Ljiljana Kljajevic - Academia.edu (original) (raw)

Papers by Ljiljana Kljajevic

Research paper thumbnail of Alkali activation of different type of ash as a production of combustion process

Nuclear Technology and Radiation Protection

Presented study deals with the final structure and radiological properties of different fly-ash b... more 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 strengthened 60 ?C for 48 hours after staying at room temperature in covering mold for 24 hours. The X-ray diffraction, Fourier transform infrared and SAM measurements were conducted on the samples after 28 days of geopolymerization process. The 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. Besides determination of physicochemical 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 a...

Research paper thumbnail of Study of nanosized hydroxyapatite material annealing at different retention times

Science of Sintering

The aim of the study was to investigate the influence of low heating temperatures with two differ... more The aim of the study was to investigate the influence of low heating temperatures with two different retention times to optimize the process for obtaining nanosized hydroxyapatite material that can possibly be used in the fields of biology and pharmacy. Nanosized hydroxyapatite was successfully obtained by wet chemical precipitation. The annealing of the material performed at 300 oC with two different retention times i.e. 3 and 6 hours in air atmosphere. Low annealing temperature with extended retention time was selected in terms to reduce energy consumption. FTIR spectroscopy was used to confirm characteristic vibrational bands of hydroxyapatite samples, and presence of carbonate bands of hydroxyapatite annealed for 3h and 6h. X-Ray powder diffraction analysis were used to examine phase composition, determine the size of unit cells and crystallite sizes, and SEM-EDS methods were used to obtain particle size and arrangement also grain growth morphology and confirmed the presence of ...

Research paper thumbnail of The effect of the concentration of alkaline activator and aging time on the structure of metakaolin based geopolymer

Research paper thumbnail of Radiological and physicochemical properties of red mud based geopolymers

Nuclear Technology and Radiation Protection

A significant amount of red mud generated as a by-product of the Bayer process in the aluminum in... more A significant amount of red mud generated as a by-product of the Bayer process in the aluminum industry may cause environmental problems if appropriate treatment is not carried out. The presented research dealt with the possibility of application of red mud as a pigment or as raw material for use in the construction material industry. In relation to the aim of this work, the physicochemical characterization was performed and the natural radioactivity of red mud as an industrial waste and a geopolymer sample based on it was determined. The presented research is a contribution to the potential solution for environmental protection through the synthesis of possible construction material based on red mud. The radiological hazard orginating from 226Ra, 232Th, and 40K in the samples was assesed throught the absorbed dose rate and the annual effective dose rate, calculated in accordance with the UNSCEAR 2010 report. Physicochemical characterization of all samples was conducted using X-ray ...

Research paper thumbnail of The influence of alumino-silicate matrix composition on surface hydrophobic properties

Science of Sintering

The purpose of this investigation is to investigate the hydrophobicity of geopolymers, new alumin... more The purpose of this investigation is to investigate the hydrophobicity of geopolymers, new alumino-silicate materials and the influence of Si/Al ratio on their surface properties. Contact angle measurement (CAM) as reliable indicator of hydrophobicity was determined for synthesized geopolymers using water and ethylene-glycol as reference liquids. Geopolymers were synthesized from various precursors: kaolin, bentonite and diatomite. Characterization of phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. Contact angle measurements confirmed that the geopolymers synthesized from metakaolin are the most porous, which can be explained by the smallest Si/Al ratio. The maximum value of contact angle and free surface energy (110.2 mJ/m2) has been achieved for geopolymer synthesized by diatoms (GPMD). SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel and is significantly different from the micrographs of other two geopol...

Research paper thumbnail of Physicochemical, mineralogical and radiological properties of red mud samples as secondary raw materials

Nuclear Technology and Radiation Protection

Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia 4 Lab o ra... more Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia 4 Lab o ra tory for Nu clear and Plasma Phys ics,Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia Sci en tific pa per

Research paper thumbnail of Microstructural characterization and adsorption properties of alkali-activated materials based on metakaolin

Science of Sintering, 2016

The microstructural characterization and adsorption properties of metakaolin (MK) and alkali-acti... more The microstructural characterization and adsorption properties of metakaolin (MK) and alkali-activated metakaolin, known as geopolymer materials (GP) were investigated. The structure and properties of the metakaolin and obtained geopolymer were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, based on the analysis of adsorption efficiency, microstructure and mineral structure, the difference between geopolymer and metakaolin on the performance of immobilizing heavy metals have been discussed. The kinetics of adsorption can be represented by pseudo-second order equation. The results of lead ions adsorption experiments were best fitted by Freundlich adsorption isotherm for both investigated adsorbents. The highest removal efficiencies of alkali-activated material based on metakaolin was found 97.5% at pH 4 and metakaolin removal efficiencies was found 92% at pH 5.5.

