Fraction Of Strontium Research Articles

DCH18C6 using strontium extraction selectivity investigation and sequential soil fractionation study

85Sr as radioindicator has been applied to strontium separation selectivity study using cisdicyclohexano-18-crown-6 (DCH18C6) as extraction agent and picric acid as counter ion with the aim to contribute to the development of a rapid method of strontium extraction. The same radioindicator has been used for strontium fractionation study in chosen soils by application of Tessier- and BCR sequential extraction procedures. Experimental results have shown, that the mentioned extraction system is applicable for IDA determination of Sr2+ in ∼1000-fold abundance of Ca2+, ∼1000-fold abundance and Mg2+, ∼10-fold abundance of K+ and ∼0.2-fold abundance of Ba2+. For the soil samples - chernozems developed on loess - from the near vicinity of NPP Jaslovské Bohunice the exchangeable strontium fraction reached as much as 50 – 60 %.

Investigations on the ion exchange process of Cs+ and Sr2+ cations by ETS materials

Ion exchange experiments were carried out for evaluation the removal capability of cesium and strontium ions by the microporous Engelhard Titanium Silicates – 4 and 10 (ETS-4 and ETS-10, respectively) synthesized from alkaline gels. Ionic selectivities were estimated from the ion exchange isotherms, Kielland and Langmuir plots. It is shown that both microporous titanosilicates perform under a similar ion exchange profile against Cs+ cations and the selectivity of ETS-4 for Sr2+ is highly depended on temperature. ETS-10 is unselective for Sr2+ over a wide range of equivalent ionic fraction of strontium in solution. The Langmuir isotherms indicate that in the absence of ionic competition both titanosilicates retain Cs+ and Sr2+ cations, as much as their ion exchange capacities. These positive results promote ETS materials as very good candidates for the removal of both cesium and strontium from nuclear waste solutions.

Content and Mobility of Strontium in Forest Soils According to North-South Transect in Poland

Abstract The investigation was carried out on forest soils collected from areas subject to variable pollution. The fraction of strontium was analyzed in soil samples from north-eastern Poland (Borki forest division), treated as a non-polluted region (natural background) and in soil samples from central (Rogów forest division) and south-western Poland (Świerklaniec forest division). The sequential extraction procedure was applied in this study to separate the fractions of strontium. Five fractions were analyzed in every genetic horizon according to the Tessier method. The concentration of strontium was also analyzed in the plants. Both results were compared in order to evaluate the mobility and bioavailability of the trace elements in the environment. The content, distribution and bioavailability of the strontium fractions were investigated with particular emphasis on the contaminated study sites. Total content of strontium in surface horizons depended on the localization. Among analysed fractions strontium, in organic soil horizons, regardless of localization, occurred predominantly in mobile fractions in all examined soils.

Effects of alkaline-earth strontium on the performance of Co/Al2O3 catalyst for methane partial oxidation

A series of Sr-Co/Al2O3 catalysts were prepared by co-impregnation method using γ-Al2O3 as the support. The effect of strontium promoter on the catalytic performance of Co/Al2O3 catalyst for partial oxidation of methane (POM) to synthesis gas was studied. The catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR) and thermogravime try (TG). The results show that both Co/Al2O3 calcined at 700°C and Sr-Co/Al2O3 calcined at 800°C exhibit low activity and deactivate at the initial stage of POM reaction. The addition of above 2% mass fraction of strontium will greatly enhance the activity and stability of Co/Al2O3. Two types of Co species were identified on the fresh calcined catalysts. One is Co3O4 which weakly interacts with Al2O3 (easily reduced by H2) and the other is the spinel CoAl2O4 (non-catalytic performance) which strongly interacts with the support. During the course of calcination, strontium can react with Al2O3 to form Sr4Al14O25 which will restrain the generation of the CoAl2O4 species and promote the stability and activity of catalysts. Without strontium promoter, CoAl2O4 is easy to be formed over Co/Al2O3 in the POM reaction. However, the formation of CoAl2O4 cannot be avoided with the addition of limited strontium when the calcination temperature is over 800°C.

