| 1. |
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| 2. |
- Aneheim, Emma, 1982, et al.
(författare)
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A TBP/BTBP-based GANEX Separation Process. Part 1: Feasibility
- 2010
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 28:4, s. 437-458
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Tidskriftsartikel (refereegranskat)abstract
- A GANEX (Group ActiNide EXtraction) separation system for transmutation has been developed. In this separation process the actinides should be extracted as a group from the lanthanides and the fission and corrosion/activation products. This can be achieved by combining BTBP (bis-triazine-bipyridine) with TBP (tri-butyl phosphate) in cyclohexanone. From 4M nitric acid this organic system extracts the actinides (log(DAm) = 2.19, log(DPu) = 2.31, log(DU) = 1.03, log(DNp) = 0.53) and also separates them from the lanthanides (log(DLa) = -2.0, log(DCe) = -1.72, log(DNd) = -1.05, log(DSm) = -0.18, log(DEu) = -0.02). One problem encountered is that some of the fission and corrosion products are also extracted. The new system however still looks feasible.
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| 3. |
- Aneheim, Emma, 1982, et al.
(författare)
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A TBP/BTBP-based GANEX Separation ProcessPart 2: Ageing, Hydrolytic, and Radiolytic Stability
- 2011
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 29:2, s. 157-175
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Tidskriftsartikel (refereegranskat)abstract
- The waste from nuclear power plants worldwide has to be isolated from man and his environment for about 100,000 years to equal the levels of natural uranium. If, however, the long-lived actinides could be separated from the spent fuel and transmuted, then the isolation time could be shortened to about 1,000 years. This does, however, require the selective separation of the actinides from the rest of the waste. Several processes exist for such a separation, of which one is the Group ActiNide Extraction (GANEX) process. A novel GANEX process has been developed at the Chalmers University of Technology utilizing the properties of already well known extractants by combining BTBP and TBP into one solvent. The stability provided by this GANEX solvent towards ageing, hydrolysis, and radiolysis has been investigated. The results show that the actinide distribution ratios are maintained after a long duration of contact with strong nitric acid. The solvent has also been found to be stable towards radiolysis up to 200 kGy in contact with 4 M nitric acid.
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| 4. |
- Aneheim, Emma, 1982, et al.
(författare)
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Development of a Novel GANEX Process
- 2010
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Ingår i: ACS Symposium Series. - Washington, DC : American Chemical Society. - 1947-5918 .- 0097-6156. ; 1046, s. 119-130
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Konferensbidrag (refereegranskat)abstract
- The waste from nuclear power plants has to be isolated from man and his environment for about 100,000 years to be considered safe. It has been suggested that if the long-lived actinides could be separated from the spent fuel and transmuted, the isolation time could be shortened to about 1,000 years. This, however, requires selective separation of parts of the waste. The partitioning for transmutation research in Europe has for the major part taken place within several European Union Framework Programmes. Within the projects NEWPART, PARTNEW and EUROPART a process scheme for the partitioning of nuclear waste from the PUREX process was developed. The scheme includes the DIAMEX, SANEX and SESAME-processes among which both the DIAMEX and SANEX process has been successfully tested on genuine spent fuel. However, in the latest EU Project ACSEPT, which started in 2008, another approach towards partitioning is being investigated. This is the so called GANEX (Group ActiNide EXtraction) process. In the GANEX process all the actinides in the dissolved spent fuel are extracted as a group and hence separated from the lanthanides as well as the rest of the fission and corrosion/activation products. A novel GANEX process has been developed at Chalmers university of Technology in Sweden. This new process utilizes the properties of already well known extractants by combining BTBP and TBP into one solvent. The system is able to extract U, Np, Pu and Am from strong nitric acid and simultaneously separate these elements from the lanthanides. This is done with sufficiently high distribution ratios and separation factors without the need for any redox control.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Ekberg, Christian, 1967, et al.
(författare)
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Thermodynamics of Dissolution for Bis(triazine)-Bipyridine-Class Ligands in Different Diluents and Its Reflection on Extraction
- 2010
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Ingår i: Journal of Chemical & Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 55:11, s. 5133-5137
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Tidskriftsartikel (refereegranskat)abstract
- Hydrochemical separation processes are one of the methods used for the treatment of spent nuclear fuel. Solvent extraction is also used in many other non-nuclear applications like the mining industry. In the nuclear case, hydrochemical separation processes are already employed in the world today for the recovery of uranium and plutonium. The method is however also considered for future separation systems for use in combination with the transmutation of the minor actinides. In a hydrochemical separation process the two phases are the pregnant (usually) aqueous feed and the organic phase comprising a diluent together with one or more extractants. One such class of extractants developed for partitioning and transmutation purposes is the bis(triazine)-bipyridine-type (BTBP) molecules. When assessing the feasibility and loading properties of such an extraction system, the solubility of the ligands is of the outmost importance. The understanding of whether the dissolution is enthalpically or entropically driven will also help the understanding of the differences in extraction observed between various diluents and temperatures. In this paper the enthalpy and entropy of dissolution of the BTBP-class ligands have been determined for different diluents. It has also been shown that it is possible to predict the extraction behavior of these molecules in the selected diluent once the solubility is known.
