Chemical study on the separation and purification of promethium-147

A chemical process for the separation of¹⁴⁷Nd/¹⁴⁷Pm from fission products of synthetic radioactive waste solution has been developed. The process includes: (1) denitration, (2) removal of high concentration of uranium by 30% TBP/kerosene extraction, (3) removal of⁹⁵Nb,¹⁰³Ru,¹³⁷Cs and part of⁹⁰Sr by 50% TBP/dodecane extraction, (4) separation of¹⁴⁷Nd/¹⁴⁷Pm from part of⁹⁰Sr and⁹⁵Zr by oxalic acid precipitation, and (5) removal of¹⁴⁴Ce by mixture of 0.4M D2EHPA and 0.2M TBP extraction. Experimental results indicate that the recovery of¹⁴⁷Nd/¹⁴⁷Pm in the final separated solution is about 90%. The purification of¹⁴⁷Nd and¹⁴⁷Pm from some other rare earth elements, viz.¹⁵³Sm,¹⁵⁴Eu and¹⁴⁴Ce was further investigated by using a Dowex 50W×8 ion-exchanger. Parameters of flow rate, eluent concentration and pH were examined. The results show that the recovery and radionuclide purity of¹⁴⁷Nd plus¹⁴⁷Pm under the present separation conditions are 77.8% and 98.6% for diethylenetriaminepentaacetic acid (DTPA) and 87.3% and 99.5% for nitrilotriacetic acid (NTA), respectively.     

Chemical separation of plutonium

Plutonium in nanogram quantities was isolated from uranium targets irradiated with charged particles. High decontamination was achieved using a method that combines anion exchange with extraction chromatography in tributyl phosphate/hydrochlorid acid solution system.     

Extraction and separation of141Ce and153Gd with HDEHP

Studies on liquid-liquid extraction of trace level cerium and gadolinium,¹⁴¹Ce and¹⁵³Gd, from HCl and HNO₃ media with liquid cation exchanger, HDEHP reveal that a quantitative separation of the elements from an admixture of the two radioisotopes can be achieved with 0.1% HDEHP and 0.01N HCl. The condition is also valid for separation of trace amount of¹⁵³Gd from bulk or macro quantity of cerium.     

Chemical separation of the unknown isotope 252Bk

Rapid chemical separation of berkelium is essential in order to measure the unknown isotope ²⁵²Bk. An anion exchange system of mineral acid and methanol was examined. An elution curve of Bk was obtained using ²⁵⁰Bk produced by the ²⁴⁸Cm+¹⁸O system and the ²⁵¹Bk activity could be measured in the preliminary experiments. The whole chemical separation was completed within 30 minutes.     

Chemical methods of stable isotope separation

The least expensive chemical methods of stable isotope separation are discussed. Between them are especially known chemical exchanges used for separation of boron, nitrogen and sulfur isotopes, low temperature rectification applied for enriching rare isotopes of carbon and oxygen and cryogenic adsorption served for obtaining very pure deuterium. The most important characteristics of installations, processes and working conditions are represented.     

Using two-dimensional time resolved light scattering to study the cure reaction induced phase separation process of epoxy-amine-polyethersulfone blend with secondary phase separation

<正>The generalized two-dimensional correlation analysis based on time-resolved light scattering patterns(2D TRLS) has been employed to study the phase separation process of an epoxy-amine-polyethersulfone blend in which the secondary phase separation takes place.The results of the 2D TRLS provided more detailed information that was not readily observed in the 1D TRLS patterns.(i) During the first process of phase separation,the sequential order of coarsening in size of the domains among the larger and smaller ones has been reversed between the diffusion regime and the hydrodynamic regime. (ii) The change of the larger domains in size,due to the hydrodynamic flow in the late stage of the first phase separation process,keeps on taking place earlier than that of the new domains appeared in the secondary phase separation process. (iii) During the secondary phase separation process the size growth of the smaller domains takes place earlier than that of the larger ones,probably due to the assumption that the coarsening mode could decrease the interface tension more quickly.     

