جستجوی مقالات مرتبط با کلیدواژه « ضریب توزیع » در نشریات گروه « فیزیک »

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 safety assessment of Anarak site as the only center for the disposal of radioactive waste is of particular importance in order to maintain human health and the environment. Distribution coefficients of radioactive materials in the soils of the area under study is one of the influential parameters in the safety assessment calculations. Therefore, in this study, the distribution coefficient of cobalt in the alluvial soil of Anarak waste was determined by the batch method and two parameters of concentration and soil to solution ratio were studied. Linear adsorption isotherms, Friendlich and Langmuir were also analyzed to determine the adsorption behavior of cobalt in Anarak soil. The average value of cobalt distribution coefficient in the mentioned soil was calculated equal to 247.18 mL / g. The adsorption behavior of cobalt in Anarak soil followed the Langmuir adsorption isotherm with a positive and significant correlation. The maximum amount of cobalt uptake was determined as 0.029 mg / g soil. The results of the distribution coefficient obtained in this study are lower than the most of the values ​​presented in the other previous researches, which can be related to the soil texture (sandy loam) and the other soil characteristics.

Calculation of distribution coefficients is one of the essential provisions in the safety assessment of radioactive waste repository and safe management of radioactive waste. Due to the importance and characteristics of thorium radionuclide in radioactive waste inventory, the distribution coefficient of thorium in the alluvium soil of Anarak Radioactive Waste Repository was determined by the Batch method two parameters of thorium concentration and soil granulation were studied. Also, the Flow-Through method studied the adsorption behavior of thorium has investigated the effect of thorium concentration and soil height. The average value of thorium distribution coefficient in Anarak soil was calculated 110960 L/kg using the Batch method. The study of adsorption behavior by the Flow-Through method demonstrated high uptake of thorium in the soil due to the strong bond created between the ion and the adsorbent. The results showed that the distribution coefficient increases with the decrease of soil particle size. Regarding the effect of concentration on the thorium distribution coefficient, first, an increasing trend and a decreasing trend were observed in the test range. The results obtained in this study were compared with the results of other studies on thorium radionuclide, which showed a good agreement with other studies.

In this study two Polyacrylonitril-Ti(IV) tungstophosphate organo-inorganic ion exchangers with different molar ratios have been synthesized. These ion exchangers have been characterized by FT-IR, X- ray diffraction, TG, SEM and CHNSO techniques and their cation exchange capacity has been measured by continuous method. Distribution coefficients (Kd) for metal ions and radionuclides were determined by batch method and with these ion exchangers, separation of metal ions was achieved on a glass column.

Hydrated cerium (IV) dioxide has been synthesized by adding excess cerium sulphate to 4M ammonia solution at 250C and pH=12.5 with constant stirring. The properties of the compound were investigated by means of infrared and thermogravimetric techniques. The effect of temperature and pH on the adsorption of Ba and Sr ions and also the distribution coefficients of Cs and Eu at various pH values on cerium (IV) dioxide were considered. The distribution coefficient results showed that with the increase of pH of the media, the amount of adsorption of Ba and Sr cations on the surface of cerium (IV) dioxide increases, and this is due to their amphoteric nature of this oxide.