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| 11. |
- Ekberg, Christian, 1967, et al.
(författare)
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Using At-211 as internal alpha radiolysis source allowing for simple detection of radiolysis products
- 2010
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 1879-0895 .- 0969-806X. ; 79:4, s. 454-456
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Tidskriftsartikel (refereegranskat)abstract
- The determination of radiolysis products is an important field both for the basic understanding of the radiolysis process and for process development. The latter case mainly dealing with processes for handling radioactive wastes. There are several kinds of radiolysis processes that originate from the different kinds of radiation. Gamma rays and high-energy beta has a high ability to penetrate barriers while alpha irradiation in principle has to be performed with the radiation emitting nuclide inside the actual sample. This can be a problem since most laboratories able to identify radiolysis products cannot handle alpha contaminated samples. In this paper we suggest the use of At-211 as internal alpha emitting radionuclide. Due to its short half-life and decay to more or less stable daughters the radiolysis products may be examined using normal equipment without causing contamination.
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| 12. |
- Fermvik, Anna, 1978
(författare)
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Comparison of the effect of alpha and gamma radiolysis on the extraction of americium by C5-BTBP in cyclohexanone.
- 2011
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - 0236-5731 .- 1588-2780. ; 289:3, s. 811-817
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Tidskriftsartikel (refereegranskat)abstract
- Solvent extraction is a separation technique suitable for the treatment of used nuclear fuel. Two immiscible phases are contacted and the metals of interest are extracted from one phase into the other, most often using so called extractants. One group of extractants is the bis(triazine)-bipyridine (BTBP) type molecules. These molecules have been developed within EU research programs for the separation of actinides from lanthanides. During such an extraction process, the components of the two phases will be exposed to ionizing radiation, since the used fuel contains many highly radioactive species. Radiolytic reactions can alter the chemistry of the extracting system, and affect the metal extraction by degradation of the extractant and the formation of degradation products. In this paper the effect of irradiation with alpha particles and gamma rays, respectively, has been studied for one of the BTBP type molecules, C5-BTBP.
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| 13. |
- Fermvik, Anna, 1978, et al.
(författare)
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Influence of dose rate on the radiolytic stability of a BTPB solvent for actinide(III)/lanthanide(III) separation
- 2009
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 97:6, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The recently developed ligand MF2-BTBP dissolved in cyclohexanone is a promising solvent for the group separation of trivalent actinides(III) from the lantha-nides(III). Its high stability against nitric acid has been demonstrated recently. Since the solvent is also exposed to a continuously high radiation level in the counter current process, the radiolytic stability of the solvent was examined in this study. Irradiation experiments were carried out up to an absorbed dose of 100 kGy and the effect of the dose rate was investigated. The extraction behaviour for An(III)/Ln(III) separation was studied after radiolysis for evaluation. It was found that during high dose rate irradia-tion the extraction efficiency for both Am(III) and Eu(III) decreased significantly with increasing absorbed dose, whereas during the low dose rate irradiation the extraction efficiencies remained more or less at the same level.
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| 14. |
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| 15. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of C5-BTBP in cyclohexanone irradiated in the absence and precence of an aqueous phase
- 2012
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 100:4, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Spent nuclear fuel contains many highly ra-dioactive species; hence solvents used in reprocessing willbe subjected to radiolysis. In this study, solvents containingone of the BTBP molecules intended for the separation oftrivalent actinides and lanthanides, the so called C5-BTBP,have been subjected to radiolysis and hydrolysis. We presenthere that this compound shows a dramatic decrease in bothdistribution ratios and separation factor when irradiated withhigher doses up to 50 kGy; particularly in the presence ofan aqueous phase. Furthermore, fast hydrolytic degradation isobserved, which significantly contributes to the overall degreeof decomposition. This is supported by speciation studies per-formed by HPLC and LC-MS methods. Proposed structuresof the highest-yield degradation products are presented andthey seem to confirm previously drawn structures for theseproducts. From these studies it can be concluded that thepresence of nitric acid or nitrate during irradiation leads tohigher content of species containing keto groups.
