Papers by Keyword: Distribution Coefficient

Abstract: The article presents the results of studies of the chemical stability of solidified radioactive waste with alkali cement through long-term leaching. Efficiency of application of alkaline slag Portland cement type LCEM IV as a matrix for reliable chemical and physical binding of caesium ions in the compound for long-term burial we confirmed. Modification of alkaline cement by additions of magnetite from 5 to 8.3% and zeolite in the amount from 4.2 to 5% promotes additional sorption of caesium ions in solidification products of alkaline matrix at maximum content of radioactive waste up to 17.5%. It they noted that the maximum values of sorption capacity of compounds (from 42000 to 68000 ml/g) we observed on the 14th day of the leaching process. They are characteristic for compounds containing magnetite from 5 to 8.3%, zeolite - from 4.2 to 7.5% and radioactive waste from 10 to 15%. It is shown that on the first day of leaching the highest rate (8.35E-02 g/сm²day) is characterised by compositions containing magnetite from 5 to 8.3%, zeolite from 4.2 to 5% and radioactive waste from 15 to 17.5%. At 56 days of the test, the leaching rate decreases exponentially to values of 3.45E-05 to 9.62E-06 g/сm²day. Characteristic of compounds, magnetite and zeolite up to 5% and radioactive waste 17.5%.

Abstract: Artificial barriers are being considered for the burial disposal of low-level radioactive waste in Japan. The artificial barrier consists of i) a low permeable layer made of bentonite materials that suppresses migration of nuclides due to advection, and ii) a low diffusion layer that uses cementitious materials that suppresses migration of nuclides due to diffusion. In addition, as methods of disposing of radioactive waste generated by the accident at the Fukushima Daiichi Nuclear Power Station, controlled disposal and isolation-type disposal are being considered. We thought that it would be effective to add adsorption performance to the performance of suppressing migration of such radioactive substances. In this study, we designed and experimented on the adsorption performance of mortar mixed with various zeolites, which had never been examined. As evaluation methods, i) fluidity, ii) strength, iii) low diffusivity, and iv) distribution coefficient of cesium and iodine were obtained. Based on the results, we reexamined the composition and conducted experiments to examine the applicability to high-adsorption artificial barriers. As a result, it was confirmed that the mass transfer resistance tends to be low due to the zeolite being porous. It was also shown that the strength of mortar mixed with zeolite depends on the cement matrix. As a result of this research, the distribution coefficient of cesium in cementitious materials using zeolite with a high cation exchange capacity designed in this research is higher than that of cementitious materials for low-level radioactive waste disposal facilities currently in operation 1,500 times was obtained. On the other hand, we were able to discover the possibility of examining construction on a full-scale regarding fluidity and compressive strength. As a future task, it was found that it is necessary to investigate a more practical artificial barrier by increasing the strength and densification of the cement paste.

Abstract: It is crucial to know the distribution coefficients of chemical elements in melts. This is essential for obtaining a given composition and properties of epitaxial layers grown from the liquid phase, for determining the regimes of high purification of materials obtained by zone melting, for producing the desired gradient of distribution of alloying elements throughout the layers of construction materials treated by chemical-thermal methods, etc. This paper presents the results of computing the distribution coefficient of arsenic during the growth of layers of phosphide-arsenide of gallium from the liquid phase (molten gallium), saturated with phosphorus. We also obtain the dependencies between the distribution coefficient of arsenic, the temperature and the concentration of arsenic inside the gallium melt during the growth of epitaxial layers. As well a practical application of the results with a given gradient of concentration for the gallium arsenide layer is demonstrated.

Abstract: Sediments play an important role on fate in the diffusion of radionuclide in aquatic systems. In this study, the investigation of the adsorption/desorption kinetic of ¹³⁷Cs in two different characteristic of marine sediment samples (organic matter, CEC, and clay content). Batch experiment was carried out from the Upper of Gulf Thailand. The results have shown that there is a significant percentage of ¹³⁷Cs is adsorbed in both marine sediments during the first 48 hour that increased adsorption percentage to 82 and 86% and after that become to stable. On the other hand, the desorption of ¹³⁷Cs was found both marine sediment were desorbed less than 10 % and become to stable desorption after 24 hours. Among different marine sediments (St.1 and St.21), the K_d value (distribution coefficients) of ¹³⁷Cs was different which K_d of sediment from station 1 more than station 21(342.9 and 247.5 L/kg respectively). Differences in the characteristics of marine sediments affect to different the K_d value.

