Fractionation of Strontium Isotopes in Cation-Exchange Chromatography

Abstract

Strontium isotope fractionation has been observed in cation-exchange chromatography of strontium salts. The heavier isotopes have been found enriched at the front parts of displacement-type chromatograms, which means that the heavier isotopes are preferentially fractionated into the solution phase. The average values of the single-stage separation factor (S) minus one per unit mass difference between isotopes have been 1.0 × 10^?6 for the strontium chloride system, 2.9 × 10^?6 for the strontium acetate system, and 3.1 × 10^?6 for the strontium lactate system at 25°C. No evidence of the odd-even anomalous isotope effects has been observed. The isotopic reduced partition function ratios (RPFRs) of the strontium species involved in the present study have been estimated; the RPFRs of the complex species have been found to be larger than that of the simple hydrated strontium ion, which accounts for the experimental results that the S values of the strontium lactate and strontium acetate systems are larger than that of the strontium chloride system.     

Contributions of Nuclear Size and Shape,Nuclear Mass,and Nuclear Spin to Enrichment Factors of Zinc Isotopes in a Chemical Exchange Reaction by a Cryptand

ABSTRACT

The isotope effect of zinc in the chemical exchange reaction using a macrocyclic ligand was not found to be ruled by the Bigeleisen-Mayer approximation, which suggested that the enrichment factor is proportional to the mass difference and is inversely proportional to the product of the masses of the isotopes. The separation factors of zinc isotopes in the chemical exchange reaction using cryptand(2_B,2,l) polymer were precisely measured by means of an ICP mass spectrometer equipped with nine collectors as ion detectors. The liquid chromatography of a column packed with the cryptand polymer was used for the separation of the zinc isotopes. The enrichment factor ε_67,66 for ⁶⁷Zn to ⁶⁶Zn was ?3.3329(3) × l0^?4.That for ⁶⁸Zn to ⁶⁶Zn was 1.846(1) × 10 ^?4 and that for ⁷⁰Zn to ⁶⁸Zn was 7.19(2) × 10^?4.They were not scaled with δm/mm′, where δm is the mass difference between the isotope pairs, and m and m′ represent the masses of the isotopes. The isotope effect of zinc is implicated with the isotope shift, and the hyperfine structure shift in the isotopomer of the zinc isotopes. The sum contribution of the vibrational energy shift from one isotope to the other and the nuclear mass shift to the enrichment factor of ⁶⁷Zn was ? 1.05 × 10^?3, and the contribution of the field shift caused by the nuclear size and shape of the isotope was 5.26 × 10^?4. The contribution of the nuclear spin or the hyperfine structure shift to the enrichment factor of ⁶⁷Zn was small: 1.94 × 10 ^?4     

Solvent Effect in Isotope Exchange Reaction of Strontium by Liquid Chromatography using a Cryptand (2B,2,2) Polymer

Abstract

Strontium isotopes were fractionated using liquid chromatography with a cryptand (2_B,2,2) polymer as a stationary phase. In this study, we observed that the single stage isotope enrichment factor of ⁸⁴Sr shows the following order, water[6.4×10^?3]>MeOH[4.9×10^?3]>DMF[1.1×10^?3]. The enrichment factors observed in this study did not show a mass‐dependent profile, indicating that the mass‐independent isotope effect affects isotope enrichment phenomena. The mass‐dependent and the mass‐independent isotope effects that influence the enrichment factor of ⁸⁴Sr are related to the donor number linearly, implying that the solvation strongly affects the isotope effect.     

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 ? 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 ? 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 ? 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.     

Chromatographic Separation of Calcium Isotopes with Polymer-Bound Ligands

Abstract

Calcium isotopes were enriched in chromatography columns containing the polymer-bound ligands cryptand [2_B22], cryptand [2_B21], and 18-Crown-6. The largest equilibrium single stage separation factor, 1.0039 ± 0.0002 for the calcium 40/44 isotope pair, was found in calcium exchange with cryptand [2_B22]. The largest separation factor found for 18-Crown-6 was 1.0025 ± 0.0003 for the 40/44 isotope pair. The size of the isotope effect was found to be highly dependent on the solvent composition. An iminodiacetate resin ion exchange column yielded small enrichments of calcium isotopes. Calcium 40/44 exchange with the chelating functional group iminodiacetate yielded a small equilibrium separation factor of 1.00011 ± 0.00003, which was more typical of calcium ion exchange isotope effects.

Comparisons of the above chemical systems based on separative power showed crown chemical exchange to be an improvement over cryptand and iminodiacetate exchange. The cryptand system was rendered impractical as a consequence of a slow exchange rate and a resulting large stage residence time contribution to the separative power, on the order of 45 min. The separation factor for the iminodiacetate system was too small for practical applicability.     

