Lithium Isotope Separation Research Articles

Separation of Lithium Isotopes by Tetraazamacrocycles Tethered to Merrifield Peptide Resin

Tetraazamacrocyclic ion exchangers tethered to Merrifield peptide resin (DTDM, TTTM) were prepared and the ion exchange capacity of these was characterized. The isotope separation of lithium was determined using breakthrough method of column chromatography. The isotope separation coefficient was strongly dependent on the ligand structure by Glueckaufs theory. We found that the isotope separation coefficients were increased as the values of distribution coefficients were increased. In this experiment the lighter isotope, 6 Li was enriched in the resin phase, while the heavier isotope, 7 Li in the solution phase. The ion radius of lighter isotope, 6 Li was shorter than the heavier isotope, 7 Li. The hydration number of lithium ion with the same charge became small as mass number was decreased. Because 6 Li was more strongly retained in the resin than 7 Li, the isotopes of lithium were separated with subsequent enrichment in the resin phase.

Laser isotope separation of lithium by two-step photoionization

Lithium isotope separation has been achieved employing the two-step photoionization technique along with a narrow band dye laser in conjunction with a time of flight mass spectrometer. The demonstrated method yields a high degree of selectivity by tuning the dye laser at the resonance levels of Li6 and Li7. It is inferred that the concentration of the natural abundance of the Li6 isotope gets enhanced up to over 47% as the exciter dye laser is tuned to the P1∕22 of Li6 even if the linewidth of the exciter laser is not sufficiently narrow to excite the isotopic level. It is also noticed that the much higher energy density of the exciter laser limits the resolution of the fine structure levels of the lithium isotopes that leads to a loss in the enrichment of Li6 due to the power-broadening effect. Measurements of the photoionization cross section of the lithium isotopes from the 2pP1∕2,3∕22, excited states for Li6 and Li7 and the corresponding number densities are reported.

Novel Syntheses Method of Phenol Type Benzo-15-Crown-5 Ether Resin and its Application for Lithium Isotope Separation

The novel synthesis method of phenol type benzo-15-crown-5 ether resin was proposed. The chemical bonding of benzo-crown ether and phenol was succeeded by using hexamethylenetetramine and trichloroacetic acid as the condensing agent and solvent, respectively. The control of the diameter and shape of resin was also succeeded by using the high porous silica beads support. The isotope fractionation by chromatography using the synthesized resin was confirmed. The lighter isotope was disproportionately located in the crown ether resin. The separation coefficient, ϵ, in the present system was 0.033.

Novel Syntheses Method of Phenol Type Benzo-15-Crown-5 Ether Resin and its Application for Lithium Isotope Separation

Novel Syntheses Method of Phenol Type Benzo-15-Crown-5 Ether Resin and its Application for Lithium Isotope Separation

Chromatographic Lithium Isotope Separation Using Cubic Antimonic Acid as Column‐Packing Material

Ion‐exchange chromatographic lithium isotope separation was performed by using granular cubic antimonic acid as column packing material at 50°C. While the single‐stage separation factor for the lithium isotopes was 1.0020, independent of the flow rate, HETP was a monotonously increasing function of flow rate both in breakthrough and reverse breakthrough experiments. After 442 cm chromatographic development, the 6Li atomic fraction increased to 0.256 in the reverse breakthrough experiment and decreased to 0.026 in the breakthrough experiment both from its original value of 0.074. The granular C‐SbA was kindly donated by Toagosei Chemical Industry Co. We acknowledge Professor M. Hosoe, the National Defense Academy, who measured the lithium isotopic ratios reported in this paper.

Periodicity in 6Li-to-7Li Isotopic Reduced Partition Function Ratios of Diatomic Lithium Compounds

The UB3LYP/LanL2DZ level calculations were carried out for sixty-seven Li-M diatomic molecules of lithium between LiH and LiBi to explore the periodic properties of their 6Li-to-7Li isotopic reduced partition function ratios (rpfrs) and some other quantities. The Li-M bond distance, the frequency shift upon 7Li/6Li isotope substitution and the rpfr all show plots typical of any chemical and physical property which is a periodic function of the atomic number. The rpfr is strongly correlated with the Li-M bond stretching force constant except for LiH. The present calculations show that the rpfrs of diatomic molecules of group 2, group 12 and group 18 elements are relatively small, which reflects the filled electron shell and subshell characters of those elements. The results of the calculations and the consideration on chemical properties of elements suggest that zinc is a possible substitute for mercury in lithium isotope separation processes utilizing the redox reaction of lithium.

Lithium Isotope Effect Accompanying Electrochemical Intercalation of Lithium into Graphite

Lithium has been electrochemically intercalated from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO4 into graphite, and the lithium isotope fractionation accompanying the intercalation was observed. The lighter isotope was preferentially fractionated into graphite. The single-stage lithium isotope separation factor ranged from 1.007 to 1.025 at 25 °C and depended little on the mole ratio of lithium to carbon of the lithium-graphite intercalation compounds (Li-GIC) formed. The separation factor inceased with the relative content of lithium. This dependence seems consistent with the existence of an equilibrium isotope effect between the solvated lithium ion in the EC/MEC electrolyte solution and the lithium in graphite, and with the formation of a solid electrolyte interfaces on graphite at the early stage of intercalation.