Research paper thumbnail of Chitosan / Itaconic acid / PVA Hybrid Polymer Networks of High Swelling Degrees and Good Mechanical Strength

Research paper thumbnail of Cesium removal from aqueous solution by natural mineral clinoptilolite

The aim of this study was to in ves ti gate the Cs + ions sorp tion on nat u ral min er als clino... more The aim of this study was to in ves ti gate the Cs + ions sorp tion on nat u ral min er als clinoptilolite. The anal y sis of clinoptilolite and clinoptilolite with ad sorbed Cs + ion was conducted by X-ray dif frac tion, scan ning elec tron mi cros copy, X-ray flu o res cence, and gamma spec trom e try. The spe cific ac tiv ity of nat u rally oc cur ring radionuclides in clinoptilolite was de ter mined by gamma spec trom e try by us ing the HPGe semi con duc tor de tec tor. Ob tained ac tiv ity con cen tra tions ranged from 49 Bq/kg to 810 Bq/kg for 40 K, 5.7 Bq/kg to 10 Bq/kg for 238 U, 5.8 Bq/kg to 70 Bq/kg for 232 Th(228 Ac), and the pres ence of ar ti fi cial radionuclides was not de tected (137 Cs < 0.02 Bq/kg). The study of the ther mal de com po si tion of raw clinoptilolite and Cs ad sorbed clinoptilolite by dif fer en tial ther mal anal y sis is pre sented in this pa per. The ac ti va tion en ergy of the re ac tion phase trans for ma tion of raw clinoptilolite is 156.7 kJ/mol, while Cs ad sorbed clinoptilolite is 121.7 kJ/mol. The lower value of ac ti va tion energy re ac tion of the phase trans for ma tion Cs ad sorbed clinoptilolite in di cates that Cs which is ad sorbed destabilizes the crys tal struc ture of clinoptilolite and thus fa cil i tates the tran si tion to the amor phous state.

Research paper thumbnail of Fabrication of ZrC/SiC, ZrO2/SiC and ZrO2 powders by carbothermal reduction of ZrSiO4

Processing and Application of Ceramics, 2011

The zirconia/silicon carbide (ZrO2 /SiC) and ZrO2 powders are prepared by carbothermal reduction ... more The zirconia/silicon carbide (ZrO2 /SiC) and ZrO2 powders are prepared by carbothermal reduction of natural mineral zircon (ZrSiO4). The zircon powder was mixed with activated carbon as a reducing agent and heattreated in a controlled flow atmosphere of Ar. Phase evolution and phase content were followed as a function of temperature (1573-1973 K) and C/ZrSiO4 ratio (C/ZrSiO4 = 1, 4, 5 and 7), by means of ex-situ X-ray diffraction and SEM/EDS analysis. By varying the temperature and C/ZrSiO4 ratio, different powder compositions were obtained (m-ZrO2; m-ZrO2/c-ZrO2; c-ZrO2; c-ZrO2/SiC). .

Research paper thumbnail of Mechanochemical treatment and structural properties of lead adsorption on kaolinite (Rudovci, Serbia)

Environmental Earth Sciences, 2014

ABSTRACT In the present work, remediation of lead-containing solution using raw and modified kaol... more ABSTRACT In the present work, remediation of lead-containing solution using raw and modified kaolinite has been presented. The micro and nanostructure of samples has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Laser diffraction and scattering (LDS), was analyzed by particle size analyzer based on laser diffraction and particle size distribution (PSD) was done. The degree of metal adsorption was evaluated analyzing the Pb(II) contaminated samples by inductively coupled plasma atomic emission spectrometry (micro- and nanostructure on immobilization efficiency correlCP AES). The results show the impact of immobilization efficiency and ation between micro- and nanostructure. The thermodynamic data (ΔH°, ΔS°, ΔG°) are calculated from the temperature-dependent sorption isotherms. The results suggest sorption process of Pb(II) on kaolinite as spontaneous and endothermic.