Entropic changes control the charge separation process in triads mimicking photosynthetic charge separation

Laser-induced optoacoustic spectroscopy (LIOAS) measurements with carotene-porphyrin-acceptor "supermolecular" triads (C-P-A, with A = C60, a naphthoquinone NQ, and a naphthoquinone derivative, Q) were carried out with the purpose of analyzing the thermodynamic parameters for the formation and decay of the respective long-lived charge separated state C*+-P-A*-. The novel procedure of inclusion of the benzonitrile solutions of the triads in Triton X-100 micelle nanoreactors suspended in water permitted the separation of the enthalpic and structural volume change contributions to the LIOAS signals, by performing the measurements in the range 4-20 degrees C. Contractions of 4.2, 5.7, and 4.2 mL mol-1 are concomitant with the formation of C*+-P-A*- for A = C60, Q and NQ, respectively. These contractions are mostly attributed to solvent movements and possible conformational changes upon photoinduced electron transfer, due to the attraction of the oppositely charged ends, as a consequence of the giant dipole moment developed in these compounds upon charge separation ( approximately 110 D). The estimations combining the calculated free energies and the LIOAS-derived enthalpy changes indicate that entropy changes, attributed to solvent movements, control the process of electron transfer for the three triads, especially for C-P-C60 and C-P-Q. The heat released during the decay of 1 mol of charge separated state (CS) is much smaller than the respective enthalpy content obtained from the LIOAS measurements for the CS formation. This is attributed to the production of long-lived energy storing species upon CS decay.     

Chemical separation and determination of traces of phosphorus

Summary A rapid procedure for the concentration of highly diluted aqueous solutions containing traces of phosphorus (down toca. 0.0025 p. p. m.) is described. The method is based upon (a) selective carrying of P(V) by ignited BaSO₄ or SrSO₄ in presence of a suitable charge determining cation, (b) stripping the carried phosphorus quantitatively in small volume of HC1 solution. The phosphorus concentrate is then spectrophotometrically determined by the molybdenum blue method, and the amount of the trace element in the original sample is estimated by applying a radiometric correction factor. Conditions have been worked out for applying the method in presence of the following interfering ions: As(III) (400 p. p. m.), Al³⁺ (200 p. p. m.), Fe³⁺ (200 p. p. m.), and over 1000 p. p. m. of each of Ca²⁺, Mg²⁺, Cu²⁺, Mn²⁺ and Cr³ ions. The net recovery (uncorrected) of phosphorus in the concentrated form comes toca. 98–99%, and the net error of estimation after correction can be minimised to the limit of accuracy of spectrophotometric determination.

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Zusammenfassung Die rasche Anreicherung von Phosphorspuren (zirka 0,0025 ppm) aus hochverdünntea wäßrigen Lösungen wurde beschrieben. Sie beruht a) auf der selektiven Adsorption von P(V) an geglühtes BaSO₄ oder SrSO₄ in Gegenwart eines geeigneten Kations; b) auf der quantitativen Überführung des adsorbierten Phosphors in ein kleines Volumen Salzsäure. Der angereicherte Phosphor wird dann nach der Molybdänblaumethode bestimmt und die Menge des in der ursprünglichen Probe enthaltenen Spurenelementes mit einem radiometrischen Korrekturfaktor ermittelt. Die Arbeitsbedingungen bei Anwesenheit der störenden Ionen As(III) (400 ppm), Al(III) (200 ppm), Fe(III) (200 ppm) und über je 1000 ppm Ca, Mg, Cu(II), Mn(II) und Cr(III) wurden ermittelt. Die unkorrigierte Ausbeute an Phosphor in der angereicherten Form beträgt etwa 98 bis 99%, der Fehler nach der Korrektur entspricht der Genauigkeitsgrenze der spektrophotometrischen Bestimmung.

     

Chemical separation techniques for neutron activation analysis as used at the Dow Chemical Co

The chemical separation techniques used at the Dow Chemical Co. are discussed.     

Forbidden transition LIINII in the spectrum of gadolinium-64

Using a 40 cm curved mica crystal spectrograph of the transmission type, the L spectrum of gadolinium has been investigated. The forbidden transition L_IIN_II at λ = 1618.9 X.U. has been reported for the first time.     

