B. licheniformis has considerable potential for the removal of uranyl from aqueous solution. (author)

Microbial reduction of uranium(VI) by anaerobic microorganisms isolated from a former uranium mine

Energy Technology Data Exchange (ETDEWEB)

Gerber, Ulrike; Krawczyk-Baersch, Evelyn [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry; Arnold, Thuro [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures

2017-06-01

The former uranium mine Koenigstein (Germany) is currently in the process of controlled flooding by reason of remediation purposes. However, the flooding water still contains high concentrations of uranium and other heavy metals. For that reason the water has to be cleaned up by a conventional waste water treatment plant. The aim of this study was to investigate the interactions between anaerobic microorganisms and uranium for possible bioremediation approaches, which could be an great alternative for the intensive and expensive waste water treatment. EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements were performed and revealed a complete reduction of U(VI) to U(IV) only by adding 10 mM glycerol.

Microbial reduction of uranium(VI) by anaerobic microorganisms isolated from a former uranium mine

International Nuclear Information System (INIS)

Gerber, Ulrike; Krawczyk-Baersch, Evelyn; Arnold, Thuro; Scheinost, Andreas C.

2017-01-01

The former uranium mine Koenigstein (Germany) is currently in the process of controlled flooding by reason of remediation purposes. However, the flooding water still contains high concentrations of uranium and other heavy metals. For that reason the water has to be cleaned up by a conventional waste water treatment plant. The aim of this study was to investigate the interactions between anaerobic microorganisms and uranium for possible bioremediation approaches, which could be an great alternative for the intensive and expensive waste water treatment. EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements were performed and revealed a complete reduction of U(VI) to U(IV) only by adding 10 mM glycerol.

Uranium extraction in phosphoric acid

International Nuclear Information System (INIS)

Araujo Figueiredo, C. de

1984-01-01

Uranium is recovered from the phosphoric liquor produced from the concentrate obtained from phosphorus-uraniferous mineral from Itataia mines (CE, Brazil). The proposed process consists of two extraction cycles. In the first one, uranium is reduced to its tetravalent state and then extracted by dioctylpyrophosphoric acid, diluted in Kerosene. Re-extraction is carried out with concentrated phosphoric acid containing an oxidising agent to convert uranium to its hexavalent state. This extract (from the first cycle) is submitted to the second cycle where uranium is extracted with DEPA-TOPO (di-2-hexylphosphoric acid/tri-n-octyl phosphine oxide) in Kerosene. The extract is then washed and uranium is backextracted and precipitated as commercial concentrate. The organic phase is recovered. Results from discontinuous tests were satisfactory, enabling to establish operational conditions for the performance of a continuous test in a micro-pilot plant. (Author) [pt

Uranium refining by solvent extraction

International Nuclear Information System (INIS)

Kraikaew, J.; Srinuttrakul, W.

2014-01-01

The solvent extraction process to produce higher purity uranium from yellowcake was studied in laboratory scale. Yellowcake, which the uranium purity is around 70% and the main impurity is thorium, was obtained from monazite processing pilot plant of Rare Earth Research and Development Center in Thailand. For uranium re-extraction process, the extractant chosen was Tributylphosphate (TBP) in kerosene. It was found that the optimum concentration of TBP was 10% in kerosene and the optimum nitric acid concentration in uranyl nitrate feed solution was 4 N. An increase in concentrations of uranium and thorium in feed solution resulted in a decrease in the distribution of both components in the extractant. However, the distribution of uranium into the extractant was found to be more than that of thorium. The equilibration study of the extraction system, UO_2(NO_3)/4N HNO_3 – 10%TBP/Kerosene, was also investigated. Two extraction stages were calculated graphically from 100,000 ppm uranium concentration in feed solution input with 90% extraction efficiency and the flow ratio of aqueous phase to organic phase was adjusted to 1.0. For thorium impurity scrubbing process, 10% TBP in kerosene was loaded with uranium and minor thorium from uranyl nitrate solution prepared from yellowcake and was scrubbed with different low concentration nitric acid. The results showed that at nitric acid normality was lower than 1 N, uranium distributed well to aqueous phase. As conclusion, optimum nitric acid concentration for scrubbing process should not less than 1 N and diluted nitric acid or de-ionized water should be applied to strip uranium from organic phase in the final refining process. (author)

Approaches to surface complexation modeling of Uranium(VI) adsorption on aquifer sediments

Science.gov (United States)

Davis, J.A.; Meece, D.E.; Kohler, M.; Curtis, G.P.

2004-01-01

Uranium(VI) adsorption onto aquifer sediments was studied in batch experiments as a function of pH and U(VI) and dissolved carbonate concentrations in artificial groundwater solutions. The sediments were collected from an alluvial aquifer at a location upgradient of contamination from a former uranium mill operation at Naturita, Colorado (USA). The ranges of aqueous chemical conditions used in the U(VI) adsorption experiments (pH 6.9 to 7.9; U(VI) concentration 2.5 ?? 10-8 to 1 ?? 10-5 M; partial pressure of carbon dioxide gas 0.05 to 6.8%) were based on the spatial variation in chemical conditions observed in 1999-2000 in the Naturita alluvial aquifer. The major minerals in the sediments were quartz, feldspars, and calcite, with minor amounts of magnetite and clay minerals. Quartz grains commonly exhibited coatings that were greater than 10 nm in thickness and composed of an illite-smectite clay with occluded ferrihydrite and goethite nanoparticles. Chemical extractions of quartz grains removed from the sediments were used to estimate the masses of iron and aluminum present in the coatings. Various surface complexation modeling approaches were compared in terms of the ability to describe the U(VI) experimental data and the data requirements for model application to the sediments. Published models for U(VI) adsorption on reference minerals were applied to predict U(VI) adsorption based on assumptions about the sediment surface composition and physical properties (e.g., surface area and electrical double layer). Predictions from these models were highly variable, with results overpredicting or underpredicting the experimental data, depending on the assumptions used to apply the model. Although the models for reference minerals are supported by detailed experimental studies (and in ideal cases, surface spectroscopy), the results suggest that errors are caused in applying the models directly to the sediments by uncertain knowledge of: 1) the proportion and types of

Retention of uranium(VI) by laumontite, a fracture-filling material of granite

International Nuclear Information System (INIS)

Baik, M.H.; Lee, S.Y.; Shon, W.J.

2009-01-01

Retention of U(VI) by laumontite, a fracture-filling material of granite as investigated by conducting dynamic and batch sorption experiments in a love-box using a granite core with a natural fracture. The hydrodynamic properties of the granite core were obtained from the elution curve of a on-sorbing tracer, Br - . The elution curve of U(VI) showed a similar behavior to Br - . This reveals that the retention of U(VI) by the fracture-filling material was not significant when migrating through the fracture at a given condition. From the dynamic sorption experiment, the retardation factor R a and the distribution coefficient K a of U(VI) were obtained as about 2.9 and 0.16 cm, respectively. The distribution coefficient K d ) of U(VI) onto laumontite obtained by conducting a batch sorption experiment resulted in a small value of 2.3±0.5 mL/g. This low K d value greed with the result of the dynamic sorption experiment. For the distribution of uranium on the granite surface investigated by an X-ray image mapping, the fracture region filled with laumontite showed a relatively lower content of uranium compared to the surrounding granite surface. Thus, the low retention of U(VI) by the fracture-filling material can be explained by following two mechanisms. One is that U(VI) exists as anionic uranyl hydroxides or uranyl carbonates at a given groundwater condition and the other is the remarkably low sorption capacity of the laumontite for U(VI). author)

Effect of calcium/silicon ratio on retention of uranium (VI) in portland cement materials

International Nuclear Information System (INIS)

Tan Hongbin; Li Yuxiang

2005-01-01

Calcium silicate hydrate (CSH) materials of varied calcium to silicon (Ca/Si) ratios were prepared by hydrothermal synthesis at 80 degree C, with calcium oxide and micro-silicon employed. These products were determined to be of gel phase by XRD. Leaching tests with 1% hydrochloric acid indicated that more Uranium (VI) was detained by CSH with lower Ca/Si ratios. Alkali-activated slag cement (with a lower Ca/Si ratio) was found to have a stronger retention capacity than Portland cement (with a higher Ca/Si ratio), at 25 degree C in 102-days leaching tests with simulated solidified forms containing Uranium (VI). The accumulative leaching fraction of Uranium (VI) for Alkali-activated slag cement solidified forms is 17.6% lower than that for Portland cement. The corresponding difference of diffusion coefficients is 40.6%. This could be correlated with the difference of Ca/Si ratios between cements of two kinds. (authors)

Thermodynamic analysis of Cr(VI) extraction using TOPO impregnated membranes

Energy Technology Data Exchange (ETDEWEB)

Praveen, Prashant; Loh, Kai-Chee, E-mail: chelohkc@nus.edu.sg

2016-08-15

Highlights: • Cr(VI) extraction by extractant impregnated membranes (EIM) was investigated. • EIM exhibited high extraction efficiency, mass transfer rate and stability. • Mass transfer mechanism was proposed based on kinetics and equilibrium data. • Uptake of Cr(VI) by EIMs was endothermic and spontaneous. • Cr(VI) extraction by EIMs was dominated by physical interactions. - Abstract: Solid/liquid extraction of Cr(VI) was accomplished using trioctylphosphine oxide impregnated polypropylene hollow fiber membranes. Extraction of 100–500 mg/L Cr(VI) by the extractant impregnated membranes (EIM) was characterized by high uptake rate and capacity, and equilibrium was attained within 45 min of contact. Extraction equilibrium was pH-dependent (at an optimal pH 2), whereas stripping using 0.2 M sodium hydroxide yielded the highest recovery of 98% within 60 min. The distribution coefficient was independent of initial Cr(VI) concentration, and the linear distribution equilibrium isotherm could be modeled using Freundlich isotherm. The mass transfer kinetics of Cr(VI) was examined using pseudo-second-order and intraparticle diffusion models and a mass transfer mechanism was deduced. The distribution coefficient increased with temperature, which indicated endothermic nature of the reaction. Enthalpy and entropy change during Cr(VI) extraction were positive and varied in the range of 37–49 kJ/mol and 114–155 J/mol, respectively. The free energy change was negative, confirming the feasibility and spontaneity of the mass transfer process. Results obtained suggest that EIMs are efficient and sustainable for extraction of Cr(VI) from wastewater.

Modification of zirconium diphosphate with salicylic acid and its effect on the uranium (Vi) sorption; Modificacion del difosfato de circonio con acido salicilico y su efecto sobre la sorcion de uranio (VI)

Energy Technology Data Exchange (ETDEWEB)

Almazan T, M. G.; Garcia G, N. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Simoni, E., E-mail: guadalupe.almazan@inin.gob.mx [Universidad Paris Sud, Instituto de Fisica Nuclear, Georges Clemenceau No. 15, Orsay (France)

2014-10-15

The surface of zirconium diphosphate (ZrP{sub 2}O{sub 7}) was modified with salicylic acid and its effect was evaluated on the uranium (Vi) sorption. The modified surface of the material was analyzed with different analytical techniques among which are included the atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. This analysis allowed showing that the salicylic acid is being held on the surface of the zirconium diphosphate. The reactivity of modified zirconium diphosphate compared with uranium (Vi) was investigated using the classical method of batch sorption. The analysis of sorption isotherms shows that the salicylic acid has an important effect in the uranium (Vi) sorption. According to the study conducted, the interaction among the uranium (Vi) and the surface of zirconium diphosphate modified with the salicylic acid most likely leads to the complexes formation of binary (U(Vi)/ZrP{sub 2}O{sub 7}) and ternary (U(Vi)/salicylate/ZrP{sub 2}O{sub 7}) surface. (Author)

Uranium(VI) retention by Ca-bentonite under (hyper)alkaline conditions

Energy Technology Data Exchange (ETDEWEB)

Philipp, Thimo; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

The sorption behavior of U(VI) on Ca-bentonite was studied in saline, (hyper)alkaline solution via batch experiments. At pH 8.5-9.5 sorption is low in the presence of CO{sub 2} due to the formation of weakly sorbing uranyl carbonate species, which have been observed to dominate speciation up to pH 10 by time-resolved laser-induced fluorescence spectroscopy (TRLFS). In the pH region 10-12, U(VI) retention is almost complete. The retention can either be attributed to strongly sorbing uranyl hydroxo complexes or to a partial precipitation of uranium due to an altered solubility of U(VI) induced by ions leached out of the bentonite.

Sequential extraction of uranium metal contamination

International Nuclear Information System (INIS)

Murry, M.M.; Spitz, H.B.; Connick, W.B.

2016-01-01

Samples of uranium contaminated dirt collected from the dirt floor of an abandoned metal rolling mill were analyzed for uranium using a sequential extraction protocol involving a series of five increasingly aggressive solvents. The quantity of uranium extracted from the contaminated dirt by each reagent can aid in predicting the fate and transport of the uranium contamination in the environment. Uranium was separated from each fraction using anion exchange, electrodeposition and analyzed by alpha spectroscopy analysis. Results demonstrate that approximately 77 % of the uranium was extracted using NH 4 Ac in 25 % acetic acid. (author)

Separation and concentration of uranium by extraction chromatography : U(VI) - H/sub 3/PO/sub 4/ system

Energy Technology Data Exchange (ETDEWEB)

Nobre, J S.M.

1981-01-01

The feasibility of using the extraction chromatographic technique as a way to recover uranium from phosphatic rocks is evaluated. The behaviour of uranium from raw phsophoric acid solutions in chromatographic systems using the mixture di(2-ethylhexyl) orthophosphoric acid (D2EHPA) - tributyl phosphate (TBP) as the stationary phase was studied. Materials as alumina, activated carbon and the macroporous resins XAD-4 and XAD-7 were used as supports for organic stationary phase. The best results were obtained with poliacrilic polymer XAD-7, due to its excellent chromatographic properties and efficient organic phase retention. Uranium was quantitatively retained by D2EHPA-TBP-XAD-7 columns from synthetic phosphoric acid solutions with typical composition of phosphatic acid liquors. The elution of uranium from this system was also studied, and the best results were obtained with phosphoric acid solutions. This chromatographic column presented a high stability, not changing their properties even after more than twenty cycles, including the conditioning, sorption, washing and elution steps. Uranium determinations were perfpormed by indirect titration with potassium dichromate and by molecular absorption spectrophotometry with hydrogen peroxide- carbonate. A new and more sensitive method for uranium determination in phosphoric medium, which might be applied to acid liquors of phosphatic ores, was developed. An extraction-photometric method was used, with Arsenazo III (1,8-dihydroxynaphtalene-3,6-disulphonic acid-2,7-bis(azo-2)-phenylarsonic acid) as the reagent for uranium.

Comprehension of synergistic mechanisms for uranium extraction from phosphate ores

International Nuclear Information System (INIS)

Pecheur, Olivia

2014-01-01

Uranium VI is commonly extracted from phosphoric ores by a well-known process exploiting the synergistic mixture of two extractant molecules: HDEHP and TOPO. In the field of liquid-liquid extraction, synergistic combinations are common but the mechanisms at the origin of the synergy are not well understood. A multi-scale approach has been used to describe these mechanisms, combining two different descriptions: the molecular scale focuses on the ion point of view, while the supramolecular scale focuses on extractants' aggregation. These two approaches have been rationalized by molecular dynamics computations. The results allow describing the synergy through the structure of the complexes and aggregates. With the same approach, some bifunctional compounds, combining the two extracting sites in one molecule, have been studied and compared to the HDEHP/TOPO system in order to identify the origin of their increased capacities in extraction and selectivity. (author) [fr

Investigation on Microbial Dissolution of Uranium (VI) from Autunite Mineral - 13421

International Nuclear Information System (INIS)

Sepulveda, Paola; Katsenovich, Yelena; Lagos, Leonel

2013-01-01

Precipitating autunite minerals by polyphosphate injection was identified as a feasible remediation strategy for sequestering uranium in contaminated groundwater and soil in situ at the Hanford Site. Autunite stability under vadose and saturated zone environmental conditions can help to determine the long-term effectiveness of this remediation strategy. The Arthrobacter bacteria are one of the most common groups in soils and are found in large numbers in Hanford soil as well as other subsurface environments contaminated with radionuclides. Ubiquitous in subsurface microbial communities, these bacteria can play a significant role in the dissolution of minerals and the formation of secondary minerals. The main objective of this investigation was to study the bacterial interactions under oxidizing conditions with uranium (VI); study the potential role of bicarbonate, which is an integral complexing ligand for U(VI) and a major ion in groundwater compositions; and present data from autunite dissolution experiments using Arthrobacter strain G968, a less U(VI)-tolerant strain. Sterile 100 mL glass mixed reactors served as the major bioreactor for initial experimentation. These autunite-containing bioreactors were injected with bacterial cells after the autunite equilibrated with the media solution amended with 0 mM, 3 mM 5 mM and 10 mM concentrations of bicarbonate. G968 Arthrobacter cells in the amount of 10 6 cells/mL were injected into the reactors after 27 days, giving time for the autunite to reach steady state. Abiotic non-carbonate controls were kept without bacterial inoculation to provide a control for the biotic samples. Samples of the solution were analyzed for dissolved U(VI) by means of kinetic phosphorescence analyzer KPA-11 (Chemcheck Instruments, Richland, WA). Analysis showed that as [HCO 3 - ] increases, a diminishing trend on the effect of bacteria on autunite leaching is observed. Viability of cells was conducted after 24 hours of cell incubation with

Investigation on Microbial Dissolution of Uranium (VI) from Autunite Mineral - 13421

Energy Technology Data Exchange (ETDEWEB)

Sepulveda, Paola; Katsenovich, Yelena; Lagos, Leonel [Applied Research Center, Florida International University. 10555 West Flagler St. Suite 2100, Miami Fl 33175 (United States)

2013-07-01

Precipitating autunite minerals by polyphosphate injection was identified as a feasible remediation strategy for sequestering uranium in contaminated groundwater and soil in situ at the Hanford Site. Autunite stability under vadose and saturated zone environmental conditions can help to determine the long-term effectiveness of this remediation strategy. The Arthrobacter bacteria are one of the most common groups in soils and are found in large numbers in Hanford soil as well as other subsurface environments contaminated with radionuclides. Ubiquitous in subsurface microbial communities, these bacteria can play a significant role in the dissolution of minerals and the formation of secondary minerals. The main objective of this investigation was to study the bacterial interactions under oxidizing conditions with uranium (VI); study the potential role of bicarbonate, which is an integral complexing ligand for U(VI) and a major ion in groundwater compositions; and present data from autunite dissolution experiments using Arthrobacter strain G968, a less U(VI)-tolerant strain. Sterile 100 mL glass mixed reactors served as the major bioreactor for initial experimentation. These autunite-containing bioreactors were injected with bacterial cells after the autunite equilibrated with the media solution amended with 0 mM, 3 mM 5 mM and 10 mM concentrations of bicarbonate. G968 Arthrobacter cells in the amount of 10{sup 6} cells/mL were injected into the reactors after 27 days, giving time for the autunite to reach steady state. Abiotic non-carbonate controls were kept without bacterial inoculation to provide a control for the biotic samples. Samples of the solution were analyzed for dissolved U(VI) by means of kinetic phosphorescence analyzer KPA-11 (Chemcheck Instruments, Richland, WA). Analysis showed that as [HCO{sub 3}{sup -}] increases, a diminishing trend on the effect of bacteria on autunite leaching is observed. Viability of cells was conducted after 24 hours of cell

Membrane extraction in preconcentration of some uranium fission products

International Nuclear Information System (INIS)

Macasek, F.; Rajec, P.; Kopunec, R.; Mikulaj, V.

1984-01-01

Theoretical comparison of the equilibria and kinetics of solvent extraction (SX) and emulsion liquid membrane extraction (MX) was performed using the distribution ratios at the outer inner boundaries of liquid membrane. Enhancement factors, pertraction factor (p) and mulitplication factor (N), were proposed to express efficiency of the MX technique. The extraction of cesium, strontium, cobalt(II), uranium(VI), cerium(III) and technetium(VII) was investigated from this point of view. The most perspective systems are those with chelating agents (e.g. di-2-ethylhexyl-phosporic acid and 8-hydroquinoline), especially at low concentrations (substioichiometric amounts), with which high enhancement factors can be achieved. The results with the ion-exchange systems (bis(1,2-dicarbollyl)-cobalt(III) and quaternary ammonium salts) may be interpreted as indicating some surface barriers which prevent the transport of ions. 20 references, 14 figures, 6 tables

Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange; Etude des solutions d'uranium (VI) en milieu carbonate par titrages potentiometriques et echange d'ions

Energy Technology Data Exchange (ETDEWEB)

Billon, A [Commissariat a l' Energie Atomique, 92 - Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1968-04-01

The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [French] Le present travail precise la fixation de l'uranium (VI) sur la resine echangeuse d'anions Dowex 2 X 8, en milieu carbonate et hydrogeno-carbonate. Nous en avons deduit que ces deux milieux sont egalement favorables a la recuperation de l'uranium a partir de solutions tres diluees. La constante d'equilibre de la reaction d'echange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} a ete determinee pour le milieu carbonate 0.1 M a 0.6 M, a partir deb courbes de partage. La fixation relative de l'uranium augmente considerablement lorsque: - la concentration du carbonate libre (respectivement hydrogenocarbonate) diminue, - la concentration de l'uranium en solution diminue. Le comportement du molybdene a ete etudie en vue de la separation uranium-molybdene. L'ion fixe sur la resine est l'ion molybdate MoO{sub 4}{sup 2-}. La separation est

TREATMENT TESTS FOR EX SITU REMOVAL OF CHROMATE & NITRATE & URANIUM (VI) FROM HANFORD (100-HR-3) GROUNDWATER FINAL REPORT

Energy Technology Data Exchange (ETDEWEB)

BECK MA; DUNCAN JB

1994-01-03

This report describes batch and ion exchange column laboratory scale studies investigating ex situ methods to remove chromate (chromium [VI]), nitrate (NO{sub 3}{sup -}) and uranium (present as uranium [VI]) from contaminated Hanford site groundwaters. The technologies investigated include: chemical precipitation or coprecipitation to remove chromate and uranium; and anion exchange to remove chromate, uranium and nitrate. The technologies investigated were specified in the 100-HR-3 Groundwater Treatability Test Plan. The method suggested for future study is anion exchange.

Synthesis of xanthate functionalized silica gel and its application for the preconcentration and separation of uranium(VI) from inorganic components

International Nuclear Information System (INIS)

Gopi Krishna, P.; Naidu, G.R.K.; Rao, K.S.

2005-01-01

A new chelating solid extractant prepared by the chemical immobilization of xanthate on silica gel was characterized by Fourier transform infra red spectrometry (FTIR), thermogravimetric analysis (TGA) and microanalysis and used for the preconcentration and separation of uranyl ion prior to its determination by Arsenazo-III. The effect of pH, weight of the solid extractant, volume of the aqueous phase and the interference of neutral electrolytes, cations and anions on the determination of uranium, have been studied in detail to optimize the conditions for trace determination of uranium(VI). The accuracy of the developed procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA-SOIL-7) reference materials. The results obtained on analysis of soil and sediment samples are comparable to standard ICP-MS values. (author)

Enhancement of uranium(VI) biosorption by chemically modified marine-derived mangrove endophytic fungus Fusarium sp. ZZF51

International Nuclear Information System (INIS)

Chen, F.; Tan, N.; Long, W.; Yang, S.K.; She, Z.G.; Lin, Y.C.

2014-01-01

Fusarium sp. ZZF51, mangrove endophytic fungus originated from South China Sea coast, was chemically modified by formaldehyde, methanol and acetic acid to enhance its affinity of uranium(VI) from waste water. The influencing factors about uranium(VI) adsorption such as contact time, solution pH, the ratio of solid/liquid (S/L) and initial uranium(VI) concentration were investigated, and the suitable adsorption isotherm and kinetic models were determined. In addition, the biosorption mechanism was also discussed by FTIR analysis. Experimental results show that the maximum biosorption capacity of formaldehyde-treated biomass for uranium(VI) at the optimized condition of pH 6.0, S/L 0.6 and equilibrium time 90 min is 318.04 mg g -1 , and those of methanol-treated and HAc-treated biomass are 311.95 and 351.67 mg g -1 at the same pH and S/L values but different equilibrium time of 60 and 90 min, respectively. Thus the maximum biosorption capacity of the three kind of modified biomass have greatly surpassed that of the raw biomass (21.42 mg g -1 ). The study of kinetic exhibits a high level of compliance with the Lagergren's pseudo-second-order kinetic models. Langumir and Freundlich models have proved to be well able to explain the sorption equilibrium with the satisfactory correlation coefficients higher than 0.96. FTIR analysis reveals that the carboxyl, amino and hydroxyl groups on the cell wall of Fusarium sp. ZZF51 play an important role in uranium(VI) biosorption process. (author)

Uranium in drinking water. A simple determination of uranium (VI) according to DIN standard 38406-17

International Nuclear Information System (INIS)

Haug, Sandro

2009-01-01

The number of reports on uranium loads in tap water and drinking water increases. Already for years, the organization Foodwatch e.V. (Berlin, Federal Republic of Germany) warns about to high concentrations of uranium in tap water. So far, only a limit value for mineral water exists in the Mineral Water Regulation which is suitable for the production of infant diet. This limit value amounts 2 microgram per litre. Temporarily, also in the policy a national limit value for uranium in drinking water is introduced. The Federal Office for Environment Protection (Dessau, FRG) designates a value of ten microgram uranium per litre of drinking water and mineral water as an approximate value. The effective control of water quality presupposes high-performance, simple and economical analysis methods. A particularly well suitable measuring technique for the determination of uranium(VI) in groundwater, raw water and drinking water is the voltammetry. In the last years, a national standard was compiled based on this measuring technique: DIN standard 38406-17

Gravimetric determination of uranium(VI) and thorium(IV) with substituted pyrazolones

International Nuclear Information System (INIS)

Arora, H.C.; Rao, G.N.

1981-01-01

4-Acylpyrazolones like 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), 1-phenyl-3-methyl-4-p-nitrobenzoyl-5-pyrazolone (PMNP) and 1-phenyl-3-methyl-4-(3,5 dinitrobenzoyl)-5-pyrazolone (PMDP) have been synthesized and developed as gravimetric reagents for the determination of U(VI) and Th(IV). Uranium(VI) is almost quantitatively precipitated with PMBP, PMNP, and PMDP at pH 2.20, 1.85 and 1.70 respectively. The pH values for the complete precipitation of thorium(IV) with PMBP, PMNP and PMDP are 2.90, 2.75 and 2.50 respectively. PMBP has proved to be an efficient ligand for gravimetric determination of U(VI) by direct weighing method after drying at 100 +- 10 deg C. The percentage relative error varies from 0.4 to 1.6 in the determination of U(VI) by this method. The effect of a number of interfering ions on the precipitation of U(VI) by PMBP has been reported. (author)

Liquid-liquid extraction of uranium from nitric acid solution using di-n-butylsulfoxide in petroleum ether as extractant

Energy Technology Data Exchange (ETDEWEB)

Khan, M.H.; Shahida, S. [Dept. of Chemistry, Univ. of Azad Jammu and Kashmir, Muzaffarabad (Pakistan); Ali, A. [Nuclear Chemistry Div., Pakistan Inst. of Nuclear Science and Technology, Nilore, Islamabad (Pakistan)

2008-07-01

A simple, efficient and economical liquid-liquid extraction method has been developed for quantitative extraction of uranium from 2 M HNO{sub 3} using di-n-butyl sulfoxide in petroleum ether. The dependence of the partition reaction of U(VI) on the concentration of HNO{sub 3}, extractant and temperature was studied. The reaction was found to be inversely dependent upon the temperature and the values for related thermodynamics functions ({delta}H, {delta}S, {delta}G) for extraction equilibrium were determined to be -33.6 kJ/mol, -1.29 kJ/mol/degree and -0.11 kJ/mol/degree, respectively. The effect of Al(NO{sub 3}){sub 3} as salting-out agent and diverse ions on the extraction was examined. The salting-out agent slightly enhanced the extraction. All cations studied have showed negligible effect on the extraction, whereas phosphate and fluoride interfered seriously. Among others, oxalate, citrate and sulphide ions affect the extraction to a lesser extent. Uranium was successfully extracted from a synthetic mixture of Ti{sup +4}, Zr{sup +4}, Hf{sup +4} and Th{sup +4} using EDTA as masking agent. Among strippants, deionized water was found most suitable, and the recovery of uranium was noted to be {>=} 96%. The stoichiometric composition of the extracted species was found to be UO{sub 2}(NO{sub 3}){sub 2} . 2DBSO. The extraction mechanism is discussed on the basis of the results obtained. The extractant has high loading as well as recycling capacity without any degradation. The method was also applied to the Standard Reference Material (NBL-49) and the measured value was found to be in agreement with the reported value within {+-}2% deviation. (orig.)

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite.

Science.gov (United States)

Meng, Fande; Yuan, Guodong; Larson, Steven L; Ballard, John H; Waggoner, Charles A; Arslan, Zikri; Han, Fengxiang X

2017-12-01

The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g -1 at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO 3 and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO 3 and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extraction and desorption of accessible uranium

International Nuclear Information System (INIS)

Payne, T.

1987-01-01

The proportion of the uranium in natural ore samples which is in isotopic equilibrium with the uranium in the groundwater may be designated accessible uranium, and can be regarded as being in short-term exchange with the aqueous phase. Some of the natural uranium is secured in resistant crystalline minerals, and is described as inaccessible, because it may not be brought into solution unless the mineral is subjected to extreme chemical attack. It is not available for groundwater transport in the short term. An estimate of the proportion of accessible uranium is therefore useful when modeling radionuclide migration. The amount of accessible natural uranium is some uranium ore samples from the Ranger deposit has been determined by combining a sequential extraction with isotopic measurements of the extracted phases. The solid samples were crushed drill core form Ranger S1/146 which had previously been used for uranium adsorption experiments and therefore contained 236 U as well as natural uranium. This Section discusses how the uranium partitioning found with the sequential extraction procedure predicts the leaching behavior of these samples

Separation of uranium(VI) by liquid-solid extraction with tri-n-octylphosphine oxide diluted with naphthalene

International Nuclear Information System (INIS)

Shigetomi, Y.; Kojima, T.; Kamba, H.; Yamamoto, Y.

1980-01-01

Liquid-liquid distribution with tri-n-octylphosphine oxide (TOPO) and molten naphthalene has been investigated for the extraction of 20 metals from nitric acid and hydrochloric acid solutions. Uranium is quantitatively extracted from 1 M nitric acid or hydrochloric acid by using 100 mg of TOPO and 200 mg of naphthalene and shaking for 5 min at 80 0 C, and separated from transition metals, alkaline earth metals and rare earth metals (except scandium). Addition of naphthalene increases the extraction efficiency. (Auth.)

Study of uranium (VI) in carbonate solution by potentiometric titrations and ion-exchange; Etude des solutions d'uranium (VI) en milieu carbonate par titrages potentiometriques et echange d'ions

Energy Technology Data Exchange (ETDEWEB)

Billon, A. [Commissariat a l' Energie Atomique, 92 - Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1968-04-01

The present work is devoted to the fixation of uranium (VI) on the conventional anion-exchange resin Dowex 2 X 8 in carbonate and hydrogen-carbonate media. Both media were successfully used for the recuperation of uranium (VI) from very dilute solutions. Equilibrium constant of the exchange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} is determined for carbonate concentration range 0.1 M to 0.6 M from partition curves. A markedly increase in the relative fixation of uranium results with: - increasing free carbonate concentration of the solution, - decreasing uranium concentration. A study in the same conditions of the fixation of molybdenum has made it possible to separate the latter from uranium by elution, the carbonate concentration being molar. It is suggested a possibility of separation on a larger scale, based upon molybdenum displacement by uranium in hydrogen-carbonate medium. (author) [French] Le present travail precise la fixation de l'uranium (VI) sur la resine echangeuse d'anions Dowex 2 X 8, en milieu carbonate et hydrogeno-carbonate. Nous en avons deduit que ces deux milieux sont egalement favorables a la recuperation de l'uranium a partir de solutions tres diluees. La constante d'equilibre de la reaction d'echange [UO{sub 2}(CO{sub 3}){sub 3}{sup 4+}]{sub S} + 2 [CO{sub 3}{sup 2-}]{sub R} {r_reversible} [UO{sub 2}(CO{sub 3}){sub 3}{sup 4-}]{sub R} + 2[CO{sub 3}{sup 2-}]{sub S} a ete determinee pour le milieu carbonate 0.1 M a 0.6 M, a partir deb courbes de partage. La fixation relative de l'uranium augmente considerablement lorsque: - la concentration du carbonate libre (respectivement hydrogenocarbonate) diminue, - la concentration de l'uranium en solution diminue. Le comportement du molybdene a ete etudie en vue de la separation uranium-molybdene. L'ion fixe sur la resine est l

Uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

Lounis, A.

1983-05-01

A study has been carried out for the extraction of uranium from phosphoric acid produced in Algeria. First of all, the Algerian phosphoric acid produced in Algeria by SONATRACH has been characterised. This study helped us to synthesize a phosphoric acid that enabled us to pass from laboratory tests to pilot scale tests. We have then examined extraction and stripping parameters: diluent, DZEPHA/TOPO ratio and oxidising agent. The laboratory experiments enabled us to set the optimum condition for the choice of diluent, extractant concentration, ratio of the synergic mixture, oxidant concentration, redox potential. The equilibrium isotherms lead to the determination of the number of theoretical stages for the uranium extraction and stripping of uranium, then the extraction from phosphoric acid has been verified on a pilot scale (using a mixer-settler)

Spectrophotometric determination of trace amount of uranium (VI) in different aqueous and organic streams of nuclear fuel processing using 2-(5-bromo-2-pyridylazo-5-diethylaminophenol)

International Nuclear Information System (INIS)

Das, S.K.; Kedari, C.S.; Tripathi, S.C.

2010-01-01

Present investigation describes the development of a spectrophotometric method for trace level determination of U(VI) encountered during the process of nuclear fuel fabrication and reprocessing industries. A chromogenic reagent, 2-(5-bromo-2-pyridylazo-5-diethylaminophenol) (Br-PADAP) is used to complex with U(VI) under optimized solution conditions. The absorption maxima of the uranyl Br-PADAP complex at 578 nm is computed to be 73540 ± 1438 for U-Br-PADAP solution containing 20% ethanol (in aqueous sample media) and 58216 ± 1208 for U-Br-PADAP solution containing 80% ethanol (for organic sample media). Employing suitable sample treatment methods, the scope of analytical method has been widened to permit accurate determination of U(VI) in the samples with variation in the relative compositions of Th(IV), Pu(IV) and Fe(III). The method is applicable to samples matrices with, acidic, alkaline highly salted media. Effect of commonly associated ionic species on the optical density of U-Br-PADAP is determined. Depending on the extent of the interfering impurities present, the method permits estimation of U(VI) either direct or after its selective extraction into tri-octyl phosphine oxide dissolved in cyclohexane. The method is precise with <5% standard error and can be used for the estimation of uranium in organic as well as in aqueous samples. The method has been validated for quantitative determination of uranium extracted in the organic phase comprising of heavy metal extractants like TBP, HDEHP, PC-88A and Aliquot 336. (author)

Solid-Phase Extraction of Trace Amounts of Uranium(VI in Environmental Water Samples Using an Extractant-Impregnated Resin Followed by Detection with UV-Vis Spectrophotometry

Directory of Open Access Journals (Sweden)

Ahmad Hosseini-Bandegharaei

2013-01-01

Full Text Available A stable extractant-impregnated resin (EIR containing Chrome Azurol B was prepared using Amberlite XAD-2010 as a porous polymeric support. The new EIR was employed for trace separation and preconcentration of U(VI ion followed by spectrophotometric determination with the arsenazo III procedure. CAB/XAD-2010 exhibited excellent selectivity for U(VI ion over coexisting ions. Experimental parameters including pH, contact time, shaking speed, and ionic strength were investigated by batch extraction methods. Maximum sorption of U(VI ions occurred at pH 4.3–6.9. The capacity of EIR was found to be 0.632 mmol·g−1. Equilibrium was reached in 25 min and the loading half-time, t1/2, was less than 6 min. The equilibrium adsorption isotherm of U(VI was fitted with the Langmuir adsorption model. In addition, a column packed with CAB/XAD-2010 was used for column-mode separation and preconcentration of U(VI ion. For the optimization of the dynamic procedure, effects of sample volume, sample and eluent flow rate, eluent concentration, and its volume were investigated. The preconcentration factors for U(VI were found out to be 160. But, for convenience, a preconcentration factor of 150 was utilized for the column-mode preconcentration. The dynamic procedure gave a detection limit of 5.0×10-10 mol·L−1 (0.12 μg·L−1 for U(VI ion. The proposed dynamic method showed good performance in analyzing environmental water samples.

A coupled mass transfer and surface complexation model for uranium (VI) removal from wastewaters

International Nuclear Information System (INIS)

Lenhart, J.; Figueroa, L.A.; Honeyman, B.D.

1994-01-01

A remediation technique has been developed for removing uranium (VI) from complex contaminated groundwater using flake chitin as a biosorbent in batch and continuous flow configurations. With this system, U(VI) removal efficiency can be predicted using a model that integrates surface complexation models, mass transport limitations and sorption kinetics. This integration allows the reactor model to predict removal efficiencies for complex groundwaters with variable U(VI) concentrations and other constituents. The system has been validated using laboratory-derived kinetic data in batch and CSTR systems to verify the model predictions of U(VI) uptake from simulated contaminated groundwater

Effect of uranium (VI) on the growth of yeast and influence of metabolism of yeast on adsorption of U (VI)

International Nuclear Information System (INIS)

Sakamoto, Fuminori; Ohnuki, Toshihiko; Kozai, Naofumi; Wakai, Eiichi; Francis, A.J.