Strontium migration in a crystalline medium: effects of the presence of bentonite colloids

The effects of bentonite colloids on strontium migration in fractured crystalline medium were investigated. We analyzed first the transport behaviour of bentonite colloids alone at different flow rates; then we compared the transport behaviour of strontium as solute and of strontium previously adsorbed onto stable bentonite colloids at a water velocity of approximately 7.1·10 − 6 m/s–224 m/yr. Experiments with bentonite colloids alone showed that – at the lowest water flow rate used in our experiments (7.1·10 − 6 m/s) – approximately 70% of the initially injected colloids were retained in the fracture. Nevertheless, the mobile colloidal fraction, moved through the fracture without retardation, at any flow rate. Bentonite colloids deposited over the fracture surface were identified during post-mortem analyses. The breakthrough curve of strontium as a solute, presented a retardation factor, R f ~ 6, in agreement with its sorption onto the granite fracture surface. The breakthrough curve of strontium in the presence of bentonite colloids was much more complex, suggesting additional contributions of colloids to strontium transport. A very small fraction of strontium adsorbed on mobile colloids moved un-retarded ( R f = 1) and this fraction was much lower than the expected, considering the quantity of strontium initially adsorbed onto colloids (90%). This behaviour suggests the hypothesis of strontium sorption reversibility from colloids. On the other hand, bentonite colloids retained within the granite fracture played a major role, contributing to a slower strontium transport in comparison with strontium as a solute. This was shown by a clear peak in the breakthrough curve corresponding to a retardation factor of approximately 20.

Human biokinetics of strontium—part II: Final data evaluation of intestinal absorption and urinary excretion of strontium in human subjects after stable tracer administration

Fractional intestinal absorption (f1 value) and urinary excretion of strontium in healthy human volunteers has been measured by simultaneous oral and intravenous administration of the stable isotopes 86Sr and 84Sr using the double-isotope method. Final evaluation of the complete data set confirmed that ingestion of different foodstuff and nutritional factors could influence the fractional gut uptake of strontium. In some cases, significant deviations from the f1 value adopted by the International Commission on Radiological Protection (ICRP) were found. The arithmetic mean (+/- standard deviation) of the f1 values of all experiments performed was determined to be 0.46 (+/- 0.24). The probability distribution function of the f1 values is represented by a lognormal curve with a geometric mean of 0.38 and a geometric standard deviation of 2.06. Urinary excretion in all subjects varied depending on the administered foodstuff in a wide range and differs from the ICRP model, up to 2 days after tracer administration. No age or gender dependence of the absorbed strontium fraction and of the urinary excretion of strontium after an oral load was found.

Oxides ferroelectric (Ba, Sr)TiO3 for microwave devices

Barium–strontium titanate (BST), ternary ceramic compounds with the molar formula (Ba1−xSrx)TiO3, were prepared by solid-state reaction from raw materials. Three compositions with x=0.25, 0.50 and 0.75, have been checked. Samples with two type of thermal treatment at 1230 and 1260°C have been manufactured and analyzed. Perovskite type, polycrystalline structure of the BST ceramics was revealed by the X-ray diffraction data at room temperature. Strontium ion (Sr2+) enters substitutionally on the Ba2+ site. A small decrease in the unit cell volume with the Sr content increase was observed. Dielectric measurements have been performed at low and high frequencies. The temperature dependence of low frequency permittivity shows large interval of ferroelectric transition, which appears to be merely due to dispersion of crystallites dimensions. The increasing concentration of Sr ion leads to a shift of the Curie point below room temperature. Experimental data show a linear decrease of the Curie point TC(°C)≈120–360x, versus x strontium fraction. Room temperature permittivity and dielectric loss have been measured in microwaves by using the Hakki–Coleman method. BST samples prepared using water as a milling medium exhibit lower porosity and lower dielectric loss in microwaves than samples prepared using acetone as a milling medium. Dielectric loss of 10−3 at 1GHz shows that this ceramic material is quite suitable for high frequency device applications.

Sintering and mechanical characteristics of lanthanum strontium manganite

The sintering and mechanical characteristics of strontium-doped lanthanum manganites are increasingly important for both processing and device integration. A-site deficiency and reduced strontium fraction were shown to improve sinterability. High-strontium compositions displayed unusual mechanical properties, including unexpectedly low Young's modulus and fracture strength. In addition, plastic deformation of a fully dense LSM plate under modest loading was observed. This surprising and novel result may result from oxygen exchange with the LSM surface at elevated temperatures.

Microstructure and dielectric properties of barium–strontium titanate with a functionally graded structure

A functionally graded perovskite material with varying Ba/Sr ratio was known to have a broad transition temperature and as a result it shows a low temperature coefficient and high dielectric constant in a wide temperature range. A multi-layered barium/ strontium titanate functionally graded material was fabricated. Optical/scanning electron microscopy, energy dispersive spectrocsopy, and X-ray diffractometer were used for microstructural, chemical, and phase analysis, respectively. An impedance/gain-phase analyzer was used for dielectric constant measurement. The microstructure and dielectric property of BaTiO 3 -SrTiO 3 system display various gradient distributions corresponding to constitutional change. The average grain size of Ba 1-x Sr x TiO 3 phase was reduced as increasing the volume fraction of strontium. The dielectric properties of BaTiO 3 SrTiO 3 functionally graded materials were discussed in terms of microstructure and chemical composition.

