Investigation of Se(IV) diffusion in compacted Tamusu clay by capillary method

Journal of Radioanalytical and Nuclear Chemistry - This study selects microalgae suitable for the decontamination of radioactive cobalt (Co-60) in radioactive solutions based on the decontamination...     

Sorption and diffusion of HTO and cesium in crushed granite compacted to different lengths

In this study, batch and through-diffusion experiments have been performed in order to determine the distribution coefficients (K _d ), apparent diffusion coefficients (D _a ) and retardation factor (Rf), respectively. Both apparent and effective diffusion coefficient (D _a and D _e ) of Cs were obtained by accumulative concentration method developed by Crank (1975). In addition, a non-reactive radionuclide, HTO, was initially conducted in through-diffusion experiment for assessing the ability of radionuclide retardation. The distribution coefficients (K _d ) obtained by batch tests in 14 days under aerobic and anaerobic systems were 2.06 and 3.52 ml/g. Moreover, it is found in through-diffusion test that Rf = 4.12 and 4.40 and K _d = 0.97 and 1.06 of Cs did not have an obvious discrepancy in a length/diameter/ (L/D) ratio of 0.44 and 1.78. However, Rf and K _d revealed a larger difference in an L/D ratio closing to 1 due to the geometric change of one-dimension diffusive hypothesis. Therefore, it demonstrates that Rf and K _d obtained by through-diffusion experiments only could be achieved at a lower or larger L/D ratio and would be reliable for long-term performance assessment.     

Sorption and diffusion processes with134Cs and85Sr in natural sorbents

Sorption and diffusion processes with¹³⁴Cs and⁸⁵Sr in natural bentonites have been investigated. The distribution coefficients (K _d ) have been determined by a batch method. Various factors affecting theK _d value as water-to-bentonite ratio, concentration of the competitive cations in the aqueous phase or bentonite-to-sand ratio in the mixed sorbents have been evaluated. A comparison of the sorption and diffusion data has been made.     

Sorption of Cs(I) and Sr(II) on a mixture of bentonite and magnetite using SCM + IExM: A parametric study

Summary The sorption of Cs(I) and Sr(II) on bentonite and magnetite was experimentally studied and numerically simulated using surface complexation (SCM) and ion-exchange (IExM) models. The empirical system consisted of: (1) synthetic granitic water with a given ionic strength (0.1 or 0.01 NaNO₃), (2) radionuclides studied (10^-6M CsCl or SrCl₂ ^. 6H₂O spiked with ¹³⁷Cs or ⁸⁵Sr), and (3) bentonite pre-treated with the aim to remove carbonates, and magnetite as a representative of steel canister corrosion products. The parametric study covered, e.g., the influence of pH, bentonite to magnetite ratio and volume-liquid ratio on the values of selectivity coefficients and K_d.     

Li ion diffusion in LiAlO2 investigated by Raman spectroscopy

The temperature dependence of Li ions behavior of γ-LiAlO₂ has been studied from 78 to 873 K. On heating, the Li ions underwent positional disordering along the structural channels, with the Li ions related modes at 220, 366 and 400 cm⁻¹ broadening and weakening dramatically. An anomalous maximum in the bandwidths of the Li ions related modes is observed. It should be apparent that there are at least two distinct thermally activated processes. A model suggested by Andrade and Porto is used to describe the linewidth of a phonon.     

Effect of Sr2+ doping on the luminescence properties of YVO4:Eu3+,Sr2+ particles prepared by a solvothermal method

Well-dispersed Eu³⁺ and Sr²⁺ co-doped YVO₄ luminescent particles (YVO₄:Eu³⁺,Sr²⁺) on the submicron scale were prepared by a facile solvothermal method at low temperature. The effect of Sr²⁺ doping on the luminescence of YVO₄:Eu³⁺,Sr²⁺ particles was investigated by fixing the Eu³⁺ doping concentration at 7 mol%. It was found that the luminescence intensity of the as-prepared YVO₄:Eu³⁺,Sr²⁺ particles increased with the Sr²⁺ doping concentration x to reach a two-fold enhancement when x = 5 %, and then decreased for higher x. We also investigated the effect of thermal annealing on the luminescence properties of the YVO₄:Eu³⁺ and YVO₄:Eu³⁺,Sr²⁺ particles. A remarkable enhancement in their luminescence properties was observed after annealing at 900 °C in air for 30 min. It was showed that the annealed YVO₄:Eu³⁺,Sr²⁺ particles exhibited a two-fold stronger emission than the annealed YVO₄:Eu³⁺. This work indicates that Sr²⁺ doping is beneficial to the luminescence enhancement for both the as-prepared and annealed YVO₄:Eu³⁺,Sr²⁺ particles.     