2005-01-01

We have carried out the growth experiments of 3 strains of yeast in a medium containing uranium (VI) to elucidate the effect of U (VI) on the growth of microorganisms. Hansenula fabianii J640 grew in the liquid medium containing 0.1 mM U (VI) at lower rate than the control, but Saccharomyces cerevisiae did not grow under this condition. The H. fabianii J640 pre-cultured for 21 h in the liquid medium without U (VI) grew even after the exposure to 1 mM U (VI), but did not grow without pre-cultivation. For the pre-cultured H. fabianii J640, radioactivity of U in the medium was the same as the initial one for 110 h, and then gradually decreased. TEM-EDS analysis of H. fabianii J640 exposed to 1 mM U (VI) for 165 h showed accumulation of U (VI) on the cells. When H. fabianii J640 was not pre-cultured, radioactivity of U in the medium was lower than the initial one. These results indicated that U (VI) inhibits the growth of yeast, and that the adsorption of U (VI) by the cells depends on the metabolism of yeast. (author)

Studies on the kinetics of uranium (VI) electro-reduction and reextraction: Pt. 2

International Nuclear Information System (INIS)

Tong Jihong; Ma Xuquan; Tai Derong; Sun Shiren

1992-01-01

The kinetics of U(VI) reextraction and U(IV) extraction in the process of U(VI) electro-reduction with the system of HNO 3 -N 2 H 5 NO 3 (H 2 O)/UO 2 (NO 3 ) 2 -HNO 3 (30% TBP-OK) is investigated with a constant interfacial area cell (Lewis cell) with cathode and anode in it. According to the experimental results and data processing, the apparent activation energy of the U(VI) reextraction process is 36.02 kJ/nol. The U(VI) reextraction rate increases when the stirring speed of two phases increases. This process is mainly diffusion controlled. For the U(VI) extraction process, the apparent activation energy is 21.13 kJ/mol. The U(IV) extraction rate also increases when the stirring speed of two phases increases. This process is mainly diffusion controlled. The lower the potential of cathode is, the higher the rates of U(VI) reextraction and U(IV) extraction are

Sorption of uranium (VI) on homoionic sodium smectite experimental study and surface complexation modeling.

Science.gov (United States)

Korichi, Smain; Bensmaili, Aicha

2009-09-30

This paper is an extension of a previous paper where the natural and purified clay in the homoionic Na form were physico-chemically characterized (doi:10.1016/j.clay.2008.04.014). In this study, the adsorption behavior of U (VI) on a purified Na-smectite suspension is studied using batch adsorption experiments and surface complexation modeling (double layer model). The sorption of uranium was investigated as a function of pH, uranium concentration, solid to liquid ratio, effect of natural organic matter (NOM) and NaNO(3) background electrolyte concentration. Using the MINTEQA2 program, the speciation of uranium was calculated as a function of pH and uranium concentration. Model predicted U (VI) aqueous speciation suggests that important aqueous species in the [U (VI)]=1mg/L and pH range 3-7 including UO(2)(2+), UO(2)OH(+), and (UO(2))(3)(OH)(5)(+). The concentration of UO(2)(2+) decreased and that of (UO(2))(3)(OH)(5)(+) increased with increasing pH. The potentiometric titration values and uptake of uranium in the sodium smectite suspension were simulated by FITEQL 4.0 program using a two sites model, which is composed of silicate and aluminum reaction sites. We compare the acidity constants values obtained by potentiometric titration from the purified sodium smectite with those obtained from single oxides (quartz and alpha-alumina), taking into account the surface heterogeneity and the complex nature of natural colloids. We investigate the uranium sorption onto purified Na-smectite assuming low, intermediate and high edge site surfaces which are estimated from specific surface area percentage. The sorption data is interpreted and modeled as a function of edge site surfaces. A relationship between uranium sorption and total site concentration was confirmed and explained through variation in estimated edge site surface value. The modeling study shows that, the convergence during DLM modeling is related to the best estimation of the edge site surface from the N(2

Extractive behavior of U(VI) in the paraffin soluble ionic liquid

International Nuclear Information System (INIS)

Rama, R.; Kumaresan, R.; Venkatesan, K.A.; Antony, M.P.; Vasudeva Rao, P.R.

2013-01-01

An Aliquat-336 based ionic liquid namely, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ((A3636) + (DEHP) - ) was prepared and studied for the extraction of U(VI) from nitric acid medium. Since the ionic liquid, (A336) + (DEHP) - , was miscible in n-dodecane (n-DD), the extraction of U(VI) in the solution of tri-n-butylphosphate (TBP) in n-DD, was investigated in the presence of small concentrations of ionic liquid. The distribution ratio of U(VI) in 0.3 M (A336) + (DEHP) - /n-DD decreased with increase in the concentration of nitric acid. The effect of concentration of TBP, ionic liquid nitric acid and nitrate ion on the extraction of U(VI) in ionic liquid medium was studied. The mechanistic aspect of extraction was investigated by the slope analysis of the extraction data. The studies indicated the feasibility of modifying the extractive properties of U(VI) in TBP/n-DD using ionic liquid. (author)

Preparation of N-1 -naphthyl benzo- and N-phenyl benzo hydroxamic acids and study of their extractability towards Fe (III), Cr (VI) and U (VI)

Energy Technology Data Exchange (ETDEWEB)

Mohamed, Eltoum Elnour [Department of Chemistry, Faculty of Science, University of Khartoum, Khartoum (Sudan)

1997-12-01

Two aryl hydroxamic acids were prepared; The N-phenyl benzo hydroxamic acid and the N-1- naphthyl benzohydroxamic acid the first one was prepared by the partial reduction of nitrobenzene to the {beta}-phenyl hydroxylamine and coupling the latter with benzyl chloride. The reduction was carried out using ammonium chloride and zinc dust; this pair failed after so many attempts to give the N-1- naphthyl hydroxylamine. So the latter was prepared by using a somewhat milder reducing agent; hydrogen sulphide and ammonia gas in absolute alcohol. The two acids were obtained using the modified procedure of Tandon coupling the hydroxylamine with benzoyl chloride. The two acids were characterized by their melting points, elemental analysis, their I.R functional group frequencies and by their characteristic colour tests with vanadium (VI) and Iron (III). The acids were used for the extraction and spectrophotometric determination for iron (III), Chromium (VI), and Uranium (VI) from different molar solution, PH and from synthetic sea water. The maximum recovery of iron (III) occurred at PH 4 and PH 5 giving 92.25 and 91.25% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 100% at PH 5 with other acid. The maximum recovery of Chromium (VI) occurred at 3MH{sup 2}SO{sup 4} of 97.50% when using N-1-naphthyl benzohydroxamic acid and a maximum of 94.25% at the same molar concentration with N-phenyl benzo hydroxamic acid. The maximum recovery for Uranium (VI) was occurred at PH 7 giving 100% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 85% at PH 7 and PH* with the other acid. The two reagents give sharp colour with both iron (III) and chromium (VI), so trials were carried out to compare the curves obtained with that of the original reagent i.e. Thiocynate and diphenylcarbazide, which give a smaller slope.(Author) 121 refs. , 15 tabs. , 13 figs

Preparation of N-1 -naphthyl benzo- and N-phenyl benzo hydroxamic acids and study of their extractability towards Fe (III), Cr (VI) and U (VI)

International Nuclear Information System (INIS)

Mohamed, Eltoum Elnour

1997-12-01

Two aryl hydroxamic acids were prepared; The N-phenyl benzo hydroxamic acid and the N-1- naphthyl benzohydroxamic acid the first one was prepared by the partial reduction of nitrobenzene to the β-phenyl hydroxylamine and coupling the latter with benzyl chloride. The reduction was carried out using ammonium chloride and zinc dust; this pair failed after so many attempts to give the N-1- naphthyl hydroxylamine. So the latter was prepared by using a somewhat milder reducing agent; hydrogen sulphide and ammonia gas in absolute alcohol. The two acids were obtained using the modified procedure of Tandon coupling the hydroxylamine with benzoyl chloride. The two acids were characterized by their melting points, elemental analysis, their I.R functional group frequencies and by their characteristic colour tests with vanadium (VI) and Iron (III). The acids were used for the extraction and spectrophotometric determination for iron (III), Chromium (VI), and Uranium (VI) from different molar solution, PH and from synthetic sea water. The maximum recovery of iron (III) occurred at PH 4 and PH 5 giving 92.25 and 91.25% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 100% at PH 5 with other acid. The maximum recovery of Chromium (VI) occurred at 3MH 2 SO 4 of 97.50% when using N-1-naphthyl benzohydroxamic acid and a maximum of 94.25% at the same molar concentration with N-phenyl benzo hydroxamic acid. The maximum recovery for Uranium (VI) was occurred at PH 7 giving 100% when using N-1-naphthyl benzo hydroxamic acid and a maximum recovery of 85% at PH 7 and PH* with the other acid. The two reagents give sharp colour with both iron (III) and chromium (VI), so trials were carried out to compare the curves obtained with that of the original reagent i.e. Thiocynate and diphenylcarbazide, which give a smaller slope.(Author)

Influence of the temperature in the uranium (Vi) sorption in zirconium diphosphate

International Nuclear Information System (INIS)

Garcia G, N.; Solis, D.; Ordonez R, E.

2012-10-01

In the present work was evaluated the uranium (Vi) sorption at 10, 20, 30, 40 and 60 C on the zirconium diphosphate (ZrP 2 O 7 ). They were carried out kinetic and isotherms using the method by lots, these will allow to fix the sorption time (kinetic) and to explain the behavior of this sorption in different ph conditions and temperature (isotherm). The quantity of retained uranium in the surface was quantified by means of the fluorescence technique. (Author)

Stability of uranium(VI) doped CSH phases in high saline water

Energy Technology Data Exchange (ETDEWEB)

Wolter, Jan-Martin; Schmeide, Katja [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

To evaluate the long-term stability of U(VI) doped calcium silicate hydrate (CSH) phases at high saline conditions, leaching experiments with NaCl, NaCl/Na{sub 2}SO{sub 4} and NaCl/NaHCO{sub 3} containing solutions were performed. Time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and X-ray powder diffraction (XRD) were applied to study the U(VI) binding onto the CSH phases and to get a deeper understanding of structural changes due to leaching. Results indicate that neither NaCl nor Na{sub 2}SO{sub 4} affect the structural stability of CSH phases and their retention potential for U(VI). However, carbonate containing solutions lead to a decomposition of CSH phases and thus, to a release of incorporated uranium.

Determination of molybdenum in uranium by differential pulse polarography

International Nuclear Information System (INIS)

Purwanto, A.; Iswani, G.S.

1996-01-01

The separation an determination of Mo (VI) in uranium dioxid (UO 2 ) samples by polarography method were studied. The determination of Mo(VI) was based on electrochemistry reduction of molybdenum (VI) quinolinolate complex (Mo VI O 2 Q 2 ). To decrease the matrix influence, this complex was extracted into chloroform. After chloroform phase was evaporate at room temperature, residues were dissolved with N,N-Dimethyl formamide (DMF). Potential wave reduction of Mo(VI) at -0,48 volt versus Ag/AgCl/KCl saturated in supporting electrolyte buffer acetate 1 M (1M CH 3 COOH-1M CH 3 COONH 4 ). Extraction was done in 0.3 M H 2 SO 4 media at optimum pH of 2.0 and 4 % oxine in 0.5 M H 2 SO 4 was used as complex compound. Extraction two times with 10 ml chloroform for 5 minutes each ratio of organic water was 1:5. This method was used to determine Mo (VI) in concentration range of 4.8 -12 μg in the presence of 200 mg uranium. It was found recovery of Mo (VI) was 95%. Mo (VI) contents in UO 2 samples determined by standard addition was 5.26±0.41 μg/g. (author)

Supercritical fluid extraction of uranium

International Nuclear Information System (INIS)

Kumar, Pradeep

2017-01-01

Uranium being strategic material, its separation and purification is of utmost importance in nuclear industry, for which solvent extraction is being employed. During solvent extraction significant quantity of radioactive liquid waste gets generated which is of environmental concern. In recent decades supercritical fluid extraction (SFE) has emerged as promising alternative to solvent extraction owing to its inherent advantage of reduction in liquid waste generation and simplification of process. In this paper a brief overview of research work carried out so far on SFE of uranium by BARC has been given

Gold and uranium extraction

International Nuclear Information System (INIS)

James, G.S.; Davidson, R.J.

1977-01-01

A process for extracting gold and uranium from an ore containing them both comprising the steps of pulping the finely comminuted ore with a suitable cyanide solution at an alkaline pH, acidifying the pulp for uranium dissolution, adding carbon activated for gold recovery to the pulp at a suitable stage, separating the loaded activated carbon from the pulp, and recovering gold from the activated carbon and uranium from solution

Uranium extraction by complexation with siderophores

Science.gov (United States)

Bahamonde Castro, Cristina

One of the major concerns of energy production is the environmental impact associated with the extraction of natural resources. Nuclear energy fuel is obtained from uranium, an abundant and naturally occurring element in the environment, but the currently used techniques for uranium extraction leave either a significant fingerprint (open pit mines) or a chemical residue that alters the pH of the environment (acid or alkali leaching). It is therefore clear that a new and greener approach to uranium extraction is needed. Bioleaching is one potential alternative. In bioleaching, complexants naturally produced from fungi or bacteria may be used to extract the uranium. In the following research, the siderophore enterobactin, which is naturally produced by bacteria to extract and solubilize iron from the environment, is evaluated to determine its potential for complexing with uranium. To determine whether enterobactin could be used for uranium extraction, its acid dissociation and its binding strength with the metal of interest must be determined. Due to the complexity of working with radioactive materials, lanthanides were used as analogs for uranium. In addition, polyprotic acids were used as structural and chemical analogs for the siderophore during method development. To evaluate the acid dissociation of enterobactin and the subsequent binding constants with lanthanides, three different analytical techniques were studied including: potentiometric titration, UltraViolet Visible (UV-Vis) spectrophotometry and Isothermal Titration Calorimetry (ITC). After evaluation of three techniques, a combination of ITC and potentiometric titrations was deemed to be the most viable way for studying the siderophore of interest. The results obtained from these studies corroborate the ideal pH range for enterobactin complexation to the lanthanide of interest and pave the way for determining the strength of complexation relative to other naturally occurring metals. Ultimately, this

Biotechnology for uranium extraction and environmental control

International Nuclear Information System (INIS)

Natarajan, K.A.

2012-01-01

India is looking forward to augmenting mining and extraction of uranium mineral for its nuclear energy needs. Being a radio-active mineral, mining and processing of uranium ore deposits need be carried out in an environmentally acceptable fashion. In this respect, a biotechnological approach holds great promise since it is environment-friendly, cost-effective and energy-efficient. There are several types of microorganisms which inhabit uranium ore bodies and biogenesis plays an important role in the mineralisation and transport of uranium-bearing minerals under the earth's crust. Uranium occurrences in India are only meagre and it becomes essential to tap effectively all the available resources. Uraninite and pitchblende occurring along with sulfide mineralisation such as pyrite are ideal candidates for bioleaching. Acidithiobacillus ferrooxidans present ubiquitously in the ore deposits can be isolated, cultured and utilised to bring about efficient acidic dissolution of uranium. Many such commercial attempts to extract uranium from even lean ores using acidophilic autotrophic bacteria have been made in different parts of the world. Anaerobes such a Geobacter and Sulfate Reducing Bacteria (SRB) can be effectively used in uranium mining for environmental control. Radioactive uranium mined wastes and tailing dumps can be cleaned and protected using microorganisms. In this lecture use of biotechnology in uranium extraction and bioremediation is illustrated with practical examples. Applicability of environment-friendly biotechnology for mining and extraction of uranium from Indian deposits is outlined. Commercial potentials for bioremediation in uranium-containing wastes are emphasised. (author)

Uranium extraction from underground deposits

International Nuclear Information System (INIS)

Wolfe, C.R.

1982-01-01

Uranium is extracted from underground deposits by passing an aqueous oxidizing solution of carbon dioxide over the ore in the presence of calcium ions. Complex uranium carbonate or bicarbonate ions are formed which enter the solution. The solution is forced to the surface and the uranium removed from it

Multisensor system for determination of iron(II), iron(III), uranium(VI) and uranium(IV) in complex solutions

International Nuclear Information System (INIS)

Legin, A.V.; Seleznev, B.L.; Rudnitskaya, A.M.; Vlasov, Yu.G.; Tverdokhlebov, S.V.; Mack, B.; Abraham, A.; Arnold, T.; Baraniak, L.; Nitsche, H.

1999-01-01

Development and analytical evaluation of a multisensor system based on the principles of 'electronic tongue' for the determination of low contents of uranium(VI), uranium(IV), iron(II) and iron(III) in complex aqueous media have been carried out. A set of 29 different chemical sensors on the basis of all- solid-state crystalline and vitreous materials with enhanced electronic conductivity and redox and ionic cross-sensitivity have been incorporated into the sensor array. Multidimensional data have been processed by pattern recognition methods such as artificial neural networks and partial least squares. It has been demonstrated that Fe(II) and Fe(III) contents in the range from 10 -7 to 10 -4 mol L -1 of total iron concentration can be determined with the average precision of about 25 %. U(VI) and U(IV) contents can been determined with the average precision of 10-40% depending on the concentration. The developed multisensor system can be applied in future for the analysis of mining and borehole waters as well other contaminated natural media, including on-site measurements. (author)

Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex

Energy Technology Data Exchange (ETDEWEB)

Lu, Erli; Cooper, Oliver J.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [Nottingham Univ. (United Kingdom). School of Chemistry; Tuna, Floriana; McInnes, Eric J.L. [Manchester Univ. (United Kingdom). School of Chemistry and Photon Science Inst.

2014-06-23

We report the uranium(VI) carbene imido oxo complex [U(BIPM{sup TMS})(NMes)(O)(DMAP){sub 2}] (5, BIPM{sup TMS}=C(PPh{sub 2}NSiMe{sub 3}){sub 2}; Mes=2,4,6-Me{sub 3}C{sub 6}H{sub 2}; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPM{sup TMS})(O){sub 2}(DMAP){sub 2}] (6).

Extractants for uranium recovery from wet phosphoric acid

International Nuclear Information System (INIS)

Musikas, C.; Benjelloun, N.; Lours, S.

1982-01-01

Synergistic mixtures containing phosphine oxide plus one of the acidic extractants: dialkyldithiophosphoric acid, dialkylthiophosphoric acid and dialkylphosphoric acid have been compared with respect to U(VI) and Fe(III) extraction from wet phosphoric acid. Distribution curves slope analysis showed that U(VI) extraction mechanisms are totally different. It has been found that U(VI) is extracted as: UO 2 (H 2 PO 4 )(DEHDTP)(TOPO) ; UO 2 (H 2 PO 4 )(DBTP)(POX) 2 and UO 2 (DEHP)(HDEHP) 2 TOPO in dodecane solutions containing di 2 ethylhexyldithiophosphoric acid (HDEHDTP) or dibutylthiophosphoric acid (HDBTP) or di-2-ethylhexylphosphoric acid (HDEHP) plus a phosphine oxide (TOPO or dihexylmethoxyoctylphosphine oxide (POX 11)). The synergistic mixtures containing HDEHDTP gave the highest U(VI) distribution coefficients. Back extraction with oxalic solutions can be achieved only with the synergistic mixtures containing the acidic thiophosphoric donors

New Data on Joint Extraction of Nitric Acid, Uranium(VI) and Tetravalent Elements by Diluted TBP and New Approach to Modeling of their Distribution

International Nuclear Information System (INIS)

Zilberman, B.Ya.; Fedorov, Yu.S.; Puzikov, E.A.; Blazheva, I.V.

2008-01-01

HNO 3 and U(IV) extraction by diluted TBP (tributyl phosphate) appeared significantly higher than believed earlier, requiring correction of mathematical model for extraction of all the species. The proposed model of HNO 3 extraction includes its dissolving in the extracted water, as well as its abduction to UO 2 (NO 3 ) 2 (TBP) 2 . Extraction of U(VI) and tetravalent elements is considered as reaction of their hydrated or partially hydrolyzed forms, the latter could be extracted themselves or as neutral forms with water liberation. The equation of element chemical reaction for modeling is determined by the slope of the linear part of the S-shaped curve representing D/S 2 function as a plot of HNO 3 concentration, where D is a distribution coefficient of the micro-component and S is a TBP concentration free of HNO 3 . The description of tetravalent element extraction in U(VI) presence needs the assumption of cation-cation interaction of element hydrolyzed forms with U(VI) in aqueous phase. Zr distribution is affected by micellar effects. (authors)

Examination of Uranium(VI) Leaching During Ligand Promoted Dissolution of Waste Tank Sludge Surrogates

Energy Technology Data Exchange (ETDEWEB)

Powell, Brian; Powell, Brian A.; Rao, Linfeng; Nash, Kenneth. L.

2008-06-10

The dissolution of synthetic boehmite (?-AlOOH) by 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) was examined in a series of batch adsorption/dissolution experiments. Additionally, the leaching behavior of {sup 233}U(VI) from boehmite was examined as a function of pH and HEDPA concentration. The results are discussed in terms of sludge washing procedures that may be utilized during underground tank waste remediation. In the pH range 4 to 10, complexation of Al(III) by HEDPA significantly enhanced dissolution of boehmite. This phenomenon was especially pronounced in the neutral pH region where the solubility of aluminum, in the absence of complexants, is limited by the formation of sparsely soluble aluminum hydroxides. At pH higher than 10, dissolution of synthetic boehmite was inhibited by HEDPA, likely due to sorption of Al(III):HEDPA complexes. Addition of HEDPA to equilibrated U(VI)-synthetic boehmite suspensions yielded an increase in the aqueous phase uranium concentration. Partitioning of uranium between the solid and aqueous phase is described in terms of U(VI):HEDPA speciation and dissolution of the boehmite solid phase.

Uranium nanoparticle synthesis from leaching solution

International Nuclear Information System (INIS)

Sadowski, Z.; Sklodowska, A.

2014-01-01

The removal of uranium from leaching and bioleaching solutions is of great significance for an environment protection. In comparison with conventional separation techniques, synthesis of uranium nanoparticles has a number of benefits. It has been demonstrated that the uranium nanoparticles show high catalytic activity. In the present studies a variety of synthesis systems have been used for reduction of uranium from bioleaching solution. Among various catalytical templates the hematite Fe_2O_3 nanoparticles are most interest It was presented the report on development of synthesis method to produce nano structured Fe_2O_3 particles. The efficiency of hematite nanoparticles for adsorption of uranium ions from bioleaching solutions was investigated. Bacterial leaching is alternate technique used to extract uranium from mining wastes. The bioleaching process is environment friendly and gives the extraction yield of over 90%. The bioleaching solutions were obtained from bioleaching experiments using waste materials from different places at Lower Silesia (Kowary, Grzmiaca, Kopaniec, Radoniow). Chemoautotrophic bacteria were used for bioleaching tests. The significant adsorption capacity of U(VI) onto iron oxide and hydroxides (goethite, hematite, and magnetite) was observed. The sorption of U(VI) onto the hematite surface was connected with the chemical reduction of U(VI) to U(IV) by Fe"2"+ ions. The initial reaction system contained excess of Fe"2"+ ions which were used to reduce of U(VI). The reduction of U(VI) occurred at pH at the vicinity of pH=2.4. The colloid particles of hematite with UO_2 nanoparticles were obtained. The results of zeta potential measurements of hematite nanoparticles showed that at the ionic strength equals 10"-"3M NaCl, the average zeta potential was +32.4±3.5 mV at pH = 2.6. The interaction of hematite nanoparticles with the bioleaching solutions led to decrease of positive zeta potential to the value of 6.4± 2.7 mV. (author)

Sorption, desorption and extraction of uranium from some sands under dynamic conditions

International Nuclear Information System (INIS)

Palagyi, S.; Laciok, A.

2006-01-01

Sorption, desorption and extraction behavior of uranium in various fluvial sands of domestic origin were investigated in continuous dynamic column experiments. For the sorption of U(VI) an aqueous 10 -4 M UO 2 (NO 3 ) 2 solution was used at a flow rate of about 0.3 cm 3 /min. Desorption was carried out with demineralized water, and the extraction with 10 -2 M Na 2 CO 3 solution following desorption. The retardation coefficients (R) and hydrodynamic dispersion coefficients (D d ), were determined using an ADE equation. From the experimentally determined values of R, bulk density and porosity, the distribution coefficients (K d ) of the UO 2 2+ species have been calculated for the respective processes. The extent of U sorption in sands, as well as the proportion of desorbed and extracted U from these sands, was also calculated. (author)

Depleted uranium processing and fluorine extraction

International Nuclear Information System (INIS)

Laflin, S.T.

2010-01-01

Since the beginning of the nuclear era, there has never been a commercial solution for the large quantities of depleted uranium hexafluoride generated from uranium enrichment. In the United States alone, there is already in excess of 1.6 billion pounds (730 million kilograms) of DUF_6 currently stored. INIS is constructing a commercial uranium processing and fluorine extraction facility. The INIS facility will convert depleted uranium hexafluoride and use it as feed material for the patented Fluorine Extraction Process to produce high purity fluoride gases and anhydrous hydrofluoric acid. The project will provide an environmentally friendly and commercially viable solution for DUF_6 tails management. (author)

Am(VI) Extraction Final Report: FY16

Energy Technology Data Exchange (ETDEWEB)

Mincher, Bruce Jay [Idaho National Lab. (INL), Idaho Falls, ID (United States); Grimes, Travis Shane [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tillotson, Richard Dean [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack Douglas [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-08-01

This report summarizes activities related to hexavalent Am extraction for FY16, in completion of FCR&D Milestone M3FT-16IN030103027. Activities concentrated on three areas of research: 1) centrifugal contactor hot testing, 2) Am(VI) stability studies, and 3) alternative oxidant studies. A brief summary of each task follows. Hot Testing: A new engineering-scale oxidation and solvent extraction test bed was built at Idaho National Laboratory to allow for solvent extraction testing of minor actinide separation concepts. The test bed consists of an oxidation vessel, filtration apparatus, four, 3D printed, 2-cm diameter centrifugal contactors, feed/product vessels, and sample ports. This system replaced the previous 3 stage, 5-cm contactor test bed that was used for the initial testing in FY14. In the FY16 hot test, a feed simulant was spiked with 243Am and 139Ce and treated with 60 g/L sodium bismuthate for two hours to oxidize the Am(III) to Am(VI). This solution was then pumped through a filter and into the four-stage centrifugal contactor setup. The organic phase solvent formulation was 1 M diethylhexylbutyramide (DEHBA)/dodecane. The test showed that Am(VI) was produced by bismuthate oxidation and the residual oxidant was successfully filtered without back pressure buildup. Sixty-four percent of Am was extracted in the contactors using DEHBA. Both Am and Ce were quantitatively stripped by 0.1 M H2O2. Successful demonstration of the utility of small, printable contactors suggests that hot testing of separations concepts can now be conducted more often, since it is cheaper, generates less waste, and entails much less radcon risk than previous testing. Am(VI) stability: A rigorous examination of reagents was conducted to determine if contaminants could interfere with Am oxidation and extraction. An series of DAm measurements showed that bismuthate particle size, water source, acid quality, and DAAP batch or pre-treatment had little effect on extraction efficiency

Uranium extraction at Rossing

International Nuclear Information System (INIS)

Kesler, S.B.; Fahrbach, D.O.E.

1982-01-01

Rossing Uranium Ltd. operates a large open pit uranium mine and extraction plant at a remote site in the Namib desert. Production started at the plant in 1978. A ferric leach process was introduced later, and the new leach plant began commissioning in October 1981. The process has proved to be reliable and easily controlled. Ferric iron is supplied through recovery from the acid plant calcine, and levels can be maintained above the design levels. Leach extractions were increased more than expected when this process was adopted, and the throughput has been considerably reduced, allowing cost savings in mining and milling

On the uptake and binding of uranium (VI) by the green alga Chlorella Vulgaris

International Nuclear Information System (INIS)

Vogel, Manja

2011-01-01

Uranium could be released into the environment from geogenic deposits and from former mining and milling areas by weathering and anthropogenic activities. The elucidation of uranium behavior in geo- and biosphere is necessary for a reliable risk assessment of radionuclide migration in the environment. Algae are widespread in nature and the most important group of organisms in the aquatic habitat. Because of their ubiquitous occurrence in nature the influence of algae on the migration process of uranium in the environment is of fundamental interest e.g. for the development of effective and economical remediation strategies for contaminated waters. Besides, algae are standing at the beginning of the food chain and play an economically relevant role as food and food additive. Therefore the transfer of algae-bound uranium along the food chain could arise to a serious threat to human health. Aim of this work was the quantitative and structural characterization of the interaction between U(VI) and the green alga Chlorella vulgaris in environmental relevant concentration and pH range with special emphasis on metabolic activity. Therefore a defined medium was created which assures the survival/growth of the algae as well as the possibility to predict the uranium speciation. The speciation of uranium in the mineral medium was calculated and experimentally verified by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results of the sorption experiments showed that both metabolic active and inactive algal cells bind uranium in significant amounts of around 14 mg U/g dry biomass and 28 mg U/g dry biomass, respectively. Another interesting observation was made during the growth of Chlorella cells in mineral medium at the environmental relevant uranium concentration of 5 μM. Under these conditions and during ongoing cultivation a mobilization of the algae-bound uranium occurred. At higher uranium concentrations this effect was not observed due to the die off of

Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex

Energy Technology Data Exchange (ETDEWEB)

Lu, Erli; Cooper, Oliver J.; McMaster, Jonathan; Lewis, William; Blake, Alexander J.; Liddle, Stephen T. [School of Chemistry, University of Nottingham (United Kingdom); Tuna, Floriana; McInnes, Eric J.L. [School of Chemistry and Photon Science Institute, University of Manchester (United Kingdom)

2014-06-23

We report the uranium(VI) carbene imido oxo complex [U(BIPM{sup TMS})(NMes)(O)(DMAP){sub 2}] (5, BIPM{sup TMS}=C(PPh{sub 2}NSiMe{sub 3}){sub 2}; Mes=2,4,6-Me{sub 3}C{sub 6}H{sub 2}; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPM{sup TMS})(O){sub 2}(DMAP){sub 2}] (6). (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Enhancement of Extraction of Uranium from Seawater

International Nuclear Information System (INIS)

Al-Sheikhly, Mohamad; Dietz, Travis; Tsinas, Zois; Tomaszewski, Claire; Pazos, Ileana M.; Nigliazzo, Olga; Li, Weixing; Adel-Hadadi, Mohamad; Barkatt, Aaron

2016-01-01

Even at a concentration of 3 @@g/L, the world@@@s oceans contain a thousand times more uranium than currently know terrestrial sources. In order to take advantage of this stockpile, methods and materials must be developed to extract it efficiently, a difficult task considering the very low concentration of the element and the competition for extraction by other atoms in seawater such as sodium, calcium, and vanadium. The majority of current research on methods to extract uranium from seawater are vertical explorations of the grafting of amidoxime ligand, which was originally discovered and promoted by Japanese studies in the late 1980s. Our study expands on this research horizontally by exploring the effectiveness of novel uranium extraction ligands grafted to the surface of polymer substrates using radiation. Through this expansion, a greater understanding of uranium binding chemistry and radiation grafting effects on polymers has been obtained. While amidoxime-functionalized fabrics have been shown to have the greatest extraction efficiency so far, they suffer from an extensive chemical processing step which involves treatment with powerful basic solutions. Not only does this add to the chemical waste produced in the extraction process and add to the method@@@s complexity, but it also significantly impacts the regenerability of the amidoxime fabric. The approach of this project has been to utilize alternative, commercially available monomers capable of extracting uranium and containing a carbon-carbon double bond to allow it to be grafted using radiation, specifically phosphate, oxalate, and azo monomers. The use of commercially available monomers and radiation grafting with electron beam or gamma irradiation will allow for an easily scalable fabrication process once the technology has been optimized. The need to develop a cheap and reliable method for extracting uranium from seawater is extremely valuable to energy independence and will extend the quantity of

A mixed-valent uranium phosphonate framework containing U{sup IV}, U{sup V}, and U{sup VI}

Energy Technology Data Exchange (ETDEWEB)

Chen, Lanhua; Zheng, Tao; Wang, Yaxing; Diwu, Juan; Chai, Zhifang; Wang, Shuao [School for Radiological and interdisciplinary Sciences (RAD-X), Soochow University, Suzhou (China); Collaborative Innovation Center of Radiation Medicine, Jiangsu Higher Education Institutions, Suzhou (China); Bao, Songsong; Zheng, Limin [State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University (China); Zhang, Linjuan; Wang, Jianqiang [Shanghai Institute of Applied Physics and, Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai (China); Liu, Hsin-Kuan [Department of Chemistry, National Central University, Jhongli (China); Albrecht-Schmitt, Thomas E. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL (United States)

2016-08-16

It is shown that U{sup V}O{sub 2}{sup +} ions can reside at U{sup VI}O{sub 2}{sup 2+} lattice sites during mild reduction and crystallization process under solvothermal conditions, yielding a complicated and rare mixed-valent uranium phosphonate compound that simultaneously contains U{sup IV}, U{sup V}, and U{sup VI}. The presence of uranium with three oxidation states was confirmed by various characterization techniques, including X-ray crystallography, X-ray photoelectron, electron paramagnetic resonance, FTIR, UV/Vis-NIR absorption, and synchrotron radiation X-ray absorption spectroscopy, and magnetism measurements. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Uranium(VI) speciation: modelling, uncertainty and relevance to bioavailability models. Application to uranium uptake by the gills of a freshwater bivalve; Speciation de l'uranium(6), modelisation, incertitude et implication pour les modeles de biodisponibilite. Application a l'accumulation dans les branchies d'un bivalve d'eau douce

Energy Technology Data Exchange (ETDEWEB)

Denison, F.H

2004-07-01

The effects of varying solution composition on the interactions between uranium(VI) and excised gills of the freshwater bivalve Corbicula fluminea have been investigated in well defined solution media. A significant reduction in the uptake of uranium was observed on increasing the concentrations of the uranium complexing ligands citrate and carbonate. Saturation kinetics as a function of uranium concentration at a pH value of 5.0 were observed, indicating that the uptake of uranium is a facilitated process, probably involving one or several trans-membrane transport systems. A relatively small change in the uptake of uranium was found as a function of pH (factor of ca. 2), despite the extremely large changes to the solution speciation of uranium within the range of pH investigated (5.0 - 7.5). A comprehensive review of the thermodynamic data relevant to the solution composition domain employed for this study was performed. Estimates of the uncertainties for the formation constants of aqueous uranium(VI) species were integrated into a thermodynamic database. A computer program was written to predict the equilibrium distribution of uranium(VI) in simple aqueous systems, using thermodynamic parameter mean-values. The program was extended to perform Monte Carlo and Quasi Monte Carlo uncertainty analyses, incorporating the thermodynamic database uncertainty estimates, to quantitatively predict the uncertainties inherent in predicting the solution speciation of uranium. The use of thermodynamic equilibrium modelling as a tool for interpreting the bioavailability of uranium(VI) was investigated. Observed uranium(VI) uptake behaviour was interpreted as a function of the predicted changes to the solution speciation of uranium. Different steady-state or pre-equilibrium approaches to modelling uranium uptake were tested. Alternative modelling approaches were also tested, considering the potential changes to membrane transport system activity or sorption characteristics on

Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

International Nuclear Information System (INIS)

Lian Ai; Xuegang Luo; Xiaoyan Lin; Sizhao Zhang

2013-01-01

Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L -1 of sunflower straw in an initial U (VI) concentration of 20 mg L -1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g -1 ) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir-Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g -1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent. (author)

Comparative EXAFS study of uranium(VI) and neptunium(V) sorption onto kaolinite

International Nuclear Information System (INIS)

Reich, T.; Amayri, S.; Reich, Ta.; Jermolajev, J.

2005-01-01

Full text of publication follows: We investigated the surface sorption process of U(VI) and Np(V) on kaolinite by extended X-ray absorption fine structure (EXAFS) spectroscopy in the 10 μM concentration range. Batch experiments with kaolinite in CO 2 -equilibrated systems showed that the adsorption edge of U(VI) occurs at pH 5.5, i.e., near the pH PZC of kaolinite. The adsorption edge of Np(V) occurs well above the pH PZC value at pH 8.5. This may indicate that the bonds between Np(V) and the surface functional groups of kaolinite are not as strong as in the case of U(VI). U(VI) and Np(V) have in common that the amount which is adsorbed decreases when the pH is increased beyond the absorption maximum. This behavior can be attributed to the formation of U(VI) and Np(V) carbonato complexes in the aqueous solutions. The aim of this comparative EXAFS study was to investigate the reason for the different affinities of U(VI) and Np(V) for kaolinite by measuring their local environments at the clay surface. Samples were prepared from 4 g/L kaolinite, 0.1 M NaClO 4 , pH 3.0 - 10.5, presence and absence of ambient CO 2 . The U L 3 - and Np L 2 -edge EXAFS spectra of the wet paste samples were measured at room temperature in fluorescence mode at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility. The measured U-O and U-Al/Si distances indicate inner-sphere sorption of U(VI) on kaolinite. There was no evidence of uranium neighbors in the EXAFS spectra, suggesting that the adsorbed U(VI) complexes were predominantly monomeric. The average distance between uranium and its equatorial oxygen atoms, O eq , increased from 2.32 to 2.38 Angstrom in the presence of atmospheric CO 2 when the pH was increased from 5.0 to 8.5. In the CO 2 -free system, the U-O eq distance was independent from pH and equal to 2.32 Angstrom. The lengthening of the average U-O eq distance in the presence of carbonate (or bicarbonate) suggests the formation of ternary U(VI

Bioremediation of Uranium-Contaminated Groundwater using Engineered Injection and Extraction

Science.gov (United States)

Greene, J. A.; Neupauer, R.; Ye, M.; Kasprzyk, J. R.; Mays, D. C.; Curtis, G. P.

2017-12-01

During in-situ remediation of contaminated groundwater, a treatment chemical is injected into the contaminated groundwater to react with and degrade the contaminant, with reactions occurring where the treatment chemical contacts the contaminant. Traditional in-situ groundwater remediation relies on background groundwater flow for spreading of treatment chemicals into contaminant plumes. Engineered Injection and Extraction (EIE), in which time-varying induced flow fields are used to actively spread the treatment chemical into the contaminant plume, has been developed to increase contact between the contaminant and treatment chemical, thereby enhancing contaminant degradation. EIE has been investigated for contaminants that degrade through irreversible bimolecular reaction with a treatment chemical, but has not been investigated for a contaminant governed by reversible reactions. Uranium primarily occurs in its aqueous, mobile form, U(VI), in the environment but can be bioreduced to its sparingly soluble, immobile form, U(IV), by iron reducing bacteria stimulated by an acetate amendment. In this study, we investigate the ability of EIE to facilitate and sustain favorable conditions to immobilize uranium during remediation, and to prevent re-mobilization of uranium into the aqueous phase after active remediation has ended. Simulations in this investigation are conducted using a semi-synthetic model based on physical and chemical conditions at the Naturita Uranium Mill Tailings Remedial Action (UMTRA) site in southwestern Colorado and the Old Rifle UMTRA site in western Colorado. The EIE design is optimized for the synthetic model using the Borg multi-objective evolutionary algorithm.

