Isotope Separation Factor Research Articles

Metal–organic frameworks (MOFs) as highly efficient agents for boron removal and boron isotope separation

A variety of MOFs were observed with ZIF-8, to our knowledge, showing the highest boron uptake and MIL-101(Cr) with an unprecedentedly high boron isotope separation factor.

Theoretical Calculation of Boron Isotopic Separation Factors in Ion-Exchange Chromatography

N-Methylglucamine-modified polystyrene (NMG = N-methylglucamine) is a boron-specific resin widely used to remove boron from water by ion-exchange chromatography, which is reported to have the highest separation factor of boron isotopes (10B and 11B) up to date. In this paper, we calculated its boron isotopic separation factor (S) by quantum chemistry. Boric acid in the mobile phase is expected to interact with the functional group of the resin to form a monochelate complex. The polymer chain of the resin is proved to have little influence on S. HF/6-31G level of theory well meets the expectation of current calculations, while the higher level theories (B3LYP, M06-2X, and MP2) lead to larger errors. The inclusion of thermal scaling factors and explicit solvent molecules bring negligible improvement to S. The change of S with different pH values was obtained as well. Finally, S of various functional groups of chelating resins were calculated, among which phenols and carboxylic acids are found to have a dist...

Hydrogen isotope effect on thermodynamic properties of Pd0.9X0.1 (X = Cu, Ag and Au) alloys

The effect of hydrogen isotopes on the thermodynamic parameters of desorption reaction in the Pd0.9X0.1-H2/D2 systems (X = Cu, Ag and Au) were investigated using Sieverts' apparatus. The hydrogen/deuterium desorption pressure-composition-temperature profiles generated in this study revealed substantial hydrogen isotope effect on the equilibrium plateau pressures with Peq (D2) > Peq (H2). A correlation was observed for the trend in equilibrium plateau pressures with the unit cell sizes of the Pd0.9X0.1 alloys. Hydrogen isotope separation factor was determined for all these alloys and Pd0.9Cu0.1 alloy was found to have highest separation factor. The results of equilibrium plateau pressure and the separation factor for Pd0.9Cu0.1 alloys merits its candidature for its applicability in gas chromatographic separation of hydrogen isotopes.

Comparison of models for multi-component hydrogen isotope mixtures absorbing in or permeating through metals

In the first place, dependences of isotope effects on temperature and compositions are discussed among hydrogen isotopes (H, D and T) absorbing in, diffusing or permeating through metals. Relation between the isotope effects and isotope separation factor is investigated when hydrogen isotope mixtures are absorbed in, diffuse or permeate through metals. Previous experimental results for the absorption of hydrogen isotopes in Pd or Li are correlated as a function of composition and temperature, and they are discussed based on several models proposed previously to explain the relation between the isotope effects and the isotope separation factor. It results in a fact that the ideal solution model with dissociation on metal surfaces can correlate most cases of absorption of hydrogen isotopes in Pd or Li. However, unresolved experimental results still remained that there is a quantitative difference in permeation rates when either H2+D2 or H2+D2+HD mixture is supplied to the high-pressure side of a gaseous phase.

Study of isotope effect upon lithium iodide complexation with benzo-15-crown-5 in water–chloroform extraction system

Extraction characteristics of chloroform–water system in lithium iodide extraction with benzo-15-crown-5 (B15C5) were studied. The complexation of the crown ether with LiI in organic phase was shown by IR spectroscopy. Isotope effect multiplication was performed by extraction chromatography technique. The magnitude of isotope separation factor (α) for 6Li-7Li pair was 1.017. The light lithium isotope is concentrated in organic phase.

Lithium isotope effects in extraction of lithium chloride by benzo-15-crown-5 in the 1,1,7-trihydrododecafluoroheptanol–water system

The extraction characteristics of the 1,1,7-trihydrododecafluoroheptanol water system have been studied for lithium chloride as the salt to be extracted and benzo-15-crown-5 as the extracting agent, as well as blank extraction of lithium chloride in this system. Single-stage lithium isotope separation factors (a) have been measured at various lithium chloride concentrations in water, and the isotope effect has been multiplied by extraction chromatography. The value of a for the Li6–Li7 pair was 1.024. The light lithium isotope is concentrated in the organic phase.

