The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)3) and they consists of particles of median particle size 2.1 mm (sample A) and 2.5 mm (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from 238U, 232Th, 40K in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45012 and Grant no. III 45005]

Presented study deals with the final structure and radiological properties of different fly ash-based geopolymers. lignite fly-ash (lignite Kolubara - Serbia) and wood fly ash were obtained in combustion process together with commercial fly ash. Synthesis of the geopolymers was conducted by mixing fly ash, sodium silicate solution, NaOH and water. The samples were cured at 60?C for 48h after staying at room temperature in covering mold for 24 h. X - ray diffraction, Fourier transform infra - red and Scanning electron microscope measurements were conducted on the samples after 28 days of geopolymerization process. X-ray diffraction measurements of lignite fly ash samples show anhydrite as the main constituent, while wood fly ash samples consist of calcite, albite and gypsum minerals. Beside of determination of physical-chemical properties, the aim of this study was radiological characterization of lignite fly ash, wood fly ash and the obtained geopolymer products. Activity concentration of 40K and radionuclides from the 238U and 232Th decay series in ash samples and fly ash-based geopolymers were determined by means of gamma-ray spectrometry, and the absorbed dose rate rate (D) and the annual effective dose rate (E) were calculated in accordance with the UNSCEAR 2000 report.

The exposure of human beings to ionizing radiation from 137Cs is a continuing and inescapable feature of life on Earth. Artificial radio nuclides are widely distributed in various geological formations and ecosystems such as rock, soil, groundwater, and foodstuffs. In the presents study, the distribution of 137Cs was measured in soil samples collected from different lithological units of the Rudovci, Lazarevac, Serbia. Analysis of the vertical soil profiles indicated that the activity of 137Cs was not extremely changed with depth. The activity concentrations of the 137Cs in measured soil samples ranged from below minimal detectable concentrations up to 38.1 Bq/kg. In order to evaluate the radiological hazards due to 137Cs in the samples, the absorbed dose rate and the annual effective dose were calculated in accordance with recommendations given in the UNSCEAR 2000 report. The distribution of radionuclides depends upon the rock composition, chemical and physical properties of the soil. The external absorbed gamma dose rates due 137Cs were found to vary from 0 to 1.16 nGy/h

Active carbon hollow fibers were prepared from regenerated polysulfone hollow fibers by chemical activation using: disodium hydrogen phosphate 2-hydrate, disodium tetraborate 10-hydrate, hydrogen peroxide, and diammonium hydrogen phosphate. After chemical activation fibers were carbonized in an inert atmosphere. The specific surface area and porosity of obtained carbons were studied by nitrogen adsorption-desorption isotherms at 77 K, while the structures were examined with scanning electron microscopy and X-ray diffraction. The activation process increases these adsorption properties of fibers being more pronounced for active carbon fibers obtained with disodium tetraborate 10-hydrate and hydrogen peroxide as activator. The obtained active hollow carbons are microporous with different pore size distribution. Chemical activation with phosphates produces active carbon material with small surface area with but with both mesopores and micropores. X-ray diffraction shows that besides turbostratic structure typical for carbon materials, there are some peaks which indicate some intermediate reaction products when sodium salts were used as activating agent. Based on data from the electrochemical measurements the activity and porosity of the active fibers depend strongly on the oxidizing agent applied.

Continuous development of new technologies leads to increasing pollution of water, thus creating the need for new materials that could be used in the processes of its purification. Therefore, adsorbents prepared from agricultural waste, resins, silica gels, zeolites, clays, flying ash, aluminosilicates and other materials are being investigated as potential sorbents. Recently, research has focused on improving the adsorption capacity by modifying the material by binding or impregnating inorganic and organic molecules on the surface. In this paper, the kaolinite modification with amino acids, histidine and cysteine, was performed to improve the efficiency of adsorption of cadmium ion. Cation exchange capacity (CEC) of raw and modified kaolinite was determined by titration with methylene blue. The influence of operating parameters, such as adsorption time, pH value of the solution, initial metal concentration and temperature, on the capacity and adsorption efficiency were examined. Better agreement of experimental results with Freundlich's adsorption isotherm and the pseudo-second order kinetics model suggest that the adsorption of cadmium ions on the investigated adsorbents takes place by chemisorption mechanism. The change of Gibbs free energy has a negative value for both adsorbents, which shows that the adsorption process is spontaneous. The efficacy of cadmium removal from the aqueous solution onto histidine-modified kaolinite increased from 78.6% to 91.8%.