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| 16. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of solvents containing C5-BTBP: identification of degradation products and their dependence on absorbed dose and dose rate
- 2009
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Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 32, s. 6421-6430
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Tidskriftsartikel (refereegranskat)abstract
- Solvents intended for the separation of trivalent actinides from trivalent lanthanides in spent nuclear fuel have been irradiated with gamma-radiation. The solvents initially contained 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone and they were exposed to doses up to 20 kGy. Identification of degradation products was done using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Structures were suggested for a number of degradation products and the relative intensity of the peaks in the MS spectra was estimated. It was clear that the content of the original molecule, C5-BTBP, decreased with dose, while the content of the various degradation products increased. It was also shown that both the choice of diluent and the dose rate (Gy/h) affect the amount of degradation products formed. A degradation scheme was proposed for the radiolytic degradation of C5-BTBP.
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| 17. |
- Fermvik, Anna, 1978
(författare)
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Radiolytic Degradation of BTBP type Molecules for Treatment of Used Nuclear Fuel by Solvent Extraction
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nuclear fuel that has been discharged from nuclear reactors is highly radiotoxic and must be kept isolated from the biosphere for very long time periods. This requires an advanced final repository. One way to decrease the long-term radiotoxicity and thermal load of the used fuel is Partitioning and Transmutation (P&T).In a transmutation process, a long-lived nuclide can be transformed into a stable nuclide, or a nuclide with a shorter half-life. Most transmutation techniques require an efficient separation (partitioning) of the elements to be transmuted. One technique suitable for separating different elements in the used nuclear fuel is solvent extraction.Because of the many highly radioactive elements in the used fuel, the solvents used in separation processes will be exposed to considerable doses of radioactivity.Solvents containing extractants belonging to the BTBP (6,6’-bis(5,6-dialkyl-[1,2,4-]triazin-3-yl)-2,2’-bipyridine) family were irradiated. Different types of radiation and different doses and dose rates were used.The effect of irradiation was studied with respect to altered metal extraction, change in BTBP concentration and formation of degradation products. In general, the BTBP concentration, the metal extraction, and the separation of different metals decreased with an increase in the absorbed dose.Degradation pathways were identified for a number of degradation products. Similar products were found regardless of whether the degradation was caused by ageing, radiolysis or hydrolysis. Products resulting from the degradation of C5-BTBP seem to extract metals. Degradation of CyMe4-BTBP, resulted in degradation products systematically different from those of C5-BTBP.
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| 18. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolytic Degradation of Heterocyclic Nitrogen Containing Ligands from Low Dose-Rate Gamma Sources
- 2010
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Ingår i: ACS Symposium Series. - Washington, DC : American Chemical Society. - 1947-5918 .- 0097-6156. ; 1046, s. 215-229
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Konferensbidrag (refereegranskat)abstract
- Chemical processes intended for the separation of various elements in used nuclear fuel will inetvitably take place in an environment exposed to ionizing radiation. Solutions used in liquid-liquid extraction processes must therefore be resistant towards radiolysis. This study presents a collection of radiolysis experiments with BTP and BTBP type molecules carried out at Chalmers University of Technology over a period of several years. The molecules both aim to extract trivalent actinides into an organic phase while leaving lanthanides in the aqueous phase. Detailed knowledge about the radiolysis behavior of BTP and BTBP type molecules can enhance the design of new, more radiolytically stable extractants and facilitate any future implementation of triazine containing ligands in an industrial process. Results show that many factors, e.g. dose rate and diluent composition, influence the radiolytic stability of these molecules. There are also strong indications that the radiolysis products of the BTBP ligand are still able to coordinate and extract metal ions, effectively altering the chemical equilibrium constants.
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| 19. |
- Fermvik, Anna, 1978, et al.
(författare)
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Semi-quantitative and quantitative studies on the gamma radiolysis of C5-BTBP
- 2011
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 99:2, s. 113-119
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Tidskriftsartikel (refereegranskat)abstract
- An industrial liquid liquid extraction process for reprocessing of spent nuclear fuel will inevitably lead to radiolysis of the phases, since the process streams contain highly radioactive species. Solvents containing one of the BTBP (6,6'-bis(5,6-dialkyl-[1,2,4]-triazin-3-yl)-2,2'-bipyridine) molecules intended for the separation of trivalent actinides (An) from lanthanides (Ln), the so called C5-BTBP, have shown a dramatic decrease in both distribution ratios and An/Ln separation factor when irradiated; hence, the molecule is highly unstable towards radiolysis. HPLC-, APCI(+)-MS and LC-MS analyses were performed on irradiated solvents containing initially 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone. The decrease in concentration of starting molecule as well as the increase in concentration of various degradation products were studied with quantitative and semi-quantitative measurements. Structures were suggested for the degradation products produced in highest yields and these were compared to previously proposed structures for the same products.