Magnesium Isotope Fractionation in Cation-Exchange Chromatography

Abstract

Band displacement chromatography of magnesium has been carried out successfully for the purpose of magnesium isotope separation by using a strongly acidic cation-exchange resin and the strontium ion as the replacement ion. A small but definite accumulation of the heavier isotopes (²⁵Mg, ²⁶Mg) has been observed at the front parts of the magnesium chromatograms. The heavier isotopes have been fractionated preferentially into the solution phase. The single-stage separation factors have been calculated for the ²⁵Mg/²⁴Mg and ²⁶Mg/²⁴Mg isotopic pairs at 25[ddot]C. The reduced partition function ratios of magnesium species involved in the present study have been estimated.     

Two-resistance mass transfer model for the adsorption of various dyestuffs onto chitin

The kinetics of the adsorption of various dyestuffs onto chitin have been studied. The dyestuffs used are Neoland Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL and a number of process variables were considered, such as adsorbent mass and dye concentration. The mass transfer model is based on the assumption of a pseudoirreversible isotherm and two resistances to mass transfer. These are external mass transfer and internal pore diffusion mass transfer. The rate of adsorption of dyestuffs onto chitin can thus be described by an external mass transfer coefficient and a pore diffusion coefficient. The external mass transfer coefficients are 5.0 × 10^?5, 5.0 × 10^?5, and 1.0 × 10^?5 m·s^?1 and the pore diffusivities are 3.0 × 10^?10 and 4.0 × 10^?11 m²·s^?1 for Neolan Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL, respectively.     

Plasma-modified Nylon 4 membrane for dialysis

The effects of plasma treatment conditions, such as supply power, treatment time, gases used in reactor, surface energy, water content, dialysis permeability, partition coefficient, diffusion coefficient, and free volume of Nylon 4 membranes, were studied. The solutes considered for dialysis system were NaCl, urea, and MgCl₂. The permeabilities of NaCl and urea of membranes with plasma treated in argon at 80 W for 20 min are 5.57 × 10^?5 and 5.89 × 10^?5 cm²/min, respectively. Much higher permeabilities of NaCl and urea obtained by oxygen plasma-treated membranes under 20 W and for 20 min are 30.74 × 10^?5 and 17.66 10^?5 cm²/min, respectively, compared to that of untreated Nylon 4 membranes.     

Superheavy Isotope Enrichment Using a Carbon Isotope Enrichment Plant

Abstract

A¹³C isotope distillation separation plant was used to search for naturally-occurring superheavy isotopes. Superheavy (X^?) isotopes of carbon in CO would be only slightly less volatile than the normal ¹²C¹⁶O. Over 100,000 mol CO were passed through the distillation columns without product withdrawal during the experiment. Following cessation of flows, 201 gas samples were collected from the bottom of the high enrichment column. An argon impurity in the CO provided a “wedge” to enrich X^? isotopes at the CO/Ar interface in the column. Carbon isotopic compositions were used to calculate which samples might contain the superheavy isotopes. Enrichments of X^? isotope concentration of ～10⁵ were obtained in several 0.1 mol samples, which were analyzed for the existence of X^? isotopes at another laboratory. A limited amount of extremely pure ¹³CO was produced as a side benefit.     

Optimal separation of n-paraffins from Kuwait kerosene using a molecular sieve adsorbent

A study has been made of the vapour-phase adsorptive separation of n-alkanes from Kuwait kerosene using zeolite molecular sieves (LMS-5A). The object was to identify the optimum operating conditions, in terms of flow rate, adsorption temperature and zeolite particle size for the separation of n-alkanes from kerosene, so that the remaining stock would also be of marketable quality. The effect of these conditions on the height of the mass transfer zone (HMTZ) and the dynamic capacity (Ad) of zeolite was also investigated. The adsorptive separation process comprised one cycle of adsorption using a fixed bed of zeolite type-5A. The bed was fed with kerosene vapour until equilibrium had been achieved, whereby the n-paraffins were adsorbed and the denormalized material excluded. The processes were carried out isobarically at one atmosphere. The optimum operating conditions were found to be a feed flow rate of 33.33 × 10^?9 m³ s^?1, an adsorption temperature of 643 K and a zeolite pellet fraction size of 1.0–2.0 × 10^?3m. This yielded an HMTZ value of 0.206 m and an Ad of 9.653 × 10^?2 kg n-paraffins kg^?1 zeolite. The data will serve as a basis for the design of commercial plant.     