Abstract: A calculation method of rotational stiffness of all-vertical-pile-supported (AVPS) wharf is discussed and a formula based on rotational stiffness is derived to evaluate the distribution of horizontal forces on an AVPS wharf. Combining with an engineering example, the rotational stiffness and the horizontal force distribution coefficients were calculated utilizing finite element method (FEM), the elastic support-rigid beam method (ESRBM) outlined in Chinese Harbor Code, as well as the proposed formula for the piles layout width-length ratio of 0.4, 0.5 and 0.6. Results indicate that the increase in width-length ratio will increase the rotational stiffness and make the distribution of horizontal forces on each bent to be more uniform. Results calculated by the proposed formula are agree well with the results by FEM. The maximum difference of the distribution coefficient on the first bent between the results obtained by the proposed formula and by ESRBM is approximately 22%.

Abstract: Batch experiments were conducted to measure the sorption capacities of estrone (E1) to aerobic activated sludge. The effect of temperature on E1 sorption was investigated at the temperatures of 5-35oC. The results showed that E1 sorption equilibrium was reached at 15min. E1 sorption on the sludge fitted both Freundlich and linear sorption isotherm models. Distribution coefficients (Kd) of E1 to aerobic inactivated sludge was 546.5 L∙kg-1 at 25oC. The effect of temperature on sorption indicated that lower temperature benefited the sorption. The distribution coefficients (Kd) and sorption rate both decreased with the increased temperature. Kd of E1 to aerobic inactivated sludge was decreased by about 44%; the sorption rate was decreased by about 13% when temperature increased from 5 to 35oC. The specific sorption coefficient KOM or KOC was also used to describe the sorption capacity, which also decreased with increased temperature. Sorption thermodynamics indicated that the sorption process was exothermic and spontaneous.

Abstract: Propionic acid has been received increasing attention due to its various usages as an antifungal agent in food and a chemical in the production of several chemical products. In order to develop an alternative production process of propionic acid such as fermentation of glycerol, the cost effective recovery process of propionic acid from its fermentation broth is needed. Differently from conventional physical extraction, long chain amine (TOA)-based extraction is the separation process using reactions between amine and materials extracted. The equilibrium distribution of propionic acid increased with amine concentration and decreased with increase of n-heptane composition in mixed diluents. From the loading values with TOA concentrations, it was found that the stoichiometries of acid-amine-1-octanol complex were (1,1) and (1,1,1). From this study, amine-based extraction can be promising separation process for the recovery of propionic acid.

Abstract: Tea (Camellia sinensis L.) has became one of the most consumed beverages in the world in the past five thousand years, and tea polyphenols (TPs) are important organic acids widely used in chemical, pharmaceutical, food and other industries, which have been shown to exhibit various biological and pharmacological properties. In order to look for new technology of downstream process for TPs separation from green tea waste, selective extraction of TPs with 12 varieties of solvents were carried out, the distribution coefficient and equilibrium experiments at various temperatures were described by extraction isotherms model. The results indicated that the optimum solvent conditions were as follow: extractent was glyceryl triacetate, extraction temperature range was 20~30°C, pH value of crude TPs and reextractant were 3.17 and 9, respectively. Equilibrium data of TPs were successfully fitted to Henry isotherm, the distribution coefficient decreases with the increasing of the temperature, which showing an exothermic adsorption process. The data obtained is useful in the designing of solvent extraction process for the recovery of TPs from green tea waste.

Abstract: It has been generally known that the refining efficiency in zone refining process depends on travel rate, number of pass and distribution coefficient of impurity. In the present study, the effect of distribution coefficient on copper purification was investigated by zone refining process. A numerical model capable of predicting the solute redistribution at any stage of zone refining was proposed. The composition profiles of each segment at the given condition were compared with the results of micro hardness profiles. After zone refining, metallic elements were analyzed by GDOS (Glow Discharge Optical Spectroscopy) and GDMS (Glow Discharge Mass Spectrometry). The impurities Ag, Pb, S and Ti, whose distribution coefficients are below 0.5, were concentrated at the finishing position. Cr, Mn, Si and Zn, whose distribution coefficients are between 0.5 and 1, were distributed irregularly. Fe and Ni, whose distribution coefficients are greater than 1, moved to the starting position. It was found that zone refining process was actually effective to remove impurities whose distribution coefficients are below 0.5. The experimental results agreed well with the simulation result.