Research paper thumbnail of Investigation of Cl- and So4 2- anion absorption in natural soils

Processing and Application of Ceramics, 2011

In this paper, the results of vertical migration of chloride and sulphate anions in soil are pres... more In this paper, the results of vertical migration of chloride and sulphate anions in soil are presented. The soil was contaminated with NaCl and CuSO4. Anions migration were monitored during one hydrological year (425 days). The first sample was taken after 150 days and afterwards samples were taken every 50 days. Before the profile contamination physical and chemical analyses of soil have been done. The obtained results show that chloride concentration in soil was in the range from 0.67 mg/kg up to 11.92 mg/kg, while sulphate concentration was in the range from 0.65 mg/kg up to 9.79 mg/kg.

Research paper thumbnail of Radiological hazards of 137Cs in cultivated and undisturbed areas

Nuclear Technology and Radiation Protection, 2011

The exposure of human beings to ionizing radiation from 137Cs is a continuing and inescapable fea... more 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 so...

Research paper thumbnail of Physico-chemical soil analysis of Rudovci region

Geonauka, 2013

Laser diffraction and pipette methods were carried out for comparative grain-size analysis of soi... more Laser diffraction and pipette methods were carried out for comparative grain-size analysis of soil samples representing a similar texture classification sampled. A detail physical-chemical analysis of soils, which involves use of XRF, XRD and SEM analysis were done. XRF and XRD analysis were done on the fractions separated by pipette method. On the obtained fraction particle size distribution and SEM analysis were done. The obtained results of these different methods are in good agreement and for detailed soil analysis comparison of both methods are recommended.

Research paper thumbnail of Structure and composition of soils

Processing and Application of Ceramics, 2010

This paper presents a study of soils structure and composition using up to date technique, such a... more This paper presents a study of soils structure and composition using up to date technique, such as scanning electronic microscopy, atomic force microscopy, X-ray diffraction, X-ray fluorescence, as well as some other characterization methods. It was shown that soil particles have porous structure and dimensions in the range from several millimeters to several hundreds of nanometers and consist of different minerals such as kaolin, quartz and feldspate.

Research paper thumbnail of Vertical distribution of natural radionuclides in soil: Assessment of external exposure of population in cultivated and undisturbed areas

Science of The Total Environment, 2012

In the present work, naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K were measured in soil ... more In the present work, naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K were measured in soil samples from the cultivated and undisturbed areas in Rudovci, municipality of Lazarevac, Serbia. There were three profiles, each profile divided into four horizons, giving the twelve soil samples. The specific activity of ²³⁸U, ²³²Th and ⁴⁰K in soil and sediment samples was determined by gamma spectrometry using the HPGe semiconductor detector. Obtained activity concentrations ranged from 28.0 to 44.0 Bq/kg for ²³⁸U, from 59.4 to 71.4 Bq/kg for ²³²Th and from 335.0 to 517.0 Bq/kg for ⁴⁰K. The evaluation of the radiological hazards originated from ²³⁸U, ²³²Th and ⁴⁰K in the samples, the absorbed dose rate (D) and the annual effective dose rate (E), calculated in accordance with the UNSCEAR 2000 report, are presented in this paper.

Research paper thumbnail of Chitosan, itaconic acid and poly(vinyl alcohol) hybrid polymer networks of high degree of swelling and good mechanical strength

Polymer International, 2009

Chitosan is a biodegradable, non-toxic, biocompatible polymer convenient for use in drug delivery... more Chitosan is a biodegradable, non-toxic, biocompatible polymer convenient for use in drug delivery. In this study, hybrid polymeric networks (HPNs) based on chitosan, itaconic acid and poly(vinyl alcohol) (PVA) were prepared and characterized. Chitosan was dissolved in itaconic acid in order to obtain ionic crosslinking with the dicarboxylic acid. In the second step, this chitosan/itaconic acid network was mixed with PVA and chemically crosslinked with glutaraldehyde. The chitosan/itaconic acid ratio was kept constant, while the concentrations of PVA and glutaraldehyde were varied. All samples were characterized using swelling studies, dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The equilibrium degrees of swelling obtained for the HPNs were higher than most of the values reported for chitosan hydrogels obtained by dissolving chitosan in acetic acid or HCl aqueous solutions. This method of synthesis also resulted in hydrogels with better mechanical properties and thermal stability. By changing the PVA content and the degree of crosslinking, it is possible to finely tune the properties of the HPNs, which could make them suitable as potential matrices in controlled drug delivery.

