[en] The aim of this work was to study the influence of mineralogical composition of bentonite adsorbents of Jelsovy potok bearing and standards of montmorillonite SAz-1 and STx-1 on adsorption behavior of strontium cations. In the experiment, Jelsovy potok bentonite showed good adsorption behavior compared with montmorillonite standards. Based on demonstration of the impact of mineralogical composition of adsorbents on adsorption percentage of strontium cations Jelsovy potok bentonite may be considered to be utilizable for multi-barrier system of a deep geological repository for high-level waste and spent nuclear fuel.

[en] The high potential of bentonites to volume changes depending on the water content is considered as their advantage for the engineered barriers in the deep geological repository of high-level radioactive waste and spent nuclear fuel because of swelling and self-healing of cracks in contact with water. On the other hand, drying may lead to opening of cracks and spaces between the bentonite blocks. This would increase the permeability and contamination risk around the hot container with high-level radioactive waste and spent nuclear fuel, especially if the host rock mass is dry. First shrinkage tests on four Slovak bentonites studied for engineered barriers were carried out. The water content at the shrinkage limit and the relative linear shrinkage are the first available shrinkage parameters received for the bentonite paste. The shrinkage hazard is higher in the best bentonites with high swelling potential - from Kopernica and Jelsovy potok. The results indicated the necessity of further shrinkage tests to determine the relative linear and volume shrinkage of bentonite elements pressed of the loose bentonite powder of low water content. (author)

[en] Uranium is naturally-occurring radioactive element, which is commonly found in very small amounts in rocks, soils, waters, plants or animals (include human body). It is harmful both through its chemical toxicity and its radioactivity (all uranium isotopes are radioactive). Exposure to uranium increases your risk of getting a variety of cancers due to its radioactivity. In case of management of radioactive waste, the adsorption of radionuclides plays significant role. Among the natural sorbents applied to the adsorption of uranium zeolites offer a number of advantages (low cost, availability, quite high sorption capacity, good hydraulic properties, thermal stability etc.) as well as no introduction of additional pollution to the environment in the case of application as permeable reactive barriers. The main aims of this work are investigations of adsorption properties of Greek zeolite Metaxades, modelling of traditional isotherms and behaviour during kinetics process, influenced by temperature. (authors)

[en] The aim of this work was to study the influence of mineralogical composition of bentonite adsorbents of Jelsovy potok bearing and standards of montmorillonite SAz-1 and STx-1 on adsorption behavior of strontium cations. In the experiment, Jelsovy potok bentonite showed good adsorption behavior compared with montmorillonite standards. Based on demonstration of the impact of mineralogical composition of adsorbents on adsorption percentage of strontium cations Jelsovy potok bentonite may be considered to be utilizable for multi-barrier system of a deep geological repository for high-level waste and spent nuclear fuel.

[en] The paper studies the absorption of uranium cations (pH_i_n_i_t 2.5, C_i_n_i_t: 10-1000 mg U/L) in the Greek zeolite Metaxades. Adsorption equilibrium was studied by batch technique. Distribution of uranium in monitored system was determined by spectrophotometric method Arsenazo III. The course of the adsorption process of uranium was interpreted by Langmuir, Freundlich and Dubinin-Raduskievich isotherms.

[en] Bentonite deposit Jelsovy potok in Slovakia has great potential for use as a engineering barrier in the multi-barrier system of deep geological repository. In this paper, HDTMA-modified bentonite J15m from Slovak bentonite Jelsovy potok was prepared and its sorption properties (sorption isotherms, kinetics) towards anionic uranium species was investigated. The removal of uranium anionic species from aqueous solutions (initial concentration: 10-1,000 mg/L) by J15m was studied in the absence of background electrolytes at initial pH range (pH_init) 8.5; 9.5; 10.5. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake capacity observed was 31.35 (mg/g) at 298 K. Experimental results were analysed by the Langmuir, Freundlich Dubinin-Redushkevich and Tempkin isotherm. The kinetics of adsorption of U(VI) ions was also discussed using the pseudo-first-order and the pseudo-second-order at three different temperatures. The activation energy of the sorption for J15m was calculated as 23.534 kJ·mol^-1. (authors)