Evaluation of Electrospray Mass Spectrometry as a Technique for Quantitative Analysis of Kinetically Labile Solution Species

The extent that a kinetically labile equilibrium reaction was perturbed by passage through the electrospray ion source has been measured. The reaction studied was strontium ion chelation by EDTA (Sr(2+) + Y(4)(-) ⇌ SrY(2)(-)) in 100% aqueous solutions. The forward reaction rate is very fast (10(9) M(-)(1) s(-)(1)) and the reverse rate is very slow (10(0) s(-)(1)) relative to the time scale of the ES process (∼10(-2) s). The SrY(2-) detected with the mass spectrometer were expected to be representative of thermodynamic equilibrium within the droplets, but the position of the equilibrium shifted to the right relative to the solution equilibrium position. Given the current status of understanding of the ion generation process in the electrospray ion source, the degree that the [Sr(2+)] changed due to passage through this ion source was smaller than expected, which is fortuitous with respect to the quantitation of such species. The pH of each calibration set determined the fraction of strontium that was uncomplexed in solution. The equilibrium shift induced by passage through the ion source was constant for solutions at constant pH but differed for solutions at different pH. Decreasing the solution pH generated smaller equilibrium shifts as measured by the change in the [Sr(2+)]. In solutions with free Sr(2+) and excess EDTA at equilibrium, the free [Sr(2+)] decreased by ∼100 and ∼10% in solutions at pH 5.85 and 4.98, respectively. Quantitation of kinetically labile species in complex, multicomponent systems will be straightforward with ES-MS, provided all species involved in the equilibria can be identified and monitored.

Individual Quantification of 89Sr and 90Sr in Nuclear Reactor Effluent

An analytical method utilizing ion chromatography, a non-radioactive strontium carrier, and liquid scintillation spectroscopy to individually quantify 89Sr and 90Sr in nuclear reactor effluent is presented. It is observed that this method is less time consuming than traditional procedures for quantifying radio-strontium, deals comprehensively with separation and subsequent isotopic quantification of strontium, and avoids difficulties reported in previous research. The equipment, solutions and operating conditions for the chromatographic separation of strontium in aqueous solution are identified, and the strontium fraction is shown to elute between 7 and 7.5 min after injection. The beta spectra of 90Sr, 89Sr and 90Y are obtained using liquid scintillation spectroscopy, and the effects of quenching are shown to be negligible. The positions of the liquid scintillation windows within the combined beta spectra facilitating isotopic analysis of 89Sr and 90Sr are identified, followed by the system of equations to quantify 89Sr and 90Sr within a sample. The performance of the method is evaluated using five solutions representing effluent containing radio-strontium at known concentrations. It is observed that when the 89Sr and 90Sr concentrations each are approximately 37 Bq mL(-1) or more, the method over-estimates the 89Sr activity by 15-20% and under-estimates the 90Sr activity by 10-30%, while yielding the total radio-strontium activity to within 1-4% of expected. The lower limit of detection of the system for either 89Sr or 90Sr is shown to be approximately 0.8 Bq mL(-1) of effluent.

Cytosolic Calcium Transient and Light Response in Limulus Ventral Nerve Photoreceptors: Supralinearity in Response-Intensity Curves

Abstract Light-evoked intracellular electrical responses were measured simultaneously with the changes in intracellular free Ca2+ or Sr2+ concentration by means of arsenazo III. The response-versus-stimulus intensity characteristics was measured in two states of relative light adaptation in strontium-containing saline (10 mᴍ Sr2+; 0.25 mᴍ Ca2+). Supralinear parts of the curves with slopes > 1 were found for the receptor current amplitude and the current­-time integral as well as for the amplitude of the arsenazo signal within at least 0.3 log units of identical stimulus intensity range. Maximum slopes of response-versus-intensity curves are on average approximately 1.7 for the receptor current and the arsenazo signal in both adaptational states. The rise in time of the arsenazo signal evoked by a light flash shows two phases. In strontium saline we observe a fast increase at the onset of the arsenazo signal which is detectable within the first 20-100 ms of the signal rise and a slow further increase to the maximum, with a duration of 0.7-6 s. In the detailed analysis of both phases we observed that the amplitude of each phase increases supralinear, i.e. disproportionate to the stimulus intensity. The fast rising phase of the arsenazo signal is not visibly voltage-dependent. This fast rising phase might be a monitor of an IP3-sensitive calcium or strontium release. Since the amplitude of the fast rising phase increases supralinear with the stimulus intensity, we propose the interpretation that more than one IP3-molecule must bind to the IP3-receptor to open this channel of the intracellular calcium store. Only the slow rising phase is voltage-dependent. The kinetic of this slow rising phase was accelerated with more negative membrane potentials. This predominant slow phase correlates with the receptor current-time integral. Therefore the slow rising phase of the arsenazo signal might be a monitor for influx of calcium or strontium through light activated ion channels in the plasma membrane. The supralinearity of the amplitude of the slow rising phase might indicate the supralinear increase in calcium or strontium, which is carried by the receptor current. Additionally, we calculated the fraction of strontium and calcium ions of the total receptor current. When calcium was replaced by strontium in the superfusate about 3-30% of the receptor current are carried by strontium and calcium ions. In physiological saline calcium contributes about 1-1.5% to the receptor current.