Separation of lithium isotopes by elution chromatography with an AB18C6 bonded Merrifield peptide resin

Cation exchange chromatographic separation of lithium isotopes was carried out with an 4'-aminobenzo-18-crown-6(AB18C6) bonded Merrifield peptide resin. This resin has a capacity of 2.25 meq/g dry resin. Upon column elution chromatography, a single stage separation factor of 1.0095, was obtained by the Glueckauf theory from the elution curve and isotopic assays. The heavier isotope, 7Li, was concentrated in the resin phase, while the lighter one, 6Li, concentrated in the solution phase.

Selectivity of metal cations and lithium isotopes on ion exchangers in the hydrogen form prepared by thermal treatment of NH4Zr2(PO4)3

NH4Zr2(PO4)3 with different particle sizes and different specific surface areas were obtained by controlling the preparation conditions. HZr2(PO4)3, cation exchangers in the hydrogen form, were prepared by the thermal treatment of NH4Zr2(PO4)3 in the temperature range of 400 to 700°C and their ion exchange properties were investigated with the main focus on the selectivity for group I and II metal ions and lithium isotopes. Irrespective of the temperature of the thermal treatment, HZr2(PO4)3 showed especially high affinity toward the lithium ion, high affinity toward the sodium ion and had little selectivity for the rubidium and cerium ions from the group I metal ions, and showed no specific affinity toward any of group II metal ions. HZr2(PO4)3 were isotopically 6Li-specific in any conditions examined. The 6Li-to-7Li isotopic separation factor was nearly independent of temperature of the thermal treatment. It depended, however, on the pH of lithium ion-containing solution used as the solution phase in an ion exchange experiment. This pH dependence of the lithium isotope separation effect was due to the appearance of the LiZr2(PO4)3 phase and/or the hydration number of the lithium ion in the ion exchanger phase.

Lithium Isotope Effect Accompanying Chemical Insertion of Lithium into Graphite

Lithiumwas chemically intercalated from 1-methoxybutane solution of lithiumand naphthalene into graphite and vice versa, and lithium isotope fractionation accompanying those intercalation and deintercalation processes was observed. 6Li was always preferentially fractionated into the graphite phase. The single-stage lithium isotope separation factor upon intercalation was about 1.023 at 25 ºC, nearly independent of the structure of the lithium-graphite intercalation compounds formed. A much smaller separation factor was observed for the deintercalation process, suggesting the existence of lithium sites (surface areas) other than the sites between graphene layers of the host graphite. Separation factor data were consistent with the following decreasing order of the 6Li-to-7Li reduced partition function ratio (RPFR): RPFR of 1-methoxybutane solution > RPFR of surface areas > RPFR of metal lithium > RPFR of graphene interlayer sites.

Syntheses and separating properties of triazacrown and AM18C6 bonded Merrifield peptide resins

Separation of lithium and magnesium isotopes by cation exchange elution chromatography was carried out with a synthesized 1,13,16-trioxa-4,7,10-triazacyclooctadecane (N 3O 3)-4,7,10-trimerrifield peptide resin and with a 2 ′-aminomethyl-18-crown-6 (AM18C6) bonded Merrifield peptide resin. The resins have a capacity of 0.1 and 2.3 meq/g dry resin. A single stage separation factor of lithium isotopes, 1.018 was obtained by the Glueckauf theory from the elution curve and isotopic assays. The heavier isotope, 7Li was concentrated in the resin phase, while the lighter isotope, 6Li concentrated in the solution phase. On the other hand, the heavier isotopes of magnesium were concentrated in the solution phase, while the lighter isotopes were concentrated in the resin phase. The separation factors of 24Mg– 25Mg, 24Mg– 26Mg, and 25Mg– 26Mg isotope pair fractionations were 1.012, 1.022, and 1.012, respectively.

Chromatographic separation of lithium and magnesium isotopes by manganese(IV) oxide

Summary Separation of lithium and magnesium isotopes was investigated by chemical ion exchange with a manganese(IV) oxide using an elution chromatography. The capacity of manganese(IV) oxide was 0.5 meq/g. Two molar sodium acetate solution was used as an eluent. The heavier isotopes of lithium and magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the MnO2 phase. The separation factors were determined according to the method of Glueckauf from the elution curves and isotopic assays. The separation factor of lithium isotopes was 1.026. In addition, the separation factors of 24Mg2+–25Mg2+, 24Mg2+–26Mg2+, and 25Mg2+–26Mg2+ isotope pair fractionations were 1.012, 1.022, and 1.011, respectively. The isotope separation system in this work can be explained by the fact that the hydration and isotope mass effects are more significant.