Effect of flow-rate on ethanol separation in membrane distillation process

The separation of diluted ethanol solutions and fermentation broths by membrane distillation was investigated. The influence of stream flow-rate on the ethanol flux was studied. An evaluation of the process conditions on the separation degree of ethanol was performed with the application of hydrophobic capillary membranes composed of polypropylene. By removing the alcohol via membrane distillation, it is possible to achieve a higher content of ethanol in the permeate than that in the broth. The enrichment coefficient amounted to 4–6.5, and decreased with an increase of the ethanol concentration in the broth. It was found that the flow-rate affects the value of the enrichment coefficient. A positive influence of carbon dioxide on the ethanol transport through the capillary membrane was observed. The evolution of CO₂ bubbles from the broth increases the stream turbulence, probably enhancing the alcohol concentration in the layer adjacent to the membrane surface.     

Chemical and radiochemical separation of strontium and yttrium

Summary A procedure is presented for the chemical and radiochemioal separation of strontium and yttrium in mixtures which is based on the selective carrying of strontium by ignited barium sulphate leaving yttrium in the solution phase; the carried strontium is recovered by leaching with aqueous hydrochloric acid solution. In order to make strontium radiochemically free from yttrium activity, an initial isotopic dilution of the latter with 1 mg of inactive yttrium is an essential requirement. The method is applicable to chemical analysis of mixtures involving 1 to 3 mg of strontium and 1 to 16 mg of yttrium, both components being determined complexometrically after separation.

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Zusammenfassung Ein Verfahren zur chemischen und radioehemischen Trennung von Strontium und Yttrium in Gemischen wurde vorgeschlagen, das auf der selektiven Abscheidung von Sr mit geglühtem Bariumsulfat beruht, wobei Y in der Lösung zurückbleibt; Sr wird dann mit wäßriger Salzsäure ausgewaschen. Um jede radiochemische Y-Aktivität aus dem Sr zu entfernen, ist es wesentlich, vorher mit 1 mg Y-Isotop zu verdünnen. Das Verfahren ist für die chemische Analyse von Gemischen aus 1 bis 3 mg Sr und 1 bis 16 mg Y verwendbar. Die beiden Komponenten werden nach der Trennung komplexometrisch bestimmt.

     

Probing the bent bonds in cyclopropane systems for gas storage and separation process: A computational study

The hydrogen, carbon dioxide, and carbon monoxide gas adsorption and storage capacity of lithium-decorated cyclopropane ring systems were examined with quantum chemical calculations at density functional theory, DFT M06-2X functional using 6-31G(d) and cc-pVDZ basis sets. To examine the reliability of M06-2X DFT functional, a few representative systems are also examined with complete basis set CBS-QB3 method and CCSD-aug-cc-pVTZ level of theory. The cyclopropane systems can bind to one Li⁺ ion; however, the corresponding the methylated systems can bind with two Li⁺ ions. The cyclopropane systems can adsorb six hydrogen molecules with an average binding energy of 3.8 kcal/mol. The binding free energy (ΔG) values suggest that the hydrogen adsorption process is feasible at 273.15 K. The calculation of desorption energies indicates the recyclable property of gas adsorbed complexes. The same number of CO₂ and CO gas molecules can also be adsorbed with an average binding energy of −14.4 kcal/mol and −10.7 kcal/mol, respectively. The carbon dioxide showed ~3–4 kcal/mol better binding energy as compared to carbon monoxide and hence such designed systems can function as a potential candidate for the separation of these flue gas molecules. The nature of interactions in complexes was examined with atoms in molecules analysis revealed the electrostatic nature for the interaction of Li⁺ ion with cyclopropane rings. The chemical hardness and electrophilicity calculations showed that the gas adsorbed complexes are rigid and therefore robust as gas storage materials.     

Two-column simulated moving-bed process for binary separation

A two-column simulated moving-bed system has been developed for binary separation. The system combines a flexible node design, robust pump configuration, and cyclic flow-rate modulation to exploit the benefits of simulated counter-current operation. The feasibility of the proposed two-column system is demonstrated on the linear separation of two nucleosides by reversed phase. Emphasis is given to the potentialities of the process compared to single-column batch chromatography with recycling for the same amount of stationary phase. The performance of the proposed two-column process is verified with laboratory-scale experiments and detailed simulations for different difficulties in separation and desorbent-to-feed ratios.     