Sorption and diffusion of gases in a polyimide

Sorption and diffusion of gases (CO₂, N₂, and He) in a polyimide (PI2080) film were measured by using an apparatus which gives the sorption rate curves from the initial state to the equilibrium state. Nonlinear isotherms observed for CO₂ sorption were interpreted successfully in terms of the dual-mode model for sorption in glassy polymers. Linear isotherms observed for N₂ and He seemed to obey Henry's law. Two diffusion coefficients (D_I and D_E) were obtained using the short-time method and the long-time method for a Fickian diffusion model, together with the equilibrium solubility (C_e) from each experiment. The initial sorption rate curves agreed with the calculated curves using D_I, however near sorption equilibrium the curves are in accord with the calculated curves using D_E. These observations suggest that some relaxation process is superimposed on the diffusion process. The non-Fickian transport data were correlated successfully with a model that combines time-dependent diffusion and the Fickian model.     

Improved method for strontium/calcium coprecipitation by phosphate for89Sr and90Sr analysis in food

When Sr and Ca phosphate are precipitated jointly, a well filterable crystalline product is formed either almost immediately by use of Mg or Mn salts, or without these crystallization starters when a waiting period is observed at the very beginning of phosphate precipitation.     

A new experimental design to investigate the concentration dependent diffusion of Eu(III) in compacted bentonite

The 'in-diffusion method was used to study the diffusion behavior of Eu(III) in compacted bentonite. The results (K _d, apparent and effective diffusion coefficients) derived from the capillary method are in good agreement with the literature data for similar bentonite dry densities and similar radionuclide concentrations, and fits the Fick's second law very well. The method was used to study the effect of solution concentration (10^-7-10^-3 mol/l) on the diffusion and sorption behavior in compacted bentonite. The experiments were carried out in synthetic groundwater, at room temperature. The results suggested that the diffusion of Eu(III) in the bentonite was independent on the density of bentonite, but dependent on the solution concentration. In agreement to the literature, the K _d values from the capillary experiments are in most cases lower than those from batch experiments, they are about one-half to one-third the value to those from batch experiments. The difference between the K _dvalues from capillary and batch experiments are a strong function of the bulk density of the bentonite. The results suggest that the content of interlaminary space plays a very important role to the transport of Eu(III) in compacted bentonite.     

Beta-spectroscopic separation of90Sr,90Y and89Sr with a scintillation detector

A -spectroscopic method for measurement of the isotope ratios and absolute activities of⁹⁰Sr,⁹⁰Y and⁸⁹Sr with an organic scintillator is described and tested. The correction factors for absorption in the sample and the detector window are calculated. The method can be used for rapid estimation of ratios and absolute activities of pure -emitters after a nuclear accident.Supported in part by the International Atomic Energy Agency, RC5633 and the National Fund for Scientific Research (Bulgaria).     

New method for90Sr determination in liquid samples

A method has been developed for measuring⁹⁰Sr activity in liquid samples. After concentrating strontium from the sample by coprecipitation with calcium phosphate, the residue is dissolved in 8N HNO₃ and passed through an extraction chromatographic column (Sr.Spec) containing a new material that selectively retains strontium. This is eluted from the column with 0.05N HNO₃ and counted by liquid scintillation. Measurement is performed using a double window method, that allows a rapid and single determination of⁹⁰Sr.     