Research paper thumbnail of Influence of chemical agents on the surface area and porosity of active carbon hollow fibers

Journal of the Serbian Chemical Society, 2011

Active carbon hollow fibers were prepared from regenerated polysulfone hollow fibers by chemical ... more 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 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.

Research paper thumbnail of The effect of gamma radiation on the properties of activated carbon cloth

Journal of the Serbian Chemical Society, 2009

Activated carbon cloth dressing is an appropriate wound healing material due to its biocompatibil... more Activated carbon cloth dressing is an appropriate wound healing material due to its biocompatibility and adsorption characteristics. The influence of gamma radiation as a sterilization process on the adsorption and mechanical properties of activated carbon cloth was investigated. The specific surface area, micropore volume, pore size distribution, surface chemistry as well as the breaking load of activated carbon cloth before and after gamma radiation were examined. Characterization by nitrogen adsorption showed that the activated carbon cloth was a microporous material with a high specific surface area and micropores smaller than 1 nm. Gamma radiation decreased the specific surface area and micropore volume but increased the pore width. The sterilization process changed the surface chemistry quantitatively, but not qualitatively. In addition, the breaking load decreased but without any influence considering the further application of this material.

Research paper thumbnail of Vertical distribution of 226Ra and radiological hazards indices of soil samples

Journal of Radioanalytical and Nuclear Chemistry, 2011

The vertical distribution of 226Ra was investigated in soils from the cultivated and undisturbed ... more The vertical distribution of 226Ra was investigated in soils from the cultivated and undisturbed areas in Rudovci, municipality Lazarevac, Serbia. There were three profiles, each profile divided on four horizons, what gives 12 soil samples. The specific activity of 226Ra in soil and sediment samples was determined by using the gamma-spectrometric method. Analysis of the vertical soil profiles indicated that the activity of 226Ra was not extremely changed with depth. To evaluate the radiological hazards of 226Ra in the samples, the absorbed dose rate, the annual effective dose rate, the radium equivalent activity, and the external hazards index were calculated according to the UNSCEAR 2000 report.

Research paper thumbnail of Alkali activation of different type of ash as a production of combustion process

Nuclear Technology and Radiation Protection

Presented study deals with the final structure and radiological properties of different fly-ash b... more 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 strengthened 60 ?C for 48 hours after staying at room temperature in covering mold for 24 hours. The X-ray diffraction, Fourier transform infrared and SAM measurements were conducted on the samples after 28 days of geopolymerization process. The 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. Besides determination of physicochemical 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 a...

Research paper thumbnail of Study of nanosized hydroxyapatite material annealing at different retention times

Science of Sintering

The aim of the study was to investigate the influence of low heating temperatures with two differ... more The aim of the study was to investigate the influence of low heating temperatures with two different retention times to optimize the process for obtaining nanosized hydroxyapatite material that can possibly be used in the fields of biology and pharmacy. Nanosized hydroxyapatite was successfully obtained by wet chemical precipitation. The annealing of the material performed at 300 oC with two different retention times i.e. 3 and 6 hours in air atmosphere. Low annealing temperature with extended retention time was selected in terms to reduce energy consumption. FTIR spectroscopy was used to confirm characteristic vibrational bands of hydroxyapatite samples, and presence of carbonate bands of hydroxyapatite annealed for 3h and 6h. X-Ray powder diffraction analysis were used to examine phase composition, determine the size of unit cells and crystallite sizes, and SEM-EDS methods were used to obtain particle size and arrangement also grain growth morphology and confirmed the presence of ...

