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[en] A number of synthetic compounds have been prepared which represent those which are considered to be present in a mature blast furnace slag (BFS)/ordinary portland cement (OPC). Some of these have been prepared with lanthanum dopant to investigate the possible inclusion of sorbed species in the structure. The compounds have been investigated by the best available tools to determine the chemical state of the sorbed species and the possible incorporation of the sorbed ions into the evolving structure of the cement. The sorption coefficients of these compounds for americium and plutonium have also been determined. The structural studies were impeded by the instability of the compounds and the surface analytical tools lacked the sensitivity to detect the sorbed elements. The extended X-ray absorption fine structure (EXAFS) technique shows considerable promise. Studies of the sorption of actinides from solution onto these compounds have shown that the sorption coefficients are no less than those determined for fresh cements. (author)
[en] Strontium sorption on HA was investigated by batch method. HA was prepared from CA(OH)2 and H3PO4 water solution. It has defined Ca/P ratio and specific surface. Strontium desorption was examined in the presence of Ca2+ ions. The amount of sorption and desorption was determined, and it was shown that HA is more effective sorbent for low concentration solutions. (author)
[en] Full text: A number of polymer sorbents was obtained on the base of polyethylene mine with the improved sorption properties.Have been shown that protonization of functional groups of polymer results in improvement sorption properties of sorbents. The sorption capacity of polymer sorbents obtained on the base completely proton zed polyethylene mine almost twice above as compared to by sorbents synthesized by a customary way was established
[en] In the present study, the sorption behavior of cesium was investigated in Ain Oussera soil around the Es-Salam reactor facility. This study was conducted using batch method under different physicochemical conditions including contact time, ionic strength, pH, solid/liquid ratio and temperature. The results showed that sorption followed pseudo-second-order kinetics with a good regression coefficients (R2 = 0.999). The activation energies were 11.26 and 15.21 kJ mol-1 which correspond to ion-exchange-type sorption mechanism. The adsorption was favored at low temperature and it was exothermic (?H0 < 0, with average value of -1.97 kJ mol-1) and spontaneous (?G0 < 0, with average value of -11.97 kJ mol-1 at 23 degC and -13.2 kJ mol-1 at 60 degC). The presence of competing cations such as K+ and Ca2+ ions in groundwater can significantly reduce the Cs adsorption onto soil. Desorption reaction was also investigated using three reagents with different ionic strengths (deionized water, groundwater and 0.1 M KCl solution). The results showed that Cs ions were preferentially distributed onto high affinity sorption sites.
[en] Sorption properties of the synthesized polymer sorbent against uranium were investigated in various concentrations and at different pH values. It has been determined that the maximum synthesis ability of the sorbent is for uranyl ions in the range of pH 4-8 of the liquid phase. The dependence of sorption of uranium by the sorbent was studied by the pH of the solution and it was found that as the pH of the solution increases, the sorption rate and the sorption capacity of the sorbent increases. At pH 7, these quantities reach their maximum value. The maximum absorption of uranium ions at pH 7 is due to the fact that uranium is converted into a double uranium hydroxy cation (UO2)2(OH)2+2) in solution.
[en] The pH dependence of sorption of uranium (V I) little quantities from low carbonate solutions on cry granulated hydroxides of some four- tri-, bivalent metals and their mixture has been studied for development of methods for concentration and separation of uranium (V I) from aqueous objects. The uranium (V I) sorption have complicated character and has two maximum at pH interval (2-13). Hydroxides of the uranium (V I) sorption is at pH 9,5-10,0 where uranium is completely in the tri carbonate complex [U O+2(CO3)3]-4 form. In the basic region (pH>10,5) degree of uranium capture increases again. To investigate the mechanism of uranium (V I) sorption on hydroxides, experiments in conditions of coprecipitation without carbonate have been carried out. Thus, taking into account obtained results, the uranium (V I) sorption on the metal hydroxides can be considered as a result of acid-basic interaction between micro- and macro components like hetero hydroxo complex formation. The main coprecipitated form is neutral hydroxo complex
[en] The adsorption of Cs on clayey materials such as bentonite and Na-montmorillonite was studied in various electrolytic conditions (concentration and composition), various solid to liquid ratios and various pH conditions. The results obtained for these different conditions were modeled considering an exchange model associated to the surface complexation concept. Then, the same approach was considered to model the sorption of Rb, which have the same chemical behavior than Cs. Experiments were carried out for various electrolyte, pH, and Rb concentrations. The stoichiometries corresponding to the sorption of Rb on bentonite and montmorillonite were then deduced from the experimental results. (author)
[en] An experiment for uranium sorption onto fresh and weathered biotites was performed. After centrifugation, concentrations of uranium in the supernatants were analyzed using ICP-MS, and biotite samples were investigated using XRD and SEM. With powdered biotites (<3 mm in size), we have conducted uranium sorption experiments about fresh and weathered biotites to obtain uranium sorption amounts in various pH conditions. The uranium sorption was not high at a low pH (e.g., pH 3), but increased with increasing pH. There were lower uranium sorption by the weathered biotites than by the fresh ones, and the difference was much larger at higher pH (e.g., pH 11). The lower sorption values of uranium by the weathered biotites may be caused by a change of mineral surfaces and a chemical behavior of surrounding dissolved elements. It seems that the uranium-mineral interaction has been diminished, especially, in the weathered biotite by a destruction and dissolution of preferential sorption sites on the mineral surfaces and by the colloidal formation from dissolved elements.
[en] As a result of nuclear weapons testing, nuclear accidents and leaks from high level waste storage sites significant quantities of radionuclides have been released to the environment. Therefore, presence of radionuclides and toxic metals in wastes are a major environmental concern. Considering that cesium (t1/2:30.1 y) radionuclide has long half-life, radioactive wastes containing cesium are considered to be dangerous pollutants and their migration by groundwater is strongly affected by their adsorption on the geologic materials. Sorption processes of radionuclides help to understand prediction of their mobility. We investigated sorption of cesium in batch experiments for different barrier materials to examine concentration effect under ambient experimental conditions. The adsorption data was subjected to four different adsorption isotherms (Freundlich, Dubinin-Radushkevich, Langmuir and Temkin). Hence, various adsorption constants were obtained from the slope and intercept of isotherm graphs. The main energy of adsorption was also calculated from the adsorption isotherms.
[en] The results of study of selectivity of caesium sorption by a natural and surface-modified glauconite as a dependence of potassium and ammonium concentrations are presented. In the case of the surface-modified glauconite at low salt content the decrease of caesium distribution coefficients with the decrease of potassium or ammonium concentration was observed; this effect might be caused by transfer of 37 ± 7 % of caesium to a non-absorbable colloidal form. However, even in the worst case, values of caesium distribution coefficients for the surface-modified glauconite were as high as 10"3-10"4 L kg"-"1. (author)