Search Results
Abstract
It is important to increase a throughput of the salt removal process from uranium deposits which is generated on the solid cathode of electro-refiner in pyroprocess. In this study, it was proposed to increase the throughput of the salt removal process by the separation of the liquid salt prior to the distillation of the LiCl–KCl eutectic salt from the uranium deposits. The feasibility of liquid salt separation was examined by salt separation experiments on a stainless steel sieve. It was found that the amount of salt to be distilled could be reduced by the liquid salt separation prior to the salt distillation. The residual salt remained in the deposits after the liquid salt separation was successfully removed further by the vacuum distillation. It was concluded that the combination of a liquid salt separation and a vacuum distillation is an effective route for the achievement of a high throughput performance in the salt separation process.
Abstract
Nuclear forensic science has become increasingly important for global nuclear security. However, many current laboratory analysis techniques are based on methods developed without the imperative for timely analysis that underlies the post-detonation forensics mission requirements. Current analysis of actinides, fission products, and fuel-specific materials requires time-consuming chemical separation coupled with nuclear counting or mass spectrometry. High-temperature gas-phase separations have been used in the past for the rapid separation of newly created elements/isotopes and as a basis for chemical classification of that element. We are assessing the utility of this method for rapid separation in the gas-phase to accelerate the separations of radioisotopes germane to post-detonation nuclear forensic investigations. The existing state of the art for thermochromatographic separations, and its applicability to nuclear forensics, will be reviewed.
The works reported in the literature (1994–2015) on the use of surfactants as separation modifiers of organic and inorganic compounds by thin-layer chromatography (TLC) is discussed. A number of adsorbents such as silica gel (plain and modified with surfactants and other compounds), stannous silicate, aminoplast, soil, urea-formaldehyde polymer with cellulose binder, and bismuth silicate have been used as layer materials. Surfactants used for the modification of the mobile and stationary phases in TLC have opened new opportunities for realizing novel separations of analytical importance. The salient features of TLC systems used in the analysis of organic and inorganic mixtures of substances have been provided in the tabular form.
Fifteen urea pesticides have been separated on RP-18WF 254 plates with methanol-water and mixed organic (acetonitrile-methanol, 1:1 v/v )-0.1% aqueous orthophosphoric acid (H 3 PO 4 ) mobile phases (RP-HPTLC), and on silica gel 60F 254 plates with benzene-methanol and benzene-ethanol mobile phases (NP-TLC). The pesticides could be classified into three groups:
- monolinuron (1), chlorotoluron (2), diuron (3), isoproturon (4), and linuron (5) dimefuron (6), diflubenzuron (7), teflubenzuron (8), and lufenuron (9); and thifensulfuron methyl (10), triasulfuron (11), chlorsulfuron (12), rimsulfuron (13), amidosulfuron (14), and tribenuron methyl (15).
Separation of the fluoroquinolone antibiotics has been examined using numerous mobile phases and commercially available TLC plates precoated with silica gel, cellulose, and chemically bonded silica gel (RP-C18). The best separation of the antibiotic standards was achieved on silica gel with methanol-acetone-1 mol L −1 citric acid-triethylamine, 2.8 + 2 + 0.2 + 0.5 ( v / v ) as mobile phase, on cellulose with dichloromethane-isopropanol-THF-25% ammonia, 4 + 6 + 3 + 3 ( v / v ), as mobile phase, and on silanized silica gel RP-C18 with methanol-0.07 mol L −1 phosphate buffer, pH 6–10 mmol L −1 benzyldimethyltetradecylammonium chloride, 6 + 3 + 1 ( v / v ), as mobile phase. The separated compounds were detected under UV irradiation at λ = 254 nm or by treatment of the plate surface with different dyeing agents.
Abstract
An inorganic ion exchanger, quinolinephosphomolybdate has been synthesized and characterized by elemental analysis, infrared (IR) and X-ray diffraction (XRD) spectroscopy. This compound is highly stable toward thermal, chemical and radiation dose. This has been employed in the separation of carrier-free 90Y from its parent 90Sr from an equilibrium mixture. The absorbed daughter was recovered by using 0.0284 mol L−1 ascorbic acid solutions at pH 5.0 as eluting agent.
Chromatographic processes are based on an adsorption-desorption mechanism. By this mechanism the sample is distributed between the porous medium and the mobile phase. External forces, for example perpendicular or parallel electric forces applied to the thin layer chromatographic plates, may effect these processes. In this work, TLC plates were placed perpendicular or parallel to 2.45 ± 0.5 GHz electromagnetic waves (microwaves) to improve chromatographic resolution. Perpendicular arrangement of the microwave field relative to the TLC plate led to the greatest improvement of the separation compared with separation under normal conditions.
Abstract
Separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) is a challenging task in the nuclear fuel cycle due to their similar charge and chemical behaviour. Some soft donor ligands show selectivity for An(III) over Ln(III) due to the formation of stronger covalent bonds with the former. The extraction behaviour of Am(III) and Eu(III) is studied in the present work with a mixture of Cyanex-301 (bis(2,4,4-trimethylpentyl)di-thiophosphinic acid) with several various ‘N’, ‘O’ or ‘S’ donor neutral ligands. Comparison of the data was done with that of the oxygen donor analogue of Cyanex-301, i.e. Cyanex-272 (bis(2,4,4-trimethylpentyl)phosphinic acid). Effect of the organic diluent on the extraction behaviour of Am(III) using Cyanex-301 in presence of ‘N’ donor synergists was also studied. Ab initio molecular orbital calculations were carried out using GAMESS software and charges on the donor atoms were calculated which helped in understanding the co-ordination chemistry of the ligands and explained the separation behaviour.
Thin-layer chromatography (TLC) of fifteen amino acids was performed using silica gel and alumina impregnated with micellar solutions of cetrimide and cetylpyridinium chloride as stationary phases and aqueous solutions of dextrose as mobile phases. TLC system comprising of silica gel impregnated with micellar solution of cetrimide (5.0 mM) as stationary phase and 40% ( w/v ) aqueous solution of dextrose as mobile phase was found the most favourable for the separation of amino acids. Impregnation of silica gel with the micellar solution of cetrimide brings about a substantial change in the mobility of lysine. Separation of lysine (ketogenic) from arginine (glucogenic) is important physiologically. Surface modification of silica gel on impregnation, as indicated by FTIR and SEM studies, was responsible for improved chromatographic performance. The effect on the separation of the presence in the sample of heavy metal cations, as impurities, was examined. Limits of detection for lysine and arginine were 0.17 μg and 0.12 μg, respectively. For validation, the stability of the mixture and the reproducibility of the chromatographic properties Δ R F , separation factor ( k ), and resolution ( R S ) were calculated. The proposed method is simple, rapid, and free from use of volatile organic solvents.
Abstract
This paper describes the development of a separation method for americium from the effluents emanating from anion exchange column, used for the recovery of plutonium from analytical waste solutions. The waste contained uranium, sodium, calcium and iron as the major impurities as estimated by ICP-AES method. ~99% pure americium was obtained by three separation steps using solvent extraction and extraction chromatography techniques. In the first step, uranium was quantitatively separated by giving five contacts of equal volumes of 30% TBP in n-dodecane. Fe and Na were separated in the next step using 0.1 M TODGA + 0.5 M DHOA as the extractant. In the last step, Am was separated from the co-extracted Ca (about 76%) using CMPO loaded extraction chromatographic column. The overall recovery was >80% with decontamination factor (D.F.) from the impurities being >3000 while the purity of the product was 99%.