Enhancement of Extraction of Uranium from Seawater

Energy Technology Data Exchange (ETDEWEB)

Al-Sheikhly, Mohamad [Univ. of Maryland, College Park, MD (United States); Dietz, Travis [Univ. of Maryland, College Park, MD (United States); Tsinas, Zois [Univ. of Maryland, College Park, MD (United States); Tomaszewski, Claire [Univ. of Maryland, College Park, MD (United States); Pazos, Ileana M. [Univ. of Maryland, College Park, MD (United States); Nigliazzo, Olga [The Catholic Univ. of America, Washington, DC (United States); Li, Weixing [The Catholic Univ. of America, Washington, DC (United States); Adel-Hadadi, Mohamad [Univ. of Maryland, College Park, MD (United States); Barkatt, Aaron [Univ. of Palermo (Italy)

2016-04-01

Even at a concentration of 3 μg/L, the world’s oceans contain a thousand times more uranium than currently know terrestrial sources. In order to take advantage of this stockpile, methods and materials must be developed to extract it efficiently, a difficult task considering the very low concentration of the element and the competition for extraction by other atoms in seawater such as sodium, calcium, and vanadium. The majority of current research on methods to extract uranium from seawater are vertical explorations of the grafting of amidoxime ligand, which was originally discovered and promoted by Japanese studies in the late 1980s. Our study expands on this research horizontally by exploring the effectiveness of novel uranium extraction ligands grafted to the surface of polymer substrates using radiation. Through this expansion, a greater understanding of uranium binding chemistry and radiation grafting effects on polymers has been obtained. While amidoxime-functionalized fabrics have been shown to have the greatest extraction efficiency so far, they suffer from an extensive chemical processing step which involves treatment with powerful basic solutions. Not only does this add to the chemical waste produced in the extraction process and add to the method’s complexity, but it also significantly impacts the regenerability of the amidoxime fabric. The approach of this project has been to utilize alternative, commercially available monomers capable of extracting uranium and containing a carbon-carbon double bond to allow it to be grafted using radiation, specifically phosphate, oxalate, and azo monomers. The use of commercially available monomers and radiation grafting with electron beam or gamma irradiation will allow for an easily scalable fabrication process once the technology has been optimized. The need to develop a cheap and reliable method for extracting uranium from seawater is extremely valuable to energy independence and will extend the quantity of

Determination of submicromolar amounts of uranium(VI) by compleximetric titration with pyridine-2,6-dicarboxylic acid

International Nuclear Information System (INIS)

Marsh, S.F.; Betts, M.R.; Rein, J.E.

1980-01-01

Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17-0.76 μmol of uranium. (Auth.)

Determination of submicromolar amounts of uranium(VI) by compleximetric titration with pyridine-2,6-dicarboxylic acid

Energy Technology Data Exchange (ETDEWEB)

Marsh, S F; Betts, M R; Rein, J E [Los Alamos Scientific Lab., NM (USA)

1980-10-01

Uranium(VI) is selectively determined by a compleximetric titration with pyridine-2,6-dicarboxylic acid, using arsenazo-I indicator and hexamethylenetetramine buffer at pH 4.9. Cyclohexanediaminetetraacetic acid and diethylenetriaminepentaacetic acid provide masking of interfering metal ions. A probe colorimeter apparatus is recommended for end-point detection. The relative standard deviation is 0.6% for 0.17-0.76 ..mu..mol of uranium.

The uranium (VI) determination method in the technological products

International Nuclear Information System (INIS)

Fursa, L.I.; Belykevich, N.A.

1994-01-01

The method includes an extraction of the uranyl nitrate by solution' hexa butyl tries amide of phosphoric acid in the hexane, a reextraction of uranium by arsenazo III solution under pH 2 and following the solution' photometry. With the purpose of excluding the emulsion' formation under uranium reextraction has been added chloroform in volume ratio to hexane 1:(3.0-7.5). tabs. 2

Extracting Uranium from Seawater: Benefits, Risks and Policy Implication

Energy Technology Data Exchange (ETDEWEB)

Ismail, Aznan Fazli; Yim, Man-Sung; Marsh, Matthew [KAIST, Daejon (Korea, Republic of)

2015-05-15

One of the key issues that need to be addressed regarding the future of nuclear power is the availability of uranium. The most economical way to this day of providing uranium for nuclear energy has been through conventional mining. However, the current projection of the well-known, easily obtainable sources of uranium indicates that global nuclear industry can be supported through the end of the century under the once-through cycle. It, however, could be extended up to 250 years if the speculative uranium sources are taken into account. Uranium is also available in seawater. Extracting uranium from seawater has both pros and cons. The only main obstacles at this point is it not economically competitive compared to the conventional mining. Solving this issue will open up a new era of the way of extracting uranium to meet the future requirement of nuclear energy. As the uranium seawater extraction technology is rapidly being developed and might become feasible in the near future, an appropriate mechanism are required to safeguard the extraction technology.

Laser enhanced reductions of uranium(VI) ion in aqueous phosphoric acid solutions

International Nuclear Information System (INIS)

Park, Y.Y.; Harada, M.; Tomiyasu, H.; Ikeda, Y.; Takashima, Y.

1991-01-01

Photochemical reactions of U(VI) ions with inorganic anions (I - , Br - , Cl - , NCS - ) and organic compounds (1-hexene, cyclohexene, pyridine) in phosphoric acid were studied for the purpose of finding an efficient method of adjusting the oxidation states of uranium ions in nuclear fuel reprocessing. The formation of U(IV) was observed in the photoreactions with I - , Br - and NCS - , but not with Cl - . The yield of U(VI) increased in the order, Br - - - . This order was the same as the quenching rate constants of the excited U(VI) ions with these anions, and the reverse of their standard redox potentials. The rates of the formation of U(IV) in the presence of Br - were measured spectrophotometrically. It was found that the rate equation was first order in both [U(VI)] and [Br - ]. The results were reasonably interpreted by a series of reaction processes involving U(V) and Br radical. With organic molecules, 1-hexene, cyclohexene, and pyridine, the formation of U(IV) were observed. The yield of U(IV) increased in the order pyridine < 1-hexene < cyclohexene. This order is the reverse of their vertical ionization potentials, suggesting an electron transfer mechanism between these organic molecules and excited U(VI). (author)

Effect of porosity and surface chemistry on the adsorption-desorption of uranium(VI) from aqueous solution and groundwater

International Nuclear Information System (INIS)

Yakout, S.M.

2016-01-01

Rice straw-based biochars modified with different chemical regents were used as an adsorbent for uranium(VI). Effect of pyrolysis temperature and nature of modifying agent's as well as surface chemistry, surface charge, and pore structure on U(VI) removal was investigated. Amount and nature of the surface groups has, in general, more influence than its porosity on U(VI) adsorption. The adsorption was maximum for the initial pH of 5.5. Rice straw derived biochars had comparable U(VI) adsorption as compared to other adsorbents. The U(VI) removal was 90 % from groundwater. NaHCO 3 was found to be the most efficient desorbent eluent for U(VI). (author)

Rate phenomena in uranium extraction by amines

International Nuclear Information System (INIS)

Coleman, C.F.; McDowell, W.J.

1979-01-01

Kinetics studies and other rate measurements are reviewed in the amine extraction of uranium and of some other related and associated metal ions. Equilibration is relatively fast in the uranium sulfate systems most important to uranium hydrometallurgy. Significantly slow equilibration has been encountered in some other systems. Most of the recorded rate information, both qualitative and quantitative, has come from exploratory and process-development work, while some kinetics studies have been directed specifically toward elucidation of extraction mechanisms. 71 references

Hazelnut shell activated carbon. A potential adsorbent material for the decontamination of uranium(VI) from aqueous solutions

International Nuclear Information System (INIS)

Mijia Zhu; Hankui Chai; Jun Yao; China University of Geosciences; Yunpeng Chen; Zhengji Yi

2016-01-01

Batch experiments were conducted to study the ability of hazelnut shell activated carbon (HSAC) to remove uranium(VI) ions from aqueous solutions. The effects of various operational parameters, such as contact time (0-200 min), pH (2.0-7.0), initial U(VI) concentration (20-240 mg/L) and adsorbent dosage (4.0-50 g/L) were examined. Results showed that the adsorption process was rapid within the first 100 min and then achieved equilibrium at 140 min. The kinetics followed a pseudo-second-order rate equation, and the adsorption process was well fit with the Langmuir model. HSAC exhibited good uranium adsorption capacity (16.3 mg/g) at pH 6.0, 140 min contact time and 8.0 g/L adsorbent dosage. Furthermore, the regeneration efficiency was 96.3 % over five cycles under the optimum operational conditions. These properties revealed that HSAC can be a suitable adsorbent for the fast and convenient removal of U(VI) from contaminated water. (author)

Highly Efficient Interception and Precipitation of Uranium(VI) from Aqueous Solution by Iron-Electrocoagulation Combined with Cooperative Chelation by Organic Ligands.

Science.gov (United States)

Li, Peng; Zhun, Bao; Wang, Xuegang; Liao, PingPing; Wang, Guanghui; Wang, Lizhang; Guo, Yadan; Zhang, Weimin

2017-12-19

A new strategy combining iron-electrocoagulation and organic ligands (OGLs) cooperative chelation was proposed to screen and precipitate low concentrations (0-18.52 μmol/L) of uranium contaminant in aqueous solution. We hypothesized that OGLs with amino, hydroxyl, and carboxyl groups hydrophobically/hydrophilically would realize precuring of uranyl ion at pH electrocoagulation would achieve faster and more efficient uranium precipitation. Experimentally, the strategy demonstrated highly efficient uranium(VI) precipitation efficiency, especially with hydrophilic macromolecular OGLs. The uranium removal efficiency at optimized experimental condition reached 99.65%. The decrease of zeta potential and the lattice enwrapping between U-OGLs chelates and flocculation precursor were ascribed to the enhanced uranium precipitation activity. Uranium was precipitated as oxides of U(VI) or higher valences that were easily captured in aggregated micelles under low operation current potential. The actual uranium tailing wastewater was treated, and a satisfied uranium removal efficiency of 99.02% was discovered. After elution of the precipitated flocs, a concentrated uranium solution (up to 106.52 μmol/L) with very few other metallic impurities was obtained. Therefore, the proposed strategy could remove uranium and concentrate it concurrently. This work could provide new insights into the purification and recovery of uranium from aqueous solutions in a cost-effective and environmentally friendly process.

The development of a material for uranium sorption in NH_3/N environment

International Nuclear Information System (INIS)

Chen Xiaotong; He Linfeng; Liu Bing; Tang Yaping

2014-01-01

An efficient hybrid silica (TD-silica) bifunctionalized with trimethyl ammonium (TMAP) and phosphonate (DPTS) for Uranium (VI) extraction in NH_3/N media has been developed in this study. The hybrid silica was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at large-pore silica. The resulting TD-modified silica were observed to possess a good stability and high efficiency for uranium (VI) sorption from solution in coexist with NH_3/N. The adsorbed uranium (VI) can be easily desorbed by using 0.05 mol/L HNO_3 and reused for at least 4 times. It is suggested that TD-silica could be a promising solid phase sorbent for highly-efficient removal of U(VI) from solution in coexist with NH_3/N. (author)

Uranium sorption to natural substrates-insights provided by isotope exchange, selective extraction and surface complexation modelling approaches

International Nuclear Information System (INIS)

Waite, T.D.; Payne T.E.; Davis, J.A.

1993-01-01

An extensive experimental program has been conducted over the last three years into the interaction of U(VI) with both single oxides and clays and complex natural substrates from the weathered zone in the vicinity of a uranium ore body in northern Australia. While iron oxides have frequently been considered to account for much of the uptake on such natural substrates, the results of laboratory open-quotes pH edgeclose quotes studies and of isotope exchange and selective extraction studies suggest that other phases must also play a significant role in controlling the partitioning of U(VI) between solid and solution phases. Supporting studies on kaolinite, the dominant clay in this system, provide insight into the most appropriate method of modelling the interaction of U(VI) with these natural substrates. The problems still remaining in adequately describing sorption of radionuclides and trace elements to complex natural substrates are discussed

Extraction of Tetravalent Uranium by Certain Acidic Organophosphorus Extractants from Phosphate Medium

International Nuclear Information System (INIS)

Daoud, J.A.; Zeid, M.M.; Aly, H.F.

1998-01-01

The extraction of U(IV) by octylphenyl acid phosphate (OPAP) or di-2-ethylhexyl phosphoric acid (HDEHP) in kerosene from phosphoric acid was carried out. The effect of extractant, phosphoric acid, uranium, Fe(II) and Fe(III) concentration on the extraction process was separately investigated. The effect of different reagents and temperature on the stripping of U(IV) was also investigated. The results obtained for the extraction of U(IV) by HDEHP showed that the extraction with the increase in HDEHP and Fe(III) concentration while it decreases with the increase in phosphoric acid, uranium and Fe(II) concentration. In case of extraction with OPAP, the extraction of U(IV) was found to decrease with the phosphoric acid, Fe(II) and initial uranium concentration while the increase in OPAP concentration slightly affected the extraction. The use of high phosphoric acid concentration as stripper at low temperature was found to give the best stripping results

Equilibrium and kinetics of co-extraction of U(VI) and HNO3 using tri-n-butyl phosphate and tri-iso-amyl phosphate in paraffin

International Nuclear Information System (INIS)

Das, Diptendu; Juvekar, V.A.; Biswas, Sujoy; Roy, S.B.; Bhattacharya, R.

2014-01-01

Tri-n-butyl phosphate (TBP) is versatile solvent for recovery of actinides as it is cheaper and the extracted actinides can be stripped from the loaded organic phase using plain water. However there are inherent problems associated TBP such as i) formation of the third phase ii) high solubility in aqueous phase iii) radiolytic hydrolysis at high radiation environment and iv) high propensity for extraction of mineral acids. The last mentioned property makes it less suitable for liquid emulsion membrane (LEM) extraction where acid transport to the strip phase drastically reduces extraction efficiency. Therefore there is need to replace TBP with an extractant which has lesser propensity for acid extraction. Many researcher reported Tri-iso-amyl phosphate (TiAP) as an alternative extractant which can sustain high radiation environment without chemical/radiative degradation. However there are no studies available on co-extraction of U(VI) and mineral acids by TiAP. In this research paper equilibrium and kinetics of co-extraction of U(VI) and HNO 3 from nitric acid medium into a hydrocarbon phase (paraffin) using Tri n- butyl phosphate (TBP), Tri-iso-amyl phosphate (TiAP) has been studied. Relative rates of extraction of uranium(VI) and HNO 3 by TiAP and TBP were measured simultaneously using bulk-liquid membrane (BLM) system. Study reveals although TiAP is less efficient in extracting U(IV), than TBP, it transfers lesser quantity of nitric acid to organic phase. Hence TiAP is more suitable as a carrier for LEM extraction than TBP

Methylbutylmalonamide as an extractant for U(VI), Pu(IV), and Am(III)

International Nuclear Information System (INIS)

Nair, G.M.; Prabhu, D.R.; Mahajan, G.R.

1994-01-01

The unsymmetrical diamide methylbutylmalonamide has been synthesized and used in the extraction of U(VI), Pu(IV), and Am(III) in benzene medium. The distribution ratio for three cations was found to increase with increasing aqueous nitric acid concentration. U(VI) and Pu(IV) were found to be extracted as disolvates while Am(III) as a trisolvate. The thermodynamic parameters determined by the temperature variation method showed the extraction reactions to be mainly enthalphy-controlled. Am(III) was found to be back-extracted with dilute nitric acid, while Pu(IV) by dilute nitric acid - hydrofluoric acid mixture and U(VI) by dilute sodium carbonate solution. (author) 6 refs.; 3 figs.; 2 tabs

Uranium recovery from phosphonitric solutions

International Nuclear Information System (INIS)

Bunus, F.T.; Miu, I.

1997-01-01

A new technology for uranium and rare earth recovery applied in a semi-industrial plant processing 5 m 3 /h phosphoric acid has been extended to phosphonitric solution, resulting in the process of nitric acid attack of phosphate rock for complex fertilizer production. In this process uranium and rare earths are obtained at larger quantities due to the complete dissolution of elements involved. The method is based on a one cycle extraction-stripping process using as extractants: di(2-ethylhexyl) phosphate (DEPA) in mixture either with tri-n-butylphosphate (TBP) or tri-n-octylphosphine oxide (TOPO) in view of obtaining a synergic effect for U (VI). A mixer-settler extractor in four steps was used. Two stripping steps are involved for the elements mentioned. Before uranium stripping a scrubbing with urea was introduced to eliminate nitric acid extracted. Uranium was obtained as green cake (hydrated uranium tetrafluoride) which can be easily transformed in hexfluoride or converted to a diuranate. At the same time the radium is also eliminated leading to a non-radioactive fertilizer product. (author),. 8 refs, 4 figs

Contribution to the study of liquid-liquid extraction dynamics in the case of fast transfers. Extractions of uranium, plutonium and neptunium in a laboratory centrifugal extractor

International Nuclear Information System (INIS)

Bergeonneau, Philippe

1978-01-01

The liquid-liquid extraction (also named solvent-based extraction) is a very important technique for the reprocessing of irradiated nuclear fuels. This research thesis is based on the use of a laboratory centrifugal extractor which allows interesting conditions to be achieved: fast transfer due to an intense solution mixing, very short duration of contact between solutions. Thus, after a report of a bibliographical study on chemical mechanisms of extraction, on the composition of extracted species, on extraction kinetics, and on centrifugal extractors, this thesis reports the design, fabrication and use of a centrifugal extractor: presentation of fundamental principles, description and characteristics (materials, hydrodynamic operation test and problems, prototype). It reports studies of fast transfer kinetics: mathematical processing, result interpretation, results and discussions of extraction kinetics for nitric acid, uranium VI and IV, plutonium IV, neptunium IV, and comparison of the different extraction kinetics

Uranium extraction technology

International Nuclear Information System (INIS)

1993-01-01

In 1983 the Nuclear Energy Agency of the Organisation for Economic Co-operation and Development (OECD/NEA) and the IAEA jointly published a book on Uranium Extraction Technology. A primary objective of this report was to document the significant technological developments that took place during the 1970s. The purpose of this present publication is to update and expand the original book. It includes background information about the principle of the unit operations used in uranium ore processing and summarizes the current state of the art. The publication also seeks to preserve the technology and the operating 'know-how' developed over the past ten years. This publication is one of a series of Technical Reports on uranium ore processing that have been prepared by the Division of Nuclear Fuel Cycle and Waste Management at the IAEA. A complete list of these reports is included as an addendum. Refs, figs and tabs

Amine synergism in uranium extraction

International Nuclear Information System (INIS)

Rinelli, G.; Abbruzzese, C.

1977-01-01

Commercial products based on C 8 to C 12 tertiary amine mixtures are now widely used in the solvent extraction of uranium from sulphuric pregnant solutions. The satisfactory results generally obtained have never required an analysis of the synergistic effects of amine combinations similar to that carried out for the organo-phosphorus compounds. In the research described the increase in the extraction power of an organic phase composed of an amine binary mixture was studied with regard to an aqueous solution from the sulphuric acid treatment of uranium ore. On the basis of the experimental results obtained, it is possible to select the best composition of the amine mixture to ensure a percentage increase in uranium recovery. Bearing in mind the tendency for the yellow-cake price to rise, the study is considered to be a useful contribution in the context of commercial products currently available on the market. (author)

Solvent extraction of uranium and molybdenum in sulfuric media

International Nuclear Information System (INIS)

Duarte Neto, J.

1980-01-01

A Solvent extraction process for recovering the uranium and molibdenum from the sulfuric acid solution produced from Figueira ores was developed. The leach solution contains molibdenum with a mean ratio Mo/U = 35%. THe solvent used was a terciary amine-Alamine 336, modified with tridecanol in querosine. An investigation was made to evaluate the variables affecting the extraction and stripping of uranium and molibdenum. The Alamine 336 showed a significant extraction power for uranium and molibdenum. In the stripping step of uranium using acidified sodium cloride it was observed the presence of an insoluble amine-molibdenum-arsenic complex. (author) [pt

Process for extracting uranium from phosphoric acid solutions

International Nuclear Information System (INIS)

1977-01-01

The description is given of a method for extracting uranium from phosphoric acid solutions whereby the previously oxided acid is treated with an organic solvent constituted by a mixture of dialkylphosphoric acid and trialkylphosphine oxide in solution in a non-reactive inert solvent so as to obtain de-uraniated phosphoric acid and an organic extract constituted by the solvent containing most of the uranium. The uranium is then separated from the extract as uranyl ammonium tricarbonate by reaction with ammonia and ammonium carbonate and the extract de-uraniated at the extraction stage is recycled. The extract is treated in a re-extraction apparatus comprising not less than two stages. The extract to be treated is injected at the top of the first stage. At the bottom of the first stage, ammonia is introduced counter current as gas or as an aqueous solution whilst controlling the pH of the first stage so as to keep it to 8.0 or 8.5 and at the bottom of the last stage an ammonium carbonate aqueous solution is injected in a quantity representing 50 to 80% of the stoichiometric quantity required to neutralize the dialkylphosphoric acid contained in the solvent and transform the uranium into uranyl ammonium tricarbonate [fr

Extractive spectrophotometric determination of uranium with malachite green

International Nuclear Information System (INIS)

Dubey, S.C.; Nadkarni, M.N.

1977-01-01

A sensitive spectrophotometric method based on the extraction of a uranium-benzoate-Malachite Green complex by chlorobenzene is described. The absorption maximum is at 635 nm and the molar absorptivity is 8.3 x 10 4 1. mole -1 cm -1 . A preliminary separation of uranium by extraction with methyl isobutyl ketone from acid-deficient aluminium nitrate solution is used to avoid interferences. An aliquot of the extract in then diluted with chlorobenzene and shaken with benzoate buffer containing Malachite Green (MG). The method has been applied for the determination of uranium in a synthetic leach solution. The complex extracted is probably [U0 2 (C 6 H 5 C00 3 - ][MG + ]. (author)

Development of Novel Sorbents for Uranium Extraction from Seawater

Energy Technology Data Exchange (ETDEWEB)

Lin, Wenbin [Univ. of Chicago, IL (United States); Taylor-Pashow, Kathryn [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2014-01-08

As the uranium resource in terrestrial ores is limited, it is difficult to ensure a long-term sustainable nuclear energy technology. The oceans contain approximately 4.5 billion tons of uranium, which is one thousand times the amount of uranium in terrestrial ores. Development of technologies to recover the uranium from seawater would greatly improve the uranium resource availability, sustaining the fuel supply for nuclear energy. Several methods have been previously evaluated including solvent extraction, ion exchange, flotation, biomass collection, and adsorption; however, none have been found to be suitable for reasons such as cost effectiveness, long term stability, and selectivity. Recent research has focused on the amidoxime functional group as a promising candidate for uranium sorption. Polymer beads and fibers have been functionalized with amidoxime functional groups, and uranium adsorption capacities as high as 1.5 g U/kg adsorbent have recently been reported with these types of materials. As uranium concentration in seawater is only ~3 ppb, great improvements to uranium collection systems must be made in order to make uranium extraction from seawater economically feasible. This proposed research intends to develop transformative technologies for economic uranium extraction from seawater. The Lin group will design advanced porous supports by taking advantage of recent breakthroughs in nanoscience and nanotechnology and incorporate high densities of well-designed chelators into such nanoporous supports to allow selective and efficient binding of uranyl ions from seawater. Several classes of nanoporous materials, including mesoporous silica nanoparticles (MSNs), mesoporous carbon nanoparticles (MCNs), meta-organic frameworks (MOFs), and covalent-organic frameworks (COFs), will be synthesized. Selective uranium-binding liagnds such as amidoxime will be incorporated into the nanoporous materials to afford a new generation of sorbent materials that will be

Development of Novel Sorbents for Uranium Extraction from Seawater

International Nuclear Information System (INIS)

Lin, Wenbin; Taylor-Pashow, Kathryn

2014-01-01

As the uranium resource in terrestrial ores is limited, it is difficult to ensure a long-term sustainable nuclear energy technology. The oceans contain approximately 4.5 billion tons of uranium, which is one thousand times the amount of uranium in terrestrial ores. Development of technologies to recover the uranium from seawater would greatly improve the uranium resource availability, sustaining the fuel supply for nuclear energy. Several methods have been previously evaluated including solvent extraction, ion exchange, flotation, biomass collection, and adsorption; however, none have been found to be suitable for reasons such as cost effectiveness, long term stability, and selectivity. Recent research has focused on the amidoxime functional group as a promising candidate for uranium sorption. Polymer beads and fibers have been functionalized with amidoxime functional groups, and uranium adsorption capacities as high as 1.5 g U/kg adsorbent have recently been reported with these types of materials. As uranium concentration in seawater is only ~3 ppb, great improvements to uranium collection systems must be made in order to make uranium extraction from seawater economically feasible. This proposed research intends to develop transformative technologies for economic uranium extraction from seawater. The Lin group will design advanced porous supports by taking advantage of recent breakthroughs in nanoscience and nanotechnology and incorporate high densities of well-designed chelators into such nanoporous supports to allow selective and efficient binding of uranyl ions from seawater. Several classes of nanoporous materials, including mesoporous silica nanoparticles (MSNs), mesoporous carbon nanoparticles (MCNs), meta-organic frameworks (MOFs), and covalent-organic frameworks (COFs), will be synthesized. Selective uranium-binding liagnds such as amidoxime will be incorporated into the nanoporous materials to afford a new generation of sorbent materials that will be

Estimation of rare earth elements in uranium matrix after solvent extraction of uranium as uranium-antipyrine-anion complex using chloroform as solvent

International Nuclear Information System (INIS)

Bose, Roopa; Murthy, D.S.R.; Malhotra, R.K.

1999-01-01

The neutron economy in a nuclear reactor dictates the occurrence of neutron absorbers at very low levels. Hence the determination of lanthanides especially Sm, Eu, Gd and Dy is one of the most difficult and complicated analytical tasks particularly in high uranium matrix. Solvent extraction is a potent and versatile technique for the separation of lanthanides. The systems generally used for lanthanide extraction are TBP-nitrate, TBP-chloride, TBP-thiocyanate TOPO, DEHPA-nitrate etc. However, these methods of extraction of lanthanides fail to give a clear cut separation for their determination from uranium matrix. Hence analytical procedures have been standardised for extraction of uranium matrix into the organic phase leaving lanthanides unextracted in the aqueous phase. In this direction Cyanex-923 a mixture of 4 trialkyl phosphine oxides, TBP- TOPO and trioctylamine in xylene have been used for extraction of uranium and consequent determination of lanthanides by ICP-AES in the aqueous phase. In this paper the authors have investigated uranium -antipyrine -anion, a different combination other than the well known phosphine oxides and tertiary amines for extraction of uranium

On the uptake and binding of uranium (VI) by the green alga Chlorella Vulgaris; Zur Aufnahme und Bindung von Uran(VI) durch die Gruenalge Chlorella Vulgaris

Energy Technology Data Exchange (ETDEWEB)

Vogel, Manja

2011-07-01

Uranium could be released into the environment from geogenic deposits and from former mining and milling areas by weathering and anthropogenic activities. The elucidation of uranium behavior in geo- and biosphere is necessary for a reliable risk assessment of radionuclide migration in the environment. Algae are widespread in nature and the most important group of organisms in the aquatic habitat. Because of their ubiquitous occurrence in nature the influence of algae on the migration process of uranium in the environment is of fundamental interest e.g. for the development of effective and economical remediation strategies for contaminated waters. Besides, algae are standing at the beginning of the food chain and play an economically relevant role as food and food additive. Therefore the transfer of algae-bound uranium along the food chain could arise to a serious threat to human health. Aim of this work was the quantitative and structural characterization of the interaction between U(VI) and the green alga Chlorella vulgaris in environmental relevant concentration and pH range with special emphasis on metabolic activity. Therefore a defined medium was created which assures the survival/growth of the algae as well as the possibility to predict the uranium speciation. The speciation of uranium in the mineral medium was calculated and experimentally verified by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results of the sorption experiments showed that both metabolic active and inactive algal cells bind uranium in significant amounts of around 14 mg U/g dry biomass and 28 mg U/g dry biomass, respectively. Another interesting observation was made during the growth of Chlorella cells in mineral medium at the environmental relevant uranium concentration of 5 {mu}M. Under these conditions and during ongoing cultivation a mobilization of the algae-bound uranium occurred. At higher uranium concentrations this effect was not observed due to the die off

Antioxidant Activity of Lawsonia inermis Extracts Inhibits Chromium(VI-Induced Cellular and DNA Toxicity

Directory of Open Access Journals (Sweden)

Gunjan Guha

2011-01-01

Full Text Available Hexavalent chromium Cr(VI is a very strong oxidant which consequently causes high cytotoxicity through oxidative stress. Prevention of Cr(VI-induced cellular damage has been sought in this study in aqueous and methanolic extracts of Lawsonia inermis Linn. (Lythraceae, commonly known as Henna. The extracts showed significant (P < .05 potential in scavenging free radicals (DPPH• and ABTS•+ and Fe3+, and in inhibiting lipid peroxidation. DNA damage caused by exposure of pBR322 to Cr(VI-UV is markedly inhibited by both extracts in varying degrees. A distinct decline in Cr(VI-induced cytotoxicity was noticed in MDA-MB-435S (human breast carcinoma cells with an increase in dosage of both extracts individually. Furthermore, both extracts proved to contain a high content of phenolic compounds which were found to have a strong and significant (P < .05 positive correlation to the radical scavenging potential, lipid peroxidation inhibition capacity and cyto-protective efficiency against Cr(VI-induced oxidative cellular damage. HPLC analysis identified some of the major phenolic compounds in both extracts, which might be responsible for the antioxidant potential and the properties of DNA and cyto-protection. This study contributes to the search for natural resources that might yield potent therapeutic drugs against Cr(VI-induced oxidative cell damage.

Bio sorption process for uranium (VI) by using algae-yeast-silica gel composite adsorbent

International Nuclear Information System (INIS)

Turkozu, D. A.; Aytas, S.

2006-01-01

Many yeast, algae, bacteria and various aquatic flora are known to be capable of concentrating metal species from dilute aqueous solution. Many researcher have found that non-living biomaterials can be used to accumulate metal ions from environment. In recent studies, mainly two process are used in biosorption experiments. These are the use of free cells and the use of immobilized cells on a solid support. A variety of inert supports have been used to immobilize biomaterials either by adsorption or physical entrapment. This uptake is often considerable and frequently selective, and occurs via a variety of mechanisms including active transport, ion exchange or complexation, and adsorption or inorganic precipitation. Biosorbent may be used as an ion exchange material. Adsorption occurs through interaction of the metal ions with functional groups that are found in the cell wall biopolymers of either living or dead organisms. In this study, the algae-yeast-silica gel composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Jania rubens.), yeast (Saccharomyces cerevisiae) and silica gel were used to prepare composite adsorbent. The ability of the composite biosorbent to adsorb uranium (VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time and matrix ion effect was also investigated. The adsorption patterns of uranium on the composite biosorbent were investigated by the Langmuir, Freundlich and Dubinin-Radushkhevic isotherms. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated. The results suggested that the macro algae-yeast-silica gel composite sorbent is suitable as a new biosorbent material for removal of uranium ions from aqueous solutions

Incorporation of Uranium into Hematite during Crystallization from Ferrihydrite

Science.gov (United States)

2014-01-01

Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite. The results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments. PMID:24580024

Synthesis of graphite intercalation compound of group VI metals and uranium hexafluorides

International Nuclear Information System (INIS)

Fukui, Toshihiro; Hagiwara, Rika; Ema, Keiko; Ito, Yasuhiko

1993-01-01

Systematic investigations were made on the synthesis of graphite intercalation compounds of group VI transition metals (W and Mo) and uranium hexafluorides. The reactions were performed by interacting liquid or gaseous metal hexafluorides with or without elemental fluorine at ambient temperature. The degree of intercalation of these metal fluorides depends on the formation enthalpy of fluorometallate anion from the original metal hexafluoride, as has been found for other intercalation reactions of metal fluorides. (author)

Extraction of uranium from seawater

International Nuclear Information System (INIS)

Kanno, M.

1977-01-01

The nuclear power generation is thought to be very important in Japan. However, known domestic uranium resources in Japan are very rare. So, extraction of uranium from sea water have been carried out since 1962 at Japan Tobacco and Salt Public Corporation. There are a number of results obtained also by Kyoto University, Shikoku Govenment Industrial Research Institute, Tokyo University and others. In order to investigate the technical and economical feasibility of extraction of uranium and other resources from sea water, a research program was started in fiscal 1975, sponsored by the Ministry of International Trade and Industry with the budget of about $440,000. In this program, the conceptional design of two types of model plants, the ''column type'' and the ''tidal type'' was drawn on the design bases set up with available information. It was found that there has been several problems waiting solution, but there were no technically fatal problems. Adsorption tests were carried out with adsorbents of more than eleven types, including titanium hydroxide, and it was found that titanium hydroxide made by titanyl surphate and urea had the largest adsorption capacity of uranium among them. Elution experiments were performed only with ammonium carbonate and the efficiency at the temperature of 60 0 C showed three times higher than that of 20 0 C. A few long term column operation was conducted, mainly with the adsorbent of granulated titanium hydroxide for 15-60 days. The maximum yield of uranium throughout the adsorption and elution operation was over 20% and macimum concentration of uranium in eluate was 7 ppm

Extractive spectrophotometric determination of uranium with malachite green

Energy Technology Data Exchange (ETDEWEB)

Dubey, S C; Nadkarni, M N [Bhabha Atomic Research Centre, Bombay (India). Fuel Reprocessing Div.

1977-04-01

A sensitive spectrophotometric method based on the extraction of a uranium-benzoate-Malachite Green complex by chlorobenzene is described. The absorption maximum is at 635 nm and the molar absorptivity is 8.3 x 10/sup 4/1. mole /sup -1/ cm/sup -1/. A preliminary separation of uranium by extraction with methyl isobutyl ketone from acid-deficient aluminium nitrate solution is used to avoid interferences. An aliquot of the extract in then diluted with chlorobenzene and shaken with benzoate buffer containing Malachite Green (MG). The method has been applied for the determination of uranium in a synthetic leach solution. The complex extracted is probably (U0/sub 2/(C/sub 6/H/sub 5/C00/sub 3//sup -/)(MG/sup +/).

Interaction of uranium(VI) with bioligands present in human biological fluids. The case study of urea and uric acid

International Nuclear Information System (INIS)

Osman, A.A.A.; Geipel, G.; Bernhard, G.

2013-01-01

The complexation of uranium(VI) with bioligands found in human biological fluids, viz, urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log β 110 = 4.67 ± 0.29 for uric acid and log β 110 = 3.79 ± 0.15 and 2.12 ± 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

Interaction of uranium(VI) with bioligands present in human biological fluids. The case study of urea and uric acid

Energy Technology Data Exchange (ETDEWEB)

Osman, A.A.A.; Geipel, G.; Bernhard, G. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Resource Ecology

2013-05-01

The complexation of uranium(VI) with bioligands found in human biological fluids, viz, urea and uric acid in aqueous solutions, has been investigated using time-resolved laser-induced fluorescence spectroscopy (TRLFS) at room temperature, I = 0.1 M (NaClO4) and pH (3 for uric acid; 4 for urea). In both complex systems a static quench effect with increasing ligand concentration and no peaks shift upon complexation were observed. With uranium(VI) both ligands formed a fairly weak 1:1 complex with average stability constants of log {beta}{sub 110} = 4.67 {+-} 0.29 for uric acid and log {beta}{sub 110} = 3.79 {+-} 0.15 and 2.12 {+-} 0.18 for relatively low and relatively high urea concentrations, respectively. Application of the newly generated data on the U(VI) speciation modelling in biofluids, e.g., human urine was also discussed.

Physicochemical aspects of extraction of uranium concentrate from the wastes and thermodynamic characteristics of thorium-uranium compounds

International Nuclear Information System (INIS)

Khamidov, F.A.

2017-01-01

The purpose of present work is elaboration of physicochemical aspects of extraction of uranium concentrate from the wastes and study of thermodynamic characteristics of thorium-uranium compounds. Therefore, the radiological monitoring of tailing dumps of Tajikistan has been conducted; the obtaining of uranium concentrate from the tailing dumps of uranium production has been studied; the obtaining of uranium concentrate from the tailing dumps of uranium production with application of local sorbents has been studied as well; thermal stability and thermodynamic characteristics of uranium-thorium compounds has been investigated; the flowsheets of extraction of uranium concentrate from the wastes have been elaborated.

Extraction of uranium low-grade ores from Great Divide Basin, Wyoming. National Uranium Resource Evaluation

International Nuclear Information System (INIS)

Judd, J.C.; Nichols, I.L.; Huiatt, J.L.

1983-04-01

The US Bureau of Mines is investigating the leachability of carbonaceous uranium ore samples submitted by the DOE under an Interagency Agreement. Studies on eight samples from the Great Divide Basin, Wyoming, are the basis of this report. The uranium content of the eight ore samples ranged from 0.003 to 0.03% U 3 O 8 and contained 0.7 to 45% organic carbon. Experiments were performed to determine the feasibility of extracting uranium using acid leaching, roast-acid leaching and pressure leaching techniques. Acid leaching with 600 lb/ton H 2 SO 4 plus 10 lb/ton NaClO 3 for 18 h at 70 0 C extracted 65 to 83% of the uranium. One sample responded best to a roast-leach treatment. When roasting for 4 h at 500 0 C followed by acid leaching of the calcine using 600 lb/ton H 2 SO 4 , the uranium extraction was 82%. Two of the samples responded best to an oxidative pressure leach for 3 h at 200 0 C under a total pressure of 260 psig; uranium extractions were 78 and 82%

Chlorination of uranium ore for extraction of uranium, thorium and radium and for pyrite removal

International Nuclear Information System (INIS)

Skeaf, J.M.

1979-01-01

The high-temperature chlorination of uranium ore was investigated. The objective was to develop a process which is both economically viable and environmentally acceptable. Test work was directed toward obtaining high extractions of uranium, thorium and radium-226, as well as iron, sulphur and the rare earths, and consists of chlorinating samples of an Elliot Lake uranium ore at elevated temperatures and repulping the resulting calcine in dilute hydrochloric acid. The effect of temperature and chlorine throughput on the extraction of the various metals was investigated. The best conditions yielded extractions of uranium, iron and sulphur (all as chlorides) greater than 95 percent. Chlorine consumption varied between 6 and 16 percent by weight of the ore charge. (author)

Rirang uranium ore processing: continuous solvent extraction of uranium from Rirang ore acid digestion solution

International Nuclear Information System (INIS)

Riza, F.; Nuri, H. L.; Waluya, S.; Subijanto, A.; Sarono, B.