Poly(crystal violet)/graphene-modified electrode for the simultaneous determination of trace lead and cadmium ions in water samples

A novel poly(crystal violet)/graphene-modified glassy carbon electrode (PCV/Gr/GCE) was fabricated for the simultaneous determination of Pb²⁺ and Cd²⁺. The electrochemical behavior of both species at the PCV/Gr/GCE was investigated employing cyclic voltammetry. In acetate buffer, the modified electrode showed an excellent electrocatalytical effect on the oxidation of both species and was further used for their determination. Under optimized analytical conditions, the oxidation peak currents of Pb²⁺ and Cd²⁺ obtained by differential pulse voltammetry in pH 4.6 acetate buffer showed a linear relationship with their concentrations in the ranges of 2.00 × 10^?8–1.95 × 10^?5 mol L^?1 and 4.00 × 10^?8–5.58 × 10^?5 mol L^?1, respectively. The developed method has excellent sensitivity, selectivity, reproducibility and has been successfully applied to the determination of Pb²⁺ and Cd²⁺ in water samples.     

Permeability of phenol through cellulose acetate membranes by reverse osmosis in various alcoholic systems

Reverse osmosis separation of phenol in various alcoholic solutions using porous cellulose acetate membranes was investigated. The permeation behavior of phenol was measured for cellulose acetate membranes having various pore size distributions which were prepared by annealing at four different temperatures. Some differences were found between the aqueous and the alcoholic solutions in solute permeabilities and product rates. Membranes annealed at 90°C showed higher permselectivity than membranes annealed at lower temperatures. The pore character was classified into two types according to the relation of the product rate of 1-propanol and that of water. It was found in a series of alcoholic solutions that the permeability of phenol, the product rate, and the apparent partition coefficient are closely related to the carbon number of the alcohols, but the values of J_v × η (ca. 1.25 × 10^?4 poise·m³/m²·day) and of the permselectivity coefficient (ca. 0.83) remain constant. The result was analyzed by using the three-dimensional solubility parameter to obtain some information for the partition mechanism of solutes in aqueous and alcoholic solutions.     

Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. I. The effects of salts on the permselectivity of cellulose membrane in pervaporation

In the separation of water/alcohol mixtures through cellulose membranes, the addition of trace amounts of specific salts to the feed mixture (10^?5?5 × 10^?3 mol/kg) caused the marked increase of the separation factor and only the salts composed of a multivalent metal ion and a multivalent counteranion were effective for the increase of the selectivity. For example, when 1.5 × 10^?3 mol/kg CoSO₄ was added to water/ethanol mixture (35/65 wt/wt), the separation factor was 194 and the permeation rate was 5.14 kg/m² h. But, in the absence of the salt, the separation factor was only 6.7 and the permeation rate was 5.63 kg/m² h. We presumed that the increase of the selectivity by the addition of specific salts would be attributed to the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of cellulose molecule.     

Ionic conductivity of unsaturated polyester resin networks containing LiCIO4

Poly(ethylene oxide) (PEO) 400-maleate-isophthalate resins have been prepared and LiCIO₄ dissolved in the resins before crosslinking with 30% of styrene, vinylpyrrolidone or vinylpyridine. The DC conductivities of the resins were measured and found to increase in the order vinylpyridine 〈vinylpyrrolidone〉 styrene for the same [EO]/[Li⁺] ratio ( = 50). For the styrene system σ = 3 × 10^?6Scm^?1 at ambient temperatures and for the vinylpyridine system σ = 1 × 10^?7 Scm^?1. The T_gs of the system were also measured using dynamic mechanical thermal analysis and were found to be very close (257-260 K). The above sequence was therefore attributed to stronger site-binding of lithium ions at the more polar comonomers. An interpenetrating network (IPN) consisting of the styrene-polyester and incorporating 40% PEO 400 was also prepared with[EO]/[Li⁺]ratios of 20 and 50. These gave ambient temperature conductivities of 1 × 10^?5 and 3 × 10^?5 Scm^?1, respectively.     

Adsorption of dyes onto bagasse pith using a solid diffusion model

The adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid-phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10^?3, 1.5 × 10^?3, 8.0 × 10^?4, and 5.0 × 10^?4 cm s^?1 and the solid diffusivities are 1.1 × 10^?8, 1.0 × 10^?8, 6.0 × 10^?9, and 3.0 × 10^?9 cm² s^?1 for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114.     

Kinetics and Thermodynamics of Neutral Hydrolytic Depolymerization of Polyurethane Foam Waste Using Different Catalysts at Higher Temperature and Autogenious Pressures

Neutral hydrolytic depolymerization of the polyurethane (PU) foam waste was done using 0.5 L high pressure autoclave at temperatures of 150°, 180°, 200° and 240°C, the autogenious pressures of 75, 160, 220 and 480 psi and time intervals of 30, 45, 60 and 90 min. The obtained product was characterized by measuring its amine value. The optimum amount of catalysts such as zinc acetate and lead acetate was found to be 1 g. Zinc acetate was more effective catalyst than lead acetate for the depolymerization of PU foam reaction. On the basis of amine value and residual weight of the depolymerized product, the velocity constant was obtained and found to be in order of 10^?3 min^?1; and the reaction was found to be first order. The energy of activation and frequency factor obtained by an Arrhenius plot were 36.86 kJ mole^?1 and 1.349 × 10² mi^?1, respectively. The enthalpy of activation at 150°C, 180°C, 200°C, and 240°C was recorded as 43.89, 44.39, 44.72 and 45.37 kJ mole^?1, respectively. The entropy of activation at the respective temperatures were recorded as 10.37 × 10^?2, 9.79 × 10^?2, 9.45 × 10^?2 and 8.84 × 10^?2 kJ mole^?1. The amine was recovered from products of depolymerization reactions.     