SEPARATION OF STRONTIUM ION FROM A LARGE AMOUNT OF CALCIUM ION BY THE USE OF A MACROCYCLIC ETHER

Abstract A small amount of Sr2+ (0.7∼20 mg) was simply separated from a large amount of Ca2+(1.5 g) by liquid–liquid extraction using dicyclohexyl-18-crown-6 chloroform solution. Average recovery of Sr2+ was 97 %, and the amount of Ca2+ in the final strontium fraction of the separation was decreased to 10−4∼10−5 part of the initial amount.

Standard potentials of the strontium amalgam electrode, and thermodynamics of the dilute strontium amalgams

From e.m.f. measurements of the cell: Pt|xSr + (1 − x)Hg|SrCl 2(aq,m)|AgCl|Ag|Pt the standard potentials of the strontium amalgam electrode have been determined over the temperature range 283.15 to 343.15 K. The results can be reproduced accurately by the equation: E °/V =−1.448013 −2.289353T/K + 2.582182 x 10−6(T/K) 2 The standard thermodynamic functions at 298.15 K for the strontium amalgam and for the strontium amalgamation reaction have been obtained. Also, the mean molar activity coefficients of SrCl 2(aq) have been determined over the temperature range 283.15 to 343.15 K at molalities up to 0.3 mol kg −1. The logarithm of the rational activity coefficient of strontium in dilute amalgams is a linear function of the mole fraction of strontium: log 10 f Sr = Qx Sr where Q is temperature-dependent and can be represented by the equation: Q = 541.347 − 2.2805(T/K) + 3.95021 X 10 −3(T/K) 2 The values of Q obtained from the e.m.f. measurements of the above cell have been confirmed from supplementary e.m.f. measurements of the amalgam concentration cell: Pt| x 2Sr + (1 − x 2)Hg|SrCl 2(non-aqueous)|x 1Sr + (1 − x 1)Hg|Pt over the same temperature interval.

Chromatographic separation of strontium from barites for mass spectrometric analysis

A simple Chromatographic method for the separation of strontium in barites containing 500 times excess barium is described. The strontium fraction is sufficiently pure for mass spectrometer studies of strontiumisotopes. The resin used is Dowex-50 and the column dimensions are 1.1 by 8 cm. The column is eluted at room temperature with 1.5M hydrochloric acid at a flow rate of ∼ 1 ml/min. Effect of column temperature on the elution peaks is pointed out.

Concentration of Fission Products in Air due to a Nuclear Detonation

Studies were made of the air concentration of radionuclides two years after detonation. Dust suspensions were made of 21,000 and 13,100 m/sup 3/ air and evaporated to dryness. The dried residues were analyzed with a 256-channel pulse analyzer. The relative ratios of the nuclides were calculated from the gamma photopeak area. A chemical analysis was made of the samples for Sr-90 and Cs-137. Strontium was separated by a fuming nitric acid method, and Sr-90 was calculated by the Y-90 activity in the strontium fraction. Cesium was precipitated as Cs/sub 2/PtCl/sub 6/, and the activity was measured by a thin window anticoincidence type low background counter. The results of the measurements are tabulated. (auth)

The estimation of trace amounts of barium or strontium in biological material by activation analysis

A neutron activation method is described for the estimation of barium or strontium in biological materials which is not disturbed by the presence of a large excess of calcium. The method is a comparative one in which a weighed amount of a pure barium or strontium salt receives the same neutron irradiation in a nuclear pile as a weighed aliquot from the unknown specimen. Following a chemical separation, the activity of the barium or strontium fraction from the unknown is compared with that from the appropriate standard. The error of the method is estimated to be about 5 per cent in specimens containing from 1 to 50 hg of either element.