1998-01-01

Separation of uranium from Rirang ore acid digestion solution by means of continuous solvent extraction using mixer-settlers has been studied and a mixture of 0.3 M D2EHPA and 0.075 M TOPO extracting agent and kerosene diluent is employed to recover and separate uranium from Th, RE, phosphate containing solution. The experiments have been conducted batch-wise and several parameters have been studied including the aqueous to organic phase ratio, A/O, the extraction and the stripping times, and the operation temperature. The optimum conditions for extraction have been found to be A/O = 2 ratio, five minute extraction time per stage at room temperature. The uranium recovery of 99.07% has been achieved at those conditions whilst U can be stripped from the organic phase by 85% H 3 PO 4 solution with an O/A = 1 for 5 minutes stripping time per stage, and in a there stage operation at room temperature yielding a 100% uranium recovery from the stripping process

Study for the extraction of uranium from commerical phosphoric acid

International Nuclear Information System (INIS)

Nogueira, A.C.R.

1984-01-01

The extraction of uranium is discribed and for which several parameters such as choice of the extracting agent, uranium oxidation, temperature, phase volume ratio, equilibrium time and number of stages are studied. A synergic mixture constituted by 0,5M DZEHPA/0,125M TOPO in kerosene is used as extracting agent. The uranium extraction is performed by using both batch process and continuous as well as discontinuous counter-current and processes in bench scale. An overall yield of 96% is obtained when the extraction experiment is performed at 45 0 C in a 5-stage continuous extraction process. (Author) [pt

Simple method for preparation of secondary amides of phosphorylacetic acids and their use for actinide extraction and sorption from nitric acid solutions

International Nuclear Information System (INIS)

Artyushin, O.I.; Sharova, E.V.; Odinets, I.L.; Lenevich, S.V.; Mastruykova, T.A.; Morgalyuk, V.P.; Tananaev, I.G.; Pribylova, G.V.; Myasoedova, G.V.; Myasoedov, B.F.

2004-01-01

An effective method of synthesis of secondary alkylamides of phosphorylacetic acids (APA), based on amidation of ethyl esters of phosphorylacetic acids with primary aliphatic amines, was developed. Extraction of americium(III) complexes with APA solutions in dichloroethane and uranium(VI) sorption by sorbents with non-covalently fixed APA from nitric acid solutions were studied. In the course of americium(III) extraction there is no correlation between Am III distribution factor and APA structure, whereas during uranium(VI) sorption a dependence of U VI extraction degree on the complexing agent structure is observed [ru

Extraction of uranium from seawater: a few facts - 5025

International Nuclear Information System (INIS)

Guidez, J.; Gabriel, S.

2015-01-01

Although uranium concentration in seawater is only about 3 micrograms/liter, the quantity of uranium dissolved in the world's oceans is estimated to amount to 4.5 billions tonnes of uranium metal (tU). In contrast, the current conventional terrestrial resource is estimated to amount to about 17 million tU. However, for a number of reasons the extraction of significant amounts of uranium from seawater remains today more a dream than a reality. Firstly, pumping the seawater to extract this uranium would need more energy more energy than what could be produced with the recuperated uranium. Then if trying to use existing industrial flow rates, as for example on a nuclear power plant, it appears that the annual possible quantity remains very low. In fact huge quantities of water must be treated. To produce the annual world uranium consumption (around 65.000 tU), it would need at least to extract all uranium of 2*10 13 tonnes of water, the volume equivalent to the entire North Sea. In fact only the great ocean currents are providing without pumping huge quantities of seawater and the idea is to try to extract even very partially this uranium. A lot of research works have been published, on the studies of adsorbents immersed in these currents. Then, after immersion, these adsorbents are chemically treated to recuperate the uranium. Final quantities remain low in comparison of the complex and costly operations to be done in sea. One kilogram of adsorbent, after one month of immersion, yields about 2 g of uranium and the adsorbent can only be used 6 times due to decreasing efficiency. The industrial extrapolation exercise made for the extraction of 1.200 tU/year give with these values a very costly installation installed on more than 1000 km 2 of sea with a lot of boats for transportation and maintenance. The ecological management of this huge installation would present significant challenges. (authors)

Synthesis of surface Cr (VI)-imprinted magnetic nanoparticles for selective dispersive solid-phase extraction and determination of Cr (VI) in water samples.

Science.gov (United States)

Qi, Xue; Gao, Shuang; Ding, Guosheng; Tang, An-Na

2017-01-01

A facile, rapid and selective magnetic dispersed solid-phase extraction (dSPE) method for the extraction and enrichment of Cr (VI) prior to flame atomic absorption spectrometry (AAS) was introduced. For highly selective and efficient extraction, magnetic Cr (VI)-imprinted nanoparticles (Fe 3 O 4 @ Cr (VI) IIPs) were prepared by hyphenating surface ion-imprinted with sol-gel techniques. In the preparation process, chromate (Cr(VI)) was used as the template ion; vinylimidazole and 3-aminopropyltriethoxysilane were selected as organic functional monomer and co-monomer respectively. Another reagent, methacryloxypropyltrimethoxysilane was adopted as coupling agent to form the stable covalent bonding between organic and inorganic phases. The effects of various parameters on the extraction efficiency, such as pH of sample solution, the amount of adsorbent, extraction time, the type and concentration of eluent were systematically investigated. Furthermore, the thermodynamic and kinetic properties of the adsorption process were studied to explore the internal adsorption mechanism. Under optimized conditions, the preconcentration factor, limit of detection and linear range of the established dSPE-AAS method for Cr (VI) were found to be 98, 0.29μgL -1 and 4-140μgL -1 , respectively. The developed method was also successfully applied to the analysis of Cr (VI) in different water samples with satisfactory results, proving its reliability and feasibility in real sample analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of the temperature in the uranium (Vi) sorption in zirconium diphosphate; Influencia de la temperatura en la sorcion de uranio (VI) en difosfato de circonio

Energy Technology Data Exchange (ETDEWEB)

Garcia G, N.; Solis, D. [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon y Paseo Tollocan, 50120 Toluca, Estado de Mexico (Mexico); Ordonez R, E., E-mail: nidgg@yahoo.com.mx [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2012-10-15

In the present work was evaluated the uranium (Vi) sorption at 10, 20, 30, 40 and 60 C on the zirconium diphosphate (ZrP{sub 2}O{sub 7}). They were carried out kinetic and isotherms using the method by lots, these will allow to fix the sorption time (kinetic) and to explain the behavior of this sorption in different ph conditions and temperature (isotherm). The quantity of retained uranium in the surface was quantified by means of the fluorescence technique. (Author)

Separation of uranium by extraction with foamed plastics

International Nuclear Information System (INIS)

Korkisch, J.

1983-07-01

Polyurethane foams are frequently used for the extraction and separation of inorganic and organic species. The attraction of the materials lies in their favourable hydrodynamic properties obviating the need for the forced-flow conditions associated with conventional chromatographic-type column packing of small particles. The research work described has been directed to providing information on the extraction and separation of uranium (and thorium) by an open-cell polyurethane foam from media containing nitrates and from hydrochloric acid systems. The influence of many different experimental parameters (concentrations, acidity, impregnation of the foam with organic extractants) on the extraction was investigated. Based on the results of these investigations two methods were developed to separate uranium from nitric acid solution and from hydrochloric acid solution, respectively. The first uses calcium or aluminium nitrate salting and foam impregnated with Aliquat 336, the second ascorbic acid addition and TOPO-impregnated foam. The methods separate uranium and thorium from each other and from most other elements and can be used analytically or in the purification of uranium from impure plant products such as yellow cake

Characterization of uranium redox state in organic-rich Eocene sediments.

Science.gov (United States)

Cumberland, Susan A; Etschmann, Barbara; Brugger, Joël; Douglas, Grant; Evans, Katy; Fisher, Louise; Kappen, Peter; Moreau, John W

2018-03-01

The presence of organic matter (OM) has a profound impact on uranium (U) redox cycling, either limiting or promoting the mobility of U via binding, reduction, or complexation. To understand the interactions between OM and U, we characterised U oxidation state and speciation in nine OM-rich sediment cores (18 samples), plus a lignite sample from the Mulga Rock polymetallic deposit in Western Australia. Uranium was unevenly dispersed within the analysed samples with 84% of the total U occurring in samples containing >21 wt % OM. Analyses of U speciation, including x-ray absorption spectroscopy and bicarbonate extractions, revealed that U existed predominately (∼71%) as U(VI), despite the low pH (4.5) and nominally reducing conditions within the sediments. Furthermore, low extractability by water, but high extractability by a bi-carbonate solution, indicated a strong association of U with particulate OM. The unexpectedly high proportion of U(VI) relative to U(IV) within the OM-rich sediments implies that OM itself does not readily reduce U, and the reduction of U is not a requirement for immobilizing uranium in OM-rich deposits. The fact that OM can play a significant role in limiting the mobility and reduction of U(VI) in sediments is important for both U-mining and remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extraction of uranium from seawater: a few facts

Directory of Open Access Journals (Sweden)

Guidez Joel

2016-01-01

Full Text Available Although uranium concentration in seawater is only about 3 micrograms per liter, the quantity of uranium dissolved in the world's oceans is estimated to amount to 4.5 billion tonnes of uranium metal (tU. In contrast, the current conventional terrestrial resource is estimated to amount to about 17 million tU. However, for a number of reasons the extraction of significant amounts of uranium from seawater remains today more a dream than a reality. Firstly, pumping the seawater to extract this uranium would need more energy than what could be produced with the recuperated uranium. Then if trying to use existing industrial flow rates, as for example on a nuclear power plant, it appears that the annual possible quantity remains very low. In fact huge quantities of water must be treated. To produce the annual world uranium consumption (around 65,000 tU, it would need at least to extract all uranium of 2 × 1013 tonnes of seawater, the volume equivalent of the entire North Sea. In fact only the great ocean currents are providing without pumping these huge quantities, and the idea is to try to extract even very partially this uranium. For example Japan, which used before the Fukushima accident about 8,000 tU by year, sees about 5.2 million tU passing every year, in the ocean current Kuro Shio in which it lies. A lot of research works have been published on the studies of adsorbents immersed in these currents. Then, after submersion, these adsorbents are chemically treated to recuperate the uranium. Final quantities remain very low in comparison of the complex and costly operations to be done in sea. One kilogram of adsorbent, after one month of submersion, yields about 2 g of uranium and the adsorbent can only be used six times due to decreasing efficiency. The industrial extrapolation exercise made for the extraction of 1,200 tU/year give with these values a very costly installation installed on more than 1000 km2 of sea with a

Selective Adsorption of Uranium (VI) on NaHCO Leached ...

African Journals Online (AJOL)

NICO

with a variety of organic and inorganic ligands to form complex species of different ... approach for the synthesis of magnetic particles for uranium .... equations (1) and (2), respectively. Extraction efficiency. (C. C ). C o e o. = −. × 100. (1).

Chapter 6. Uranium extraction possibilities from natural uranium-bearing waters of complex salt composition. 6.2. Technology for uranium extraction from brine with a high content of ion-chlorine

International Nuclear Information System (INIS)

Khakimov, N.; Nazarov, Kh.M.; Mirsaidov, I.U.

2012-01-01

Present article is devoted to technology for uranium extraction from brine with a high content of ion-chlorine. The content of basic anions and cations in lake waters of Sasik-Kul deposit was defined. Results of X-ray spectral analysis of salt residual after water evaporation from Sasik-Kul lake was discussed. Investigations revealed that uranium extraction from brines containing ion-chlorine is possible. The developed basic process flow diagram of uranium extraction from Sasik-Kul Lake' brine consists of the following basic stages: evaporation, leaching, catching of formed gases (HCl), sorption, desorption, deposition, drying and tempering.

Chapter 6. Uranium extraction possibilities from natural uranium-bearing waters of complex salt composition. 6.2. Technology for uranium extraction from brine with a high content of ion-chlorine

International Nuclear Information System (INIS)

Khakimov, N.; Nazarov, Kh.M.; Mirsaidov, I.U.

2011-01-01

Present article is devoted to technology for uranium extraction from brine with a high content of ion-chlorine. The content of basic anions and cations in lake waters of Sasik-Kul deposit was defined. Results of X-ray spectral analysis of salt residual after water evaporation from Sasik-Kul lake was discussed. Investigations revealed that uranium extraction from brines containing ion-chlorine is possible. The developed basic process flow diagram of uranium extraction from Sasik-Kul Lake' brine consists of the following basic stages: evaporation, leaching, catching of formed gases (HCl), sorption, desorption, deposition, drying and tempering.

Uranium extraction from sulfuric acid solution using anion exchange resin

International Nuclear Information System (INIS)

Sheta, M. E.; Abdel Aal, M. M.; Kandil, A. T.

2012-12-01

Uranium is currently recovered from sulfuric acid leach liquor using anion exchange resin as Amberlite IRA 402 (CT). This technology is based on fact that, uranium exists as anionic complexes. This takes place by controlling the pH of the solution, agitation time, temperature and resin to solution ratio (R/S). In this work, batch stirrer tank used for uranium extraction from sulfate medium and after extraction, elution process was done using 1M NaCl solution. After extraction and elution process, the resin was separated from the system and uranium was determined in the solution. (Author)

Towards a consistent geochemical model for prediction of uranium(VI) removal from groundwater by ferrihydrite

International Nuclear Information System (INIS)

Gustafsson, Jon Petter; Daessman, Ellinor; Baeckstroem, Mattias

2009-01-01

Uranium(VI), which is often elevated in granitoidic groundwaters, is known to adsorb strongly to Fe (hydr)oxides under certain conditions. This process can be used in water treatment to remove U(VI). To develop a consistent geochemical model for U(VI) adsorption to ferrihydrite, batch experiments were performed and previous data sets reviewed to optimize a set of surface complexation constants using the 3-plane CD-MUSIC model. To consider the effect of dissolved organic matter (DOM) on U(VI) speciation, new parameters for the Stockholm Humic Model (SHM) were optimized using previously published data. The model, which was constrained from available X-ray absorption fine structure (EXAFS) spectroscopy evidence, fitted the data well when the surface sites were divided into low- and high-affinity binding sites. Application of the model concept to other published data sets revealed differences in the reactivity of different ferrihydrites towards U(VI). Use of the optimized SHM parameters for U(VI)-DOM complexation showed that this process is important for U(VI) speciation at low pH. However in neutral to alkaline waters with substantial carbonate present, Ca-U-CO 3 complexes predominate. The calibrated geochemical model was used to simulate U(VI) adsorption to ferrihydrite for a hypothetical groundwater in the presence of several competitive ions. The results showed that U(VI) adsorption was strong between pH 5 and 8. Also near the calcite saturation limit, where U(VI) adsorption was weakest according to the model, the adsorption percentage was predicted to be >80%. Hence U(VI) adsorption to ferrihydrite-containing sorbents may be used as a method to bring down U(VI) concentrations to acceptable levels in groundwater

Uranium(VI) coordination polymers with pyromellitate ligand: Unique 1D channel structures and diverse fluorescence

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yingjie, E-mail: yzx@ansto.gov.au [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Bhadbhade, Mohan [Mark Wainwright Analytical Centre, University of New South Wales, Kensington, NSW 2052 (Australia); Karatchevtseva, Inna [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Price, Jason R. [Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168 (Australia); Liu, Hao [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology Sydney, PO Box 123, Broadway, Sydney, NSW 2007 (Australia); Zhang, Zhaoming; Kong, Linggen [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Čejka, Jiří [Department of Mineralogy, National Museum, Václavské náměstí, 68, Prague 1, 115 79-CZ (Czech Republic); Lu, Kim; Lumpkin, Gregory R. [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

2015-03-15

Three new coordination polymers of uranium(VI) with pyromellitic acid (H{sub 4}btca) have been synthesized and structurally characterized. (ED)[(UO{sub 2})(btca)]·(DMSO)·3H{sub 2}O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH{sub 4}){sub 2}[(UO{sub 2}){sub 6}O{sub 2}(OH){sub 6}(btca)]·~6H{sub 2}O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO{sub 2}){sub 2}(H{sub 2}O)(btca)]·4H{sub 2}O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ{sub 5}-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5 Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. - Graphical abstract: Table of content: three new uranium(VI) coordination polymers with pyromellitic acid (H{sub 4}btca) have been synthesized via room temperature and hydrothermal synthesis methods, and structurally characterized. Two to three dimensional (3D) frameworks are revealed. All 3D frameworks have unique 1D large channels. Their vibrational modes, thermal stabilities and photoluminescence properties have been investigated. - Highlights: • Three new coordination polymers of U(VI) with pyromellitic acid (H{sub 4}btca). • Structures from a 2D layer to 3D frameworks with unique 1D channels. • Unusual µ{sub 5}-(η{sub 1}:η{sub 2}:η{sub 1}:η{sub 2:}η{sub 1}) coordination mode of btca ligand. • Vibrational modes, thermal stabilities and luminescent properties reported.

Extraction of uranium from simulated ore by the supercritical carbon dioxide fluid extraction method with nitric acid-TBP complex

International Nuclear Information System (INIS)

Dung, Le Thi Kim; Imai, Tomoki; Tomioka, Osamu; Nakashima, Mikio; Takahashi, Kuniaki; Meguro, Yoshihiro

2006-01-01

The supercritical fluid extraction (SFE) method using CO 2 as a medium with an extractant of HNO 3 -tri-n-butyl phosphate (TBP) complex was applied to extract uranium from several uranyl phosphate compounds and simulated uranium ores. An extraction method consisting of a static extraction process and a dynamic one was established, and the effects of the experimental conditions, such as pressure, temperature, and extraction time, on the extraction of uranium were ascertained. It was found that uranium could be efficiently extracted from both the uranyl phosphates and simulated ores by the SFE method using CO 2 . It was thus demonstrated that the SFE method using CO 2 is useful as a pretreatment method for the analysis of uranium in ores. (author)

Analytical applications of N-phenyl-n-butyro hydroxamic and N-p-tolyl-n-butyro hydroxamic acids towards chromium (VI), copper (II), iron (III) and uranium (VI)

International Nuclear Information System (INIS)

Elkhadir, A. Y. F.

2001-05-01

Two aliphatic hydroxamic acids were prepared; N-phenyl-n-butyro hydroxamic acid and N-p-tolyl-n-butyro hydroxamic acid, by the reaction of β-phenylhydroxylamine and p-tolyl hydroxylamine with n-butyryl chloride. The acids were identified by: their melting points, characteristic reactions with acidic solutions of vanadium (V) and iron (III), infrared spectroscopy, nitrogen content and molecular weight determination. The extractability of these acids towards Cr (VI), Cu (II), Fe (III) and U (VI) were investigated at different pH values and molar acid concentrations. N-phenyl-n- butyro hydroxamic acid has a maximum extraction (98.80%) for Cr (VI) at 4 M H 2 SO 4 , (83.25%) for Cu (II) at pH 6, (99.17%) for Fe (III) at pH 5 and (99.76%) at 4 M HNO 3 for U (VI) respectively. N-p-tolyl-n-butyro hydroxamic acid has a maximum extraction (98.40%) for Cr (VI)at 4 M H 2 SO 4 , (81.30%) for Cu (II) at pH 6, (92.80%) for Fe (III) at pH 5 and (99.64%) for U (VI) at 4 M HNO 3 , respectively. The ratios of the metal to ligands were determined by job method (continuous variation method) and were found to be 1:2 for Cr (VI) and U (VI). (Author)

Analytical applications of N-phenyl-n-butyro hydroxamic and N-p-tolyl-n-butyro hydroxamic acids towards chromium (VI), copper (II), iron (III) and uranium (VI)

Energy Technology Data Exchange (ETDEWEB)

Elkhadir, A Y. F. [Department of Chemistry, Faculty of Science, University of Khartoum, Khartoum (Sudan)

2001-05-01

Two aliphatic hydroxamic acids were prepared; N-phenyl-n-butyro hydroxamic acid and N-p-tolyl-n-butyro hydroxamic acid, by the reaction of {beta}-phenylhydroxylamine and p-tolyl hydroxylamine with n-butyryl chloride. The acids were identified by: their melting points, characteristic reactions with acidic solutions of vanadium (V) and iron (III), infrared spectroscopy, nitrogen content and molecular weight determination. The extractability of these acids towards Cr (VI), Cu (II), Fe (III) and U (VI) were investigated at different pH values and molar acid concentrations. N-phenyl-n- butyro hydroxamic acid has a maximum extraction (98.80%) for Cr (VI) at 4 M H{sub 2}SO{sub 4}, (83.25%) for Cu (II) at pH 6, (99.17%) for Fe (III) at pH 5 and (99.76%) at 4 M HNO{sub 3} for U (VI) respectively. N-p-tolyl-n-butyro hydroxamic acid has a maximum extraction (98.40%) for Cr (VI)at 4 M H{sub 2} SO{sub 4}, (81.30%) for Cu (II) at pH 6, (92.80%) for Fe (III) at pH 5 and (99.64%) for U (VI) at 4 M HNO{sub 3}, respectively. The ratios of the metal to ligands were determined by job method (continuous variation method) and were found to be 1:2 for Cr (VI) and U (VI). (Author)

Enhancement of Extraction of Uranium from Seawater - Final Report

International Nuclear Information System (INIS)

Dietz, Travis Cameron; Tsinas, Zois; Tomaszewski, Claire; Pazos, Ileana; Nigliazzo, Olga; Li, Weixing; Adel-Hadadi, Mohammad; Barkatt, Aaron; Al-Sheikhly, Mohamad

2016-01-01

Even at a concentration of 3 μg/L, the world's oceans contain a thousand times more uranium than currently know terrestrial sources. In order to take advantage of this stockpile, methods and materials must be developed to extract it efficiently, a difficult task considering the very low concentration of the element and the competition for extraction by other atoms in seawater such as sodium, calcium, and vanadium. The majority of current research on methods to extract uranium from seawater are vertical explorations of the grafting of amidoxime ligand, which was originally discovered and promoted by Japanese studies in the late 1980s. Our study expands on this research horizontally by exploring the effectiveness of novel uranium extraction ligands grafted to the surface of polymer substrates using radiation. Through this expansion, a greater understanding of uranium binding chemistry and radiation grafting effects on polymers has been obtained. While amidoxime-functionalized fabrics have been shown to have the greatest extraction efficiency so far, they suffer from an extensive chemical processing step which involves treatment with powerful basic solutions. Not only does this add to the chemical waste produced in the extraction process and add to the method's complexity, but it also significantly impacts the regenerability of the amidoxime fabric. The approach of this project has been to utilize alternative, commercially available monomers capable of extracting uranium and containing a carbon-carbon double bond to allow it to be grafted using radiation, specifically phosphate, oxalate, and azo monomers. The use of commercially available monomers and radiation grafting with electron beam or gamma irradiation will allow for an easily scalable fabrication process once the technology has been optimized. The need to develop a cheap and reliable method for extracting uranium from seawater is extremely valuable to energy independence, and will extend the

Studies on the extraction of uranium by N-octanoyl-N-phenylhydroxamic acid

International Nuclear Information System (INIS)

Saha, B.; Venkatesan, K.A.; Antony, M.P.; Vasudeva Rao, P.R.; Natarajan, R.

2002-01-01

N-octanoyl-N-phenylhydroxamic acid (OHA) has been prepared by partial reduction of nitrobenzene with Zn dust/NH 4 Cl, followed by acylation with n-octanoyl chloride. Structure of OHA was confirmed by 1 H NMR, IR spectra and CHNS microanalysis. The extraction of uranium by OHA has been studied as a function of pH, temperature and concentration of OHA. The extraction of uranium was found to increase with increase in pH. Uranium forms a 1 : 2 complex with OHA. IR Spectra and NMR Spectra of the uranium-OHA complex and slope analysis obtained from extraction studies indicated that the extraction of uranium was due to the formation of a chelate. The enthalpy change accompanied by the extraction of uranium by OHA has been obtained by temperature variation method. The extraction process was found to be endothermic at pH 2 and exothermic at pH 6. (orig.)

Extraction of uranium from seawater: evaluation of uranium resources and plant siting

International Nuclear Information System (INIS)

Rodman, M.R.; Gordon, L.I.; Chen, A.C.T.

1979-02-01

This report deals with the evaluation of U.S. coastal waters as a uranium resource and with the selection of a suitable site for construction of a large-scale plant for uranium extraction. Evaluation of the resource revealed that although the concentration of uranium is quite low, about 3.3 ppB in seawater of average oceanic salinity, the amount present in the total volume of the oceans is very great, some 4.5 billion metric tons. Of this, perhaps only that uranium contained in the upper 100 meters or so of the surface well-mixed layer should be considered accessible for recovery, some 160 million tonnes. The study indicated that open ocean seawater acquired for the purpose of uranium extraction would be a more favorable resource than rivers entering the sea, cooling water of power plants, or the feed or effluent streams of existing plants producing other products such as magnesium, bromine, or potable and/or agricultural water from seawater. Various considerations led to the selection of a site for a pumped seawater coastal plant at a coastal location. Puerto Yabucoa, Puerto Rico was selected. Recommendations are given for further studies. 21 figures, 8 tables

Extraction of uranium from seawater: evaluation of uranium resources and plant siting

Energy Technology Data Exchange (ETDEWEB)

Rodman, M.R.; Gordon, L.I.; Chen, A.C.T.

1979-02-01

This report deals with the evaluation of U.S. coastal waters as a uranium resource and with the selection of a suitable site for construction of a large-scale plant for uranium extraction. Evaluation of the resource revealed that although the concentration of uranium is quite low, about 3.3 ppB in seawater of average oceanic salinity, the amount present in the total volume of the oceans is very great, some 4.5 billion metric tons. Of this, perhaps only that uranium contained in the upper 100 meters or so of the surface well-mixed layer should be considered accessible for recovery, some 160 million tonnes. The study indicated that open ocean seawater acquired for the purpose of uranium extraction would be a more favorable resource than rivers entering the sea, cooling water of power plants, or the feed or effluent streams of existing plants producing other products such as magnesium, bromine, or potable and/or agricultural water from seawater. Various considerations led to the selection of a site for a pumped seawater coastal plant at a coastal location. Puerto Yabucoa, Puerto Rico was selected. Recommendations are given for further studies. 21 figures, 8 tables.

Uranium extraction in northern Bohemia by leaching and provisions for remediation of its adverse impacts on the environment

International Nuclear Information System (INIS)

Tomas, J.

1992-01-01

The problems of uranium extraction at the Straz pod Ralskem and Hamr sites in northern Bohemia are highlighted. The geological situation at the two deposits is described. At Hamr, uranium is mined conventionally, whereas at Straz, hydrochemical extraction is practised. The two deposits are located close to each other, they affect one another and affect adversely the rock environment. A remedial programme has been worked out, based on (i) abandoning deep mining at the Hamr 1 mine and shutting down the ore treatment plant, (ii) preparation of a membrane project to decontaminate the Turonian groundwater body and ore processing lagoons, (iii) sustaining a protective hydraulic barrier between the Hamr 1 mine and the chemical extraction site, (iv) design preparation and construction of a desalination station, (v) monitoring the Turonian drinking water quality, and (vi) preparation of technologies for a final separation and use of alum and inert leachates. The technology of thermal concentration by evaporation followed by concentrate treatment was chosen for the decontamination of the polluted waters. The entire decontamination of the deposits is expected to take 50 to 70 years. (J.B.). 1 tab., 3 figs

Liquid-liquid extraction of Th4+ and UO22+ by LIX-26 and its mixtures

International Nuclear Information System (INIS)

Singh, S.; Panda, C.R.; Chakravortty, V.; Dash, K.C.

1988-01-01

Solvent extractions of thorium(IV) and uranium(VI) by a commercially available chelating extractant LIX-26 (an alkylated 8-hydroxyquinoline) of 8-hydroxyquinoline, benzoic or salicylic acid, dipentyl sulfoxide (DPSO) and their mixtures with butanol as modifier in benzene/methylisobutyl ketone (MIBK) as a diluent were studied. The influence of concentration of various anions on the extraction of Th 4+ by mixtures of LIX-26 and benzoic acid was studied. Studies on extraction of thorium(IV) and uranium(VI) by mixtures of LIX-26 (HQ) and DPSO show that the extracted species are possibly of the type [(ThQ 2 (DPSO) 2 (SCN) 2 )] and [(UO 2 Q 2 (DPSO)]), respectively. (author) 22 refs.; 8 figs

Uranium and Molybdenum extraction from a Cerro Solo deposit ore

International Nuclear Information System (INIS)

Becquart, Elena T.; Arias, Maria J.; Fuente, Juan C. de la; Misischia, Yamila A.; Santa Cruz, Daniel E.; Tomellini, Guido C.

2009-01-01

Cerro Solo, located in Chubut, Argentina, is a sandstone type uranium-molybdenum deposit. Good recovery of both elements can be achieved by acid leaching of the ore but the presence of molybdenum in pregnant liquors is an inconvenient to uranium separation and purification. A two steps process is developed. A selective alkaline leaching of the ore with sodium hydroxide allows separating and recovering of molybdenum and after solid-liquid separation, the ore is acid leached to recover uranium. Several samples averaging 0,2% uranium and 0,1% molybdenum with variable U/Mo ratio have been used and in both steps, leaching and oxidant reagents concentration, temperature and residence time in a stirred tank leaching have been studied. In alkaline leaching molybdenum recoveries greater than 96% are achieved, with 1% uranium extraction. In acid leaching up to 93% of the uranium is extracted and Mo/U ratio in solvent extraction feed is between 0,013 and 0,025. (author)

Study of polyethyleneimine- and amidoxime-functionalized hybrid biomass of Spirulina (Arthrospira) platensis for adsorption of uranium (VI) ion.

Science.gov (United States)

Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

2015-11-01

This study investigates the potential application of the polyethyleneimine- (PEI) and amidoxime-modified Spirulina (Arthrospira) platensis biomasses for the removal of uranium ion in batch mode using the native biomass as a control system. The uranium ion adsorption was also characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, zeta potential analysis, and surface area measurement studies. The effects of pH, biomass amount, contact time, initial uranium ion concentration, and ionic strength were evaluated by using native and modified algal biomass preparations. The uranium ion removal was rapid, with more than 70% of total adsorption taking place in 40 min, and equilibrium was established within 60 min. From the experimental data, it was found that the amount of adsorption uranium ion on the algal preparations decreased in the following series: amidoxime-modified algal biomass > PEI-modified algal biomass > native algal biomass. Maximum adsorption capacities of amidoxime- and PEI-modified, and native algal biomasses were found to be 366.8, 279.5, and 194.6 mg/g, respectively, in batchwise studies. The adsorption rate of U(VI) ion by amidoxime-modified algal biomass was higher than those of the native and PEI-modified counterparts. The adsorption processes on all the algal biomass preparations followed by the Dubinin-Radushkevitch (D-R) and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters were determined at four different temperatures (i.e., 15, 25, 35, and 45 °C) using the thermodynamics constant of the Temkin isotherm model. The ΔH° and ΔG° values of U(VI) ion adsorption on algal preparations show endothermic heat of adsorption; higher temperatures favor the process. The native and modified algal biomass preparations were regenerated using 10 mM HNO3. These results show that amidoxime-modified algal biomass can be a potential candidate for effective removal of U(VI) ion from

Uranium extraction from Uro area phosphate ore, Nuba mountains, Sudan

International Nuclear Information System (INIS)

Mohammed, A. A.; Eltayeb, M. A. H.

2003-01-01

This study was carried out mainly to extract uranium from Uro area phosphate ore in the eastern part of Nuba mountains near Abu Gibiha town in southern Kurdufan state. For this purpose first, the phosphate ore samples were decomposed with sulphuric acid. the resulting phosphoric acid was filtered off, and pretreated with pyrite and activated charcoal. the chemical analysis of the obtained grain phosphoric acid showed that about 98% of uranium content of the phosphate ore was rendered soluble in the phosphoric acid. The clear green phosphoric acid was introduced to uranium extraction by 25% tributylphosphate (Tbp) in kerosene. The effect of several factors on the extraction and stripping processes namely, interference's effect, the suitable strip solution, the required number of extraction and stripping stages, the optimum phase ratio have been studied in details. A three stage extraction at a phase ratio (aqueous/organic) of 1:2, followed by two stages stripping using 0.5 M sodium carbonate solution at a phase ratio (A/O) of 1:4 were found to be the optimum conditions to report more than 98% of uranium content in green phosphoric acid to the aqueous phase as uranyl tricarbonate complex (UO 2 (CO 3 ) 3 ) 4- . By applying sodica decomposition upon the stripping carbonate solution using 50% sodium hydroxide, about 98% of uranium content was precipitated as sodium diuranate concentrate (Na 2 U 2 O 7 ). The chemical analysis using atomic absorption spectrometry (Aas) showed a good agreement between the specification of the obtained uranium concentrate with the standard commercial specification of sodium diuranate concentrate. Further purification was achieved for the yellow cake by selective precipitation of uranium from the solution as uranium peroxide (UO 4 .2H 2 O) using 30% hydrogen peroxide. Finally the uranium peroxide precipitated was calcined at 450 degree C to obtain the orange powder uranium trioxide (UO 3 ). The chemical analysis of the final uranium trioxide

Studies on supercritical fluid extraction of uranium from sodium diuranate

International Nuclear Information System (INIS)

Prabhat, Parimal; Vithal, G.K.; Rao, Ankita; Kumar, Pradeep; Tomar, B.S.

2014-01-01

Crude sodium diuranate (SDU) produced from phosphoric acid by solvent extraction process with di-2-ethyl hexyl phosphoric acid (D2EHPA) and tri-n-butyl phosphate(TBP) contains iron and other rare earth impurities along with uranium. For further use of this uranium for fuel fabrication and its subsequent use in nuclear reactors, it has to be purified up to nuclear grade ammonium diuranate (ADU) specifications. Conventionally crude SDU is being purified by dissolving it in nitric acid followed by solvent extraction process using TBP in diluent. Use of large amount of acid and organic solvents for industrial processes is an environmental concern. Nowadays there are efforts to minimize use of acid and organic solvents in industrial processes. Supercritical Fluid Extraction (SFE) of uranium from different matrices (solid as well as liquid) has been reported by several authors in recent years. Near complete extraction of uranium from UO 2 (powder, green pellet and sintered pellet) using TBP-HNO 3 adduct by SFE has been reported. We attempted to explore possibility to purify crude SDU to nuclear grade by SFE of uranium from crude SDU matrix and study the effect of different operational parameters, mode of extraction and complexation

Extraction mechanism of U(VI) ions by N,N-dialkylamides

International Nuclear Information System (INIS)

Descouls, N.; Musikas, C.

1985-09-01

N,N dialkylamides are good extractants of UO 2 2+ ions from the nitric solutions obtained on dissolution of nuclear irradiated fuels. The extraction mechanism of U(VI) ions proved to be rather complex. Two species were identified by spectrophotometry in the organic phase: UO 2 (NO 3 ) 2 L 2 (1) and UO 2 (NO 3 ) 3 HL (2), L standing for the amide molecule. The complex (1) is typical for neutral molecules extractants. However, when log D(U(VI)) is plotted against log C (amide), the slope of the straight line obtained is greater than 2, which suggests that amide (1) interactions take place in the 2sup(nd) coordination sphere of U(VI) ions. The crystal structure of (1) where L is the N,N-di-n-butyldodecanamide show that Van der Waals interactions occur between the dodecyl chains of two (1) molecules. The complex (2) is characteristic for anionic extractants. For the amide molecules studied, it takes place in very acidic media. In order to investigate the nature of the UO 2 (NO 3 ) 3 HL complex, the infra-red shift of νc=0 vibration were compared in the following compounds: free amide, HNO 3 - L, phenol L, UO 2 (NO 3 ) 3 HL. The results are discussed. 14 refs [fr

Speciation of bioaccumulated uranium(VI) by Euglena mutabilis cells obtained by laser fluorescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Brockmann, Sina; Bernhard, Gert [Technical Univ. Dresden (Germany). Radiochemistry; Helmholtz-Zentrum Dresden-Rossendorf (HZDR) e.V., Dresden (Germany). Inst. of Resource Ecology; Arnold, Thuro [Helmholtz-Zentrum Dresden-Rossendorf (HZDR) e.V., Dresden (Germany). Inst. of Resource Ecology

2014-07-01

The ability of Euglena mutabilis cells - a unicellular protozoan with a flexible pellicle, which is typically found in acid mine drainage (AMD) environments - to bioaccumulate uranium under acid conditions was studied in batch sorption experiments at pH 3 and 4 using Na{sub 2}SO{sub 4} and NaClO{sub 4} as background media. It was found that axenic cultures of Euglena mutabilis Schmitz were able to bioaccumulate in 5 days 94.9 to 99.2% of uranium from a 1 x 10{sup -5} mol/L uranium solution in perchlorate medium and 95.1 to 95.9% in sodium sulfate medium, respectively. The speciation of uranium in solution and uranium bioaccumulated by Euglena mutabilis cells, were studied by laser induced fluorescence spectroscopy (LIFS). The LIFS investigations showed that the uranium speciation in the NaClO{sub 4} systems was dominated by free uranyl(VI) species and that the UO{sub 2}SO{sub 4} species was dominating in the Na{sub 2}SO{sub 4} medium. Fluorescence spectra of the bioaccumulated uranium revealed that aqueous uranium binds to carboxylic and/or (organo)phosphate groups located on the euglenid pellicle or inside the Euglena mutabilis cells. Reduced uranium immobilization rates of 0.93-1.43 mg uranium per g Euglena mutabilis biomass were observed in similar experiments, using sterile filtrated AMD waters containing, 4.4 x 10{sup -5} mol/L uranium. These lower rates were attributed to competition with other cations for available sorption sites. Additional LIFS measurements, however, showed that the speciation of the bioaccumulated uranium by the Euglena mutabilis cells was found to be identical with the uranium speciation found in the bioaccumulation experiments carried out in Na{sub 2}SO{sub 4} and NaClO{sub 4} media. The results indicate that Euglena mutabilis has the potential to immobilize aqueous uranium under acid condition and thus may be used in future as promising agent for immobilizing uranium in low pH waste water environments. (orig.)

