Amounts Of Sr Research Articles

Influence of pH, concentration and ionic strength during batch and flow-through continuous stirred reactor experiments of Sr2+-adsorption onto montmorillonite

Sorption/desorption experiments in batch and continous flow-through stirred reactor under different experimental conditions were carried out using montmorillonite (<2 μm clay fractions). The Sr2+ amount desorbed at pH 4 is only half of the amount desorbed at pH 8, revealing that the retention of Sr2+ onto montmorillonite was enhanced at pH 4. The largest adsorption value was obtained at pH 8.0 ([KNO3] = 10−3 mol/L) with q m = 41.49 mg Sr2+/g from the Langmuir isotherm. The gradient of concentration acted as an increasing driving force since the amount of Sr2+ adsorbed increased as increasing of Sr2+ concentration during the flow-through experiments.

Validation of an extraction paper chromatography (EPC) technique for estimation of trace levels of 90Sr in 90Y solutions obtained from 90Sr/90Y generator systems

While the extraction paper chromatography (EPC) technique constitutes a novel paradigm for the determination of few Becquerels of 90Sr in MBq quantities of 90Y obtained from 90Sr/90Y generator, validation of the technique is essential to ensure its usefulness as a real time analytical tool. With a view to explore the relevance and applicability of EPC technique as a real time quality control (QC) technique for the routine estimation of 90Sr content in generator produced 90Y, a systematic validation study was carried out diligently not only to establish its worthiness but also to broaden its horizon. The ability of the EPC technique to separate trace amounts of Sr2+ in the presence of large amounts of Y3+ was verified. The specificity of the technique for Y3+ was demonstrated with 90Y obtained by neutron irradiation. The method was validated under real experimental conditions and compared with a QC method described in US Pharmacopeia for detection of 90Sr levels in 90Y radiopharmaceuticals.

The new data on the origin of the Patom Crater (East Siberia)

It has been found that the origin of the Patom Crater is related to endogenous processes with the main role played by deep flow of fluid components, which determine formation of the ejecta cone at about 500 years ago or more. This is evidenced by the zonal structure of the crater and geochemical peculiarities of rocks, caused by the long formation time for particular zones. Sandstone and schist blocks that were included into eruptive breccia within the crater were affected by gaseous or fluid components and intensively carbonized. During carbonatization, these rocks within the crater were being enriched in Ca and Sr, but the shares of the 87Sr and, consequently, 87Sr/86Sr ratio in them abruptly decrease. This is explained by the influence of deep fluids on terrigenous rocks, which were initially depleted in the radiogenic strontium isotope and might flow from a magmatic source with a low 87Sr/86Sr ratio. However, these fluids were enriched in CO2 and transported significant quantities of Sr, which led to enrichment of all terrigenous rocks in the crater in this element. The discovery of individual sandstone blocks with high concentrations of summarized rare earth elements (up to 557 g/t) and higher Sr and Ba contents among the fragments of host stratum within the Patom Crater allows us to suppose that there is a magmatic source enriched in fluid components at depths. The effect of the active fluid phase with low strontium isotopic ratios on rocks during the Patom Crater formation might lead to an abrupt decrease in values of the initial 87Sr/86Sr ratio in carbonized sandstones and schists.

Kinetic Study of Sr2+ Sorption by Bone Char

The effect of particle size, bone char mass, initial pH, and metal concentration on the kinetics of Sr2+ sorption by bone char was studied and discussed. Considering the sorbed amounts of Sr2+, solution pH changes, changes of Ca2+ concentrations and Ca/Sr molar ratios, with time, it was concluded that surface complexation reactions are dominant in the first, more rapid stage of the sorption process, while the contribution of the ion-exchange mechanism increases with time and becomes more significant in the second, slower phase. Under all investigated experimental conditions, the pseudo-second-order model was found to provide high correlation coefficients and the equilibrium amounts of Sr2+ sorbed comparable to the values obtained experimentally.