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| 20. |
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| 21. |
- Fermvik, Anna, 1978
(författare)
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The effect of radiolysis of BTBP type molecules on distribution ratios
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Partitioning and transmutation of spent nuclear fuel enables a decrease in the long term radiotoxicity and volume of the waste to be disposed. By transforming the long-lived nuclides into shorter-lived or even stable ones, the time required for a final repository to be regarded safe for the environment can decrease from 100,000 years to less than 1,000 years. To enable these transformations, the elements with long-lived nuclides need to be separated from the rest of the fuel, and possibly also from each other. One way to perform this separation is solvent extraction and one type of organic ligands developed to be used in the separation process is the BTBP (6,6’ bis(5,6 dialkyl [1,2,4-]triazin 3 yl) 2,2’-bipyridine) family.This work aims at investigating how organic solvents containing BTBP type molecules are affected when exposed to irradiation. In an industrially implemented process the feed streams can contain many highly radioactive nuclides and the radiation will be extensive, and it is thus important that the radiolytic stability of the solvent is well known. It was shown that γ irradiation may increase or decrease both distribution ratios and separation factors for solvents containing BTBP ligands. The behaviour depends on both the type of BTBP molecule and the diluent.The effect of varying the dose rate was also investigated, and a number of future studies are suggested.
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| 22. |
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| 23. |
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| 24. |
- Retegan Vollmer, Teodora, 1979, et al.
(författare)
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Electrospray Ionization Mass Spectrometry Investigation of BTBP - Lanthanide(III) and Actinide(III) Complexes
- 2009
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 27:5-6, s. 663-682
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of nuclear waste reprocessing, the separation processes of minor actinides from fission products are developed using liquid-liquid extraction. To gain an understanding of the mechanism involved in the extraction process, a complex formation of actinides and lanthanides with BTBPs (6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines) was characterized using the Electrospray Ionization Mass Spectrometry (ESI-MS) technique. This study was carried out to compare the influence of diluents and side groups of the extractants on complex formation. Three different diluents, nitrobenzene, octanol and cyclohexanone, and two extractants, C5-BTBP and CyMe4-BTBP, were selected for this experiment. It was found that the change of the diluent and of the substituent on the BTBP moiety does not modify the stoichiometry of the complexes which is L2M(NO3)3. It is proposed that one nitrate is directly coordinated to the metal ion, the two other anions probably remaining in the outer coordination sphere. The difference observed in extracting properties is probably due to the solvation of the complexes by the diluent. The noncovalent force that holds complexes together are likely to be largely governed by electrostatic interactions even if the hydrophobic exterior of the complexes plays an important role in the complexation/extraction mechanism. The study of the stability of the ions in the gas phase shows that the C5-BTBP ligand has a labile hydrogen atom, which is a fragility point of C5-BTBP.
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| 25. |
- Retegan Vollmer, Teodora, 1979, et al.
(författare)
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Extraction of actinides with different 6,60-bis(5,6-dialkyl-[1,2,4]-triazin-3-yl)[2,20]-bipyridines (BTBPs)
- 2007
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Ingår i: SOLVENT EXTRACTION AND ION EXCHANGE. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 25:4, s. 417-431
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Tidskriftsartikel (refereegranskat)abstract
- The extraction of Am(III), Th(IV), Np(V), and U(VI) from nitric acid by 6,6′‐bis(5,6‐dialkyl‐[1,2,4]‐triazin‐3‐yl)‐[2,2′]‐bipyridines (C2‐, C4‐, C5‐, and CyMe4‐BTBP) was studied. Since only americium and neptunium extraction was dependent on the BTBP concentration, computational chemistry was used to explain this behavior. It has been shown that the coordination of the metal played an important role in forming an extractable complex into the organic phase, thus making it possible to extract pentavalent and trivalent elements from tetravalent and hexavalent elements. This is very important, especially because it shows other possible utilizations of a group of molecules meant to separate the actinides from the lanthanides. In addition, the level of extraction at very low or no BTBP concentration was explained by coordination chemistry.
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| 26. |
- Retegan Vollmer, Teodora, 1979, et al.
(författare)
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Synthesis and Screening of t-Bu-CyMe4-BTBP, and Comparison with CyMe4-BTBP
- 2014
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 32:7, s. 720-736
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Tidskriftsartikel (refereegranskat)abstract
- The effect of adding a t-butyl group to the core molecule of CyMe4-BTBP, with the aim of improving solubility in organic diluents, has been studied with regard to the extraction of Am(III) and Eu(III) from HNO3. Synthesis of t-Bu-CyMe4-BTBP is described in detail. Metal nitrates are extracted from nitric acid in the form of 1:2 complexes, M(NO3)(3)(BTBP)(2). Whether in 1-octanol, kerosene, or cyclohexanone diluents, t-Bu-CyMe4-BTBP extracts with larger distribution ratios but with slower kinetics than CyMe4-BTBP. The general trends previously observed for CyMe4-BTBP regarding the diluent and modifier influence were also found for t-Bu-CyMe4-BTBP.
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| 27. |
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| 28. |
- Ahlström, Per-Erik, et al.
(författare)
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- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)
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