Speciation of bioaccumulated uranium(VI) by Euglena mutabilis cells obtained by laser fluorescence spectroscopy

International Nuclear Information System (INIS)

Brockmann, Sina; Bernhard, Gert; Helmholtz-Zentrum Dresden-Rossendorf; Arnold, Thuro

2014-01-01

The ability of Euglena mutabilis cells - a unicellular protozoan with a flexible pellicle, which is typically found in acid mine drainage (AMD) environments - to bioaccumulate uranium under acid conditions was studied in batch sorption experiments at pH 3 and 4 using Na 2 SO 4 and NaClO 4 as background media. It was found that axenic cultures of Euglena mutabilis Schmitz were able to bioaccumulate in 5 days 94.9 to 99.2% of uranium from a 1 x 10 -5 mol/L uranium solution in perchlorate medium and 95.1 to 95.9% in sodium sulfate medium, respectively. The speciation of uranium in solution and uranium bioaccumulated by Euglena mutabilis cells, were studied by laser induced fluorescence spectroscopy (LIFS). The LIFS investigations showed that the uranium speciation in the NaClO 4 systems was dominated by free uranyl(VI) species and that the UO 2 SO 4 species was dominating in the Na 2 SO 4 medium. Fluorescence spectra of the bioaccumulated uranium revealed that aqueous uranium binds to carboxylic and/or (organo)phosphate groups located on the euglenid pellicle or inside the Euglena mutabilis cells. Reduced uranium immobilization rates of 0.93-1.43 mg uranium per g Euglena mutabilis biomass were observed in similar experiments, using sterile filtrated AMD waters containing, 4.4 x 10 -5 mol/L uranium. These lower rates were attributed to competition with other cations for available sorption sites. Additional LIFS measurements, however, showed that the speciation of the bioaccumulated uranium by the Euglena mutabilis cells was found to be identical with the uranium speciation found in the bioaccumulation experiments carried out in Na 2 SO 4 and NaClO 4 media. The results indicate that Euglena mutabilis has the potential to immobilize aqueous uranium under acid condition and thus may be used in future as promising agent for immobilizing uranium in low pH waste water environments. (orig.)

Importance of c-Type cytochromes for U(VI reduction by Geobacter sulfurreducens

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Leang Ching

2007-03-01

Full Text Available Abstract Background In order to study the mechanism of U(VI reduction, the effect of deleting c-type cytochrome genes on the capacity of Geobacter sulfurreducens to reduce U(VI with acetate serving as the electron donor was investigated. Results The ability of several c-type cytochrome deficient mutants to reduce U(VI was lower than that of the wild type strain. Elimination of two confirmed outer membrane cytochromes and two putative outer membrane cytochromes significantly decreased (ca. 50–60% the ability of G. sulfurreducens to reduce U(VI. Involvement in U(VI reduction did not appear to be a general property of outer membrane cytochromes, as elimination of two other confirmed outer membrane cytochromes, OmcB and OmcC, had very little impact on U(VI reduction. Among the periplasmic cytochromes, only MacA, proposed to transfer electrons from the inner membrane to the periplasm, appeared to play a significant role in U(VI reduction. A subpopulation of both wild type and U(VI reduction-impaired cells, 24–30%, accumulated amorphous uranium in the periplasm. Comparison of uranium-accumulating cells demonstrated a similar amount of periplasmic uranium accumulation in U(VI reduction-impaired and wild type G. sulfurreducens. Assessment of the ability of the various suspensions to reduce Fe(III revealed no correlation between the impact of cytochrome deletion on U(VI reduction and reduction of Fe(III hydroxide and chelated Fe(III. Conclusion This study indicates that c-type cytochromes are involved in U(VI reduction by Geobacter sulfurreducens. The data provide new evidence for extracellular uranium reduction by G. sulfurreducens but do not rule out the possibility of periplasmic uranium reduction. Occurrence of U(VI reduction at the cell surface is supported by the significant impact of elimination of outer membrane cytochromes on U(VI reduction and the lack of correlation between periplasmic uranium accumulation and the capacity for uranium

Application of liquid-liquid extraction in uranium hydrometallurgy (Paper No. : V-1)

Energy Technology Data Exchange (ETDEWEB)

Murthy, T K.S.; Koppiker, K S

1979-01-01

Uranium recovery from the ores is carried out exclusively by hydrometallurgical techniques. The initial solubilisation of uranium is achieved by either sodium carbonate or sulphuric acid leaching, the latter being more common. Further purification and upgrading of uranium from the sulphate liquors is carried out by an ion-exchange process. Solid resin type anion exchangers or liquid ion-exchangers are employed. The processing of uranium liquors is, perhaps, the first major application of liquid-liquid extraction in metal recovery. Organophosphoric acids were initially used but later the long-chain aliphatic amines have superseded them. The amine extraction system has been widely studied and several variations are now known. Chloride, nitrate, carbonate or sulphate or acid stripping can be used for getting back the uranium into the aqueous phase. Combination of ion exchange (resin type) and solvent extraction processes called Eluex processes are developed for special applications. Studies have also been made of solvent extraction of uranium from leach pulps instead of clear liquors. Tributylphosphate has found wide application in the refining of uranium concentrates to meet the stringent needs of nuclear purity. liquid-liquid extraction is, perhaps, the only successful technique for the recovery of uranium, as by-product, from wet-process phosphoric acid. This has opened up a new source of uranium.

Study of kinetics of extraction of actinides in processes of reprocessing of nuclear fuels

International Nuclear Information System (INIS)

Lamotte, Claude

1978-01-01

This research thesis reports a bibliographical study on extraction kinetics. After some generalities on solvent-based extraction, and on the chemistry of actinides in solution, on the methods of kinetics study which are generally used and their mathematical treatments, the author compares the published results for the extraction kinetics of nitric acid, uranium VI, uranium IV, neptunium IV and plutonium IV [fr

Standardization of solvent extraction procedure for determination of uranium in seawater

International Nuclear Information System (INIS)

Sukanta Maity; Sahu, S.K.; Pandit, G.G.

2015-01-01

Solvent extraction procedure using ammonium pyrolidine dithiocarbamate complexing agent in methyl isobutyl ketone organic phase and acid exchange back-extraction is described for the simultaneous quantitative pre-concentration of uranium in seawater followed by its determination by differential pulse adsorptive stripping voltammetry. Solvent extraction time is optimized for extraction of uranium from seawater. Solvent extraction efficiency for uranium in seawater at different pH was carried out. The method gives a recovery of 98 ± 2 % for 400 mL sample at pH 3.0 ± 0.02, facilitating the rapid and interference free analysis of seawater samples. (author)

Separation of molybdenum(VI) by extraction with n-octylaniline from hydrochloric acid medium

International Nuclear Information System (INIS)

Sawant, S.S.; Anuse, M.A.; Chavan, M.B.

1997-01-01

N-Octylaniline in benzene was used for the extractive separation of molybdenum(VI) from hydrochloric acid medium. Molybdenum(VI) was extracted quantitatively from 10 ml aqueous solution 1.5M in hydrochloric acid and 10M in lithium chloride into 10 ml of 10% n-octylaniline in benzene. It was stripped from the organic phase with 5% aqueous ammonia solution and estimated spectrophotometrically with thiocyanate at 465 nm. The interference of various ions has been studied in detail and conditions have been established for the determination of molybdenum(VI) in synthetic mixtures and alloy samples. (author)

Valence-associated uranium isotope fractionation of uranium enriched phosphate in a shallow aquifer, Lee County, Florida

International Nuclear Information System (INIS)

Weinberg, J.M.; Levine, B.R.; Cowart, J.B.

1993-01-01

The source of anomalously high concentrations of uranium, characterized by U-234/U-238 activity ratios significantly less than unity, in shallow groundwaters of Lee County, Florida, was investigated. Uranium in cores samples was separated into U(IV) and U(VI) oxidation state fractions, and uranium analyses were conducted by alpha spectrometry. Uranium mobility was also studied in selected leaching experiments. Results indicate that mobilization of unusually soluble uranium, present in uranium enriched phosphate of the Pliocene age Tamiami Formation at determined concentrations of up to 729 ppm, is the source for high uranium concentrations in groundwater. In leaching experiments, approximately one-third of the uranium present in the uranium enriched phosphate was mobilized into the aqueous phase. Results of previous investigations suggest that U-234, produced in rock by U-238 decay, is selectively oxidized to U(VI). The uranium enriched phosphate studied in this investigation is characterized by selective reduction of U-234, with a pattern of increasing isotopic fractionation with core depth. As a consequence, U-234/U-238 activity ratios greater than 1.0 in the U(IV) fraction, and less than 1.0 in the U(VI) fraction have developed in the rock phase. In leaching experiments, the U(VI) fraction from the rock was preferentially mobilized into the aqueous phase, suggesting that U-234/U-238 activity ratios of leaching groundwaters are strongly influenced by the isotopic characteristics of the U(VI) fraction of rock. It is suggested that preferential leaching of U(VI), present in selectivity reduced uranium enriched phosphate, is the source for low activity ratio groundwaters in Lee County

Investigation of the binding of tiron to uranium(IV) and uranium(VI) found in soil

International Nuclear Information System (INIS)

Birnbaum, E.R.; Iams, H.D.; del Rio Garcia, M.; Ford, D.K.; Smith, P.H.; Strietelmeier, B.; Brainard, J.

1993-01-01

The authors are investigating the utility of a chelate-reductant system to extract uranium from 2 million yards of contaminated soil at the Fernald uranium reprocessing plant near Cincinnati, Ohio. It has been found that reduction of the uranyl contaminants using Tiron as the ligand. Of concern is whether the increased mobilization is simply a result of the higher affinity of Tiron to U(IV), or whether reduction of amorphous iron oxides contained in the soil is exposing greater amounts of uranyl ions to the ligand. It is important to establish if the latter mechanism is occurring, since a removal process which does not damage the soil is desired. Potentiometric and spectrophotometric studies of Tiron binding to soluble uranyl and U(V) salts will be presented as models to help understand the soil studies. Extraction behavior of UO 2 (OH) 2 will also be presented

Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal.

Science.gov (United States)

Bots, Pieter; Morris, Katherine; Hibberd, Rosemary; Law, Gareth T W; Mosselmans, J Frederick W; Brown, Andy P; Doutch, James; Smith, Andrew J; Shaw, Samuel

2014-12-09

The favored pathway for disposal of higher activity radioactive wastes is via deep geological disposal. Many geological disposal facility designs include cement in their engineering design. Over the long term, interaction of groundwater with the cement and waste will form a plume of a hyperalkaline leachate (pH 10-13), and the behavior of radionuclides needs to be constrained under these extreme conditions to minimize the environmental hazard from the wastes. For uranium, a key component of many radioactive wastes, thermodynamic modeling predicts that, at high pH, U(VI) solubility will be very low (nM or lower) and controlled by equilibrium with solid phase alkali and alkaline-earth uranates. However, the formation of U(VI) colloids could potentially enhance the mobility of U(VI) under these conditions, and characterizing the potential for formation and medium-term stability of U(VI) colloids is important in underpinning our understanding of U behavior in waste disposal. Reflecting this, we applied conventional geochemical and microscopy techniques combined with synchrotron based in situ and ex situ X-ray techniques (small-angle X-ray scattering and X-ray adsorption spectroscopy (XAS)) to characterize colloidal U(VI) nanoparticles in a synthetic cement leachate (pH > 13) containing 4.2-252 μM U(VI). The results show that in cement leachates with 42 μM U(VI), colloids formed within hours and remained stable for several years. The colloids consisted of 1.5-1.8 nm nanoparticles with a proportion forming 20-60 nm aggregates. Using XAS and electron microscopy, we were able to determine that the colloidal nanoparticles had a clarkeite (sodium-uranate)-type crystallographic structure. The presented results have clear and hitherto unrecognized implications for the mobility of U(VI) in cementitious environments, in particular those associated with the geological disposal of nuclear waste.

Understanding Uranium Behavior in a Reduced Aquifer

Science.gov (United States)

Janot, N.; Lezama-Pacheco, J. S.; Williams, K. H.; Bernier-Latmani, R.; Long, P. E.; Davis, J. A.; Fox, P. M.; Yang, L.; Giammar, D.; Cerrato, J. M.; Bargar, J.

2012-12-01

Uranium contamination of groundwater is a concern at several US Department of Energy sites, such Old Rifle, CO. Uranium transport in the environment is mainly controlled by its oxidation state, since oxidized U(VI) is relatively mobile, whereas U(IV) is relatively insoluble. Bio-remediation of contaminated aquifers aims at immobilizing uranium in a reduced form. Previous laboratory and field studies have shown that adding electron donor (lactate, acetate, ethanol) to groundwater stimulates the activity of metal- and sulfate-reducing bacteria, which promotes U(VI) reduction in contaminated aquifers. However, obtaining information on chemical and physical forms of U, Fe and S species for sediments biostimulated in the field, as well as kinetic parameters such as U(VI) reduction rate, is challenging due to the low concentration of uranium in the aquifers (typically bio-remediation experiment at the Old Rifle site, CO, from early iron-reducing conditions to the transition to sulfate-reducing conditions. Several in-well chromatographic columns packed with sediment were deployed and were sampled at different days after the start of bio-reduction. X-ray absorption spectroscopy and X-ray microscopy were used to obtain information on Fe, S and U speciation and distribution. Chemical extractions of the reduced sediments have also been performed, to determine the rate of Fe(II) and U(IV) accumulation.

Enhancement of Extraction of Uranium from Seawater – Final Report

Energy Technology Data Exchange (ETDEWEB)

Dietz, Travis Cameron [Univ. of Maryland, College Park, MD (United States); Tsinas, Zois [Univ. of Maryland, College Park, MD (United States); Tomaszewski, Claire [Univ. of Maryland, College Park, MD (United States); Pazos, Ileana [Univ. of Maryland, College Park, MD (United States); Nigliazzo, Olga [University of Palermo, Palermo (Italy); Li, Weixing [Univ. of Maryland, College Park, MD (United States); Adel-Hadadi, Mohammad [Univ. of Maryland, College Park, MD (United States); Barkatt, Aaron [The Catholic Univ. of America, Washington, DC (United States); Al-Sheikhly, Mohamad [Univ. of Maryland, College Park, MD (United States)

2016-05-16

Even at a concentration of 3 μg/L, the world’s oceans contain a thousand times more uranium than currently know terrestrial sources. In order to take advantage of this stockpile, methods and materials must be developed to extract it efficiently, a difficult task considering the very low concentration of the element and the competition for extraction by other atoms in seawater such as sodium, calcium, and vanadium. The majority of current research on methods to extract uranium from seawater are vertical explorations of the grafting of amidoxime ligand, which was originally discovered and promoted by Japanese studies in the late 1980s. Our study expands on this research horizontally by exploring the effectiveness of novel uranium extraction ligands grafted to the surface of polymer substrates using radiation. Through this expansion, a greater understanding of uranium binding chemistry and radiation grafting effects on polymers has been obtained. While amidoxime-functionalized fabrics have been shown to have the greatest extraction efficiency so far, they suffer from an extensive chemical processing step which involves treatment with powerful basic solutions. Not only does this add to the chemical waste produced in the extraction process and add to the method’s complexity, but it also significantly impacts the regenerability of the amidoxime fabric. The approach of this project has been to utilize alternative, commercially available monomers capable of extracting uranium and containing a carbon-carbon double bond to allow it to be grafted using radiation, specifically phosphate, oxalate, and azo monomers. The use of commercially available monomers and radiation grafting with electron beam or gamma irradiation will allow for an easily scalable fabrication process once the technology has been optimized. The need to develop a cheap and reliable method for extracting uranium from seawater is extremely valuable to energy independence, and will extend the quantity of

Separation of neptunium from uranium and plutonium in the Purex process

International Nuclear Information System (INIS)

Kolarik, Z.; Schuler, R.

1984-01-01

The possibility of removing neptunium from the Purex process in the first extraction cycle was investigated. Butyraldehyde was found to reduce Np(VI) to Np(V), but not Pu(IV) to Pu(III). Up to 99.7% Np can be separated from uranium and plutonium in the 1A extractor or, much more favourably, in an additional partitioning extractor. Hydroxylamine nitrate can be used for reducing Np(VI) to Np(V) in a uranium purification cycle at a high U concentration in the feed solution. Here the decontamination factor for Np can be as high as 2300 and is lowered if iron is present in the feed. (author)

Terminal uranium(V/VI) nitride activation of carbon dioxide and carbon disulfide. Factors governing diverse and well-defined cleavage and redox reactions

International Nuclear Information System (INIS)

Cleaves, Peter A.; Gardner, Benedict M.; Liddle, Stephen T.; Kefalidis, Christos E.; Maron, Laurent; Tuna, Floriana; McInnes, Eric J.L.; Lewis, William

2017-01-01

The reactivity of terminal uranium(V/VI) nitrides with CE 2 (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(Tren TIPS )(N)][K(B15C5) 2 ] (1, Tren TIPS =N(CH 2 CH 2 NSiiPr 3 ) 3 ; B15C5=benzo-15-crown-5) reacts with CO 2 to give [U(Tren TIPS )(O)(NCO)][K(B15C5) 2 ] (3), whereas the uranium(VI) nitride [U(Tren TIPS )(N)] (2) reacts with CO 2 to give isolable [U(Tren TIPS )(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(Tren TIPS )(O)] (5) with concomitant formation of N 2 and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS 2 to give [U(Tren TIPS )(κ 2 -CS 3 )][K(B15C5) 2 ] (6), 2, and [K(B15C5) 2 ][NCS] (7), whereas 2 reacts with CS 2 to give [U(Tren TIPS )(NCS)] (8) and ''S'', with the latter trapped as Ph 3 PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE 2 follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS 2 as a reactivity surrogate for CO 2 . (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

U(VI) speciation and reduction in acid chloride fluids in hydrothermal conditions: from transport to deposition of uranium in unconformity-related deposits

International Nuclear Information System (INIS)

Dargent, Maxime

2014-01-01

Circulations of acidic chloride brines in the earth's crust are associated with several types of uranium deposits, particularly unconformity-related uranium (URU) deposits. The spectacular high grade combined with the large tonnage of these deposits is at the origin of the key questions concerning the geological processes responsible for U transport and precipitation. The aim of this work is to performed experimental studies of U(VI) speciation and its reduction to U(IV) subsequently precipitation to uraninite under hydrothermal condition. About uranium transport, the study of U(VI) speciation in acidic brines at high temperature is performed by Raman and XAS spectroscopy, showing the coexistence of several uranyl chloride complexes UO 2 Cl n 2-n (n = 0 - 5). From this study, complexation constants are proposed. The strong capability of chloride to complex uranyl is at the origin of the transport of U(VI) at high concentration in acidic chloride brines. Concerning uranium precipitation, the reactivity of four potential reductants under conditions relevant for URU deposits genesis is investigated: H 2 , CH 4 , Fe(II) and the C-graphite. The kinetics of reduction reaction is measured as a function of temperature, salinity, pH and concentration of reductant. H 2 , CH 4 , and the C-graphite are very efficient while Fe(II) is not able to reduce U(VI) in same conditions. The duration of the mineralizing event is controlled by (i) the U concentration in the ore-forming fluids and (ii) by the generation of gaseous reductants, and not by the reduction kinetics. These mobile and efficient gaseous reductant could be at the origin of the extremely focus and massive character of ore in URU deposits. Finally, first partition coefficients uraninite/fluid of trace elements are obtained. This last part opens-up new perspectives on (i) REE signatures interpretation for a given type of uranium deposit (ii) and reconstruction of mineralizing fluids composition. (author) [fr

The technology of uranium extraction from the brine with high chlorine-ion content

International Nuclear Information System (INIS)

Khakimov, N.; Nazarov, Kh.M.; Mirsaidov, I.U.; Negmatov, Sh.I.; Barotov, B.B.

2010-01-01

Present article is devoted to technology of uranium extraction from the brine with high chlorine-ion content. The research results on uranium extraction from the brine of Sasik-Kul Lake by means of sorption method were considered. The chemical composition of salt was determined. The process of uranium sorption was described and analyzed. The technology of uranium extraction from the brine with high chlorine-ion content was proposed.

Refining of crude uranium by solvent extraction for production of nuclear pure uranium metal

International Nuclear Information System (INIS)

Gupta, S.K.; Manna, S.; Singha, M.; Hareendran, K.N.; Chowdhury, S.; Satpati, S.K.; Kumar, K.

2007-01-01

Uranium is the primary fuel material for any nuclear fission energy program. Natural uranium contains only 0.712% of 235 U as fissile constituent. This low concentration of fissile isotope in natural uranium calls for a very high level of purity, especially with respect to neutron poisons like B, Cd, Gd etc. before it can be used as nuclear fuel. Solvent extraction is a widely used technique by which crude uranium is purified for reactor use. Uranium metal plant (UMP), BARC, Trombay is engaged in refining of uranium concentrate for production of nuclear pure uranium metal for fabrication of fuel for research reactors. This paper reviews some of the fundamental aspects of this refining process with some special references to UMP, BARC. (author)

Effect of flavin compounds on uranium(VI) reduction- kinetic study using electrochemical methods with UV-vis spectroscopy

International Nuclear Information System (INIS)

Yamasaki, Shinya; Tanaka, Kazuya; Kozai, Naofumi; Ohnuki, Toshihiko

2017-01-01

The reduction of uranium hexavalent (U(VI)) to tetravalent (U(IV)) is an important reaction because of the change in its mobility in the natural environment. Although the flavin mononucleotide (FMN) has acted as an electron shuttle for the U(VI) reduction in vivo system, which is called an electron mediator, only the rate constant for the electron transfer from FMN to U(VI) has been determined. This study examined the rate constant for the U(VI) reduction process by three flavin analogues (riboflavin, flavin mononucleotide, flavin adenine dinucleotide) to elucidate their substituent group effect on the U(VI) reduction rate by electrochemical methods. The formation of the U(IV) was monitored by UV-vis spectrometry at 660 nm during the constant potential electrolysis of the U(VI) solution in the presence of the mediator. The cyclic voltammograms indicated that the three flavin analogues behaved as electron mediator to reduce U(VI). The logarithmic rate constant for the U(VI) reduction was related to the standard redox potential of the mediators. This linear relationship indicated that the redox-active group of the mediator and the substituent group of the mediator dominate capability of the U(VI) reduction and its rate, respectively. The apparent reduction potential of U(VI) increased about 0.2 V in the presence of the mediators, which strongly suggests that the biological electron mediator makes the U(VI) reduction possible even under more oxidative conditions. - Highlights: • The rate constant for the U(VI) reduction by flavin analogues was determined. • The flavins showed a mediator effect on the U(VI) reduction. • The logarithmic rate constants for the U(VI) reduction was proportional to redox potential of the mediator. • The presence of the mediator increased about 0.2 V apparent redox potential of U(VI) to U(IV).

Liquid-liquid extraction of chromium (VI) from sulfuric acid solutions using tri-n-dodecylamine/kerosene

International Nuclear Information System (INIS)

Stas, J.

2008-01-01

Extraction of chromium (VI) from sulfuric acid solutions with tri-n-dodecylamine containing octanol-1 as a modifier in kerosene was investigated. All parameters influencing the extraction of chromium (VI) (time of agitation, concentrations of chromium (VI), sulfuric acid, tri-n-dodecylamine and temperature) were studied. Forst of all, tri-n-dodecylamine reacts with sulfuric acid to form tri-n-dodecylamine sulfate and bisulfate salts, then, dichromate ions is extracted by amine bisulfate. The mathematical treatment of the obtained date enabled us to calculate the formation of equilibrium constant of (TDAH) 2 SO 4 TDAHHSO 4 and (TDAH) 2 Cγ 2 O 7 at 25 Centigrade and have been found to be K 1 =10 9.642 (14/mol 4 ), K 2 = 10 -0.899 (L/mol) and K ex 10 10.55 respectively. Stripping of more than 99% of chromium (VI) from the organic phase of tri-n-dodecylamine/kerosene can be easily achieved in two stages using 0.05 M sodium carbonate solution. The synergistic effect of tri-n-butylphosphate and tri-n-octylphosphine oxide on the extraction of chromium (VI) were also studied. (author)

Separation of Th(IV) and U(VI) by extraction chromatography

International Nuclear Information System (INIS)

Nadkarni, M.N.; Mayankutty, P.C.; Pillai, N.S.

1984-01-01

Application of extraction chromatography to the analytical separation of Th(IV) and U(VI) has been investigated. The stationary phase was a macroporous resin Amberlite XE-270 impregnated with undiluted tri-n-butylphosphate (TBP) and the mobile phase was either 5.0M HNO 3 or 6M HCl. Separation of traces of Th(IV) from large quantities of U(VI) was achieved on a laboratory column by elution of the absorbed Th(IV) with 6M HCl. (author)

Contribution to the study of the redox couple Np(VI)/Np(V) in the presence of uranium(VI) in solutions of nitric acid and nitrous acid; Contribution a l'etude du comportement redox du couple Np(VI)/Np(V) en presence d'uranium VI dans les solutions constituees d'acide nitrique et d'acide nitreux

Energy Technology Data Exchange (ETDEWEB)

Arpigny, S. [CEA Marcoule, Dept. de Radiochimie et Procedes, DRP, 30 (France)

2001-07-01

The redox behavior of the Np(VI)/Np(V) couple was the subject of a spectrometric study of the Np(VI) reduction reaction in nitric acid solutions (4 to 5 M) containing variable concentrations (1.5 to 3.5 x 10{sup -3} M) of nitrous acid. A low nitrous acid concentration and a high nitric acid concentration were found to favor the stabilization of Np(VI). The stoichiometric coefficients of nitrous acid and nitric acid in the Np(VI) reduction reaction were determined thermodynamically, although only the reaction order with respect to HNO{sub 2} could be calculated from a kinetic analysis. Adding nitrate ions to a HNO{sub 3}/HNO{sub 2} solution enhanced the stability of neptunium at oxidation state +VI, but also increased the reduction rate. When uranium(VI) was added to the HNO{sub 3}/HNO{sub 2} solutions, the total quantity of neptunium at oxidation state +V (either free or as a Np(V)-U(VI) complex) remained practically unchanged, as did the Np(VI) reduction rate. The electrochemical behavior of the Np(VI)/Np(V) couple was investigated in a weak acidic medium by voltammetry with an ultra-micro-electrode (UME). The oxidation wave limiting current variation was a linear function of the Np(V) concentration when a gold UME was used, but not with a platinum UME; the reduction wave limiting current variation versus the Np(V) concentration was linear with either gold or platinum UMEs. The presence of the Np(V)-U(VI) complex in the neptunium solutions was characterized by a shift in the normal apparent potential of the Np(VI)/Np(V) couple toward anodic potentials consistent with the previously determined values of the complexation constants. (author)

Multisensor system for determination of iron(II), iron(III) and uranium(VI) in complex solutions

International Nuclear Information System (INIS)

Legin, A.V.; Seleznev, B.L.; Rudnitskaya, A.M.; Vlasov, Yu.G.

1998-01-01

The aim of the present paper is the development and analytical evaluation of a multisensor system for determination of low content of iron(II), iron(III) and uranium(VI) in complex aqueous media. Sensor array included sensors on the basis of chalcogenide vitreous materials with redox and ionic cross-sensitivities, crystalline silver sulphide electrode, noble metal electrodes Pt, Au, Ag and redox sensor on the basis of oxide glass. Potentiometric measurements have been taken in a conventional electrochemical cell vs. a standard Ag/AgCl reference electrode. All measurements have been taken at room temperature. Calibration solutions contained UO 2 (NO 3 ) 2 in concentration range 10 -6 -1,610 -5 mol/L, K 3 Fe(CN) 6 and K 4 Fe(CN) 6 or FeSO 4 (NH 4 ) 2 SO 4 and FeCl 3 , with the ratio of Fe(II)/Fe(III) concentration from 100:1 to 1:100, the total concentration of Fe was 10 -4 and 10 -5 mol/L. All solutions have been made on the background electrolyte of calcium and magnesium chlorides and sulphates with the fixed content of 5-27 mmol/L of each component which is a typical one for groundwater or mining water. Sensor potentials have been processed by a back-propagation artificial neural net. Average error of determination of Fe(II) and Fe(III) is about 20 %, of uranium(VI) - 40 %. It was found that sensitivity of the sensor array to iron and uranium is irrespective of the chemical form of these species

Determination of trace uranium by resonance fluorescence method coupled with photo-catalytic technology and dual cloud point extraction.

Science.gov (United States)

Li, Jiekang; Li, Guirong; Han, Qian

2016-12-05

In this paper, two kinds of salophens (Sal) with different solubilities, Sal1 and Sal2, have been respectively synthesized, and they all can combine with uranyl to form stable complexes: [UO2(2+)-Sal1] and [UO2(2+)-Sal2]. Among them, [UO2(2+)-Sal1] was used as ligand to extract uranium in complex samples by dual cloud point extraction (dCPE), and [UO2(2+)-Sal2] was used as catalyst for the determination of uranium by photocatalytic resonance fluorescence (RF) method. The photocatalytic characteristic of [UO2(2+)-Sal2] on the oxidized pyronine Y (PRY) by potassium bromate which leads to the decrease of RF intensity of PRY were studied. The reduced value of RF intensity of reaction system (ΔF) is in proportional to the concentration of uranium (c), and a novel photo-catalytic RF method was developed for the determination of trace uranium (VI) after dCPE. The combination of photo-catalytic RF techniques and dCPE procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimal conditions, the linear calibration curves range for 0.067 to 6.57ngmL(-1), the linear regression equation was ΔF=438.0 c (ngmL(-1))+175.6 with the correlation coefficient r=0.9981. The limit of detection was 0.066ngmL(-1). The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0-103.5%. The mechanisms of the indicator reaction and dCPE are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Feasibility studies on supercritical fluid extraction of uranium from phosphoric acid

International Nuclear Information System (INIS)

Dubey, B.P.; Agarwal, A.K.

2014-01-01

Supercritical fluid extraction (SFE) is a promising novel technology for extraction of many materials. Work has been carried out worldwide on SFE of uranium from various matrices. However, there are no references indicating the R and D on uranium extraction from phosphoric acid using this technology. Heavy Water Board is involved in technology development for recovery of uranium from secondary source, hence it was considered prudent to investigate the technology of SFE for this purpose. Various experiments were carried out with both WPA (P 2 O 5 content 28%) and MGPA (P 2 O 5 content 54%) using bench scale facility available with one of the private party. Extraction experiments were carried out using several chelating agents including TBP, D2EHPA, D2EHPA+TBP/TOPO, TTA, TTA+TBP etc. Feasibility studies revealed the hydrodynamics of operation indicating liquid expansion by about three times during flow of super critical (SC) CO 2 . No flooding was observed when the extraction column filled 20% of its volume capacity, no carryover of entrained/extracted liquid with SC CO 2 with MGPA, material balance of inputs and outputs established i.e. 100% recovery of MGPA and chelating agent, No operational problems with raw MGPA (untreated). No significant extraction of impurities from phosphoric acid to SC CO 2 , 40℃ temperature and 160 bar pressure found ideal for extraction experiments since no other materials found extracted at these conditions and no apparent change/deterioration in PA and chelating agents. Experiments established feasibility of SCE with CO 2 , proper recovery of PA and chelating agents, no need for pretreatment/gunk removal from PA; however, extraction of uranium was found inadequate even though ORP of feed acid was boosted by H 2 O 2 addition. Investigations revealed that SCE column created reducing environment in phosphoric acid, which was not favourable for uranium extraction, which resulted in difficulty in extraction of Uranium. HWB has now designed

Inorganic-Organic hybrid materials for uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

El-Mourabit, Sabah

2013-01-01

Phosphate rocks are industrially processed in large quantities to produce phosphoric acid and fertilisers. These rocks contain significant concentration of uranium (50 to 300 ppm) which could be interesting for nuclear industry. This work deals with the valorisation of uranium as a by-product from fertiliser industry. The aim of this study is to develop a hybrid material, constituted of an inorganic solid support grafted with an extractant (complexing molecule), which can extract selectively uranium from phosphoric acid medium. The first step of our approach was to identify an inorganic support which is stable under these particular conditions (strong acidity and complexing medium). The chemical and mechanical stability of different meso-porous materials, such as silica, glass and carbon was studied. In a second phase, we focused on the identification and the optimisation of complexing molecules, specific of uranium in phosphoric acid. These ligands were then grafted on the most stable solids. Finally, the efficiency of these hybrid systems was evaluated through different tests of extraction, selectivity and de-extraction. (author) [fr

Uranium extraction from colofanite via organic solvents

International Nuclear Information System (INIS)

Ribeiro, Valeria Aparecida Leitao

2007-01-01

This work describes the use of pure or combined extractants dissolved in organic solvents for quantitative uranium recovery from colofanite, a fluoroapatite ore, from Itataia, Santa Quiteria, Ceara, Brazil. This ore contains the highest brazilian uranium reserve. The metal is associated to phosphate species. The ore is digested with sulfuric acid (wet process), producing phosphoric acid, which is used for manufacturing of fertilizers and animal food. >From the acid leaching, some systems for uranium recovery were tested. Among them, PC88A (2-ethyl-hexyl phosphonic acid, mono-2-ethyl-hexyl ester) 40% vol. and DEHPA (di(2-ethyl-hexyl)phosphoric acid) 40% vol. in kerosene presented the highest values for the distribution coefficient (D) for uranium. When synergistic systems were employed, the best results were obtained for DEHPA 40%vol. + PC88A 40%vol. and DEHPA 40% vol. + TOPO (trioctylphosphine oxide) 5% vol. in kerosene. 15% wt/v sodium carbonate was the best medium for uranium stripping and separation from iron, the main interfering element. Uranium was precipitated as sodium diuranate by adding sodium hydroxide (5,0 mol L -1 ). Thorium in the raffinate was extracted by TOPO (0,1% vol.) in cyclohexane. The radioactivity level of the final aqueous waste is similar to natural background, according to CNEN-NE 6.05 Norm. After neutralization, the solid can be co-processed, according to the Directory 264 from the National Brazilian Environmental Council (CONAMA), whereas the treated effluent can be discarded according to the Directory 357 from CONAMA. (author)

Potentiometric titration in a low volume of solution for rapid assay of uranium. Application to quantitative electro-reduction of uranium(VI)

International Nuclear Information System (INIS)

Sahoo, P.; Ananthanarayanan, R.; Murali, N.; Mallika, C.; Falix Lawrence; Kamachi Mudali, U.

2012-01-01

A simple, inexpensive PC based potentiometric titration technique for the assay of uranium using low volumes of sample aliquot (25-100 μL) along with all reagents (total volume of solution being less than 2.5 mL) is presented. The technique involves modification of the well known Davies and Gray Method recommended for assay of uranium(VI) in nuclear materials by introducing an innovative potentiometric titration device with a mini cell developed in-house. After appropriate chemical conditioning the titration is completed within a couple of minutes with display of online titration plot showing the progress of titration. The first derivative plot generated immediately after titration provides information of end point. The main advantage of using this technique is to carry out titration with minimum volumes of sample and reagents generating minimum volume of wastes after titration. The validity of the technique was evaluated using standard certified samples. This technique was applied for assay of uranium in a typical sample collected from fuel reprocessing laboratory. Further, the present technique was deployed in investigating the optimum conditions for efficient in situ production of U(IV). The precision in the estimation of uranium is highly satisfactory (RSD less than 1.0%). (author)

Symposium 'geology, mining and extractive processing of uranium, with special reference to Europe'

International Nuclear Information System (INIS)

Pietsch, H.B.

1977-01-01

This review of the symposium 'Geology, mining and extractive processing of uranium' gives a survey from the point of view of ore processing rather than exploration. A reason for the uranium consumption assumed is given, and uranium deposits and availability, methods of exploration, and interesting facts on uranium extraction from ores are gone into. (HK) [de

A solvent proceed for the extraction of the irradiate uranium and plutonium in the reactor core; Un procede par solvant pour l'extraction du plutonium de l'uranium irradie dans les piles

Energy Technology Data Exchange (ETDEWEB)

Goldschmidt, B; Regnaut, P; Prevot, I [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

Description of the conditions of plutonium, fission products and of uranium separation by selective extraction of the nitrates by organic solvent, containing a simultaneous extraction of plutonium and uranium, followed by a plutonium re-extraction after reduction, and an uranium re-extraction. The rates of decontamination being insufficient in this first stage, we also describes the processes of decontamination permitting separately to get the rates wanted for uranium and plutonium. Finally, we describes the beginning of the operation that consists in a nitric dissolution of the active uranium while capturing the products of gaseous fission, as well as the final concentration of the products of fission in a concentrated solution. (authors) [French] Description des conditions de separation du plutonium, des produits de fission et de l'uranium au moyen d'une extraction selective des nitrates par solvant organique, comprenant une extraction simultanee du plutonium et de l'uranium, suivie d'une reextraction du plutonium apres reduction, et d'une reextraction de l'uranium. Les taux de decontamination etant insuffisants dans ce premier stade, on decrit egalement les processus de decontamination permettant separement d'obtenir les taux desires pour l'uranium et le plutonium. Enfin, on decrit aussi le debut de l'operation qui consiste en une dissolution nitrique de l'uranium actif en captant les produits de fission gazeux, ainsi que la concentration finale des produits de fission sous forme de solution concentree. (auteurs)

Enzymatic U(VI) reduction by Desulfosporosinus species

International Nuclear Information System (INIS)

Suzuki, Y.; Kelly, S.D.; Kemner, K.M.; Banfield, J.F.

2004-01-01

Here we tested U(VI) reduction by a Desulfosporosinus species (sp.) isolate and type strain (DSM 765) in cell suspensions (pH 7) containing 1 mM U(VI) and lactate, under an atmosphere containing N 2 -CO 2 -H 2 (90: 5: 5). Although neither Desulfosporosinus species (spp.) reduced U(VI) in cell suspensions with 0.25% Na-bicarbonate or 0.85% NaCl, U(VI) was reduced in these solutions by a control strain, desulfovibrio desulfuricans (ATCC 642). However, both Desulfosporosinus strains reduced U(VI) in cell suspensions depleted in bicarbonate and NaCl. No U(VI) reduction was observed without lactate and H 2 electron donors or with heat-killed cells, indicating enzymatic U(VI) reduction. Uranium(VI) reduction by both strains was inhibited when 1 mM CuCl 2 was added to the cell suspensions. Because the Desulfosporosinus DSM 765 does not contain cytochrome c 3 used by Desulfovibrio spp. to reduce U(VI), Desulfosporosinus species reduce uranium via a different enzymatic pathway. (orig.)