The batch study of Sr2 + sorption by bone char

Considering the excellent sorption properties of synthetic calcium hydroxyapatite (HAP) towards many divalent cations, the potential application of bone char, the natural source of HAP, for sequestering Sr2 +ions from aqueous solutions has been studied in batch conditions. Contact time, initial solution pH and initial Sr2 + concentrations were varied to examine the effect of these process parameters on the amount of Sr2 + sorbed. The kinetics of Sr2+ sorption was found to be a 2-step process, with contact time of 24 h required for attaining equilibrium. The sorption isotherm was well fitted with Langmuir and DKR theoretical models. Sorption of Sr2 + on bone char was found to be a favorable, thermodynamically feasible and spontaneous process, with the maximum sorption capacity of 0.271 mmol/g and sorption energy of 11.09 kJ/mol. The sorption was pH-independent in the initial pH range 4-10, as a result of excellent buffering properties of bone char (constant final pH), while for pH > 10 sorbed amounts of Sr2 + increased due to attractive electrostatic forces between negatively charged sorbent surface and positively charged metal ions. On the basis of the amount of Ca2 + released and final pH decrease in respect to the point of zero charge of bone char (pHPZC), two possible mechanisms of Sr2 + sorption were identified: ion-exchange and the formation of complex compounds with HAP and carbon active surface sites. The amounts of Sr2 + leached from bone char increased with the increase of Ca2 + content and the decrease of solution pH. In comparison with synthetic HAP, bone char represents a cost-effective alternative for Sr2 + sequestering.

Removal of strontium ions by a crosslinked copolymer containing methacrylic acid functional groups&lt;/p&gt; &lt;/p&gt;

A tail-made polymer matrix is proposed to remove strontium ions from aqueous solutions. The removal behavior of strontium ions on a crosslinked copolymer containing methacrylic acid as functional groups was investigated as a function of sorptive concentration, time, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solution. It is found that a maximum adsorption of Sr(II) ions can be obtained on the crosslinked copolymer after 30 minutes and at pH 8. The increase of Sr(II) ion concentration in the solution resulted in an increase in the amount of Sr(II) ions adsorbed on the crosslinked copolymer containing methacrylic acid as functional groups. However, after a maximum of Sr(II) concentration in the solution, the percentage of adsorbed Sr(II) ions decreased. The adsorption data are well represented by the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The adsorption capacity of the copolymer and the free energy change were calculated by using the D-R isotherm. For the adsorption of Sr(II) ions on the crosslinked copolymer the thermodynamic parameters (DH°,DS° andDG°) were calculated.

Determination and validation of dietary fiber in food by the enzymatic gravimetric method

An adequate and validated method for the analysis of any nutrient is a fundamental step in achieving a good analytical result. The purpose of this study was to analyze dietary fibers (DF) and validate the results without the availability of a standard reference material (SRM). Ten samples of cracker biscuits in duplicate were analyzed using the enzymatic–gravimetric method. To validate, cracker biscuit was used as a matrix food and a fiber-rich product (47.63%) was used as a secondary reference standard (SRS). Three aspects were evaluated: (1) Precision—Samples from 10 assays in two lots of cracker biscuits and in the RS; (2) Accuracy—recovery test on biscuit plus three quantities of SR: 1.5, 2.5 and 5.0 g in 50 g of biscuit, (3) Linearity—recovery curve, through the correlation coefficient ( R 2). Results obtained for coefficient of variation were 4.89 and 4.10% for biscuits and 1.37% for the RS, showing a good precision of approximately 20%. The accuracy values obtained were 4.10, 4.90 and 6.55 g/100 g, which represents recoveries of 101, 108 and 110%. These results indicate acceptable accuracy, since the replicates of the fortified samples showed analyte recovery within the acceptance range of 70–120%. The correlation coefficient ( R 2) was 0.9999 indicating an excellent linearity in the method's response. The conclusion is that DF results obtained through the EGM method are reliable, considering the cracker biscuit sample parameters analyzed.

The effect of doping and processing conditions on properties of La1−xSrxGa1−yMgyO3−α

The phase composition and electrical conductivity of ceramics based on La1−xSrxGa1−yMgyO3−α (LSGM) were studied after doping with different quantities of Sr and Mg. The effect of the processing conditions on the density of the LSGM ceramics was analysed. By means of microprobe X-ray analysis it was found that the limit solubility of Sr and Mg in LaGaO3 corresponded to x=y ≈ 0.16. If excess Sr and/or Mg is added, LaSrGa3O7 and/or La4Ga2O9 phases are formed respectively in addition to the main LaGaO3 perovskite phase. No other impurity phases were detected. The maximum electrical conductivity of LSGM was achieved in the region of the limit solubility of the dopants.

Preparation of Uniform Colloidal Strontium Ferrite Particles

A procedure is described that yields uniform ferrite particles containing strontium. The process consists of crystallizing the solids from a ferrous hydroxide gel in the presence of SrCl2 and a mild oxidizing agent (KNO3) at 90°C. The amount of Sr2+ in the particles can be varied with the concentration of the SrCl2 in the original system, but its content decreases with extensive washings. Calcination of the powder partially inhibits the leaching of Sr2+. Magnetic properties of such materials are also given.