Research paper thumbnail of The effect of the concentration of alkaline activator and aging time on the structure of metakaolin based geopolymer

Research paper thumbnail of Radiological and physicochemical properties of red mud based geopolymers

Nuclear Technology and Radiation Protection

A significant amount of red mud generated as a by-product of the Bayer process in the aluminum in... more A significant amount of red mud generated as a by-product of the Bayer process in the aluminum industry may cause environmental problems if appropriate treatment is not carried out. The presented research dealt with the possibility of application of red mud as a pigment or as raw material for use in the construction material industry. In relation to the aim of this work, the physicochemical characterization was performed and the natural radioactivity of red mud as an industrial waste and a geopolymer sample based on it was determined. The presented research is a contribution to the potential solution for environmental protection through the synthesis of possible construction material based on red mud. The radiological hazard orginating from 226Ra, 232Th, and 40K in the samples was assesed throught the absorbed dose rate and the annual effective dose rate, calculated in accordance with the UNSCEAR 2010 report. Physicochemical characterization of all samples was conducted using X-ray ...

Research paper thumbnail of The influence of alumino-silicate matrix composition on surface hydrophobic properties

Science of Sintering

The purpose of this investigation is to investigate the hydrophobicity of geopolymers, new alumin... more The purpose of this investigation is to investigate the hydrophobicity of geopolymers, new alumino-silicate materials and the influence of Si/Al ratio on their surface properties. Contact angle measurement (CAM) as reliable indicator of hydrophobicity was determined for synthesized geopolymers using water and ethylene-glycol as reference liquids. Geopolymers were synthesized from various precursors: kaolin, bentonite and diatomite. Characterization of phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. Contact angle measurements confirmed that the geopolymers synthesized from metakaolin are the most porous, which can be explained by the smallest Si/Al ratio. The maximum value of contact angle and free surface energy (110.2 mJ/m2) has been achieved for geopolymer synthesized by diatoms (GPMD). SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel and is significantly different from the micrographs of other two geopol...

Research paper thumbnail of Physicochemical, mineralogical and radiological properties of red mud samples as secondary raw materials

Nuclear Technology and Radiation Protection

Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia 4 Lab o ra... more Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia 4 Lab o ra tory for Nu clear and Plasma Phys ics,Vin~a In sti tute of Nu clear Sci ences, Uni ver sity of Bel grade, Bel grade, Ser bia Sci en tific pa per

Research paper thumbnail of Microstructural characterization and adsorption properties of alkali-activated materials based on metakaolin

Science of Sintering, 2016

The microstructural characterization and adsorption properties of metakaolin (MK) and alkali-acti... more The microstructural characterization and adsorption properties of metakaolin (MK) and alkali-activated metakaolin, known as geopolymer materials (GP) were investigated. The structure and properties of the metakaolin and obtained geopolymer were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, based on the analysis of adsorption efficiency, microstructure and mineral structure, the difference between geopolymer and metakaolin on the performance of immobilizing heavy metals have been discussed. The kinetics of adsorption can be represented by pseudo-second order equation. The results of lead ions adsorption experiments were best fitted by Freundlich adsorption isotherm for both investigated adsorbents. The highest removal efficiencies of alkali-activated material based on metakaolin was found 97.5% at pH 4 and metakaolin removal efficiencies was found 92% at pH 5.5.

Research paper thumbnail of Chitosan / Itaconic acid / PVA Hybrid Polymer Networks of High Swelling Degrees and Good Mechanical Strength

Research paper thumbnail of Cesium removal from aqueous solution by natural mineral clinoptilolite