Oxygen non-stoichiometry and diffusion in RBA2CU3O6+x (R=Y, Gd, Ho) investigated by TG method

By means of thermogravimetry (TG) and chemical analysis equilibrium dependencies of oxygen content in GdBa₂Cu₃O_6+x and HoBa₂Cu₃O_6+x on temperature and were studied. It is found that at equal temperature and the oxygen content in RBa₂Cu₃O_6+x increased in order Ho-Y-Gd.On the basis of Fick 2nd law mathematical procedures to determine diffusion coefficients of oxygen from TG data were developed. The oxygen diffusion coefficients in RBa₂Cu₃O_6+x (R=Y, Gd, Ho) were evaluated in a wide temperature (300–900°C) range (at =0.21 bar). The developed model rather satisfactory decribes oxygen diffusion processes in phases under investigation. It is found that for all studied compounds oxygen diffusion in orthorhombic phase happened faster than in tetragonal one. The values of diffusion coefficients increase in order Ho-Y-Gd with increasing of ionic radius of the rare earth element.     

Evaluation of Eu(III) migration in compacted bentonite

The distribution coefficient of Eu(III) derived from batch experiments is used to predict the migration of Eu(III) in compacted bentonite with time. The effect of the dispersion coefficient and the pore water velocity on the migration of Eu(III) are also taken into account. It was found that the dispersion coefficient does not influence the migration, while the variation of the distribution coefficient and the water velocity affected the behavior of Eu(III) in compacted bentonite. Most of the europium is retained in the first several meters. So, 30 m of backfill bentonite may be sufficient to prevent the release of Eu(III) to the environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sorption characteristics of Am(III), Sr(II) and Cs(I) on bentonite and granite

The ability of the back-fill and the host rock materials to take up radioisotopes like ²⁴¹Am, ^85,89Sr and ¹³⁷Cs has been examined as a function of contact time, pH, amount of sorbent, sorbate concentration, and the presence of complementary cations. A batch technique using actual borehole water from the granite formation has been utilized. In general, the uptake of nuclides by bentonite is much higher than that with granite. The sorption order of nuclides on bentonite is Am>Cs>Sr. The presence of complementary cations, Na⁺, K⁺, Ca²⁺ and Mg²⁺ depresses the sorption of Cs and Sr on bentonite. The sorption data have been interpreted in terms of Freundlich and Langmuir isotherm equations. Utilizing the Langmuir isotherm equation, the monolayer capacity, V _m ,and the binding constant, K, have been evaluated. The change in free energy for the sorption of nuclides on bentonite has also been calculated.     

Sorption of Co2+, Pb2+, and Sr2+ Ions on Hydroxyapatite,Synthesized in the Presence of Oxyethylidenediphosphonic Acid

Russian Journal of Applied Chemistry - The physicochemical and sorption properties of hydroxyapatite synthesized in the presence of oxyethylidenediphosphonic acid, as crystallization inhibitor,...     

Determination of 90Sr in urine samples and 89Sr/90Sr in water samples by chemical separation and Cherenkov counting with LSC system

Journal of Radioanalytical and Nuclear Chemistry - In order to determine radiostrontium with a satisfactory chemical yield, calculated by an external standard, and a low level of MDC a...     

A rapid method for analysis of non-equilibrated 90Sr/90Y in infant formula

Journal of Radioanalytical and Nuclear Chemistry - A rapid analytical method for quantifying 90Sr in infant formula prior to secular equilibrium is presented. The approach is dependent on the use...     

Effect of fulvic acid on the sorption and desorption of 90Sr2+ on red earth

Summary Sorption and desorption of radiostrontium on the red earth and its solid components in the presence and absence of fulvic acid were investigated by a batch technique under ambient conditions at pH 5.3±0.1 and T = 25±2 °C. The organic matter in the red earth is a significant trap of ⁹⁰Sr²⁺ and the presence of fulvic acid enhances the sorption of ⁹⁰Sr²⁺ on the red earth at pH 5.3. It was found that all the sorption and desorption isotherms are linear and the sorption of ⁹⁰Sr²⁺ on the red earth can be described by a reversible sorption process and the sorption mechanism is mainly ion-exchange. The effect of ionic strength on ⁹⁰Sr²⁺ sorption was also investigated.