Lithium and boron isotope effects in extraction systems

Extraction characteristics of chloroform-water system were studied using lithium chloride and tetrafluoroborate as extracted salts and benzo-15-crown-5 as an extractant. Single-stage isotope separation factors (α) for lithium isotopes at different concentrations of lithium chloride in water were measured and multiplication of isotope effect was made by extraction chromatography. The magnitude of α for Li6-Li7 pair was 1.036 for chloride and 1.030 for tetrafluoroborate. Light lithium isotope is concentrated in organic phase. Extraction chromatography experiments were conducted in 1,1,7-trihydrododecafluoroheptanol-water extraction system for boron isotope separation using boric acid as extracted compound and trioctylamine as an extractant as well as in chloroform-water system with lithium tetrafluoroborate as extracted compound and benzo-15-crown-5 as an extractant. The upper assessment of α values for B10-B11 boron isotopes was found to be not larger than 1.005 for both systems.

Lithium Isotope Effects upon Electrochemical Release from Lithium Manganese Oxide

Abstract Lithium was electrochemically released from lithium manganese oxide (LiMn 2 O 4 ) to an electrolyte solution, a 1:2 v/v mixed solution of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) containing 1 M lithium perchlorate or sodium perchlorate (EC/EMC/LiClO 4 or EC/EMC/NaClO 4 ) to observe the lithium isotope effects that accompanied the lithium release. The lighter isotope of lithium, 6 Li, was preferentially fractionated to the electrolyte solution phase, with the value of the lithium isotope separation factor ranging from 0.989 to 0.971 at 25 °C. The degree of the lithium isotope fractionation was slightly smaller in the LiMn 2 O 4 -EC/EMC/NaClO 4 system than in the LiMn 2 O 4 -EC/EMC/LiClO 4 system. The present systems are in great contrast with the lithium cobalt oxide (LiCoO 2 )-the electrolyte solution systems concerning the direction and magnitude of the lithium isotope effects, which seems mostly ascribable to the structural difference between LiMn 2 O 4 and LiCoO 2。

Nano Cavity Induced Isotope Separation of Zinc: Density Functional Theoretical Modeling

Density functional theoretical calculation was performed to understand the isotopic fraction of zinc in the nano cavity of different crown ethers and crown ethers anchored on solid resin matrix. The structure, energetic, thermodynamics, and vibration IR spectra were also evaluated. The gas phase binding energy of Zn2+ with crown ether of varied cavity can be correlated with NPA charge transfer but no such correlation is obtained with the fraction of electron transfer, ΔN. The reduced partition function ratio (RPFR) of complexes of Zn2+ ion with different solvents, crown ethers, and grafted crown ethers was also computed to predict the isotope separation factor of the Zn2+ ion. The present study reveals that with increasing cavity size of the crown ether the RPFR was found to be decreased leading to a high value of isotope separation factor as observed in the experiments. An attempt was made to correlate the calculated RPFR and separation factor with binding energy of different zinc-crown ether systems. Fu...

Observation of H/D isotope effects on polymer electrolyte membrane fuel cell operations

The hydrogen isotope effects upon operation of a polymer electrolyte membrane fuel cell have been observed. The deuterium concentration in the exhaust hydrogen gas from the cell was found lower than that of the hydrogen gas fed to the cell, which indicated that the heavier isotope of hydrogen was preferentially oxidized at the anode. The overall hydrogen isotopic separation factor between the oxidized and non-oxidized hydrogen ranged from 3.46 to 3.99 and increased with decreasing flow rate of the feed gas or increasing rate of hydrogen utilization.

