جستجوی مقالات مرتبط با کلیدواژه "استرانسیم" در نشریات گروه "فیزیک"

Due to the importance of removing strontium ions in nuclear wastes, in the present work, while synthesizing hydroxybenzaldehyde propyltriethoxysilane ((EtO)3Si-HL) and pyridylmethylidene propyltriethoxysilane ((EtO)3Si-L) ligands, we investigated the properties of silica nanoparticles modified with these ligands as solid adsorbents in The removal of strontium ion from the aqueous solution was investigated and parameters such as pH, time, the mass of adsorbent, temperature, and interfering ions were tested. The adsorption behavior of the adsorbents showed that by modifying the surface of the nano adsorbent, the ability of the adsorbents to adsorb strontium ion at pH=6 increased from 6.31% to 86% and 22.11% using the (EtO)3Si-HL and (EtO)3Si-L ligands, respectively. The results of isotherms and adsorption kinetics indicate that the adsorption process follows the Longmuir isotherm and the pseudo-second-order model, respectively. Also, thermodynamic parameters show that strontium removal from the aqueous solution is an endothermic process. The positive entropy values are the driving force behind the adsorption process.

In this study, graphene oxide (GO) adsorbent was prepared by modified Hummer’s method and functionalized with aminomethylphosphonic acid. Its application to the adsorption of Sr ions from aqueous solutions in a batch sorption process was investigated. Adsorbents were characterized by TEM and FT-IR. The TEM images of functionalized graphene oxide showed that graphene sheets are formed in wavy sheets. The FTIR spectrum revealed that graphene oxide was highly functionalized with aminomethylphosphonic acid and oxygenated functional groups were reduced. Response surface methodology investigates pH, adsorbent dosage, and temperature parameters. The quadratic model corresponds well with the experimental data. The results illustrated that there is no systematic error in the experiments. The verification of the model with random experiments showed a low error in the values predicted by the model. The kinetic data were analyzed by Pseudo-first-order, Pseudo-second-order, and Double- exponential kinetic models, and experimental data were well modeled by the pseudo-second-order kinetic model. The research results showed that graphene oxide functionalized with aminomethylphosphonic acid has a good ability to strontium adsorption from aqueous solutions.

This research investigates the transfer factor in the soil to plant (as one of the important parameters in safety analysis calculations and determining the amount of radiation of people) of strontium ion (a conventional radionuclide in pollution caused by nuclear accidents) to two plant samples including radish (Raphanus sativus var. sativus) and watercress (Lepidium sativum) as highly consumed plants in the food chain grown in the southern soil of Tehran. In this research, experiments were carried out in pots with a diameter of 15.5 cm and a height of 15.7 cm. These pots contained 2 kg of soil mixed with compost under the natural sunlight conditions of Tehran. In order to investigate the effect of strontium ion concentration on the transfer factor, the desired soil was first mixed with compost at a ratio of 3:1 and, using strontium nitrate salt solution in four different concentrations (50-200-500-1000 mg/kg) was infected. Pots were irrigated weekly with a specific volume of water at two different acidity levels (pH = 5 and 6) to investigate the effect of pH on the transfer factor. Also, the concentration of strontium ions in two tissues of the leaf and root of radish and watercress was done. This was examined to determine the accumulation of strontium ions in each of the tissues and their influence on the transfer factor. The results showed that with the increase in soil strontium concentration, the amount of adsorption of this element in both plants increases and the transfer factor decreases. Also, the plant had more adsorption in the soil with lower pH and a higher transfer factor was reported. The comparison of transfer factor and strontium adsorbed between the two plants also showed that radish adsorbed more strontium than watercress and had more transfer factor. Also, using an experimental method, the distribution coefficient, which is a crucial and practical parameter in pollutant transfer modeling and pollution risk assessment in soil and water resources, was determined by using the transfer factor from soil to plant. In this research, the possibility of decontamination of strontium from the soil by applying radish was investigated. The results showed that this plant could be used as a purifier to purify soils contaminated with strontium.

