On the Diluent and Solvent Effects in Liquid-Liquid Extraction Systems based on Bis-triazine-bipyridine (BTBP) ligands
Doktorsavhandling, 2014

Used nuclear fuel is dangerous for mankind and her environment for a long time. If however, the minor actinides together with uranium and plutonium could be transmuted, i.e. transformed, into more shortlived or stable isotopes the volume of the waste could be significantly reduced together with a reduction in the radiotoxicity. In order to be able to transmute the actinides they need to be separated from fission and corrosion/activation products. One way of achieveing such a separation is through liquid-liquid extraction. One group of specially designed ligands that can achieve a separation of the trivalent actinides from the chemically similar lanthanides is the so called BTBPs (biz-triazine-bi-pyridine). By combining these ligands with tributyl phosphate, TBP, an extraction of all the actinides as one group, (Grouped ActiNide EXtraction) GANEX, can be achieved. As of today, cyclohexanone has been the diluent of choice in this solvent. The solvent has shown very promising extraction and separation results, however, both cyclohexanone and TBP have some drawbacks as parts in a process solvent why alternative diluents to cyclohexanone (hexanol and hexanoic acid) and an alternative ligand to TBP, DEHBA, have been investigated in this work. Thermodynamic extraction data and interfacial tension in BTBP extraction systems have also been investigated. Hexanoic acid did not work as a process diluent, since the extraction of americium and curium was much lower compared to that of plutonium. Hexanol would probably be a better choice, however, not as good as the cyclohexanone based solvent, due to mainly solubility issues of the ligand. The thermodynamic data for the americium extraction has been measured in three different diluents in order to investigate the diluent effect as well as compare the results with older data using C5-BTBP. For process development, the thermodynamic data shows that the extraction of americium and europium as well as their separation decreases as the temperature increases in several diluents. During the work it was also shown that short phase contact time favors the separation of americium from europium.

Solvent effects

Diluent effects

GANEX

Interfacial tension

Density

10an
Opponent: Bruce Moyer

Författare

Elin Löfström Engdahl

Chalmers, Kemi- och bioteknik, Kärnkemi

Solvent effects on the extraction rate in proposed GANEX processes

19th international solvent extraction conference, ISEC 2011,; (2011)

Paper i proceeding

A reinterpretation of C5-BTBP extraction data, performed in various alcohols

Journal of Radioanalytical and Nuclear Chemistry,; Vol. 296(2012)p. 733-737

Artikel i vetenskaplig tidskrift

Comparison of the Extraction as a Function of Time in two GANEX solvents -Influence of Metal Loading, Interfacial Tension and Density

Solvent Extraction and Ion Exchange,; Vol. 31(2013)p. 604-616

Artikel i vetenskaplig tidskrift

Extraction thermodynamics of Am(III) and Eu(III) using CyMe4-BTBP in various organic diluents

Journal of Chemical Thermodynamics,; Vol. 76(2014)p. 64-69

Artikel i vetenskaplig tidskrift

Hexanoic acid as an alternative diluent in a GANEX process: feasibility study

Journal of Radioanalytical and Nuclear Chemistry,; Vol. 290(2014)p. 1261-1266

Artikel i vetenskaplig tidskrift

A Comparison of Americium Extractions as a Function of Time using Two Bis-Triazine-Bipyridine Ligands in Long-Chained Alcohol Diluents

Separation Science and Technology,; Vol. 49(2014)p. 2060-2065

Artikel i vetenskaplig tidskrift

Kärnbränsle som bestrålats i en reaktor är farligt för natur och människor i så lång tid som hundratusentals år. Genom att transmutera, förvandla, de långlivade ämnena i det använda kärnbränslet till mer kortlivade eller stabila isotoper kan det göras mindre farligt. För att kunna transmutera aktiniderna måste de dock separeras från resten av avfallet. Denna separation kan erhållas genom vätske-vätskeextraktion. Vätske-vätskeextraktion bygger på principen att vatten och olja inte blandar sig med varandra. Genom att lösa upp kärnavfallet i syra och sedan tillsätta en oljefas, en organisk fas, innehållande ligander, speciella molekyler som enbart binder och extraherar aktinider, erhålls separationen. En speciell sådan organisk blandning har under de senaste åren komponerats på Chalmers. Fördelen med denna är att den extraherar alla aktinider (uran, plutonium, americium, curium och neptunium) från resten av kärnavfallet i en grupp, varpå hanteringen av rent plutonium minskar och processen därmed blir mer spridningssäker. Processen blir också billigare eftersom antalet extraktionssteg minskar. I detta arbete har denna speciella oljefas undersökts. Även alternativa organiska faser har undersökts. Ytspänning mellan syran och oljefasen har uppmätts. Hur lång tid det tar att extrahera aktiniderna och hur väl de separeras från resten av avfallet har också varit i fokus för arbetet.

Ämneskategorier

Annan kemi

Kemi

ISBN

978-91-7597-085-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

10an

Opponent: Bruce Moyer