Chemical separation for identification of new isotope202Pt

A separation procedure of trace platinum from large amounts of mercury and other interfering elements is described. After irradiation, the HgO target was dissolved in concentrated HCl solution. The thallium fraction was removed by solvent extraction with ether. In the aqueous phase after extraction the radioisotope of platinum produced by irradiation was precipitated as (NH₄)₂PtCl₆ by adding a saturated solution of NH₄Cl in the presence of H₂PtCl₆·6H₂O as stable carrier. The decontamination factor of mercury, gold and thallium and the recovery of platinum in the process of separation are satisfactory.     

Chemical recycling of polyurethanes and separation of the components by supercritical ammonia

Chemical recycling of a polyurethane elastomer and a flexible foam based on methylenebis(phenyl isocyanate) (MDI) and a polyetherpolyol was performed by ammonolytic cleavage of urethane and urea bonds under supercritical conditions. Resulting products were the polyols, the amines corresponding to the isocyanates used, and unsubstituted urea. Under suitable conditions the polyetherpolyol was completely separated from the other ammonolysis products which in turn can be further separated and used for the manufacture of polyurethanes or for the synthesis of diisocyanates.     

Chemical cross-linking modification of polyimide membranes for gas separation

We have developed an extremely simple room temperature chemical cross-linking technology for the modification of polyimide films for gas separations of He/N₂ and O₂/N₂. Using 6FDA-durene as an example, chemical modification is performed by immersing the dense 6FDA-durene films in a p-xylenediamine methanol solution for a certain period of time followed by washing with fresh methanol and drying at ambient temperature. The chemical structure changes during the cross-linking process were monitored by FTIR, which indicated that imide groups were turned to amide groups during the modification process. TGA analyses showed cross-linked polyimides were thermally stable for gas separation applications. Gas permeation properties of modified polyimides to He, O₂, N₂ and CO₂ were measured at 35°C and 10 atm. It is found that the gas permeability decreased significantly in the order of CO₂>N₂>O₂>He with an increase in the degree of cross-linking, which were mainly attributed to the significant decreases in diffusion coefficients. The permselectivities of He/N₂ and O₂/N₂ increased from 10 to 86 and from 4.1 to 5.9, respectively, but CO₂/N₂ decreased from 12 to 5.4, which suggest this cross-linking approach is most useful for the application of He/N₂ and O₂/N₂ separations.     

Chemical separation of thallium from mercury by extraction chromatography

Thallium-201 was obtained by irradiating natural mercury with protons from IPEN's CV-28 Cyclotron. The chemical separation process chosen to separate thallium from mercury was an extraction chromatography technique. It consists on the passage of aqueous solutions (mobile phase), containing the elements that will be separated, through a glass column packed with an inert powder (support) saturated with the extractant (stationary phase).     

Comparative study on separation of diastereomers by HPLC

Summary Reversed (RP-HPLC) and normal phase chromatographic (NP-HPLC) separations have been developed for diastereomers ofN-acyl-1-methyl-1,2,3,4-tetrahydo-β-carbolines which are acylated derivatives of simple natural β-carboline alkaloids. Separations of derivatives having different acyl moieties in theO,O-diacyl-tartaric acid ester subtituent differed remarkably. Little or no resolution in either NP-HPLC or RP-HPLC could be achieved with the diacetyl-tartrate derivative. Base-line separation by RP-HPLC but no separation by NP-HPLC was possible with the bulkier and more apolar dipivaloyl derivative. Retention order of the bis-benzoylated diastereomers was reversed and separation time increased dramatically by RP-HPLC. Good separation of the medium polarity, but rigid,N-camphanyl derivative by NP-HPLC has been achieved, whereas RP-HPLC could not be used for separation of these diastereomers. Separability of different diastereomers was highly dependent on polarity and rigidity of the derivatizingN-acyl moieties. Conformational analysis by molecular mechanics and comparison of the lowest energy conformational states of the diastereomers was applied to rationalise separation-retention behaviour of stereoisomers by RP-HPLC. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001