Interactions of uranium (VI) with biofilms

International Nuclear Information System (INIS)

Brockmann, Sina; Arnold, Thuro; Bernhard, Gert

2013-01-01

In this study a detailed investigation was made of natural biofilms from two uranium-contaminated sites, namely the former uranium mine in Koenigstein (Saxony) and the ground surface of the former Grassenhalde tailing heap in Thuringia. A predominance of uranyl sulphate (UO 2 SO 4 ), a highly mobile, solute uranium species, was found in the mine waters of both sites. In this study an investigation was made of the capacity of Euglena mutabilis cells for bioaccumulation of uranium in a pH range of 3 to 6 using living cells and sodium perchlorate (9 g/l) or sodium sulphate (3.48 g/l) as background media. At acidic pH values in the range from 3 to 4 it was possible to remove more than 90% of the original uranium content from the test solution regardless of the medium being used. The speciation of the uranium accumulated in the Euglena cells was investigated by laser-induced fluorescence spectroscopy (LIFS). It was found that a new uranium species of low variability forms on the cells independent of the background medium, state of life of the cells and pH value. By comparing the data from the LIFS measurements with reference values it was possible to narrow down the identity of the uranium species to one bonded to (organo) phosphate and/or carboxylic functional groups. Using time-resolved FT-IR spectroscopy it was possible to demonstrate carboxylic bonding of uranium to dead cells. However it was not possible to exclude (organo) complexation with this method. An investigation of the specific location of the uranium on or in the cells using combined CLSM/LIFS technology yielded first indications of intracellular accumulation of uranium in the living cells. Supplementary TEM/EDX measurements confirmed the intracellular uptake, showing it to occur in round to oval cell organelles which are thought to be vacuoles or vacuole-like vesicles. It was not possible to detect uranium on dead cells using these methods. This points to passive, homogeneously distributed biosorption of

Phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resin for the adsorption of uranium(VI) in aqueous

Energy Technology Data Exchange (ETDEWEB)

Cao, Qiong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Liu, Yaochi, E-mail: liuyaochi72@163.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Wang, Chunzhi [Baling Company, China Petroleum and Chemical Corporation (China); Cheng, Jiashun [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

2013-12-15

Highlights: • A series of phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resins were synthesized. • The materials were commercially available and economic. • The new resins were high effective and selective adsorbents. • U(VI) adsorption is fitted with pseudo-second-order equation and Langmuir model. • The new resins can be regenerated. -- Abstract: Polyamidoamine (PAMAM) modified poly(styrene-co-divinylbenzene) absorbents carrying phosphorus functional groups (PS-PAMAM-PPA) were prepared and used as adsorbents for the adsorption of uranium(VI) from aqueous solution. Different generations of PAMAM were used for obtaining different chelating resins, PS-PPA, PS-1.0G PAMAM-PPA, PS-2.0G PAMAM-PPA, PS-3.0G PAMAM-PPA and PS-4.0G PAMAM-PPA. The synthesized resins were characterized by FTIR and XPS. The effects of many physio-chemical properties on metal ion adsorption to adsorbent phase, such as solution pH, kinetic studies, initial uranium concentration, temperature, were investigated using batch method. The results showed that the maximum adsorption capacity (99.89 mg/g) was observed at the pH 5.0 and 25 °C with initial U(VI) concentration 100 mg/L and adsorbent dose 1 g/L. PS-1.0G PAMAM-PPA had the largest adsorption capacity for U(VI) compared with other prepared adsorbents. The adsorption kinetics of U(VI) onto PS-1.0G PAMAM-PPA followed the mechanism of the pseudo-second-order equation, indicating that the chemical adsorption was a rate-limiting step. The calculated thermodynamic parameters (ΔG, ΔH, ΔS) stated that the adsorption of U(VI) onto PS-1.0G PAMAM-PPA were spontaneous, endothermic and feasible. The adsorption isotherms obeyed the Langmuir isotherm models. The desorption studies showed that PS-1.0G PAMAM-PPA could be used repeatedly and adsorption and desorption percentage did not have any noticeable loss after 27 cycles in a fixed bed.

Extraction of sulfuric acid with TOPO

International Nuclear Information System (INIS)

Shuyun, Xue; Yonghui, Yang; Yanzhao, Yang; Sixiu, Sun; Borong, Bao

1998-01-01

A study on solvent extraction of sulfuric acid by tri-octylphosphine oxide (TOPO) in n-heptane has been made. Extraction coefficients of H 2 SO 4 as a function of H 2 SO 4 concentration in aqueous phase, and extractant concentrations in organic phase have been studied. The composition of extracted species, equilibrium constants of extraction reaction have been evaluated. These results are important for interpreting extraction equilibrium data of uranium(VI) or other metal ions with TOPO in sulfuric acid media. (author)

U(VI) extraction by 8-hydroxyquinoline. A comparison study in ionic liquid and in dichloromethane

Energy Technology Data Exchange (ETDEWEB)

Yuan, Li-Yong; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Lab. of Nuclear Energy Chemistry; Liao, Xiang-Hong [Chinese Academy of Sciences, Beijing (China). Lab. of Nuclear Energy Chemistry; East China Institute of Technology, Nanchang (China). School of Nuclear Engineering and Geophysics; Liu, Zhi-Rong [East China Institute of Technology, Nanchang (China). School of Nuclear Engineering and Geophysics; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Lab. of Nuclear Energy Chemistry; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences and Collaborative Innovation Center of Radiation Medicine

2017-08-01

Room temperature ionic liquids (RTILs) represent a recent new class of solvents with potential application in liquid/liquid extraction based nuclear fuel reprocessing due to their unique physical and chemical properties. The work herein provides a comparison of U(VI) extraction by 8-hydroxyquinoline (HOX) in a commonly used RTIL, i.e. 1-butyl-3-methylimidazolium hexafluorophosphate ([C{sub 4}mim][PF{sub 6}]) and in conventional solvent, i.e. dichloromethane (CH{sub 2}Cl{sub 2}). The effect of HOX concentration, solution acidity and nitrate ions on the extraction were discussed in detail, and the speciation analyses of the extracted U(VI) were performed. One of the main emphasis of this work is the extraction mechanism of U(VI) extracted from aqueous phase into RTILs and conventional solvent. In CH{sub 2}Cl{sub 2}, the extraction occurs through a combination of ion change and neutral complexation, and the extracted complex is proposed as UO{sub 2}(OX){sub 2}HOX. In [C{sub 4}mim][PF{sub 6}], although a cation-change mechanism as previously reported for RTILs-based system was involved, the extracted complex of UO{sub 2}(OX){sub 1.5}(HOX){sub 1.5}(PF6){sub 0.5} gave a clear indication that the usage of HOX as an acidic extractant markedly inhibited the solubility loss of [C{sub 4}mim][PF{sub 6}] during the extraction by leaching H{sup +} to aqueous phase. Moreover, the extracted U(VI) in [C{sub 4}mim][PF{sub 6}] can be easily stripped by using 0.01 M nitric acid, which provides a simple way of the ionic liquid recycling.

Supercritical fluid extraction of uranium and thorium from nitric acid medium using organophosphorous compounds

Energy Technology Data Exchange (ETDEWEB)

Pitchaiah, K.C.; Sujatha, K.; Rao, C.V.S. Brahmmananda; Subramaniam, S.; Sivaraman, N.; Rao, P.R. Vasudeva [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Chemistry Group

2015-06-01

In recent years, Supercritical Fluid Extraction (SFE) technique has been widely used for the extraction of metal ions. In the present study, extraction of uranium from nitric acid medium was investigated using supercritical carbon dioxide (Sc-CO{sub 2}) containing various organophosphorous compounds such as trialkyl phosphates e.g. tri-iso-amyl phosphate (TiAP), tri-sec-butyl phosphate (TsBP) and tri-n-butyl phosphate (TBP), dialkylalkyl phosphonates, e.g. diamylamyl phosphonate (DAAP) and dibutyl butyl phosphonate (DBBP), dialkyl hydrogen phosphonates, e.g. dioctyl hydrogen phosphonate (DOHP), dioctylphosphineoxide (DOPO), trioctyl phosphine oxide (TOPO), n-octylphenyl N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO) and di-2-ethyl-hexyl phosphoric acid (HDEHP). Some of these ligands have been investigated for the first time in the supercritical phase for the extraction of uranium. The extraction efficiency of uranium was studied with TiAP, DAAP and DBBP as a function of nitric acid concentration; the kinetics of the equilibration period (static extraction) and transportation of the metal complex (dynamic extraction) was investigated. The influence of pressure and temperature on the extraction behaviour of uranium with DAAP was studied from 4 N HNO{sub 3}. The extraction efficiency of uranium from 4 N nitric acid medium was found to increase in the order of phosphates < phosphonates < HDEHP < TOPO < CMPO. In the case of phosphates and phosphonates, the maximum extraction of uranium was found to be from 4 N HNO{sub 3} medium. The acidic extractants, HDEHP and DOHP showed relatively higher extraction at lower acidities. The relative extraction of uranium and thorium from their mixture was also examined using Sc-CO{sub 2} containing phosphates, phosphonates and TOPO. The ligand, TsBP provided better fractionation between uranium and thorium compared to trialkyl phosphates, dialkyl alkyl phosphonates and TOPO.

Solvent Extraction of Tungsten(VI) from Moderate Hydrochloric Acid Solutions with LIX 63

Energy Technology Data Exchange (ETDEWEB)

Truong, Hoai Thanh; Lee, Man Seung [Mokpo National University, Jeollanamdo (Korea, Republic of); Kim, Yong Hwan [Incheon Technology Service Centre, Incheon (Korea, Republic of)

2017-06-15

The solvent extraction of tungsten(VI) from hydrochloric acid solutions using 5,8-diethyl-7-hydroxydodecan-6-one oxime (LIX 63) was analyzed in solutions having an initial pH range from 2 to 5, by varying the concentration of metal and extractant. In our experimental range, the cationic exchange reaction as well as the solvation reaction occurred simultaneously. The cation exchange reaction was identified by applying a slope analysis method to the extraction data. The existence of cationic tungsten(VI) species was confirmed by ion exchange experiments with Diphonix resin at pH 3. Further study is needed to identify the nature of this tungsten cationic species.

Spectral and structural correlation for Bis (dibenzoyl methanato) dioxo uranium(VI) diphenyl sulfoxide. [UO2(DBM)2. PhSOPh

International Nuclear Information System (INIS)

Kannan, S.; Raj, S.S.S.; Fun, Hoong Kun

2001-01-01

In the complex [UO 2 (DBM) 2 . PhSOPh]. the sulfoxide ligand is bonded to uranium (VI) ion through sulfoxide oxygen atom and DBM ligands through the oxygen atoms to give a distorted pentagonal bipyramidal geometry. The structural study is in consistence with the spectral studies. (author)

Solvent extraction of W(VI) with malachite green into nitrobenzene

International Nuclear Information System (INIS)

Patil, V.B.; Turel, Z.R.

1995-01-01

A rapid and selective method has been developed for the extraction of W(VI) with malachite green into nitrobenzene. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of various cations and anions have been evaluated. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction was found to be 1:1. It was further supported by the slope ratio method. (author). 6 refs., 2 tabs., 2 figs

Solvent extraction of W(VI) with malachite green into nitrobenzene

Energy Technology Data Exchange (ETDEWEB)

Patil, V B; Turel, Z R [The Institute of Science, Bombay (India). Nuclear Chemistry Division

1995-04-01

A rapid and selective method has been developed for the extraction of W(VI) with malachite green into nitrobenzene. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of various cations and anions have been evaluated. The stoichiometry of metal to reagent determined by the method of substoichiometric extraction was found to be 1:1. It was further supported by the slope ratio method. (author). 6 refs., 2 tabs., 2 figs.

Terminal uranium(V/VI) nitride activation of carbon dioxide and carbon disulfide. Factors governing diverse and well-defined cleavage and redox reactions

Energy Technology Data Exchange (ETDEWEB)

Cleaves, Peter A.; Gardner, Benedict M.; Liddle, Stephen T. [School of Chemistry, The University of Manchester (United Kingdom); Kefalidis, Christos E.; Maron, Laurent [LPCNO, CNRS and INSA, Universite Paul Sabatier, Toulouse (France); Tuna, Floriana; McInnes, Eric J.L. [School of Chemistry and Photon Science Institute, The University of Manchester (United Kingdom); Lewis, William [School of Chemistry, The University of Nottingham (United Kingdom)

2017-02-24

The reactivity of terminal uranium(V/VI) nitrides with CE{sub 2} (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(Tren{sup TIPS})(N)][K(B15C5){sub 2}] (1, Tren{sup TIPS}=N(CH{sub 2}CH{sub 2}NSiiPr{sub 3}){sub 3}; B15C5=benzo-15-crown-5) reacts with CO{sub 2} to give [U(Tren{sup TIPS})(O)(NCO)][K(B15C5){sub 2}] (3), whereas the uranium(VI) nitride [U(Tren{sup TIPS})(N)] (2) reacts with CO{sub 2} to give isolable [U(Tren{sup TIPS})(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(Tren{sup TIPS})(O)] (5) with concomitant formation of N{sub 2} and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS{sub 2} to give [U(Tren{sup TIPS})(κ{sup 2}-CS{sub 3})][K(B15C5){sub 2}] (6), 2, and [K(B15C5){sub 2}][NCS] (7), whereas 2 reacts with CS{sub 2} to give [U(Tren{sup TIPS})(NCS)] (8) and ''S'', with the latter trapped as Ph{sub 3}PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE{sub 2} follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS{sub 2} as a reactivity surrogate for CO{sub 2}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Uranium geochemistry and dating of Pacific island apatite

Energy Technology Data Exchange (ETDEWEB)

Roe, K K; Burnett, W C [Florida State Univ., Tallahassee (USA). Dept. of Oceanography

1985-07-01

Uranium-series disequilibrium dating of island phosphate deposits is evaluated in terms of known associated coral ages, uranium geochemistry, and stratigraphic sequences as well as the concordance between the geochronometers /sup 234/U//sup 238/U, /sup 230/Th//sup 234/U and /sup 226/Ra//sup 238/U. U(VI) is the predominant oxidation state of uranium in island phosphorites and by analogy to the youngest surficial deposits, most of the uranium initially bound is in the form of U(VI) sorbed by surfaces from seawater. Insular deposits contain more organic matter than even very young ocean floor samples and this leads to a greater probability of reduction of available recoil uranium than occurs in marine deposits. As a consequence, R(VI) <= R(T) <= R(VI), where R represents the /sup 234/U//sup 238/U activity ratio. This situation is completely opposite from that observed for marine-origin phosphorites. We determined that a fraction of U(VI) in ancient insular phosphorites is very labile and lost to alkaline carbonate solutions with a uranium activity ratio even more depleted in /sup 234/U than the bulk R(VI). The results are discussed.

Rapid extraction and assay of uranium from environmental surface samples

Energy Technology Data Exchange (ETDEWEB)

Barrett, Christopher A.; Chouyyok, Wilaiwan; Speakman, Robert J.; Olsen, Khris B.; Addleman, Raymond Shane

2017-10-01

Extraction methods enabling faster removal and concentration of uranium compounds for improved trace and low-level assay are demonstrated for standard surface sampling material in support of nuclear safeguards efforts, health monitoring, and other nuclear analysis applications. A key problem with the existing surface sampling swipes is the requirement for complete digestion of sample and sampling matrix. This is a time-consuming and labour-intensive process that limits laboratory throughput, elevates costs, and increases background levels. Various extraction methods are explored for their potential to quickly and efficiently remove different chemical forms of uranium from standard surface sampling material. A combination of carbonate and peroxide solutions is shown to give the most rapid and complete form of uranyl compound extraction and dissolution. This rapid extraction process is demonstrated to be compatible with standard inductive coupled plasma mass spectrometry methods for uranium isotopic assay as well as screening techniques such as x-ray fluorescence. The general approach described has application beyond uranium to other analytes of nuclear forensic interest (e.g., rare earth elements and plutonium) as well as heavy metals for environmental and industrial hygiene monitoring.

Precise coulometric titration of uranium in a high-purity uranium metal and in uranium compounds

International Nuclear Information System (INIS)

Tanaka, Tatsuhiko; Yoshimori, Takayoshi

1975-01-01

Uranium in uranyl nitrate, uranium trioxide and a high-purity uranium metal was assayed by the coulometric titration with biamperometric end-point detection. Uranium (VI) was reduced to uranium (IV) by solid bismuth amalgam in 5M sulfuric acid solution. The reduced uranium was reoxidized to uranium (VI) with a large excess of ferric ion at a room temperature, and the ferrous ion produced was titrated with the electrogenerated manganese(III) fluoride. In the analyses of uranium nitrate and uranium trioxide, the results were precise enough when the error from uncertainty in water content in the samples was considered. The standard sample of pure uranium metal (JAERI-U4) was assayed by the proposed method. The sample was cut into small chips of about 0.2g. Oxides on the metal surface were removed by the procedure shown by National Bureau of Standards just before weighing. The mean assay value of eleven determinations corrected for 3ppm of iron was (99.998+-0.012) % (the 95% confidence interval for the mean), with a standard deviation of 0.018%. The proposed coulometric method is simple and permits accurate and precise determination of uranium which is matrix constituent in a sample. (auth.)

Uranium recovery from phosphate fertilizer in the form of a high purity compound

International Nuclear Information System (INIS)

Bunus, F.; Coroianu, T.; Filip, G.; Filip, D.

2001-01-01

Uranium recovery from phosphate fertilizer industry is based on a one cycle extraction-stripping process. The process was experimented on both sulfuric and nitric acid attack of phosphate rock when uranium is dissolved in phosphoric acid (WPA) or phosphonitric (PN) solution respectively. The WPA and PN solution must be clarified. In the first alternative by ageing and settling and in the second by settling in the presence of flocculant. The organic components must be removed on active carbon for WPA only since in the case of nitric attack calcined phosphates are used. In both alternatives uranium is extracted from aqueous acidic solutions in the same time with the rare earths (REE), by di(2-ethylhexyl) phosphate (DEPA) as basic extractants, eventually in the presence of octylphosphine oxide (TOPO) as synergic agent. The stripping process is carried out in two stages: in the first stage REE are stripped and precipitated by HF or NH 4 F + H 2 S0 4 and in the second stage uranium as U(VI) is stripped by the same reagents but in the presence of Fe(II) as reductant for U(VI) to U(IV) inextractible species. Tetravalent uranium is also precipitated as green cake either UF 4 xH 2 0 or (NH 4 ) 7 U 6 F 31 as dependent on reagents HF or NH 4 F + H 2 S0 4 . Uranium stripping is possible for PN solution only if HNO 3 partially extracted is previously washed out by a urea solution. The green cake washed and filtered is dissolved in nitric acid in presence of Al(OH)3 as complexant for F. The filtered nitric solution is adjusted to 3-5 mol/L HNO 3 and extracted by 20% TBP when uranium is transferred to the organic phase which after scrubbing is stripped in the classic way with acidulated (HN0 3 ) demineralized water. Uranium is precipitated as diuranate of high purity. Rare earths left in the aqueous raffinate are extracted by pure TBP from 8-10 mol/L HNO 3 medium. The stripping process takes place with acidulated water. Rare earths are precipitated as hydroxides. (author)

Radiating toxicological and ecological consequences of extraction of uranium

International Nuclear Information System (INIS)

Svambaev, Z.A.; Svambaev, E.A.; Sultanbekov, G.A; Tusupbekova, S.T.

2010-01-01

In scientific work researchers take up questions of radiation, toxicity and ecological danger at extraction of natural uranium. In work it is resulted results of gauging of radiation in separate parts of a cycle, and also as a whole at underground extractions of uranium. The level of ionization actions of photon radiation in a radiating field with a productive solution which represents the big radiating, toxicological and ecological danger to Wednesday is shown on the average on cycles of feature of work.

A modelling exercise on the importance of ternary alkaline earth carbonate species of uranium(VI) in the inorganic speciation of natural waters

International Nuclear Information System (INIS)

Vercouter, Thomas; Reiller, Pascal E.; Ansoborlo, Eric; Février, Laureline; Gilbin, Rodolphe; Lomenech, Claire; Philippini, Violaine

2015-01-01

Highlights: • The U(VI) speciation in natural waters has been modelled through a modelling exercise. • The results evidence the importance of alkaline earth U(VI) carbonate complexes. • Possible solubility-controlling phases were reported and discussed. • The differences were related to the choice and reliability of thermodynamic data. • Databases need to be improved for reliable U(VI) speciation calculations. - Abstract: Predictive modelling of uranium speciation in natural waters can be achieved using equilibrium thermodynamic data and adequate speciation software. The reliability of such calculations is highly dependent on the equilibrium reactions that are considered as entry data, and the values chosen for the equilibrium constants. The working group “Speciation” of the CETAMA (Analytical methods establishment committee of the French Atomic Energy commission, CEA) has organized a modelling exercise, including four participants, in order to compare modellers’ selections of data and test thermodynamic data bases regarding the calculation of U(VI) inorganic speciation. Six different compositions of model waters were chosen so that to check the importance of ternary alkaline earth carbonate species of U(VI) on the aqueous speciation, and the possible uranium solid phases as solubility-limiting phases. The comparison of the results from the participants suggests (i) that it would be highly valuable for end-users to review thermodynamic constants of ternary carbonate species of U(VI) in a consistent way and implement them in available speciation data bases, and (ii) stresses the necessary care when using data bases to avoid biases and possible erroneous calculations

Study on extraction of uranium from clayey sandstone with floatation-leaching process

International Nuclear Information System (INIS)

Meng Guangshou; Zhao Manchang; Wu Peisheng; Song Wenlan; Li Wenxia.

1985-01-01

An improved floatation-leaching process is proposed to extract uranium from some clayey sandstone type of ore. By two-step flotation, the ground feed ore can be divided into three urani-ferous sections, i.e., the sulfidic concentrate carrying organic matter, the carbonate concentrate, and the tailings. The sulfidic concentrate is mixed with the tailings and then treated by acid-leaching with the result that 93% uranium extraction can be attained. The excess free acid of the leached slurry is further neutralized with the carbonate concentrate instead of lime commonly used. As a result, approximately 60% uranium extraction can be attained. As a whole, by the flotation-leaching process the acid consumption can be reduced from 200 kg/t down to < 80 kg/t and the uranium extraction can be raised from 85% to 90% as compared with the conventional acid-leaching process

Kinetic analysis and modeling of oleate and ethanol stimulated uranium (VI) bio-reduction in contaminated sediments under sulfate reduction conditions

Energy Technology Data Exchange (ETDEWEB)

Zhang Fan, E-mail: zhangfan@itpcas.ac.cn [Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Wu Weimin [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 (United States); Parker, Jack C. [Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Mehlhorn, Tonia [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kelly, Shelly D.; Kemner, Kenneth M. [Biosciences Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Zhang, Gengxin [Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Schadt, Christopher; Brooks, Scott C. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Criddle, Craig S. [Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305 (United States); Watson, David B. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Jardine, Philip M. [Biosystems Engineering and Soil Science Department, University of Tennessee, Knoxville, TN 37996 (United States)

2010-11-15

Microcosm tests with uranium contaminated sediments were performed to explore the feasibility of using oleate as a slow-release electron donor for U(VI) reduction in comparison to ethanol. Oleate degradation proceeded more slowly than ethanol with acetate produced as an intermediate for both electron donors under a range of initial sulfate concentrations. A kinetic microbial reduction model was developed and implemented to describe and compare the reduction of sulfate and U(VI) with oleate or ethanol. The reaction path model considers detailed oleate/ethanol degradation and the production and consumption of intermediates, acetate and hydrogen. Although significant assumptions are made, the model tracked the major trend of sulfate and U(VI) reduction and describes the successive production and consumption of acetate, concurrent with microbial reduction of aqueous sulfate and U(VI) species. The model results imply that the overall rate of U(VI) bioreduction is influenced by both the degradation rate of organic substrates and consumption rate of intermediate products.

Kinetic analysis and modeling of oleate and ethanol stimulated uranium (VI) bio-reduction in contaminated sediments under sulfate reduction conditions

International Nuclear Information System (INIS)

Zhang Fan; Wu Weimin; Parker, Jack C.; Mehlhorn, Tonia; Kelly, Shelly D.; Kemner, Kenneth M.; Zhang, Gengxin; Schadt, Christopher; Brooks, Scott C.; Criddle, Craig S.; Watson, David B.; Jardine, Philip M.

2010-01-01

Microcosm tests with uranium contaminated sediments were performed to explore the feasibility of using oleate as a slow-release electron donor for U(VI) reduction in comparison to ethanol. Oleate degradation proceeded more slowly than ethanol with acetate produced as an intermediate for both electron donors under a range of initial sulfate concentrations. A kinetic microbial reduction model was developed and implemented to describe and compare the reduction of sulfate and U(VI) with oleate or ethanol. The reaction path model considers detailed oleate/ethanol degradation and the production and consumption of intermediates, acetate and hydrogen. Although significant assumptions are made, the model tracked the major trend of sulfate and U(VI) reduction and describes the successive production and consumption of acetate, concurrent with microbial reduction of aqueous sulfate and U(VI) species. The model results imply that the overall rate of U(VI) bioreduction is influenced by both the degradation rate of organic substrates and consumption rate of intermediate products.

Solvent extraction of uranium from high acid leach solution

International Nuclear Information System (INIS)

Ramadevi, G.; Sreenivas, T.; Navale, A.S.; Padmanabhan, N.P.H.

2010-01-01

A significant part of the total uranium reserves all over the world is contributed by refractory uranium minerals. The refractory oxides are highly stable and inert to attack by most of the commonly used acids under normal conditions of acid strength, pressure and temperature. Quantitative dissolution of uranium from such ores containing refractory uranium minerals requires drastic operating conditions during chemical leaching like high acid strength, elevated pressures and temperatures. The leach liquors produced under these conditions normally have high free acidity, which affects the downstream operations like ion exchange and solvent extraction

Comparative synergistic (technetium-actinide) extraction chemistry by tributylphosphate and some amide extractants

International Nuclear Information System (INIS)

Condamines, N.; Musikas, C.

1993-01-01

In nuclear fuel reprocessing, technetium (TcO 4 - ) leads to bad interferences in the extractions, being synergistically co-extracted with different actinide cations as Uranium (VI), Plutonium (IV) and Zirconium (IV). It destroys the hydrazine in the reductive partition of U and Pu, it decreases the decontamination of U and Pu from fission products. Thus, its extraction behaviour with new extractants as N,N-diakylamides is useful to be known. TcO 4 - extraction in nitric acid media is compared for TBP and different amides. The influence of nitric acidity is related to the amides formula

Non-enzymatic U(VI) interactions with biogenic mackinawite

Science.gov (United States)

Veeramani, H.; Qafoku, N. P.; Kukkadapu, R. K.; Murayama, M.; Hochella, M. F.

2011-12-01

Reductive immobilization of hexavalent uranium [U(VI)] by stimulation of dissimilatory metal and/or sulfate reducing bacteria (DMRB or DSRB) has been extensively researched as a remediation strategy for subsurface U(VI) contamination. These bacteria derive energy by reducing oxidized metals as terminal electron acceptors, often utilizing organic substrates as electron donors. Thus, when evaluating the potential for in-situ uranium remediation in heterogeneous subsurface media, it is important to understand how the presence of alternative electron acceptors such as Fe(III) and sulfate affect U(VI) remediation and the long term behavior and reactivity of reduced uranium. Iron, an abundant subsurface element, represents a substantial sink for electrons from DMRB, and the reduction of Fe(III) leads to the formation of dissolved Fe(II) or to reactive biogenic Fe(II)- and mixed Fe(II)/Fe(III)- mineral phases. Consequently, abiotic U(VI) reduction by reactive forms of biogenic Fe(II) minerals could be a potentially important process for uranium immobilization. In our study, the DMRB Shewanella putrefaciens CN32 was used to synthesize a biogenic Fe(II)-bearing sulfide mineral: mackinawite, that has been characterized by XRD, SEM, HRTEM and Mössbauer spectroscopy. Batch experiments involving treated biogenic mackinawite and uranium (50:1 molar ratio) were carried out at room temperature under strict anoxic conditions. Following complete removal of uranium from solution, the biogenic mackinawite was analyzed by a suite of analytical techniques including XAS, HRTEM and Mössbauer spectroscopy to determine the speciation of uranium and investigate concomitant Fe(II)-phase transformation. Determining the speciation of uranium is critical to success of a remediation strategy. The present work elucidates non-enzymatic/abiotic molecular scale redox interactions between biogenic mackinawite and uranium.

Study on the uranium-cerium extraction and his application to the treatment of irradiated uranium

International Nuclear Information System (INIS)

Lobao, Afonso dos Santos Tome

1979-01-01

It was made a study on the behavior of uranium and cerium(IV) extraction, using the latter element as a plutonium simulator in a flowsheet of the treatment of irradiated uranium. Cerium(IV) was used under the same conditions as a plutonium in the Purex process because the admitted similar properties. An experimental work was initiated to determine the equilibrium curves of uranium, under the following conditions: concentration of 1 to 20 g U/1 and acidity varying from 1 to 5M in HNO 3 . Other parameters studied were the volumetric ratio of the phases and the influence of the concentration of TBP (tri-n-butyl phosphate). To guarantee the cerium(IV) extraction, the diluent (varsol) was previously treated with 10% potassium dichromate in perchloric acid, potassium permanganate in 1M sulphuric acid and concentrated sulphuric acid at 70 deg to eliminate reducing compounds. The results obtained for cerium extraction, allowed a better understanding of its behavior in solution. The results permitted to conclude that the decontamination for cerium are very high in the first Purex extraction cycle. The easy as cerium(IV) is reduced to the trivalent state contributes a great deal to its decontamination. (author)

Extraction photometric determination of uranium (6) with use of malachite green

International Nuclear Information System (INIS)

Stepanenko, Yu.V.; Bagdasarov, K.N.; Shchemeleva, G.G.

1975-01-01

A study of the reaction between uranium (6) and malachite green in the presence of sodium benzoate has indicated that, in a weakly acid medium (pH 4.5 to 5.5), the reaction yields a poorly soluble greenish compound which tends to be extracted by a 1-to-1 mixture of benzene and chloroform. The compound comprises uranium, a benzoate and a malachite green in a ratio of 1/3/1. A method has been developed for an extraction-photometric determination of uranium in metallic lead

Extraction photometric determination of uranium (6) with use of malachite green

Energy Technology Data Exchange (ETDEWEB)

Stepanenko, Yu V; Bagdasarov, K N; Shchemeleva, G G [Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR)

1975-12-01

A study of the reaction between uranium (6) and malachite green in the presence of sodium benzoate has indicated that, in a weakly acid medium (pH 4.5 to 5.5), the reaction yields a poorly soluble greenish compound which tends to be extracted by a 1-to-1 mixture of benzene and chloroform. The compound comprises uranium, a benzoate and a malachite green in a ratio of 1/3/1. A method has been developed for an extraction-photometric determination of uranium in metallic lead.

Technical progress review of extraction of uranium from fly ash

International Nuclear Information System (INIS)

Gao Renxi; Gao Junning; Wu Qingming; Chen Gang; Wan Hongjin; Zhang Ziyue

2014-01-01

The increasing of fly ash in coal-fired power plants at home and abroad year by year and the potential impacts to the environment attracted media attention. Although the extraction of uranium from the fly ash in coal-fired power plants had optional process from technique aspect and sufficient preliminary researches, but considering the low grade of the uranium in fly ash and particularity of the mineral composition, it is easy to have a high cost of extraction. As a consequence, it is not included in the development plan of uranium mining and metallurgy. The present applications of fly ash are only building materials, building roads and pit valley backfill, the resource utilization rate was low and was still in its early stages of development and application. In view of this, the research advances and the latest development trends of extraction of uranium from fly ash at home and abroad were introduced from the technical aspect, and the beneficial analyzes of the prospect and advices to this industry were given. (authors)

Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples; Untersuchungen zur Uransorption an Bentonit bzw. Montmorillonit sowie von Uran in Umweltproben

Energy Technology Data Exchange (ETDEWEB)

Azeroual, Mohamed

2010-09-22

The geotechnical barrier is an important component of a geological repository and consists of compacted bentonite surrounding radioactive waste containers. Its most important functions are, to retard the radionuclide migration into the biosphere and to prevent groundwater contact with containers. lt is therefore of central importance to investigate the bentonite material on its capacity to sorb radionuclides under near-natural chemical and physical conditions. The purpose of this work was to study the adsorption of uranium(VI) on bentonit and on montmorillonite-standards at high uranium concentrations. Thereby, a special account was given to the calcium-uranyl-carbonate complexation, which leads to the formation of very stable and mobile uncharged Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} complex. Results of batch experiments showed that the dicalcium-uranyl-tricarbonate complexation lowers the uranium(VI) sorption on natural clay (bentonite) by a factor of up to 3. After 21 days of contact time, about 40 % and 20 % of the initial uranium(VI)concentration were sorbed on Na-bentonite and ea-bentonite, respectively, from a solution with Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} dominating the uranium(VI) speciation. On the contrary, about 55 % of the initial uranium(VI)-concentration were sorbed on thes clays from the solution, in which (UO{sub 2}){sub 2}CO{sub 3}(OH){sub 3}{sup -} complex dominated the uranium(VI) speciation. Thus uranium(VI) sorption is more strongly influenced by the solution composition than by bentonite type. Na-bentonite should be used instead of ea-bentonite as a geotechnical barrier, since calcium-uranyl-carbonate complexation may be a realistic scenario. Further SEM-EDX and HREM-EDX studies showed that uranium(VI) sorption occurred predominantly on montmorillonite, which is the main component of bentonite. Uranium(VI) sorption on bentonite's accessory Minerals (pyrite, calcite, mica, and feldspar) was not observed. Investigation of uranium(VI

Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

Science.gov (United States)

Gallegos, Tanya J.; Campbell, Kate M.; Zielinski, Robert A.; Reimus, P.W.; J.T. Clay,; N. Janot,; J. J. Bargar,; Benzel, William M.

2015-01-01

Drill-core samples from a sandstone-hosted uranium (U) deposit in Wyoming were characterized to determine the abundance and distribution of uranium following in-situ recovery (ISR) mining with oxygen- and carbon dioxide-enriched water. Concentrations of uranium, collected from ten depth intervals, ranged from 5 to 1920 ppm. A composite sample contained 750 ppm uranium with an average oxidation state of 54% U(VI) and 46% U(IV). Scanning electron microscopy (SEM) indicated rare high uranium (∼1000 ppm U) in spatial association with P/Ca and Si/O attributed to relict uranium minerals, possibly coffinite, uraninite, and autunite, trapped within low permeability layers bypassed during ISR mining. Fission track analysis revealed lower but still elevated concentrations of U in the clay/silica matrix and organic matter (several 10 s ppm) and yet higher concentrations associated with Fe-rich/S-poor sites, likely iron oxides, on altered chlorite or euhedral pyrite surfaces (but not on framboidal pyrite). Organic C (mining, the likely sequestration of uranium within labile iron oxides following mining and sensitivity to changes in redox conditions requires careful attention during groundwater restoration.

Study of uranium oxidation states in geological material.

Science.gov (United States)

Pidchenko, I; Salminen-Paatero, S; Rothe, J; Suksi, J

2013-10-01

A wet chemical method to determine uranium (U) oxidation states in geological material has been developed and tested. The problem faced in oxidation state determinations with wet chemical methods is that U redox state may change when extracted from the sample material, thereby leading to erroneous results. In order to quantify and monitor U redox behavior during the acidic extraction in the procedure, an analysis of added isotopic redox tracers, (236)U(VI) and (232)U(IV), and of variations in natural uranium isotope ratio ((234)U/(238)U) of indigenous U(IV) and U(VI) fractions was performed. Two sample materials with varying redox activity, U bearing rock and U-rich clayey lignite sediment, were used for the tests. The Fe(II)/Fe(III) redox-pair of the mineral phases was postulated as a potentially disturbing redox agent. The impact of Fe(III) on U was studied by reducing Fe(III) with ascorbic acid, which was added to the extraction solution. We observed that ascorbic acid protected most of the U from oxidation. The measured (234)U/(238)U ratio in U(IV) and U(VI) fractions in the sediment samples provided a unique tool to quantify U oxidation caused by Fe(III). Annealing (sample heating) to temperatures above 500 °C was supposed to heal ionizing radiation induced defects in the material that can disturb U redox state during extraction. Good agreement between two independent methods was obtained for DL-1a material: an average 38% of U(IV) determined by redox tracer corrected wet chemistry and 45% for XANES. Copyright © 2013 Elsevier Ltd. All rights reserved.

Separation of uranium from molybdenum by alkyl phosphoric acid extraction

Energy Technology Data Exchange (ETDEWEB)

Zhongshi, Li

1986-08-01

The regularities of separation of uranium from molybdenum by alkyl phosphoric acid extraction are described. Two parameters, i.e., density ratio of uranium to molybdenum in organic phase at first stage and density of uranium in raffinate at last stage are presented. The relationship between these parameters and purity of molybdenum and uranium products is given. The method of adjusting and controlling these parameters in experiments and production is worked out. The technical key problem in comprehensive utilization of sedimentary type uranium ore containing molybdenum with close concentration of these to elements has been solved.

Genes for Uranium Bioremediation in the Anaerobic Sulfate-Reducing Bacteria

Energy Technology Data Exchange (ETDEWEB)

Wall, Judy D.

2003-06-01

Surprising results were obtained following an attempt to induce or derepress the machinery for U(VI) reduction by growing Desulfovibrio desulfuricans G20 in the presence of 1 mM uranyl acetate. G20 cells grown on lactate-sulfate medium amended with U(VI) reduced uranium at a slower rate than cells grown in the absence of this metal. When periplasmic extracts of these cells were prepared, Western analysis of the proteins revealed that the cytochrome c3 was absent. This observation has been further investigated.

ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

Energy Technology Data Exchange (ETDEWEB)

A.P. Deditius; S. Utsunomiya; R.C. Ewing

2006-02-21

Uranium-(VI) phases are the primary alteration products of the UO{sub 2} in spent nuclear fuel and the UO{sub 2+x}, in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO{sub 2}{sup 2+} polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO{sub 2+x}, to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements.

ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

International Nuclear Information System (INIS)

A.P. Deditius; S. Utsunomiya; R.C. Ewing

2006-01-01

Uranium-(VI) phases are the primary alteration products of the UO 2 in spent nuclear fuel and the UO 2+x , in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO 2 2+ polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO 2+x , to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements

Spectrophotometric determination of uranium (VI) with arsenazo III in a nitric medium

International Nuclear Information System (INIS)

Yamaura, Mitiko; Wada, Luciana Yukie; Ribeiro, Fernando Castilho

2002-01-01

Arsenazo III is an organic reagent usually used for the photometric determination of various elements, including the uranium, thorium, plutonium, barium, strontium, hafnium, bismuth and the rare earth elements. The reactions of arsenazo III with many elements are very sensitive and, consequently is not specific for any element. Arsenazo III with U(VI) gives a 1:1 coloured complex in diluted acid solution of pH 1 to 3, and in strong acid media forming 1:1, 1:2 and 1:3 species. In this work, a detailed study of the influence of pH is described. The stability of formed complex and the interference of Fe(III) ions were also studied. (author)

Leaching and solvent extraction at Mary Kathleen Uranium Ltd

International Nuclear Information System (INIS)

Richmond, G.D.