Separation of Gallium and Indium Isotopes by Cation and Anion Exchange Chromatography

Ion exchange chromatography was applied to study chemical isotope effects of gallium and indium in ligand exchange reactions. A strongly acidic cation and a strongly basic anion exchange resin were used as a solid phase, and aqueous HCl as a liquid phase. On the cation exchanger, the light isotope 69Ga was enriched at the front part of the elution band and the heavy isotope 71Ga at the end part. Instead, the light 113In isotope was enriched at the end part, and the heavy isotope 115In at the front part. The isotope separation factor ϵ is equal to 3.3 × 10–5 for gallium and 2.0 × 10–4 for indium. On the anion exchanger, the heavy gallium isotope was enriched at the front part, whereas the heavy indium isotope at the end part of the band, with ϵ equal to ∼10–3 and 1.7 × 10–4, respectively. This pattern of enrichment is caused by stronger Ga3+–OH2 than Ga3+–Cl− bond, and by inverse order of bond strength for indium. In the displacement method, gallium and indium on anion exchanger also show opposite enrichment of their isotopes, but the ϵ values (1.5 × 10–2 for gallium and 5 × 10–3 for indium) are greater than those found in the elution method, probably due to much higher concentrations of the metals.

Green and efficient extraction strategy to lithium isotope separation with double ionic liquids as the medium and ionic associated agent

The paper reported a green and efficient extraction strategy to lithium isotope separation. A 4-methyl-10-hydroxybenzoquinoline (ROH), hydrophobic ionic liquid—1,3-di(isooctyl)imidazolium hexafluorophosphate ([D(i-C8)IM][PF6]), and hydrophilic ionic liquid—1-butyl-3-methylimidazolium chloride (ILCl) were used as the chelating agent, extraction medium and ionic associated agent. Lithium ion (Li+) first reacted with ROH in strong alkali solution to produce a lithium complex anion. It then associated with IL+ to form the Li(RO)2IL complex, which was rapidly extracted into the organic phase. Factors for effect on the lithium isotope separation were examined. To obtain high extraction efficiency, a saturated ROH in the [D(i-C8)IM][PF6] (0.3 mol l−1), mixed aqueous solution containing 0.3 mol l−1 lithium chloride, 1.6 mol l−1 sodium hydroxide and 0.8 mol l−1 ILCl and 3:1 were selected as the organic phase, aqueous phase and phase ratio (o/a). Under optimized conditions, the single-stage extraction efficiency was found to be 52 %. The saturated lithium concentration in the organic phase was up to 0.15 mol l−1. The free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) of the extraction process were −0.097 J mol−1, −14.70 J mol K−1 and −48.17 J mol−1 K−1, indicating a exothermic process. The partition coefficients of lithium will enhance with decrease of the temperature. Thus, a 25 °C of operating temperature was employed for total lithium isotope separation process. Lithium in Li(RO)2IL was stripped by the sodium chloride of 5 mol l−1 with a phase ratio (o/a) of 4. The lithium isotope exchange reaction in the interface between organic phase and aqueous phase reached the equilibrium within 1 min. The single-stage isotope separation factor of 7Li–6Li was up to 1.023 ± 0.002, indicating that 7Li was concentrated in organic phase and 6Li was concentrated in aqueous phase. All chemical reagents used can be well recycled. The extraction strategy offers green nature, low product cost, high efficiency and good application prospect to lithium isotope separation.

Electrochemical and Isotopic Investigation of 13C-Enriched Oxalic Acid Facilitated with a Vacuum Electrochemical Reactor