Chromatographic Separation of Lithium Isotopes with Silica Based Monobenzo-15-crown-5 Resin

Chromatographic Separation of Lithium Isotopes with Silica Based Monobenzo-15-crown-5 Resin

Separation of lithium and magnesium isotopes by hydrous manganese(IV) oxide

Lithium and magnesium isotopes were separated by chemical ion exchange using hydrous manganese(IV) oxide and elution chromatography. The capacity of manganese(IV) oxide was 0.5 meq/g. The glass ion exchange column used was 35 cm long with an inner diameter of 0.2 cm, and 2.0M CH3COONH4 solution served as eluent. The single stage separation factor was determined from the elution curves and isotopic assays according to the method of Glueckauf. The separation factor of 6Li+-7Li+ was 1.022±0.002, those of 24Mg2+-25Mg2+, 24Mg2+-26Mg2+, and 25Mg2+-26Mg2+ were 1.012±0.001, 1.021±0.002, and 1.011±0.001, respectively.

Synthesis and Separating Properties of Tris(Merrifield Peptide Resin)

A triazacrown ion exchanger, 1,13,16-trioxa-4,7,10-triazacyclooctadecane (TOTA)-4,7,10- tris(Merrifield peptide resin) was synthesized. This resin has a capacity of 0.1 meq/g dry resin. The resin was used for the elution chromatographic separation of lithium isotopes. Upon column chromatography [0.2 cm I. D. x 35 cm height] using 3.0 M NH4Cl solution as an eluent, the single stage separation factor of 1.027 was obtained. The heavier isotope, 7Li+, was enriched in the resin phase, while the lighter isotope, 6Li+, was enriched in the solution phase.

Enrichment of lithium isotopes by a triazacrown trimerrifield peptide resin

A study on the elution chromatographic separation of lithium isotopes was carried out with a triazacrown trimerrifield peptide resin. The capacity of the triazacrown trimerrifield peptide resin has a value of 0.08 meq/g. Upon column chromatography [0.2 cm (I.D)×35 cm (height)] using 4.0M NH4Cl solution as an eluent, the single stage separation factor of 1.028 was obtained by the Glueckauf theory. The heavier isotope, 7Li, was concentrated in the resin phase, while the lighter isotope, 6Li, was enriched in the solution phase.

Chromatographic Separation of Lithium Isotopes with Silica Based Monobenzo-15-crown-5 Resin.

Click to increase image sizeClick to decrease image sizeKEYWORDS: lithium isotopesisotope separationchromatographycrown etherbenzo-15-crown-5 resin

Ab initio Molecular Orbital Calculations of Reduced Partition Function Ratios of Hydrated Lithium Ions in Ion Exchange Systems

Abstract Molecular orbital (MO) calculations at the HF/6-31G(d) level were carried out for the aquolithium ions, Li+(H2O)n (n = 3, 4, 5, 6, 8, 10 and 12) and the aquolithium ions interacting with the methyl sul­fonate ion (MeS-), Li+MeS-(H2O)n (n = 0, 3,4, 5, 6, 7, 8 and 10) which were, respectively, intended to be substitutes for lithium species in the solution and resin phases of ion exchange systems for lithium isotope separation. For each of the species considered, at least one optimized structure with no negative frequency was obtained, and the 7Li-to-6Li isotopic reduced partition function ratio (RPFR) was esti­mated for the optimized structure. The solvation number in the primary solvation sphere was four, both in the solution and resin phases; three waters and MeS" formed the primary solvation sphere in the res­ in phase. Additional water molecules moved off to the secondary solvation sphere. It was found that consideration on the primary solvation sphere alone was insufficient for estimations of reduced parti­tion function ratios of aquolithium ions. Although the agreement between the experimentally obtained lithium isotope fractionation and the calculated results is not satisfactory, it is pointed out that the HF/6-31 G(d) level of the theory is usable for elucidation of lithium isotope effects in aqueous ion exchange systems.

Separation of lithium isotopes by NTOE-bonded Merrifield peptide resin

A study of the elution chromatographic separation of lithium isotopes was carried out with NTOE-bonded Merrifield peptide resin. This resin had a capacity of 0.29 meq/g dry resin. Upon column chromatography [0.2 cm(I.D)×32 cm (height)] using 1.0M NH4Cl solution as an eluent, a single separation factor of 1.026 was obtained by the Glueckauf theory. The heavier isotope, 7Li was concentrated in the resin phase, while the lighter isotope, 6Li was enriched in the solution phase.

Lithium Isotopic Fractionations in the Solvent Extraction by Ion-exchange-type Extractants with Different Ion Selectivity.

Ion-exchange-type extractants showed lithium isotopic fractionations in the solvent extraction reaction, depending on their ion selectivity. The extractants having high Na+ selectivity, calix [4] arene derivative and monensin, showed high lithium isotope separation factors of 1.030 and 1.022, respectively.