1978-01-01

Mary Kathleen Uranium Ltd. recommenced operations in early 1976 following a twelve year period of care and maintenance. Several sections of the plant were modified or completely changed for the second operation. The most important change was the replacement of ion exchange with solvent extraction as the means of purifying and upgrading uranium rich solutions. Most of the problems experienced in the solvent extraction system originate from the leach liquor which has a strong tendency to form stable emulsions. This has been countered by some careful control of leaching conditions and by closer observation of operations in the solvent extraction area. Most problems have now been resolved and plant recoveries are quite satisfactory

Co-extraction and co-stripping of U(VI) and Pu(IV) using tri-iso-amyl phosphate and tri-n-butyl phosphate in n-dodecane from nitric acid media under high loading conditions

Energy Technology Data Exchange (ETDEWEB)

Sreenivasulu, Balija; Suresh, Ammath; Sivaraman, Nagarajan; Rao, P.R. Vasudeva [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Chemistry Group

2016-08-01

The extraction of Pu(IV) using 1.1 M solution of tri-iso-amyl phosphate (TiAP)/n-dodecane (DD) from plutonium nitrate solutions in nitric acid media was examined as a function of equilibrium aqueous phase metal ion concentration and equilibrium aqueous phase acidity at 303 K. The nitric acid concentration in the organic phase was measured as a function of equilibrium organic phase plutonium concentration. The co-extraction of U(VI) and Pu(IV) was studied using 1.1 M TiAP/DD system as a function of their equilibrium aqueous phase metal ion concentration and compared with 1.1 M tri-n-butyl phosphate (TBP)/n-DD system under identical conditions. Co-extraction and co-stripping of U(VI) and Pu(IV) were studied using 1.1 M TiAP/DD and 1.1 M TBP/DD systems in cross current mode to evaluate the number of stages required for the extraction and stripping of heavy metal ions (uranium and plutonium). The extraction and stripping efficiencies were calculated for both the systems. The saturation limit of the organic phase was also established in these studies.

Co-extraction and co-stripping of U(VI) and Pu(IV) using tri-iso-amyl phosphate and tri-n-butyl phosphate in n-dodecane from nitric acid media under high loading conditions

International Nuclear Information System (INIS)

Sreenivasulu, Balija; Suresh, Ammath; Sivaraman, Nagarajan; Rao, P.R. Vasudeva

2016-01-01

The extraction of Pu(IV) using 1.1 M solution of tri-iso-amyl phosphate (TiAP)/n-dodecane (DD) from plutonium nitrate solutions in nitric acid media was examined as a function of equilibrium aqueous phase metal ion concentration and equilibrium aqueous phase acidity at 303 K. The nitric acid concentration in the organic phase was measured as a function of equilibrium organic phase plutonium concentration. The co-extraction of U(VI) and Pu(IV) was studied using 1.1 M TiAP/DD system as a function of their equilibrium aqueous phase metal ion concentration and compared with 1.1 M tri-n-butyl phosphate (TBP)/n-DD system under identical conditions. Co-extraction and co-stripping of U(VI) and Pu(IV) were studied using 1.1 M TiAP/DD and 1.1 M TBP/DD systems in cross current mode to evaluate the number of stages required for the extraction and stripping of heavy metal ions (uranium and plutonium). The extraction and stripping efficiencies were calculated for both the systems. The saturation limit of the organic phase was also established in these studies.

Solvent. I. Extraction systems applied to uranium analysis. I. Extraction studies with Tributyl phosphate-Methyl-isobutyl-ketone

International Nuclear Information System (INIS)

Vera Palomino, J.; Palomares Delgado, F.; Petrement Eguiluz, J. C.

1964-01-01

A factorial study of the selective extraction of uranium with a mixture of TBP-MIC was carried out using 0,8 N nitric acid and different salting agents. We use the most suitable salting agent to develop new factorial experiments in order to get an equation involving the percent of extracted uranium, E, the concentration of the extraction agent in the organic phase, c, and the concentration of the slating agent in the aqueous phase, n. (Author) 3 refs

Neptunium separation in trace levels from uranium solutions by extraction chromatography

International Nuclear Information System (INIS)

Figols, M.E.B.

1991-01-01

Neptunium and uranium behavior in extraction chromatography system, aiming the separation of microquantities of neptunium from uranyl nitrate solutions is described. Tri-n-octylamina (TOA), tri-n-butylphosphate (TBP), thenoyltrifluoroacetone (TTA) as stationary phase, alumina, Voltalef-UF-300, silica as support material were verified. The impregnation conditions as well as the best stationary phase/support material ratio were established. TBP/alumina, TBP/Voltalef and TOA/alumina system were selected to uranium and neptunium separation studies. In the system using TBP as extractant agent uranium and neptunium separation was reached by selective elution after the retention of both elements on the column. U-Np separation by selective retention of Np was possible with TOA system. The capacity of the column was the 66.6 mg U/mL and 191.6mg U/mL for the TBP/alumina and TBP/Voltalef systems, respectively. An application of extraction chromatography system in the final phase of irradiated uranium treatment process is proposed. (author)

Retention and reduction of uranium on pyrite surface

International Nuclear Information System (INIS)

Eglizaud, N.

2006-12-01

In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS 2 ). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH ≥ 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10 -9 mol g -1 , an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. ≥ -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 ± 0.8) x 10 -7 mol L -1 of uranium(VI). Modelling of uranium sorption at high surface coverage (≥ 4 x 10 -9 mol g -1 ) by the Langmuir model yields an adsorption constant of 8 x 10 7 L mol -1 . Finally, a great excess of uranium(VI) above the saturation concentration allows the observation of

Uranium and plutonium extraction from fluoride melts by lithium-tin alloys

International Nuclear Information System (INIS)

Kashcheev, I.N.; Novoselov, G.P.; Zolotarev, A.B.

1975-01-01

Extraction of small amounts of uranium (12 wt. % concentration) and plutonium (less than 1.10sup(-10) % concentration) from lithium fluoride melts into the lithium-tin melts is studied. At an increase of temperature from 850 to 1150 deg the rate of process increases 2.5 times. At an increase of melting time the extraction rapidly enhances at the starting moment and than its rate reduces. Plutonium is extracted into the metallic phase for 120 min. (87-96%). It behaves analogously to uranium

Interactions of uranium (VI) with biofilms; Wechselwirkung von Uran(VI) mit Biofilmen

Energy Technology Data Exchange (ETDEWEB)

Brockmann, Sina; Arnold, Thuro; Bernhard, Gert

2013-07-01

In this study a detailed investigation was made of natural biofilms from two uranium-contaminated sites, namely the former uranium mine in Koenigstein (Saxony) and the ground surface of the former Grassenhalde tailing heap in Thuringia. A predominance of uranyl sulphate (UO{sub 2}SO{sub 4}), a highly mobile, solute uranium species, was found in the mine waters of both sites. In this study an investigation was made of the capacity of Euglena mutabilis cells for bioaccumulation of uranium in a pH range of 3 to 6 using living cells and sodium perchlorate (9 g/l) or sodium sulphate (3.48 g/l) as background media. At acidic pH values in the range from 3 to 4 it was possible to remove more than 90% of the original uranium content from the test solution regardless of the medium being used. The speciation of the uranium accumulated in the Euglena cells was investigated by laser-induced fluorescence spectroscopy (LIFS). It was found that a new uranium species of low variability forms on the cells independent of the background medium, state of life of the cells and pH value. By comparing the data from the LIFS measurements with reference values it was possible to narrow down the identity of the uranium species to one bonded to (organo) phosphate and/or carboxylic functional groups. Using time-resolved FT-IR spectroscopy it was possible to demonstrate carboxylic bonding of uranium to dead cells. However it was not possible to exclude (organo) complexation with this method. An investigation of the specific location of the uranium on or in the cells using combined CLSM/LIFS technology yielded first indications of intracellular accumulation of uranium in the living cells. Supplementary TEM/EDX measurements confirmed the intracellular uptake, showing it to occur in round to oval cell organelles which are thought to be vacuoles or vacuole-like vesicles. It was not possible to detect uranium on dead cells using these methods. This points to passive, homogeneously distributed

Retention and reduction of uranium on pyrite surface; Retention et reduction de l'uranium a la surface de la pyrite

Energy Technology Data Exchange (ETDEWEB)

Eglizaud, N

2006-12-15

In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS{sub 2}). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH {>=} 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10{sup -9} mol g{sup -1}, an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. {>=} -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 {+-} 0.8) x 10{sup -7} mol L{sup -1} of uranium(VI). Modelling of uranium sorption at high surface coverage ({>=} 4 x 10{sup -9} mol g{sup -1}) by the Langmuir model yields an adsorption constant of 8 x 10{sup 7} L mol{sup -1}. Finally, a great excess of uranium(VI) above the

Application of Solvent-In-Pulp Technique for Uranium Extraction from Mineralization Granite

International Nuclear Information System (INIS)

Ali, M.M.; Hussein, A.E.M.; Youseif, W.M.; El Didamony, A.M.

2017-01-01

Investigations on uranium extraction from a representative mineralized granite sample (Gattar granite GII) by solvent-in-pulp (SIP) technique were carried out in the present study. For this purpose, the solvent (tri-butyl amine) (TBA) was mixed with the leaching slurry without prior filtration. The influence of various factors affecting the SIP process, such as contact time, solvent concentration, dilution factor, type of surfactant, surfactant/solid ratio were studied. About 91% uranium extraction efficiency was attained by the application of the chosen extraction SIP conditions. Also, about 96% of the loaded uranium could be stripped by using sulfuric acid as an effective stripping agent

EXTRACTION DU Cr(VI PAR MEMBRANE POLYMERE A INCLUSION

Directory of Open Access Journals (Sweden)

O KEBICHE SENHADJI

2008-06-01

Le pH de la solution aqueuse constituant la phase source est un paramètre clé dans l’opération de transport du Cr(VI à travers les MPIs étudiées. Un pH de 1,2 est recommandé pour la réalisation de l’extraction dans les conditions optimales déterminées.

Recovery of uranium from phosphoric acid medium by polymeric composite beads encapsulating organophosphorus extractants

Energy Technology Data Exchange (ETDEWEB)

Singh, D.K.; Yadav, K.K.; Varshney, L.; Singh, H. [Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2013-07-01

The present study deals with the preparation and evaluation of the poly-ethersulfone (PES) based composite beads encapsulating synergistic mixture of D2EHPA and Cyanex 923 (at 4:1 mole ratio) for the separation of uranium from phosphoric acid medium. SEM was used for the characterization of the composite materials. Addition of 1% PVA (polyvinyl alcohol) improved the internal morphology and porosity of the beads. Additionally, microscopic examination of the composite bead confirmed central coconut type cavity surrounded by porous polymer layer of the beads through which exchange of metal ions take place. Effect of various experimental variables including aqueous acidity, metal ion concentration in aqueous feed, concentration of organic extractant inside the beads, extractant to polymer ratio, liquid to solid (L/S) ratio and temperature on the extraction of uranium was studied. Increase in acidity (1-6 M), L/S ratio (1- 10), metal ion concentration (0.2-3 g/L U{sub 3}O{sub 8}) and polymer to extractant ratio (1:4 -1:10) led to decrease in extraction of uranium. At 5.5 M (comparable to wet process phosphoric acid concentration) the extraction of uranium was about 85% at L/S ratio 5. Increase in extractant concentration inside the bead resulted in enhanced extraction of metal ion. Increase in temperature in the range of 30 to 50 Celsius degrees increased the extraction, whereas further increase to 70 C degrees led to the decrease in extraction of uranium. Amongst various reagents tested, stripping of uranium was quantitative by 12% Na{sub 2}CO{sub 3} solution. Polymeric beads were found to be stable and reusable up-to 10 cycles of extraction/stripping. (authors)

Study of the properties of dialkyl thiophosphoric acids. Application to the extraction of U, in phosphoric and nitric solutions

International Nuclear Information System (INIS)

Benjelloun, N.

1983-09-01

A study is made of complex formation and liquid-liquid extraction of uranium (VI) by dialkyl-thiophosphoric acids of formula (RO) 2 POSH and by the synergic mixtures: dialkylthiophosphoric acids-phosphine oxides. The aqueous phases studied consist of concentrated phosphoric acid solutions and nitric acid solutions. Several methods, including distribution coefficient measurements, U.V., visible and infrared absorption spectrophotometries and magnetic resonance, were used to study the extraction mechanisms and the structures of species formed in the organic phase. The influence of different parameters (partition of extraction agent, dimerisation, acid ligand-phosphine oxide association, extraction of inorganic acids...) on the uranium (VI) distribution coefficients enabled the constants of complex formation in the aqueous phase and extraction in the organic phase to be determined. These various properties were compared with those of dialkyl phosphoric and dithiophosphoric acids. The mechanisms established prove that sulfur donors ligands form stable complexes with UO 2 2+ ions although U(VI) is considered as a ''hard class a'' acceptor according to Ahrland's classification [fr

Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO_3/Ca–U(VI)–CO_3 complexes

International Nuclear Information System (INIS)

Zhang, Zhibin; Liu, Jun; Cao, Xiaohong; Luo, Xuanping; Hua, Rong; Liu, Yan; Yu, Xiaofeng; He, Likai

2015-01-01

Highlights: • NZVI can be used for adsorbing U(VI)–CO_3 complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO_3 complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO_3 and Ca–U(VI)–CO_3 complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q_e) and distribution constant (K_d) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q_e and K_d values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO_3 complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO_2CO_3"− or SO–UO_2 (CO_3)_2"3"−. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

Fuel Cycle Impacts of Uranium-Plutonium Co-extraction

International Nuclear Information System (INIS)

Taiwo, Temitope; Szakaly, Frank; Kim, Taek-Kyum; Hill, Robert

2008-01-01

A systematic investigation of the impacts of uranium and plutonium co-extraction during fuel separations on reactor performance and fuel cycle has been performed. Proliferation indicators, critical mass and radiation source levels of the separation products or fabricated fuel, were also evaluated. Using LWR-spent-uranium-based MOX fuel instead of natural-uranium-based fuel in a PWR MOX core requires a higher initial plutonium content (∼1%), and results in higher Np-237 content (factor of 5) in the spent fuel, and less consumption of Pu-238 (20%) and Am-241 (14%), indicating a reduction in the effective repository space utilization. Additionally, minor actinides continue to accumulate in the fuel cycle, and thus a separate solution is required for them. Differences were found to be quite smaller (∼0.4% in initial transuranics) between the equilibrium cycles of advanced fast reactor cores using spent and depleted uranium for make-up, in additional to transuranics. The critical masses of the co-extraction products were found to be higher than for weapons-grade plutonium (WG-Pu) and the decay heat and radiation sources of the materials (products) were also found to be generally higher than for WG-Pu in the transuranics content range of 10% to 100% in the heavy-metal. (authors)

Role of U(VI) adsorption in U(VI) Reduction by Geobacter species

International Nuclear Information System (INIS)

Lovely, Derrick

2008-01-01

Previous work had suggested that Acholeplasma palmae has a higher capacity for uranium sorption than other bacteria studied. Sorption studies were performed with cells in suspension in various solutions containing uranium, and results were used to generate uranium-biosorption isotherms. Results from this study showed that the U(VI) sorption capacity of G. uraniireducens was relatively similar in simple solutions, such as sodium chloride or bicarbonate. However, this ability to sorb uranium significantly decreased in groundwater. This suggested that certain chemicals present in the groundwater were inhibiting the ability of cell components of Geobacter to adsorb uranium. It was hypothesized that uranium removal would also be diminished in the bicarbonate solution. However, this did not seem to be the case, as uranium was as easily removed in the bicarbonate solution as in the sodium chloride solution.

Radiochemical investigations to the complex formation of uranium (VI) with silicic acid

International Nuclear Information System (INIS)

Hrnecek, E.

1997-12-01

The complexation of tracer amounts of UO 2 2+ by silicic acid was investigated by an extraction method using 2,5. 10 -3 M 1-(2-thenoyl)-3,3,3-trifloroacetone (IMA) in benzene as extractant at 25 degree C. The tracer used in the experiments was uranium-232, which has been separated from its daughter nuclides by ion exchange from 10 M HCl on Dowex 1x2. The ionic strength in the aqueous phase for the extractions was kept constant at 0,2 M (Na, H)ClO 4 and the pH was varied between pH 2,5 and pH 4,5. For the determination of the stability constants, a silicic acid concentration of 0,01 M, 0,03 M and 0,067 M in the (Na, H)ClO 4 solution was used. The time- and pH- dependence of the polymerization of these silicic acid solutions was determined by kinetical investigations with an ammoniumheptamolybdate-reagent. The uranium concentration in the aqueous and organic phases was determined by liquid scintillation counting using α/β -discrimination. The stability constants determined were log Q1, = -2,20 for the reaction UO 2 2+ Si(OH) 4 = UO 2 OSi(OH) 3 + + H + and Q 2 = -5,87 for the reaction of the polymeric silicate UO 2 2+ (-SiOH) j (-SiOH) j-2 (SiO) 2 UO 2 +2 H + . The influence of silicate on the speciation calculations for uranium in a model natural water is also discussed. (author)

Solvent extraction of uranium: Towards good practice in design, operation and management

International Nuclear Information System (INIS)

Bartsch, P.; Hall, S.; Ballestrin, S.; Hunt, A.

2014-01-01

Uranium solvent extraction, USX has been applied commercially for recovery and concentration for over 60 years. Uranium in acidic liquor, which is prepared following ore leaching, solid/liquid separation and clarification, can be treated through a sequence of operations; extraction-scrubbing-stripping, to obtain purified liquor, and hence precipitation of marketable products. USX has dominated the primary uranium industry as the preferred technological route for recovery of uranium into converter grade yellowcake or Uranium Ore Concentrate. The practices of design and operation of USX facilities has found renewed interest as new mines are developed following decades of industry dormancy. Development of the Olympic Dam and Honeymoon operations in Australia has lead to innovative design and operation of pulsed columns technology in applications of solvent extraction. This article seeks to outline principles of design and operation from the practitioner’s perspective. The discussion also reviews historical developments of USX applications and highlights recent innovations. This review is hoped to provide guidance for technical personnel who wish to learn more about good practices that leads to reliable USX performance. (author)

Extraction of uranium with emulsion membrane process use tributylphosphate extractant

International Nuclear Information System (INIS)

Basuki, K.T.; Sudibyo, R.; Bambang EHB; Muhadi, A.W.

1996-01-01

To increase the effectiveness of extraction process with so for to occur, it was tried the extraction with a couple of extraction and stripping process. This couple process was called liquid membrane emulsion. As membrane was used mix surfactant (Span-80), tributylphosphate in kerosene, natrium carbonate, while as a feeder was uranium solution with 500 concentration ppm in 0.5 - 3 M nitrate acid. In this experiment the variable investigated were % surfactant (1 - 5 %), rotary speed for membrane making (2,500 - 10.000 rpm). The optimal condition result of experiment were 5 % surfactant, 3 M nitrate acid, rotary speed 10.000 rpm and (Kd eksU ) 57 %, and (Kd strippU ) 87 %, Kd eksU at liquid-liquid extraction is 44 %. (author)

Studies on supercritical fluid extraction of uranium and thorium from liquid and solid matrix

International Nuclear Information System (INIS)

Kumar, Pradeep; Pal, Ankita; Saxena, M.K.; Ramakumar, K.L.

2006-05-01

Supercritical fluid extraction (SFE) is being widely used in pharmaceutical and food industry. Because of its simplicity, ease of operation and more importantly the reduction in the analytical waste generation, this technique is being viewed as a potential application technique in nuclear industry also. CO 2 is employed as supercritical fluid (SCF) as it is easily recyclable, non-toxic, chemically inert, radiochemically stable and inexpensive. Radioanalytical chemistry section (Radiochemistry and Isotope group) has recently procured a supercritical fluid extraction/chromatography system. The present report describes the work carried out on the system. Detailed study on uranium and thorium extraction from highly acidic medium and tissue paper matrix has been carried out. Direct dissolution and extraction of uranium compounds employing SCF has been carried out. CO 2 was employed as supercritical fluid along with very small amount of Tri n-butyl phosphate (TBP) and Tri n-octyl phosphine oxide (TOPO) as co-solvents. The effect of various operating parameters like CO 2 flow rate, co-solvent percentage, temperature and pressure on extraction was investigated and parameters for maximum extraction were optimized. For comparison, the modes of extraction viz. static and dynamic and modes of complexation viz. in-situ and online were studied. Uranium extraction of ∼98% has been achieved from nitric acid medium employing TBP as co-solvent in 30 minutes extraction time, whereas with TOPO ∼99% uranium extraction could be achieved. Uranium from tissue paper matrix could be extracted upto the extent of 98% with TOPO as co-solvent whereas with TBP extraction of (66.83± 9.80)% was achievable. Direct dissolution of UO 2 , U 3 O 8 , U metal, U-Al alloy solids into SCF CO 2 was carried out employing TBP-HNO 3 complex and SFE of uranium was performed using TBP as co-solvent. UO 2 and U 3 O 8 solids could be dissolved within 20 minutes and extraction of ∼98% was achieved. For U

Modifier free supercritical fluid extraction of uranium from sintered UO2, soil and ore samples

International Nuclear Information System (INIS)

Kanekar, A.S.; Pathak, P.N.; Acharya, R.; Mohapatra, P.K.; Manchanda, V.K.

2011-01-01

Direct extraction of uranium from different samples viz. sintered UO 2 , soil and ores was carried out by modifier free supercritical fluid using tri-n-butyl phosphate-nitric acid (TBP-HNO 3 ) adduct as extractant. These studies showed that pre-equilibration with more concentrated nitric acid helps in better dissolution and extraction of uranium from sintered UO 2 samples. Modifier free supercritical fluid extraction appears attractive with respect to minimization of secondary wastes. This method resulted 80-100% extraction of uranium from different soil/ore samples. The results were confirmed by performing neutron activation analysis of original (before extraction) and residue (after extraction) samples. (author)

Supercritical fluid extraction of uranium for its purification from various yellow cake matrices

International Nuclear Information System (INIS)

Prabhat, Parimal; Rao, Ankita; Tomar, B.S.; Kumar, Pradeep

2016-01-01

Uranium is produced from different uranium ores as crude yellow cake of different chemical composition such as sodium diuranate (SDU), ammonium diuranate (ADU), magnesium diuranate (MDU), high temperature uranium peroxide (HTUP) etc. This depends on nature of ores and ore processing methods, availability of required facilities at processing site and other economic as well as environmental factors. These yellow cakes are further processed to produce pure uranium suitable for fuel fabrication facility by conventional solvent extraction process. Supercritical Fluid Extraction (SFE) is being developed as an alternate method for separation in nuclear fields due to its inherent potential to minimize liquid waste generation and process simplification. In present study, SFE of uranium from various yellowcake of different chemical composition has been carried out. Chemical parameter such as effect of TBP amount on SFE of uranium has been carried out and optimized at 2 ml for 200 mg SDU. Instrumental parameter such as temperature and pressure on SFE of uranium has been optimized at 323 K and 15.2 MPa. Extraction efficiency (%) achieved at optimized condition is 91.45 ± 0.2, 97.01 ± 0.75 and 96.72 ± 0.27 for SDU, MDU and HTUP respectively. Purity of uranium before SFE and after has been compared. Further studies is in progress for better understanding of chemical composition of matrix on SFE of uranium and improving purity of uranium separated from this route. (author)

Spectrophotometric determination of U(vi) in 30% tbp using dibenzoyl methane (DBM) and methanol (abstract)

International Nuclear Information System (INIS)

Islam, N.; Naqvi, A.

2011-01-01

The Spectrophotometric method for the determination of trace amount of Uranium in aqueous and organic samples has been developed. The method is proved very accurate and precise for rapid determination of Uranium with Dibenzoyl Methane (DBM) in Methanol medium instead of Pyridine medium. The maximum absorbance occurs at 410 nm with a molar absorptivity of 4.5 x 104 L.mole/sup -1/.cm/sup -1/.The linear calibration curve through the point of origin was obtained up to 10 mu gm L/sup -1/ of Uranium (VI). The relative standard deviation is +- 2%. In case of aqueous samples extraction procedure is adopted to obtain organic phase while organic samples are treated as such. (author)

Correction in the efficiency of uranium purification process by solvent extraction

International Nuclear Information System (INIS)

Franca Junior, J.M.

1981-01-01

An uranium solvent extraction, of high purification, with full advantage of absorbed uranium in the begining of process, is described. Including a pulsed column, called correction column, the efficiency of whole process is increased, dispensing the recycling of uranium losses from leaching column. With the correction column the uranium losses go in continuity, for reextraction column, increasing the efficiency of process. The purified uranium is removed in the reextraction column in aqueous phase. The correction process can be carried out with full efficiency using pulsed columns or chemical mixer-settlers. (M.C.K.) [pt

Spectrophotometric Microdetermination of Thorium(IV and Uranium(VI with Chrome Azurol-S in Presence of Cationic Surfactant

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A. B. Upase

2011-01-01

Full Text Available Cationic surfactant, cetyldimethylethylammonium bromide (CDMEAB, sensitize the color reactions of Th(IV and U(VI with chrome azurol-S(CRAS. Formation of water soluble deeply colored ternary complexes of metal ions show large bathochromic shift. Same stoichiometric composition of ternary complexes with 1:2:4 molar ratio (M-CRAS-CDMEAB have been observed for both the metal ions and are responsible for enhancement in molar absorptivities and sensitivities at shifted wavelength. The ternary complexes of thorium(IV and uranium(VI exhibit absorption maxima at 640 and 620 nm with molar absorptivities 85500 and 69600 L.mol-1.cm-2 respectively. Beer’s law were obeyed in concentration range 0.12-0.185 ppm for Th(IV and 0.13-0.162 ppm for U(VI in presence of CDMEAB. Conditional formation constants and various analytical parameters have been evaluated and compared the results of binary and ternary complexes. Enhancement in the molar absorptivities in presence of CDMEAB clearly indicated the usefulness of these colored reactions for microdetermination.

Comparison of U(VI) adsorption onto nanoscale zero-valent iron and red soil in the presence of U(VI)–CO{sub 3}/Ca–U(VI)–CO{sub 3} complexes

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhibin [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Liu, Jun [State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Cao, Xiaohong, E-mail: xhcao@ecit.cn [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Luo, Xuanping [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Hua, Rong; Liu, Yan [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang 330013 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); Yu, Xiaofeng; He, Likai [Chemistry, Biological and Materials Sciences Department, East China Institute of Technology, Nanchang 330013 (China); and others

2015-12-30

Highlights: • NZVI can be used for adsorbing U(VI)–CO{sub 3} complexes. • Use of NZVI is feasible for remediation of uranium-contaminated soils. • The mechanism of U(VI)–CO{sub 3} complexes adsorbing onto NZVI has been explained. - Abstract: The influence of U(VI)–CO{sub 3} and Ca–U(VI)–CO{sub 3} complexes on U(VI) adsorption onto red soil and nanoscale zero-valent iron (NZVI) was investigated using batch adsorption and fixed-bed column experiments to simulate the feasibility of NZVI as the reactive medium in permeable- reactive barriers (PRB) for in situ remediation of uranium-contaminated red soils. The adsorption capacity (q{sub e}) and distribution constant (K{sub d}) of NZVI and red soil decreased with increasing pH, dissolved carbonate and calcium concentrations, but the q{sub e} and K{sub d} values of NZVI were 5–10 times higher than those of red soil. The breakthrough pore volume (PV) values increased with the decrease of pH, dissolved carbonate and calcium concentration; however, the breakthrough PV values of the PRB column filled with 5% NZVI were 2.0–3.5 times higher than the 100% red soil column. The U(VI)–CO{sub 3} complexes adsorbed onto the surface of red soil/NZVI (≡SOH) to form SO–UO{sub 2}CO{sub 3}{sup −} or SO–UO{sub 2} (CO{sub 3}){sub 2}{sup 3−}. XPS and XRD analysis further confirmed the reduction of U(VI) to U(IV) and the formation of FeOOH on NZVI surfaces. The findings of this study are significant to the remediation of uranium-contaminated red soils and the consideration of practical U(VI) species in the natural environment.

Economic evaluation of in situ extraction for copper, gold, and uranium

International Nuclear Information System (INIS)

Lewis, F.M.; Chase, C.K.; Bhappu, R.B.

1976-01-01

In situ extraction for copper, gold, and uranium, generally involves several common alternative processes and techniques. These include dump leaching, heap leaching, leaching of fractured ore in-place or bore hole mining and unit operations such as cementation, solvent extraction, ion-exchange, or carbon-in-pulp. Since the metallurgical effectiveness and economics of such processes and unit operations are well established, it would be possible to select the optimum alternative for extracting either copper, gold, or uranium from their ores using in situ extraction technology. Efforts made to provide metallurgical evaluation as well as capital and operating costs for the various processes and unit operations are reported. These costs are used in preparing feasibility studies for in situ extraction of these metals

Present status of uranium extraction from seawater

International Nuclear Information System (INIS)

Kusakabe, Katsuki; Morooka, Shigeharu

1993-01-01

For the research on the extraction of uranium from seawater, various processes have been examined, but the most promising process is adsorption. Its key point is the performance of the adsorbent. The system as compact as possible, in which a large quantity of seawater effectively contacts with the adsorbent, must be constructed economically. As the inorganic adsorbent, titanium oxide is the best, but organic amidoxime is superior to it. The present state of the development of the adsorbent, the rate of adsorption of the adsorbenbt, the seawater uranium adsorption system and the experiment in Imari Bay are reported. (K.I.)

Removal of uranium(VI) from the aqueous phase by iron(II) minerals in presence of bicarbonate

Energy Technology Data Exchange (ETDEWEB)

Regenspurg, Simona, E-mail: regens@gfz-potsdam.de [Industrial Ecology, Royal Institute of Technology (KTH), SE 10044 Stockholm (Sweden); Schild, Dieter; Schaefer, Thorsten; Huber, Florian [Institut fuer Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen (Germany); Malmstroem, Maria E. [Industrial Ecology, Royal Institute of Technology (KTH), SE 10044 Stockholm (Sweden)

2009-09-15

Uranium(VI) mobility in groundwater is strongly affected by sorption of mobile U(VI) species (e.g. uranyl, UO{sub 2}{sup 2+}) to mineral surfaces, precipitation of U(VI) compounds, such as schoepite (UO{sub 2}){sub 4}O(OH){sub 6}.6H{sub 2}O), and by reduction to U(IV), forming sparingly soluble phases (uraninite; UO{sub 2}). The latter pathway, in particular, would be very efficient for long-term immobilization of U. In nature, Fe(II) is an important reducing agent for U(VI) because it frequently occurs either dissolved in natural waters, sorbed to matrix minerals, or structurally bound in many minerals. Redox reactions between U(VI) and Fe(II) depend not only on the availability of Fe(II) in the environment, but also on the chemical conditions in the aqueous solution. Under natural groundwater condition U(VI) forms complexes with many anionic ligands, which strongly affect its speciation. Carbonate, in particular, is known to form stable complexes with U, raising the question, if U(VI), when complexed by carbonate, can be reduced to UO{sub 2}. The goal of this study was to find out if Fe(II) when structurally bound in a mineral (as magnetite, Fe{sub 3}O{sub 4}) or sorbed to a mineral surface (as corundum, Al{sub 2}O{sub 3}) can reduce U(VI) to U(IV) in the presence of HCO{sub 3}{sup -}. Batch experiments were conducted under anaerobic conditions to observe U removal from the aqueous phase by the two minerals depending on HCO{sub 3}{sup -} addition (1 mM), U concentration (0.01-30 {mu}M) and pH value (6-10). Immediately after the experiments, the mineral surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) to obtain information on the redox state of U bound to the solid surfaces. XPS results gave evidence that U(VI) can be reduced both by magnetite and by corundum amended with Fe(II). In the presence of HCO{sub 3}{sup -} the amount of reduced U on the mineral surfaces increased compared to carbonate-free solutions. This can be explained by the formation

Application and improvement of reciprocating-sieve plate extraction column in natural uranium extraction and purification process

International Nuclear Information System (INIS)

Wang Xuejun; Li Linyan; Liu Jing; Liu Xin; Yang Lifeng; Xiao Shaohua; Liu Hao

2013-01-01

Reciprocating-sieve plate extraction column is commonly used in the extraction process. Optimization and application were conducted successfully via production practice in some chemical and pharmaceutical plants, and good results are obtained while it is applied in the natural uranium extraction and purification process. The key component of reciprocating-sieve plate extraction column is gear-drive equipment in which drive motor serves as its core. Hence, it is important to select appropriate mode of speed regulation. In this paper, the principle and performance of several mode of speed regulation are compared. Both electromagnetic slip and frequency speed-regulation can be applied in general industrial process, but frequency speed-regulation with low energy cost can be used in wider operating range. The application of frequency speed-regulation mode used in reciprocating-sieve plate extraction column will increase the convenience and stability of natural uranium extraction and purification process. (authors)

Extraction of U(VI) with unsymmetrical N-methyl-N-octyl alkylamides in toluene

International Nuclear Information System (INIS)

Sun Guoxin; Li Yexin; Zhang Zhenwei; Cui Yu; Shandong University, Jinan; Sun Sixiu

2005-01-01

Extraction of U(VI) with three new unsymmetrical monoamides, N-methyl-N-octyloctylamide (MOOA), N-methyl-N-octyldecanamide (MODA), and N-methyl-N-octyldodecanamide (MODOA), from nitric acid solution employing toluene as diluent is discussed. The effects of nitric acid, sodium nitrate and extractant concentrations and also the temperature on the distribution ratio have been investigated. The extracted species were studied by IR spectrometry. (author)

Solvent-extraction methods applied to the chemical analysis of uranium. III. Study of the extraction with inert solvents

International Nuclear Information System (INIS)

Vera Palomino, J.; Palomares Delgado, F.; Petrement Eguiluz, J. C.

1964-01-01

The extraction of uranium on the trace level is studied by using tributylphosphate as active agent under conditions aiming the attainment of quantitative extraction by means of a single step process using a number of salting-out agents and keeping inside the general lines as reported in two precedent papers. Two inert solvents were investigated, benzene and cyclohexane, which allowed to derive the corresponding empirical equations describing the extraction process and the results obtained were compared with those previously reported for solvents which, like ethyl acetate and methylisobuthylketone, favour to a more or less extend the extraction of uranium. (Author) 4 refs

Detection of uranium extraction zone by axial temperature profiles in a pulsed column for Purex process

International Nuclear Information System (INIS)

Tsukada, T.; Takahashi, K.

1991-01-01

A new method was presented for detecting uranium extraction zone in a pulsed column by means of measuring axial temperature profile originated from reaction heat during uranium extraction. Key parameters of the temperature profiles were estimated with a code developed for calculating temperature profiles in a direct-contact heat exchanger such as a pulsed column, and were verified using data from a small pulsed column simulating reaction heat with injecting hot water. Finally, the results were compared with those from an actual uranium extraction tests, indicating that the method presented was promising for detecting uranium extraction zone in a pulsed column. (author)

Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

International Nuclear Information System (INIS)

Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

2015-01-01

Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

USE OF MEMBRANE EMULSION SPAN 80 AND TOPO IN URANIUM EXTRACTION AND STRIPPING

Directory of Open Access Journals (Sweden)

Kris Tri Basuki

2017-01-01

Full Text Available ABSTRACT USE OF MEMBRANE EMULSION SPAN 80 AND TOPO IN URANIUM EXTRACTION AND STRIPPING. Membrane emulsion span 80 and TOPO used in uranium extraction and stripping has been done. The extraction was carried outby emulsion membrane H3PO4 in TOPO-Kerosene. The feed or external aqueous phase was uranium in  HNO3. The emulgator span-80 was used to obtain a stable emulsion membrane system. The influence factors were percentage of TOPO-Kerosene, time extraction,  molarity of external aqueous phase and  molarity of internal aqueous. After the emulsion membrane was formed, the extractionand stripping process was performed. The ratio volume feed : volume membrane phase equal to 1 : 1 and volume of 5 % TOPO-Kerosene : Volume 3 M H3PO4 equal 1 : 1 were used. The relative good yield were obtained at concentration of TOPO in Kerosene and 3 M H3PO4 was 5 %, molarity of internal aqueous phase equal to 1 M, molarity of external aqueous phase 3 M H3PO4 and time extraction equalto 10 minutes with the speed of emulsification was 8000 rpm. At this condition the extraction efficiency of uranium obtained was 97.8 %, the stripping efficiency 52.56 %, and the total efficiency was 53.80 %. Keywords: membrane emulsion, extraction, stripping, span 80, kerosene, uranium. ABSTRAK PENGGUNAAN MEMBRAN EMULSI SPAN 80 DAN TOPO UNTUK EKSTRASI DAN STRIPPING URANIUM. Telah dilakukan penelitian membran emulsi span 80 dan TOPO yang digunakan untuk ekstraksi uranium. Extraksi dengan membran emulsi H3PO4 dalam TOPO-Kerosen. Larutan umpan untuk fasa air eksternal adalah uranium dalam asam nitrat. Untuk memperoleh sistem emulsi yang stabil dipakai emulgator Span 80. Parameter yang berpengaruh adalah persen TOPO-Kerosene, molaritas fasa air internal H3PO4, molaritas fasa air eksternal HNO3 dan waktu ekstraksi. Setelah diperoleh membran emulsi, kemudian dilakukan proses ekstraksi dan stripping, dengan rasio volume umpan : volume membran sebesar 1 : 1; volume 5% TOPO-Kerose : volume 3M

Remediation of U(VI)-contaminated water using zero-valent iron

International Nuclear Information System (INIS)

Abdelouas, A.; Gong, W.; Lutze, W.; Nuttall, E.

1999-01-01

We investigated the possibility of U(VI) reduction by zero-valent iron (Fe 0 ). We conducted batch experiments with granular iron and solutions containing 0.25 and 9.3 mg L -1 U(VI) at 24 deg C. The solution pH ranges between 2 and 9. In all experiments uranium removal was complete within several hours to several days regardless of the pH value. The reduced uranium precipitated as poorly crystallized hydrated uraninite, UO 2 .nH 2 O. The reduction of U(VI) to U(IV) by Fe 0 was found to be the principal mechanism of U removal from the solution. Other mechanisms such as U(VI) sorption on the newly formed Fe(III) hydroxides are insignificant. These results show that zero-valent iron can be used to remedy U-contaminated waters from uranium mines and mill tailings sites, the pH of which usually ranges between 2 and 9. (authors)

Titrimetric determination of uranium

International Nuclear Information System (INIS)

Florence, T.M.