The electrolytic decomposition of 13C-enriched oxalic acid was investigated. Oxalic acid and oxalic acid-13C2 were pre-purified by vacuum sublimation and characterized by assay, melting range, and FTIR. An Integrated Vacuum Electrochemical Reactor (IVER) was employed to convert aqueous-phase oxalic acid to CO2 for the 13C-enrichment determinations: oxalic acid solvation, vacuum degas, electrolysis, and mass spectrometric analysis. Highly enriched oxalic acid-13C2 was electrolyzed at 1.5-VDC and the CO2 determined to be 99.5 atom%-13C. Blends of H2C2O4 and H213C2O4 were prepared from 50.5 to 99.5 atom%-13C, dissolved in water, and electrolyzed. For each blend solution, the [12C/13C] isotope separative effect was observed as increases in the (CO2) 13C-enrichment when the aqueous-phase was repeatedly electrolyzed. Furthermore, 50 atom%-13C oxalic acid was electrolyzed while the IVER current was monitored, and thereby the electrolytic isotope separation factor α[12C/13C] is estimated to be 1.03 ± 0.01, at 295 K on platinum. Cyclic voltammograms of 0.10-mole% oxalic acid in water displayed an irreversible oxidation peak at E = +0.95 volt (oxalic acid) and another oxidation peak at E ≥+1.6 volt (water). Cyclic voltammograms of oxalic acid in EMI+BETI− indicate that H2C2O4 can also be oxidized in liquid salts (voltammetric window ∼ 1.4 volt versus Ag/AgCl).

테트라아자 거대고리화합물(TDM, TPM)을 이용한 마그네슘동위원소의 분리에 관한 연구

Tetraazamacrocyclic ion-exchangers, 1,4,8,11-tetraazacyclotetradecane bonded Merrifield peptide resin(TDM), 1,4,8,12-tetraazacyclopentadecane bonded Merrifield peptide resin(TPM) were prepared, and the ion-exchange capacity of these TDM and TPM were characterized. The distribution coefficients in various conc. of NH4Cl for magnesium with ion exchangers were determined by using the batch method. We found the isotope separation factors on new prepared tetraazamacrocyclic ion-exchangers bonded Merrifield peptide resin(TDM, TPM). The isotope separation of magnesium was determined by using of breakthrough method of column chromatography.

Lithium isotope effects upon electrochemical lithium insertion to host material from ionic liquid medium

Lithium was electrochemically inserted from a Li + ion containing ionic liquid into graphite or tin to observe lithium isotope effects that accompanied the insertion. While no preferential uptake of the lithium isotopes was detected with graphite, the lighter isotope, 6Li, was preferentially fractionated into tin with the single-stage lithium isotope separation factors, S, ranging from 1.004 to 1.008 at 25 °C. It was speculated that a Li + ion was inserted into graphite together with an anionic component of the ionic liquid and, upon the reduction of the Li + ion to a lithium atom, the anion was released from graphite, while a Li + ion alone was inserted into tin. Molecular orbital calculations supported this speculation in a qualitative fashion.

High-efficiency technology for lithium isotope separation using an ionic-liquid impregnated organic membrane

The tritium needed as a fuel for fusion reactors is produced by the neutron capture reaction of lithium-6 ( 6Li) in tritium breeding materials. New lithium isotope separation technique using ionic-liquid impregnated organic membranes (Ionic-Liquid-i-OMs) have been developed. Lithium ions are able to move by electrodialysis through certain Ionic-Liquid-i-OMs between the cathode and the anode in lithium solutions. In this report, the effects of protection cover and membrane thickness on the durability of membrane and the efficiency of isotope separation were evaluated. In order to improve the durability of the Ionic-Liquid-i-OM, we developed highly-durable Ionic-Liquid-i-OM. Both surfaces of the Ionic-Liquid-i-OM were covered by a nafion 324 overcoat or a cation exchange membrane (SELEMION™ CMD) to prevent the outflow of the ionic liquid. It was observed that the durability of the Ionic-Liquid-i-OM was improved by a nafion 324 overcoat. On the other hand, the organic membrane selected was 1, 2 or 3 mm highly-porous Teflon film, in order to efficiently impregnate the ionic liquid. The 6Li isotope separation factor by electrodialysis using highly-porous Teflon film of 3 mm thickness was larger than using that of 1 or 2 mm thickness.