[en] In the first part of this work were compared two-parameter models of linear and nonlinear isotherms to describe the adsorption equilibrium U (VI) on the Slovak bentonite Jelsovy stream (J15). The adsorption equilibrium (VI) was studied by batch technique (BF = 100) from aqueous solutions of UO_2(NO_3)_2 (initial concentration: 10-1000 mg/L) at an initial pH of 2.5. The amount of adsorbed U(VI) in the sample J15 was determined by spectrophotometry with Arsenazo III method. Linear and nonlinear forms of two-parameter isotherms were modelled: Langmuir (L), Freundlich (F), Dubinin-Raduskievich (L-R) and Tempkin (T) [6]. By comparing the values of reliability R"2 we determined that the non-linear forms of isotherms more accurately describe the adsorption process of U(VI) on the sample J15.In the second part three-parameter non-linear isotherms form were consequently modelled: Redlich-Peterson (R-P), Toth (T), Sips (S) and Khan (C). Based on the statistical parameters of reliability values (R"2), Akaike Information Criteria (AIC) and the chi-square test (Χ"2) were compared used 2-parameter and 3-parameter models and description accuracy of adsorption process of U(VI) to J15 was evaluated.

[en] In the first part of this work were compared two-parameter models of linear and nonlinear isotherms to describe the adsorption equilibrium U (VI) on the Slovak bentonite Jelsovy stream (J15). The adsorption equilibrium (VI) was studied by batch technique (BF = 100) from aqueous solutions of UO_2(NO_3)_2 (initial concentration: 10-1000 mg/L) at an initial pH of 2.5. The amount of adsorbed U(VI) in the sample J15 was determined by spectrophotometry with Arsenazo III method. Linear and nonlinear forms of two-parameter isotherms were modelled: Langmuir (L), Freundlich (F), Dubinin-Raduskievich (L-R) and Tempkin (T). By comparing the values of reliability R"2 we determined that the non-linear forms of isotherms more accurately describe the adsorption process of U(VI) on the sample J15.In the second part three-parameter non-linear isotherms form were consequently modelled: Redlich-Peterson (R-P), Toth (T), Sips (S) and Khan (C). Based on the statistical parameters of reliability values (R"2), Akaike Information Criteria (AIC) and the chi-square test (Χ"2) were compared used 2-parameter and 3-parameter models and description accuracy of adsorption process of U(VI) to J15 was evaluated. (Authors)

[en] Using the Slovak bentonite barriers in the repository is predestined by their mineralogical, erosion and rheological properties as well as by the favorable adsorption and retardation behavior to the ionic forms of radionuclides. Usability in practice depends on the speed of the adsorption of adsorbate on the surface of the adsorbent. The aim of this work was to study the effect of mixing time of bentonite and model sample on the distribution ratios and percentage of strontium adsorption. Adsorption of radionuclides Sr-85 on bentonite J250 is relatively fast. Equilibrium is reached almost immediately, up to 1 to 1.5 minutes from the start of contact of solid and liquid phases. (authors)

[en] Bentonite with suitable mineralogical, erosion and rheological properties as well as with favorable adsorption and retardation behaviour to the ionic forms of radionuclides are useful in multi-barrier system of deep geological repository for high level radioactive wastes and spent nuclear fuel. Central European significant bentonite deposit Jelsovy potok from Kremnicka site, which is located in Slovakia, has a great potential for use just as a bentonite barrier in this repository. The aim of this work was to study the effect of the mineralogical composition of bentonite Jelsovy potok and on the adsorption behaviour of strontium cations by montmorillonite standards BET-1 and STx-1. The strontium-90 isotope, which is found in spent nuclear fuel is a biological analogue of calcium, and has every malignant effect on the body. From this point of view, it is important to study and monitor the migration of strontium in the biosphere.