Reactivity ratios and monomer partitioning in the microemulsion copolymerization of vinyl acetate and butyl acrylate

The true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij‐35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 ± 3.2 × 10^?3 for vinyl acetate and 6.219 ± 3.1 × 10^?1 for butyl acrylate, and these were in agreement with those reported in the literature for bulk copolymerizations but differed from values reported for other compartmentalized copolymerizations. Thus, these results indicate that the monomer partitioning and cumulative copolymer composition throughout the reaction have to be duly accounted for in the determination of monomer reactivity ratios in heterogeneous polymerizations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chromatographic Enrichment of 10B by Using Weak-Base Anion-Exchange Resin

Abstract

In order to enrich ¹⁰B isotope, a boron adsorption band was eluted 620 m in a reverse-breakthrough displacement manner. Thereafter the band was stopped for 10 days and then eluted again up to a total distance of 754 m. The rear boundary of the adsorption band was kept sharp throughout the elution. From monitoring of the isotope abundance during elution, the lighter isotope ¹⁰B was confirmed to be accumulated in the band end region. The maximum enrichment of ¹⁰B reached 98.43% (¹⁰B atomic fraction) at a migration distance of 620 m. The interruption in the operation caused no serious damage in isotope accumulation, but there was a slight broadening of the accumulation curve. The isotopic accumulation was examined based on theoretical equations previously proposed. The results indicate that the HETP of the system is constant, 1.8 mm, up to a migration distance of 620 m and increases slightly at the distance of 754 m. The separation coefficient shows a gradual decrease with an increase of migration distance: ε = 9 × 10^?3 (at 200 m) and 7.8 × 10^?3 (at 754 m).     

Separation of Zinc Isotopes by Liquid-Liquid Extraction Using a Crown Ether

Abstract

The zinc isotope effect in a liquid-liquid extraction system using dicyclohexano-18-crown-6 was investigated. The enrichment factor for a unit difference of mass number was ?_u = 0.018 as a maximum, which is greater than that for magnesium isotopes. The enrichment factor to eliminate ⁶⁴Zn from ⁶⁶Zn, ⁶⁷Zn, ⁶⁸Zn, or ⁷⁰Zn is over 0.036. The isotope with an odd mass number, ⁶⁷Zn, behaved differently from those with even mass numbers. This odd/even isotope effect was ?_O/E = 0.056. From the values of ?_u and ?_O/E, it was found that the crown ether separated the zinc isotopes more effectively on the basis of an odd or an even mass number than of mass difference. The separation factors vary with the concentrations of salt and/or conjugated acid in the initial aqueous phases of extraction. The optimal concentration necessary to obtain the largest separation factor had components of 2.0 M ZnCl₂ and 1.0 M HCl. The large value of ?_u for the high atomic number zinc and the notable ?_O/E make it clear that the vibration frequencies of the intramolecular bonds should have an isotope shift which is recognized in the orbital energy of the atoms.     

NUCLEAR SIZE AND SHAPE EFFECT IN CHEMICAL ISOTOPE EFFECT OF GADOLINIUM USING DICYCLOHEXANO-18-CROWN-6

ABSTRACT

Gadolinium isotopes were fractionated in a liquid-liquid extraction system using dicyclohexano-18-crown-6. The isotope enrichment factors showed breakdowns of the conventional Bigeleisen-Mayer approximation for every condition of the initial phases; the concentrations of gadolinium and hydrochloric acid and the type of organic solvents. The nuclear mass effect and the field shift effect were estimated by use of the isotope pairs ¹⁵²Gd-¹⁶⁰Gd and ¹⁵⁴Gd-¹⁶⁰Gd. Since both isotopes, ¹⁵²Gd and ¹⁵⁴Gd, have the unique characteristics of the nuclear charge radii, <r²>'s, the unusual isotope effects due to the field shifts took place, while the mass effects of the other isotopes canceled the field shift effects. The maximum isotope effect was observed to be ε_160,152 =0·0252 ± 0·0024 whose initial aqueous phase was 0·023 M GdCl₃ in 12 M HC1, and its organic phase was 0·2 M DC18C6 in chloroform: this was 0·00315 ± 0·00030 in terms of the enrichment factor for unit mass.