1989-01-01

Titrimetric methods are almost invariably used for the high precision assay of uranium compounds, because gravimetric methods are nonselective, and not as reliable. Although precipitation titrations have been used, for example with cupferron and ferrocyanide, and chelate titrations with EDTA and oxine give reasonable results, in practice only redox titrations find routine use. With all redox titration methods for uranium a precision of 01 to 02 percent can be achieved, and precisions as high as 0.003 percent have been claimed for the more refined techniques. There are two types of redox titrations for uranium in common use. The first involves the direct titration of uranium (VI) to uranium (IV) with a standard solution of a strong reductant, such as chromous chloride or titanous chloride, and the second requires a preliminary reduction of uranium to the (IV) or (III) state, followed by titration back to the (VI) state with a standard oxidant. Both types of redox titrations are discussed. 4 figs

Solvent extraction of W(VI) and Hg(II) with malachite green and rhodamine-B respectively into organic solvents

International Nuclear Information System (INIS)

Patil, V.B.; David, M.M.; Turel, Z.R.

1992-01-01

Aqueous malachite green and alcoholic rhodamine-B have been used for the extraction of tungsten( W(VI)) and mercury( Hg(II)) respectively into nitrobenzene. This paper deals with developing a rapid method and selective method for the extraction of tungsten(W(VI)) and mercury (Hg(II)) using malachite green and rhodamine-B respectively. 185 W and 203 Hg were used as tracers for studying the extraction process.(author). 2 refs., 2 tab

Studies on supercritical fluid extraction behaviour of uranium and thorium nitrates using amides

International Nuclear Information System (INIS)

Sujatha, K.; Kumar, R.; Sivaraman, N.; Srinivasan, T.G.; Vasudeva Rao, P.R.

2007-01-01

Supercritical fluid extraction studies of uranyl nitrate and thorium nitrate in mixture were carried out using various amides such as N,N-di(2-ethylhexyl) isobutyramide (D2EHIBA),N,N-dihexyl octanamide (DHOA) and Diisooctyl Butanamide (DiOBA). These studies established a preferential extraction of uranium over thorium. Among the various amides studied, D2EHIBA offered the best rate of preferential extraction of uranium over thorium. (author)

Proceedings of the meeting on uranium exploration, mining and extraction

International Nuclear Information System (INIS)

1996-01-01

Meeting on uranium exploration, mining, and extraction is aimed to expedite information exchange among researchers from the National Atomic Energy Agency (BATAN), their international colleagues, the higher education institutions,and other interested scientific communities on the latest development on Kalan uranium minerals exploration, mining, and extraction. Nuclear Minerals Development Centre (PPBGN) roles in nuclear energy provision, the theme of the meeting, reflect current advancements of the Centre in fulfilling its major tasks and responsibilities. In order to assist PPBGN better to assume its roles and responsibilities, the meeting is expected to bring forth essential solutions for problems and difficulties relevant to PPBGN's activities. Hence, the scope of the meeting will be limited to discussion on the status of nuclear minerals exploration, mining, and extraction technologies in Indonesia as well as the related environmental and workplace safeties in uranium mining and milling. Ten technical papers were presented in meeting, including four topics on exploration status and technology, three subject matter on mining, two presentations on milling, and one paper on environmental and workplace safeties

Complex formation between uranium(VI) and α-D-glucose 1-phosphate

International Nuclear Information System (INIS)

Koban, A.; Geipel, G.; Bernhard, G.

2003-01-01

The complex formation of uranium(VI) with α-D-glucose 1-phosphate (C 6 H 11 O 6 PO 3 2- , G1P) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at pH 4 and potentiometric titration in the pH range from 3 to 10. Both measurements show the formation of a 1 : 1 complex at lower pH values. The formation constant of UO 2 (C 6 H 11 O 6 PO 3 ) was calculated from TRLFS measurements to be log β 11 = 5.72±0.12, and from potentiometric titration log β 11 = 5.40±0.25, respectively. It was found by potentiometric titration that at higher pH values the complexation changes to a 1 : 2 complex. The stability constant for this complex was calculated to be log β 12 = 8.96±0.18. (orig.)

Determination of the uranium content of phosphate rocks

International Nuclear Information System (INIS)

Levin, R.; Ronen, S.

1977-03-01

A method is described for the spectrophotometric determination of uranium (VI) in the presence of various elements by extraction with 0.1M trioctylphosphine oxide (TOPO) dissolved in cyclohexane from 1.5M nitric acid. The colour is developed directly in the organic phase using Arsenazo I. The optical absorbance is measured at a wavelength of 600 nm. Possible interferences of accompanying elements can be eliminated by reduction with ascorbic acid and by screening with sodium fluoride. This method allows the determination of any uranium content, in the 20 to 200 μg range, of phosphate rocks containing up to 1 g (PO 4 ) 3-

A Preliminary Study for Development of Amidoxime-functionalized Silica Adsorbents for Uranium(IV) Extraction from Seawater

Energy Technology Data Exchange (ETDEWEB)

Lee, Minseok; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of)

2016-10-15

4 billion tons of uranium, which can supply the electricity for tens of thousands of years, is contained in seawater. Therefore, development of techniques for uranium sequestering from the ocean has been regarded as a great challenging for making nuclear energy to be more economical and sustainable. Despite the inexhaustible uranium resource, it is still hard to produce uranium economically from seawater due to its extremely low level of concentration (3.0 μg/L) and stable complex chemical formation, UO{sub 2}(CO3)34-. Various methods for uranium extraction from seawater have been suggested such as precipitation, solvent extraction, ion exchange, adsorption and etc. The most preferred method for extracting uranium is adsorption due to ease of separation from the liquid phase, environment friendliness and cost-effectiveness. Organic or inorganic solids functionalized with amidoxime (AO, -R-C(NH2)=NOH) groups, which has high affinity to uranium species, is the one of candidate material for uranium adsorbents. For long-term nuclear power generation, developing uranium extraction technologies from seawater has been a crucial issue. AO-based adsorbent has been considered as the most effective methods for uranium extraction from seawater, and collaboration with nanotechnology has been tried to enhance the traditional adsorbents, recently. Despite the attempts, most AO-based adsorbents were suffered from complexation of uranyl ions with carbonate ions and under the effect of pH. To achieve more efficient uranium uptake, bi-functionalized mesoporous silica with AO group and acidic groups was chosen as a model for this study.

Uranium extraction process in a sulfuric medium by means of liquid emulsified membranes

International Nuclear Information System (INIS)

Monteillet, A.

1985-02-01

Uranium ore processing, after leaching by sulfuric acid, by liquid-liquid extraction is a rather heavy process, not suitable for small deposits. Extraction by emulsions was suggested. In this process the leachate is contacted with an oil in water type emulsion, a liquid organic membrane is formed by the continuous phase. Uranium complexes diffuse through the liquid membrane towards the dispersed aqueous phase of the emulsion (stripping solution). Uranium is recovered by breaking the emulsion. Are successively studied: development of stable emulsions, influence of emulsion composition on uranium transfer kinetics, transfer mechanisms through the membrane and modelling of kinetics data obtained in the experimental study [fr

Extraction of uranium from aqueous solution by phosphonic acid-imbedded polyurethane foam

International Nuclear Information System (INIS)

Katragadda, S.; Gesser, H.D.; Chow, A.

1997-01-01

Phenylphosphonic acid was imbedded into the matrix of the polyurethane foam during the fabrication process of the polymer. The extraction of uranium by phosphonic acid-imbedded polyurethane foam and blank polyurethane (i.e., foam without phosphonic acid functional groups) was investigated. Phosphonic acid-imbedded foam showed superior extractability of uranium from solutions with pH = 7.0 ± 1.5 over a wide range of temperatures. (author)

Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments.

Science.gov (United States)

Stewart, Brandy D; Mayes, Melanie A; Fendorf, Scott

2010-02-01

Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO(2)(2+) speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-1) for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption.

Kinetics and equilibrium modeling of uranium(VI) sorption by bituminous shale from aqueous solution

International Nuclear Information System (INIS)

Ortaboy, Sinem; Atun, Gülten

2014-01-01

Highlights: • Oil shales are sedimentary rocks containing a polymeric matter in a mineral matrix. • Sorption potential of bituminous shale (BS) for uranium recovery was investigated. • U(VI) sorption increased with decreasing pH and increasing temperature. • Kinetic data were analyzed based on single and two resistance diffusion models. • The results fit well to the McKay equation assuming film and intraparticle diffusion. - Abstract: Sorption of U(VI) onto a bituminous shale (BS) from a nuclear power plant project site in Black Sea region was investigated for potential risk assessment when it releases into the environment with contaminated ground and surface water. The sorption characteristics of the BS for U(VI) recovery were evaluated as a function of contact time, adsorbent dosage, initial concentration, pH and temperature. Kinetic results fit better with pseudo-second-order model rather than pseudo-first-order. The possibility of diffusion process was analyzed based on Weber–Morris intra-particle diffusion model. The McKay equation assuming film- and intraparticle diffusion better predicted the data than the Vermeulen approximation presuming surface diffusion. Equilibrium sorption data were modeled according to the Langmuir, Dubinin–Radushkevich (D–R) and Freundlich isotherm equations. Sorption capacity increased from 0.10 to 0.15 mmol g −1 in 298–318 K temperature range. FT-IR analysis and pH dependent sorption studies conducted in hydroxide and carbonate media revealed that U(VI) species were sorbed in uranyl and its hydroxo forms on the BS. Desorption studies showed that U(VI) leaching with Black Sea water was negligible from the loaded BS. The activation parameters (E a , ΔH ∗ and ΔG ∗ ) estimated from diffusion coefficients indicated the presence of an energy barrier in the sorption system. However, thermodynamic functions derived from sorption equilibrium constants showed that overall sorption process was spontaneous in nature

Uranium extraction from high content chlorine leach liquor

International Nuclear Information System (INIS)

Fatemi, K.

1998-01-01

In this work uranium solution has been leached out by leaching process of uranium ores from Bandar-Ab bass port using sea water, since fresh water could not be available when it is processed in large scale. Two samples of different batches containing 11 and 20 gr./lit chlorine underwent two stages of precipitation by lead nitrate. As the result of this treatment the chlorine removed and its final concentration reduced to 530 p.p.m. which is well below allowances. Then, the uranium of this recent dechlorinated solu ton has been extracted by T.B.P. Uranium in organic phase was stripped out into inorganic phase by sodium carbonate and precipitated in a form of yellow cake and converted to U3o8. The total recovery of U, was well above 90% and the purity of the conc. U was better than 94%. The lead used at the beginning of the process was recovered for next use

Use of a pulsed column with discs and crowns for uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

1982-04-01

The physico-chemistry of the system phosphoric acid-uranium-dioctylpyrophosphoric acid is studied for the determination of analytical methods and extraction parameters (oxidation state of uranium and iron, phosphorus concentration, extractant concentration). Extraction is then realized on a pilot scale with a liquid-liquid extraction column 4m high and of 50 mm in diameter with a column packing made of discs and crowns. Column efficiency is evaluated by studying uranium transfer as a function of operating conditions. The results obtained are extrapolated to an industrial scale and a comparative economic evaluation is made between a pulsed column and a mixer-settler [fr

Characterization of the sorption of uranium(VI) on different complexing resins

Energy Technology Data Exchange (ETDEWEB)

Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela [Dipartimento di Chimica Generale dell' Universita degli Studi di Pavia, Via Taramelli 12, 27100, Pavia (Italy)

2003-08-01

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log{beta}{sub 110i}=-1.16, in more acidic solution, and ML{sub 2}with log {beta}{sub 120i}=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML {sub 2}, in more acidic solution, with log {beta}{sub 120i}=-3.16. In the presence of the ligand EDTA, the complex ML {sub 2}(OH) {sub 2}was characterized with log {beta}{sub 12-2i}=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

Characterization of the sorption of uranium(VI) on different complexing resins

International Nuclear Information System (INIS)

Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela

2003-01-01

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with logβ 110i =-1.16, in more acidic solution, and ML 2 with log β 120i =-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML 2 , in more acidic solution, with log β 120i =-3.16. In the presence of the ligand EDTA, the complex ML 2 (OH) 2 was characterized with log β 12-2i =-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

Retention and chemical speciation of uranium in an oxidized wetland sediment from the Savannah River Site

Energy Technology Data Exchange (ETDEWEB)

Li, Dien; Seaman, John C.; Chang, Hyun-Shik; Jaffe, Peter R.; Koster van Groos, Paul; Jiang, De-Tong; Chen, Ning; Lin, Jinru; Arthur, Zachary; Pan, Yuanming; Scheckel, Kirk G.; Newville, Matthew; Lanzirotti, Antonio; Kaplan, Daniel I.

2014-05-01

Uranium speciation and retention mechanism onto Savannah River Site (SRS) wetland sediments was studied using batch (ad)sorption experiments, sequential extraction desorption tests and U L{sub 3}-edge X-ray absorption near-edge structure (XANES) spectroscopy of contaminated wetland sediments. U was highly retained by the SRS wetland sediments. In contrast to other similar but much lower natural organic matter (NOM) sediments, significant sorption of U onto the SRS sediments was observed at pH <4 and pH >8. Sequential extraction tests indicated that the U(VI) species were primarily associated with the acid soluble fraction (weak acetic acid extractable) and NOM fraction (Na-pyrophosphate extractable). Uranium L3- edge XANES spectra of the U-retained sediments were nearly identical to that of uranyl acetate. The primary oxidation state of U in these sediments was as U(VI), and there was little evidence that the high sorptive capacity of the sediments could be ascribed to abiotic or biotic reduction to the less soluble U(IV) species. The molecular mechanism responsible for the high U retention in the SRS wetland sediments is likely related to the chemical bonding of U to organic carbon.

Extraction of Uranium Using Nitrogen Dioxide and Carbon Dioxide for Spent Fuel Reprocessing

Energy Technology Data Exchange (ETDEWEB)

Kayo Sawada; Daisuke Hirabayashi; Youichi Enokida [EcoTopia Science Institute, Nagoya University, Nagoya, 464-8603 (Japan)

2008-07-01

For the reprocessing of spent nuclear fuels, a new method to extract actinides from spent fuel using highly compressed gases, nitrogen dioxide and carbon dioxide was proposed. Uranium extraction from broken pieces, whose average grain size was 5 mm, of uranium dioxide pellet with nitrogen dioxide and carbon dioxide was demonstrated in the present study. (authors)

Extraction of uranium and copper from sulphate leach liquors of West Central Sinai uraniferrous siltstone of Egypt

International Nuclear Information System (INIS)

Amer, T.E.; Mahdy, M.A.; El-Hazek, N.T.; El Bayoumi, R.M.; Hassanein, S.

2000-01-01

Extraction of uranium and copper from sulphate leach liquors of west central Sinai ore samples were performed using solvent extraction technique. Sulphate leach solutions were processed for the extraction of copper using 3% v/v LIX 973N. Copper extractions higher than 98.1% were obtained. Then, uranium was extracted using a tertiary amine. Two amines have been studied 2% v/v tri-n-octyl amine and 1.5% Alamine 336. Parameters studied included solvents concentration, contact time and solution pH. Stripping of uranium and copper were studied using sodium carbonate and sulphuric acid, respectively. Conditions were established for determining the number of stages required for extraction and stripping of copper and uranium through the construction of the corresponding McCabe-Theile diagrams. The results obtained have been utilized to formulate a proposed flowsheet for the production of uranium and copper from west central Sinai ore samples. (author)

Determination of uranium and plutonium in high active solutions by extractive spectrophotometry

International Nuclear Information System (INIS)

Subba Rao, R.V.; Damodaran, K.; Santosh Kumar, G.; Ravi, T.N.

2000-01-01

Plutonium and uranium was extracted from nitric acid into trioctyl phosphine oxide in xylene. The TOPO layer was analysed by spectrophotometry. Thoron was used as the chromogenic agent for plutonium. Pyridyl azoresorcinol was used as chromogenic agent for uranium. The molar absorption coefficient for uranium and plutonium was found to be 19000 and 19264 liter/mole-cm, respectively. The correlation coefficient for plutonium and uranium was found to be 0.9994. The relative standard deviation for the determination of plutonium and uranium was found to be 0.96% and 1.4%, respectively. (author)

Spectrophotometric Quantification of Toxicologically Relevant Concentrations of Chromium(VI in Cosmetic Pigments and Eyeshadow Using Synthetic Lachrymal Fluid Extraction

Directory of Open Access Journals (Sweden)

Sarah Wurster

2012-01-01

Full Text Available Chromium(VI salts are possible contaminants of the chromium(III pigments used as colorants in eyeshadow preparations. The use of products containing these contaminants poses acute risks for sensitization and contact allergies. Chromium(VI compounds are also classified as carcinogenic to humans (IARC group 1. An analytical method to analyse trace levels of chromium(VI in eyeshadow was developed in this study. The method is based on an extraction of the chromium(VI from the sample using a maximum extraction with alkali and additionally with synthetic lachrymal fluid to simulate physiological conditions. Following derivatization with 1,5-diphenylcarbazide, the extracted chromium(VI is then quantified by spectrophotometry (540 nm. Validation tests indicated a method standard deviation (inter- and intraday of 8.7% and a linear range up to 25 mg/kg. The average recovery was 107.9%, and the detection limit was 2.7 mg/kg. The applicability of the procedure was confirmed by the analysis of pigments and authentic eyeshadow matrices.

Enzymatic reduction of U(VI) in groundwaters; Reduction enzymatique de U(VI) dans des eaux souterraines

Energy Technology Data Exchange (ETDEWEB)

Addelouas, A.; Gong, W. [Center for Radioactive Waste Management, Advanced Materials Laboratory, 1001 University, Albuquerque (United States); Lutze, W.; Nuttall, E. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Chemical and Nuclear Engineering; Fritz, B.; Crovisier, J.L. [Centre National de la Recherche Scientifique (CNRS), 67 - Strasbourg (France). Centre de Sedimentologie et Geochimie de la Surface

1999-03-01

The use of enzymatic reduction of U(VI) in remediation of groundwater contaminated with U(VI) is receiving considerable attention. Certain strains of bacteria can combine the oxidation of an organic compound to the reduction of U(VI) to U(IV), which precipitates as uraninite. In the present study, we tested the reduction of U(VI) in groundwaters with various origins and compositions. In all groundwaters u(VI) was reduced by sulfate reducing bacteria that had been activated by ethanol and tri-metaphosphate. The reduction rate of U(VI) depends on sulfate concentration in water and the abundance of bacteria in the system. This work shows that bacteria capable of U(VI) reduction are ubiquitous in nature, and suggests the possibility of a large application of the enzymatic reduction of U(VI) for in situ clean up of groundwaters contaminated with uranium. (authors) 12 refs.

Uranium Extraction from Phosphates: - Background, Opportunities, Process Overview & Way Forward for Commercialisation

International Nuclear Information System (INIS)

Tulsidas, Harikrishnan; Hilton, Julian; Kumar Haldar, Tapan

2014-01-01

Uranium Extraction from Phosphate - an attractive proposition: • Uranium is co-product of phosphate Industry and makes phosphate Industry economically viable & socially more acceptable; • Enable utilisation of mineral deposits having low Phosphate value through economic co-production of Phosphatic fertiliser & Uranium; • Bring new countries in global map of Uranium resources; • Enables socio-economic up-gradation of major part of global population by achieving Energy, food & Environmental security - so important in today’s scenario

Contribution of molecular modeling and of structure-activity relations to the liquid-liquid extraction. Application to the case of U(VI) extraction by monoamides; Apport de la modelisation moleculaire et des relations structure -activite a l`extraction liquide-liquide. Application au cas de l`extraction d`U(VI) par les monoamides

Energy Technology Data Exchange (ETDEWEB)

Rabbe, C.

1996-06-07

In France, spent fuels are in most cases reprocessed. The aim of the reprocessing is to separate the recyclable fissile materials (for instance, uranium and plutonium) of radioactive wastes. The industrial process used until now is the Purex (Plutonium Uranium Refining by EXtraction) process. Recently (1991), the CEA has undertaken researches on the fields of separation and transmutation of long-lived radionuclides as minor actinides. Some molecules with an amide function have been at first considered especially for the uranium extraction. In order to rationalize the research of new extracting molecules, some molecular modeling methods (quantum chemistry calculations, molecular mechanics) have been used. In fact, there are three determining parameters for a molecule to be a good extractant: it has to own: (1) one or several sites which present a sufficient electron density in order that the metallic cation be complexed (2) the smallest possible substituents to avoid interferences with the complexation (3) a sufficient lipophilic effect. (O.M.). 139 refs., 43 figs., 36 tabs.

Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI)

Energy Technology Data Exchange (ETDEWEB)

Gerber, U., E-mail: u.gerber@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Zirnstein, I. [Research Institute of Leather and Plastic Sheeting (FILK) gGmbH, Meissner Ring 1-5, 09599 Freiberg (Germany); Krawczyk-Bärsch, E. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Lünsdorf, H. [Helmholtz Centre for Infection Research, Central Facility for Microscopy, Inhoffenstr. 7, D-38124 Braunschweig (Germany); Arnold, T. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden (Germany); Merroun, M.L. [University of Granada, Department of Microbiology, Campus Fuentenueva, E-18071 Granada (Spain)

2016-11-05

Highlights: • Acidovorax facilis is able to remove 130 mg U/g dry biomass from solution. • Kinetically temperature-dependent uranium removal was studied. • Cell viability and metabolic activity was tested by flow cytometry. • Uranium was removed by active biosorption and passive bioaccumulation. - Abstract: The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation by means of controlled underground flooding. Nevertheless, the flooding water has to be cleaned up by a conventional wastewater treatment plant. In this study, the uranium(VI) removal and tolerance mechanisms of the gram-negative betaproteobacterium Acidovorax facilis were investigated by a multidisciplinary approach combining wet chemistry, flow cytometry, and microscopy. The kinetics of uranium removal and the corresponding mechanisms were investigated. The results showed a biphasic process of uranium removal characterized by a first phase where 95% of uranium was removed within the first 8 h followed by a second phase that reached equilibrium after 24 h. The bacterial cells displayed a total uranium removal capacity of 130 mg U/g dry biomass. The removal of uranium was also temperature-dependent, indicating that metabolic activity heavily influenced bacterial interactions with uranium. TEM analyses showed biosorption on the cell surface and intracellular accumulation of uranium. Uranium tolerance tests showed that A. facilis was able to withstand concentrations up to 0.1 mM. This work demonstrates that A. facilis is a suitable candidate for in situ bioremediation of flooding water in Königstein as well as for other contaminated waste waters.

Extraction of uranium from carnotite/tyuyamunite

International Nuclear Information System (INIS)

Li Shengnian; Fang Xuxia

1998-01-01

According to the characters of a carnotite/tyuyamunite and chemical properties of vanadate, the technological process, heap leaching-ion exchange-precipitation, is adopted for extracting uranium. It has been proved through laboratory test and industrial trial production that process is simple and convenient in method, advanced in technology, simple in equipment, and the product quality conforms to the criterion. The technological process is applied to small-sized hydrometallurgy plant at mine

Extraction of molybdenum with TBP-dodecane mixture in nitric medium. Application to uranium refining

International Nuclear Information System (INIS)

Donnet, Louis

1993-01-01

Uranium ores may contain high quantities of molybdenum which represents an undesirable impurity in the uranium conversion process. Thus it is necessary to check carefully its extraction and its stripping during the purification step. The purpose of this study was to investigate the molybdenum behaviour during this step. We have developed a radiochemical method for the determination of the molybdenum concentration in each phase. This method used gamma radiation of technetium 99m issued from molybdenum 99 disintegration. After a systematic study of all the extraction parameters, we have proposed mechanisms accounting for molybdenum extraction and we have calculated the constants for the different equilibria. In particular, we have furnished new data concerning the extraction of polymerised molybdenum species with tri butyl phosphate. We have also determined the polymerization constants of molybdenum in the aqueous phase. The influence of uranium and phosphate ions on the molybdenum behaviour during the extraction and stripping has been investigated. We have shown that the extraction of molybdenum was not modified by uranium but improved in the presence of phosphate ions. In the general case, we have shown that uranium, phosphate ions and the ageing of the solvent have an unfavourable effect on stripping. We have explained this result by the evolution of the complex in the organic phase to an un-stripped polymeric form. In conclusion, our study has allowed to explain the behaviour of molybdenum during the purification process, and the role of impurities present in the industrial solutions. It would serve as a guide to improve the exploitation for a better molybdenum-uranium separation. (author) [fr

Kinetic studies on uranium stripping in D2EHPA+TBP/phosphoric acid system

International Nuclear Information System (INIS)

Yadav, K.K.; Singh, D.K.; Kotekar, M.K.; Anitha, M.; Vijayalakshmi, R.; Singh, H.

2010-01-01

Full text: A novel process based on synergistic mixture of 1.5 M D2EHPA (di 2 ethyl hexyl phosphoric acid) + 0.2 M TBP (tri-n-butyl phosphate) to recover uranium from wet process phosphoric acid (WPA) has been developed. Though the equilibrium study for the above process has been investigated in detail its kinetic behavior has not been reported so far. The work presented in the paper is an attempt to study the kinetics of U(VI) stripping from extractant phase to aqueous phase in a constant interfacial area cell (Lewis cell). Kinetic study of the solvent extraction process helps in designing of equipment and optimizing process condition for the better utilization of solvent inventory. Mass transfer kinetics of stripping of U(VI) from loaded 1.5M D2EHPA+ 0.2M TBP with phosphoric acid (AR) has been studied over a wide range of experimental conditions such as stirring speed, interfacial contact area, phosphoric acid concentration, uranium concentration, extractant concentration in organic phase and temperature. Investigation on effect of stirring speed (100-500 rpm) on stripping of U(VI) showed that the rate constant (k) values increases linearly with increase in stirring speeds from 100 to 300 rpm (0.03 to 0.075 cm/min), while the k values were almost constant (0.0819 cm/min) in 300 to 400 rpm range, beyond 450 rpm the k values again increased due to increased turbulence at the interface. The rate constant value (∼0.0814 cm/min) was found to be independent of interfacial contact area (24.6 to 67.02 cm 2 ) available for mass transfer. The rate constants were found to increase with increase in phosphoric acid concentration (6-10M) and temperature (30-60 deg C), the values being in the range of 0.01 to 0.082 cm/min. The slopes of ln-ln plot showed that the stripping of U(VI) has a second order dependence on phosphoric acid concentration (slope∼2) at temperatures ranging from 30 to 60 deg C. The activation energy value for uranium stripping was found to be in the

Adsorption property of Br-PADAP-impregnated multiwall carbon nanotubes towards uranium and its performance in the selective separation and determination of uranium in different environmental samples.

Science.gov (United States)

Khamirchi, Ramzanali; Hosseini-Bandegharaei, Ahmad; Alahabadi, Ahmad; Sivamani, Selvaraju; Rahmani-Sani, Abolfazl; Shahryari, Taher; Anastopoulos, Ioannis; Miri, Mohammad; Tran, Hai Nguyen

2018-04-15

A newer efficient U(VI) ion adsorbent was synthesized by impregnating Br-PADAP [2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol] onto multiwall carbon nanotubes (MWCNTs). The effects of various operation conditions on uranium adsorption (i.e., pH contact time, temperature, and initial uranium concentration) were systematically evaluated using batch experiments. The results indicated that the uranium adsorption on modified MWNCTs (5.571 × 10 -3 g/mg × min) reached faster equilibrium than that on pristine MWNCTs (4.832 × 10 -3 g/mg × min), reflecting the involvement of appropriate functional groups of Br-PADAP on the chelating ion-exchange mechanism of U(VI) adsorption. Modified MWNCTs (83.4mg/g) exhibited significantly higher maximum Langmuir adsorption capacity than pristine MWNCTs (15.1mg/g). Approximately 99% of uranium adsorbed onto modified MWNCTs can be desorbed by 2.5mL of 1M HNO 3 solution. Therefore, Br-PADAP-modified MWNCTs can server as a promising adsorbent for efficient uranium adsorption applications in water treatment. Subsequently, the proposed solid-phase extraction (using a mini-column packed with Br-PADAP/MWCNT) was successfully utilized for analysing trace uranium levels by the ICP-AES method in different environmental samples with a pre-concentration factor of 300-fold. The coexistence of other ions demonstrated an insignificant interference on the separative pre-concentration of uranium. the detection limit was recognized as 0.14μg/L, and the relative standard deviation was approximately 3.3% (n = 7). Copyright © 2017 Elsevier Inc. All rights reserved.

Spectrophotometric Determination of Microamounts of Uranium previous Extraction with TBP-MIC

International Nuclear Information System (INIS)

Vera Palomino, J.; Palomares Delgado, F.; Petrement, J.; Fernandez Cellini, R.

1962-01-01

Selective extraction of uranium in nitric acid medium with a mixture of Tbp-MIC (1:10) has been achieved. Aluminium nitrate was used as salting agent. Complexing agents were added in order to avoid extraction of impurities. Extraction conditions have been studied so that extraction is almost practically complete in a single run. (Author) 19 refs

Simultaneous determinations of uranium, thorium, and plutonium in soft tissues by solvent extraction and alpha-spectrometry

International Nuclear Information System (INIS)

Singh, N.P.; Zimmerman, C.J.; Lewis, L.L.; Wrenn, M.E.

1984-01-01

A radiochemical procedure for the simultaneous determination of uranium, thorium, and plutonium, in soft tissues has been developed. The weighed amounts of tissues, spiked with 232 U, 242 Pu, and 229 th tracers, are wet ashed. Uranium, thorium, and plutonium are coprecipitated with iron as hydroxides, dissolved in concentrated HCl and the acidity adjusted to 10 M. Uranium and plutonium are extracted into 20% TLA solution in xylene, leaving thorium in the aqueous phase. Plutonium is back-extracted by reducing to the trivalent state with 0.05 M NH 4 I solution in 8 M HCl, and uranium is back-extracted with 0.1 M HCl. Thorium is extracted into 20% TLA solution from 4 M HNO 3 and back-extracted with 10 M HCl. Uranium, thorium and plutonium are electrodeposited separately onto platinum discs and counted alpha-spectrometrically using surface barrier silicon diodes and a multichannel analyzer. The method was developed using bovine liver and applied to dog and human tissues. The mean radiochemical recoveries of these actinides in different organs were better than 70%. 6 references, 2 tables

Behaviour study of trace radioelements in the cycles of uranium conversion

International Nuclear Information System (INIS)

Bertaux, M.

1998-01-01

The aim of this work was to study the presence of ultra-trace radioelements in the cycles of uranium conversion. Radiochemical methods for determining ultra-trace amounts of various elements in uranium have been perfected. These methods are based on the chromatographic separation of anionic complexes and on the measurement of various activities by alpha spectrometry. Thus, the source of these traces has been determined and a work of tracing has been carried out in the Malvesi site (uranium purification unit). This work has revealed an accumulation of these traces in the uranium purification column, consequently to their extraction by the TBP. A decontamination process of weakly contaminated uranium batches has been proposed using the Parex computer model and tested at the industrial scale. This process is based on the U(VI) extraction by the TBP/ISOPAR mixture and on the use of oxalic acid as the complexing agent of the tetravalent actinides in aqueous phase. It has been tested with success during a purification study of a batch of about 4 tons of uranium contaminated by traces of various radioelements. The preliminary study had taken into account the influence of metallic impurities (iron, nickel, copper) on the radioelements complexation by the oxalate ions. (O.M.)

Solid phase extraction of uranium and thorium on octadecyl bonded silica modified with Cyanex 302 from aqueous solutions

International Nuclear Information System (INIS)

Nilchi, A.; Shariati Dehaghan, T.; Rasouli Garmarodi, S.

2013-01-01

A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85-95%. (author)

Probing uranyl(VI) speciation in the presence of amidoxime ligands using electrospray ionization mass spectrometry.

Science.gov (United States)

Mustapha, Adetayo M; Pasilis, Sofie P

2013-10-15

Extraction processes using poly(acrylamidoxime) resins are being developed to extract uranium from seawater. The main complexing agents in these resins are thought to be 2,6-dihydroxyiminopiperidine (DHIP) and N(1),N(5)-dihydroxypentanediimidamide (DHPD), which form strong complexes with uranyl(VI) at the pH of seawater. It is important to understand uranyl(VI) speciation in the presence of these and similar amidoxime ligands to understand factors affecting uranyl(VI) adsorption to the poly(acrylamidoxime) resins. Experiments were carried out in positive ion mode on a quadrupole ion trap mass spectrometer equipped with an electrospray ionization source. The ligands investigated were DHIP, DHPD, and N(1),N(2)-dihydroxyethanediimidamide (DHED). DHED and DHPD differ only in the number of carbons separating the oxime groups. The effects on the mass spectra of changes in uranyl(VI):ligand ratio, pH, and ligand type were examined. DHIP binds uranyl(VI) more effectively than DHPD or DHED in the pH range investigated, forming ions derived from solution-phase species with uranyl(VI):DHIP stoichiometries of 1:1, 1:2, and 2:3. The 2:3 uranyl(VI):DHIP complex appears to be a previously undescribed solution species. Ions related to uranyl(VI):DHPD complexes were detected in very low abundance. DHED is a more effective complexing agent for uranyl(VI) than DHPD, forming ions having uranyl(VI):DHED stoichiometries of 1:1, 1:2, 1:3, and 2:3. This study presents a first look at the solution chemistry of uranyl(VI)-amidoxime complexes using electrospray ionization mass spectrometry. The appearance of previously undescribed solution species suggests that the uranyl-amidoxime system is a rich and relatively complex one, requiring a more in-depth investigation. Copyright © 2013 John Wiley & Sons, Ltd.

Solvent extraction of uranium from lean grade acidic sulfate leach liquor with alamine 336 reagent

International Nuclear Information System (INIS)

Ramadevi, G.; Sreenivas, T.; Navale, A.S.; Padmanabhan, N.P.H.

2012-01-01

This paper describes the solvent extraction studies carried out on an acidic low assay uranium bearing leach liquor generated during sulfuric acid leaching of a refractory uranium ore using alamine 336-isodecenol-kerosene reagent combine. The leach liquor has a U 3 O 8 content of about 270 mg/L, free acidity 2.4 N H 2 SO 4 and total dissolved solids concentration of 260 g/L. Process parameteric variation studies indicated strong influence of free acidity of the leach liquor, alamine 336 concentration and aqueous to organic phase ratio on the extraction efficiency of uranium. An extraction efficiency of about 95% was achieved when the free acidity of leach liquor was 1 N H 2 SO 4 or lower, using 2% (v/v) alamine 336 at ambient temperature with an aqueous to organic phase ratio of 1:1. The loading capacity under these conditions was 1.2 g/L of U 3 O 8 . About 98% of the uranium values could be stripped from the loaded organic using 1 N NaCl in 0.2 N H 2 SO 4 . The solvent extraction studies aided in developing a suitable process flowsheet for treating refractory uranium ores which need high acidity during leaching and relatively lower acidity for purification by solvent extraction. (author)

Remediation of soils contaminated with particulate depleted uranium by multi stage chemical extraction

Energy Technology Data Exchange (ETDEWEB)

Crean, Daniel E. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield (United Kingdom); Centre for Radiochemistry Research, School of Chemistry, The University of Manchester (United Kingdom); Livens, Francis R.; Sajih, Mustafa [Centre for Radiochemistry Research, School of Chemistry, The University of Manchester (United Kingdom); Stennett, Martin C. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield (United Kingdom); Grolimund, Daniel; Borca, Camelia N. [Swiss Light Source, Paul Scherrer Institute, Villigen (Switzerland); Hyatt, Neil C., E-mail: n.c.hyatt@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield (United Kingdom)

2013-12-15

Highlights: • Batch leaching was examined to remediate soils contaminated with munitions depleted uranium. • Site specific maximum extraction was 42–50% total U in single batch with NH{sub 4}HCO{sub 3}. • Analysis of residues revealed partial leaching and secondary carbonate phases. • Sequential batch leaching alternating between NH{sub 4}HCO{sub 3} and citric acid was designed. • Site specific extraction was increased to 68–87% total U in three batch steps. -- Abstract: Contamination of soils with depleted uranium (DU) from munitions firing occurs in conflict zones and at test firing sites. This study reports the development of a chemical extraction methodology for remediation of soils contaminated with particulate DU. Uranium phases in soils from two sites at a UK firing range, MOD Eskmeals, were characterised by electron microscopy and sequential extraction. Uranium rich particles with characteristic spherical morphologies were observed in soils, consistent with other instances of DU munitions contamination. Batch extraction efficiencies for aqueous ammonium bicarbonate (42–50% total DU extracted), citric acid (30–42% total DU) and sulphuric acid (13–19% total DU) were evaluated. Characterisation of residues from bicarbonate-treated soils by synchrotron microfocus X-ray diffraction and X-ray absorption spectroscopy revealed partially leached U(IV)-oxide particles and some secondary uranyl-carbonate phases. Based on these data, a multi-stage extraction scheme was developed utilising leaching in ammonium bicarbonate followed by citric acid to dissolve secondary carbonate species. Site specific U extraction was improved to 68–87% total U by the application of this methodology, potentially providing a route to efficient DU decontamination using low cost, environmentally compatible reagents.

Mechanism of extraction of uranium (6) by mixtures of phosphororganic extractants

International Nuclear Information System (INIS)

Skorovarov, D.I.; Ul'yanov, V.S.; Meshcheryakov, N.M.; Lagutenkov, V.A.; Mikheev, M.V.

1988-01-01

Extraction of uranium (6) from sulfuric acid solutions by solution of D2EHPA-TBP(TOPO) mixture in CCl 4 was studied by NMR method (D2HPA-di-2-ethylhexylphosphoric acid, TBP-tributylphosphate, TOPO-trioctylphosphine oxide). It is shown that stability and stoichiometry of formed solvates depends largely on electron-donor ability of organophosphoric base (TBP or TOPO). The presence of neutral base in extractive system leads to blocking of the coordination center of free D2EHPA molecules, growth of the active acid concentration, assisting in additional solvation of uranyl D2EHP molecules and formation of UO 2 (D2EHP) 2 ·nS type complexes. This results in extraction of additional U(6) quantities to organic phase

The thermodynamics of extraction of U(VI) and Th(IV) from nitric acid by neutral phosphorus-based organic compounds

International Nuclear Information System (INIS)

Kalina, D.G.; Mason, G.W.; Horwitz, E.P.

1981-01-01

The extraction of Th(IV) and U(VI) from dilute nitric acid solution by several neutral phosphorus-based extractants has been studied as a function of temperature in the range of 0 to 50 0 C. From the variation of the distribution ratio (Ksub(d)) with temperature the thermodynamic quantities ΔG, ΔH and ΔS have been calculated for these extractions. The results of this study indicate that the steric bulk of the extractant plays a major role in determining how well Th(IV) is extracted. The size of the extractant appears to be of little or no importance in the extraction of U(VI). Similarly, the basicity of the extractant is of lesser importance in the extraction of uranyl ion relative to thorium ion. (author)

Feasibility studies on electrochemical recovery of uranium from solid wastes contaminated with uranium using 1-butyl-3-methylimidazorium chloride as an electrolyte