In the current work, the graphene oxide was synthesized through Hummer’s method and modified with nickel hexacyanoferrate nanoparticles. The product was characterized by a Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The characterization results confirm the successful synthesis of graphene oxide and the immobilization of nanoparticles on it. The obtained graphene oxide-nickel hexacyanoferrate (GO-NiHCF) was applied for the removal of Sr(II) from the aqueous media in the batch method. The influence of effective factors such as pH, time, and initial concentration of strontium on adsorption was studied. The pH study showed that Sr(II) uptake increases in the pH range of 1-7 and the uptake reduces slightly or remains constant at higher pH values. The adsorption capacity under optimum conditions was obtained at about 140 mg g-1 adsorbent. The kinetic data of Sr(II) sorption by GO-NiHCF were investigated by pseudo-first-order and pseudo-second-order models. The results showed that the kinetic data fitted well to the pseudo-second-order rate model. The equilibrium data suggest the data are relatively fitted well to the Langmuir adsorption isotherm. Therefore, it can be understood that adsorbents’ dispersion on graphene oxide sheets or interlayers is homogenous. The separation factor(RL) value extracted from the Langmuir curve was estimated as 0<RL<1, showing the sorption behavior is favorable.

This study investigates the distribution coefficient of strontium in a soil sample in the south of Tehran. In this research, the columnar method  was used to determine the distribution coefficient of strontium. Also, the effect of three factors, pH, strontium concentration, and soil height in the column was studied using the RSM method's experimental design. For this purpose, five different levels were considered for each parameter, and the experiments were designed and performed by MiniTab software. According to the results obtained in the predicted model, pH, column height, interaction between pH and column height, the interaction between pH and strontium concentration, and interaction between strontium concentration and column height are important. The square of the coefficients as well as the concentration of strontium, did not have much effect on the distribution coefficient. The most significant effect is due to the height of the column, which increases with increasing the height of the column. The rate of conformity of the predictive equation with the actual values ​​is 96.39%, which is an acceptable value.

The chemical isotope exchange with macrocyclic polyethers is one of the relatively new methods for isotope separation. These separations are based on the phenomenon of isotope effect, in which the kinetic and the stability of the complex formation between the ligand and the isotopes of an element are different. In particular, crown ethers and cryptands, with high affinity and size selectivity for some metal ions, have been investigated for isotope separation in various extraction processes. In the present study, the isotope effect in a solid-liquid extraction of strontium with Merrifield resin having 2.2.2-Cryptand anchor groups was investigated. The effects of various experimental parameters such as pH, concentration of strontium, type of anion, equilibrium time, and temperature on the separation factor of strontium isotopes were studied and discussed. The results showed that the separation factor had an inverse correlation with the isotope mass and for the lighter isotopes this factor was greater. Under the optimum conditions, the separation factors for 84Sr/88Sr, 86Sr/88Sr, and 87Sr/88Sr were 1.028, 1.017, and 1.014, respectively.

In this study, initialy the effect of time on the removal of strontium from aqueous solutions by continuous electrodeionization (CEDI) with H+ form resin was investigated. Then, by using an orthogonal L9 array in the Taguchi method, the effect of voltage, flow rate and feed concentration on the removal of Sr and Cs from aqueous solutions by the CEDI with the saturated resin was applied. The analysis of variance (ANOVA) method was used to evaluate the relative effect corresponding to each factor. The results showed that by increasing the applied voltage and decreasing the flow rate improve the performance. The effect of input voltage was more significant and the feed concentration did not have any perceptible effect on the Sr and Cs removal efficiency. The removal of both elements from binary solutions were also investigated. In this experiment, the removal efficiency of Sr was also found to be higher than those of Cs. Based on the results, electrodeionization was considered to be effective for Sr and Cs removal from aqueous solutions.

Yttrium-90 as a β emitting with the maximum energy of 2.3MeV, and due to the long half-life of its parent-strontium-90, is considered as one of the most important radionuclides in nuclear medicine. In this context, a highly selective and rapid method for the separation of 90Y from its parent is required for its use in nuclear medicine. In this study, adsorption behavior of yttrium (III) and strontium (II) ions were studied on the Amberlite XAD-4 resin impregnated with (2-ethylhexyl) phosphate (HDEHP) by batch and continuous methods. The effects of extraction time in different media, nitric acid and hydrochloric acid concentrations on the sorption and desorption of ions were investigated. Different kinetic models were examined to determine the adsorption mechanism of yttrium. For the separation of yttrium from strontium in 0.05M nitric acid media, a solution containing 5ppm yttrium and 1000ppm strontium was passed with a flow rate of 1ml/min through a chromatography column. In this condition, while yttrium was retained by the resin, strontium passed through the column. A ratio of 200 was calculated for Y/Sr in eluate. The results of the present experiment can be used for separation of yttrium-90 from strontium-90.