Carbon isotope fractionation during dechlorination of 1,2,3,4-tetrachlorodibenzo- p-dioxin by a Dehalococcoides-containing culture

Carbon isotope fractionation was observed during dechlorination of 1,2,3,4-tetrachlorodibenzo- p-dioxin (1,2,3,4-TeCDD) by a mixed culture containing Dehalococcoides ethenogenes strain 195. Fractionation was examined when 1,2,3,4-TeCDD was added as the only chlorinated compound and when 1,2,3,4-TeCDD was added with a known growth substrate, tetrachloroethene (PCE). The 1,2,3,4-TeCDD was dechlorinated to 1,2,4-trichlorodibenzo- p-dioxin (1,2,4-TrCDD) which was enriched in 13C relative to 1,2,3,4-TeCDD with isotope separation factors, ε C, of 1.3 ± 0.2‰ and 1.7 ± 0.4‰ (average ± 95% confidence interval (CI)) in cultures with and without PCE, respectively. The 1,2,4-TrCDD was further dechlorinated to 1,3-dichlorodibenzo- p-dioxin (1,3-DCDD) which was depleted in 13C relative to 1,2,4-TrCDD with ε C of −2.4 ± 0.4‰ and −2.9 ± 0.8‰ (average ± 95% CI) in cultures with and without PCE, respectively. This demonstrates carbon isotope fractionation during sequential reductive dechlorination of PCDDs, where isotope fractionation during dechlorination of the intermediate was substantial and a 13C depleted lightly chlorinated PCDD congener was ultimately formed during dechlorination of more highly chlorinated PCDD congeners. Despite reproducible, statistically significant differences between isotope compositions of the parent, 1,2,3,4-TeCDD and daughter, 1,2,4-TrCDD and 1,3-DCDD congeners in triplicate bottles of both treatments, fractionation factors for 1,2,3,4-TeCDD could not be determined for all replicates by regression analysis of the plot of the Rayleigh equation. It is possible that dissolution of 1,2,3,4-TeCDD imposed a kinetic limitation on dechlorination, thus masking isotope fractionation during its dechlorination.

Lithium Isotope Effect Accompanying Electrochemical Insertion of Lithium into Liquid Gallium

Lithium was electrochemically inserted from a 1 : 2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1M LiClO4 into liquid gallium to observe lithium isotope effects accompanying the insertion. It was observed that the lighter isotope 6Li was preferentially fractionated into liquid gallium with the single-stage lithium isotope separation factors S, ranging from 1.005 to 1.031 at 50 °C and 1.003 to 1.024 at 25 °C. The lithium isotope effects estimated by molecular orbital calculations at the B3LYP/6-311G(d) level of theory agreed qualitatively with those of the experiments, but the quantitative agreement of the two was not satisfactory

Study of uranium isotope separation using CO 2 laser and CO laser

First, the kinetic investigation of UF 6 + HCl reaction and the isotopic selectivity under CO laser irradiation is performed. On this investigation, the kinetics of UF 6 + HCl reaction by using an intracativity CO laser and CO 2 laser irradiation system, and the isotopic selectivity for this process are studied theoretically. It is found that under the resonant CO laser and CO 2 laser irradiations, the laser-catalyzed reaction rate can increase, and a good selectivity can be achieved. The uranium isotope separation factors β calculated are about 2.44 ∼ 4.05 at laser intensity 50 ∼ 100 W cm −2 and temperature 235 K.

Optimization for the tritium isotope separation factor and permeation by selecting temperature and thickness of the diffusion Pd–Ag alloy cathode

Large quantities of tritiated water will be produced in the controlled fusion reactors for power generation. To eliminate the concentrated tritiated water and for recycling tritium, an industrial electrolyzer was developed. The aim of this paper is to give the design of this electrolyzer and the results for optimization in diffusion and in isotopic exchange by selecting thickness of a thimble-shaped Pd–25%Ag cathode working at high temperature and current. In this process, the tritium recovery system is based on the principle of the tritium diffusion Pd–Ag cathode which produces very pure hydrogen isotopes from enriched tritiated water.