The aim of this study was to in ves ti gate the Cs + ions sorp tion on nat u ral min er als clino... more The aim of this study was to in ves ti gate the Cs + ions sorp tion on nat u ral min er als clinoptilolite. The anal y sis of clinoptilolite and clinoptilolite with ad sorbed Cs + ion was conducted by X-ray dif frac tion, scan ning elec tron mi cros copy, X-ray flu o res cence, and gamma spec trom e try. The spe cific ac tiv ity of nat u rally oc cur ring radionuclides in clinoptilolite was de ter mined by gamma spec trom e try by us ing the HPGe semi con duc tor de tec tor. Ob tained ac tiv ity con cen tra tions ranged from 49 Bq/kg to 810 Bq/kg for 40 K, 5.7 Bq/kg to 10 Bq/kg for 238 U, 5.8 Bq/kg to 70 Bq/kg for 232 Th(228 Ac), and the pres ence of ar ti fi cial radionuclides was not de tected (137 Cs < 0.02 Bq/kg). The study of the ther mal de com po si tion of raw clinoptilolite and Cs ad sorbed clinoptilolite by dif fer en tial ther mal anal y sis is pre sented in this pa per. The ac ti va tion en ergy of the re ac tion phase trans for ma tion of raw clinoptilolite is 156.7 kJ/mol, while Cs ad sorbed clinoptilolite is 121.7 kJ/mol. The lower value of ac ti va tion energy re ac tion of the phase trans for ma tion Cs ad sorbed clinoptilolite in di cates that Cs which is ad sorbed destabilizes the crys tal struc ture of clinoptilolite and thus fa cil i tates the tran si tion to the amor phous state.

Research paper thumbnail of Fabrication of ZrC/SiC, ZrO2/SiC and ZrO2 powders by carbothermal reduction of ZrSiO4

Processing and Application of Ceramics, 2011

The zirconia/silicon carbide (ZrO2 /SiC) and ZrO2 powders are prepared by carbothermal reduction ... more The zirconia/silicon carbide (ZrO2 /SiC) and ZrO2 powders are prepared by carbothermal reduction of natural mineral zircon (ZrSiO4). The zircon powder was mixed with activated carbon as a reducing agent and heattreated in a controlled flow atmosphere of Ar. Phase evolution and phase content were followed as a function of temperature (1573-1973 K) and C/ZrSiO4 ratio (C/ZrSiO4 = 1, 4, 5 and 7), by means of ex-situ X-ray diffraction and SEM/EDS analysis. By varying the temperature and C/ZrSiO4 ratio, different powder compositions were obtained (m-ZrO2; m-ZrO2/c-ZrO2; c-ZrO2; c-ZrO2/SiC). .

Research paper thumbnail of Mechanochemical treatment and structural properties of lead adsorption on kaolinite (Rudovci, Serbia)

Environmental Earth Sciences, 2014

ABSTRACT In the present work, remediation of lead-containing solution using raw and modified kaol... more ABSTRACT In the present work, remediation of lead-containing solution using raw and modified kaolinite has been presented. The micro and nanostructure of samples has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Laser diffraction and scattering (LDS), was analyzed by particle size analyzer based on laser diffraction and particle size distribution (PSD) was done. The degree of metal adsorption was evaluated analyzing the Pb(II) contaminated samples by inductively coupled plasma atomic emission spectrometry (micro- and nanostructure on immobilization efficiency correlCP AES). The results show the impact of immobilization efficiency and ation between micro- and nanostructure. The thermodynamic data (ΔH°, ΔS°, ΔG°) are calculated from the temperature-dependent sorption isotherms. The results suggest sorption process of Pb(II) on kaolinite as spontaneous and endothermic.

Research paper thumbnail of Investigation of Cl- and So4 2- anion absorption in natural soils

Processing and Application of Ceramics, 2011

In this paper, the results of vertical migration of chloride and sulphate anions in soil are pres... more In this paper, the results of vertical migration of chloride and sulphate anions in soil are presented. The soil was contaminated with NaCl and CuSO4. Anions migration were monitored during one hydrological year (425 days). The first sample was taken after 150 days and afterwards samples were taken every 50 days. Before the profile contamination physical and chemical analyses of soil have been done. The obtained results show that chloride concentration in soil was in the range from 0.67 mg/kg up to 11.92 mg/kg, while sulphate concentration was in the range from 0.65 mg/kg up to 9.79 mg/kg.

Research paper thumbnail of Radiological hazards of 137Cs in cultivated and undisturbed areas

Nuclear Technology and Radiation Protection, 2011

The exposure of human beings to ionizing radiation from 137Cs is a continuing and inescapable fea... more 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 so...

Research paper thumbnail of Physico-chemical soil analysis of Rudovci region

Geonauka, 2013

Laser diffraction and pipette methods were carried out for comparative grain-size analysis of soi... more Laser diffraction and pipette methods were carried out for comparative grain-size analysis of soil samples representing a similar texture classification sampled. A detail physical-chemical analysis of soils, which involves use of XRF, XRD and SEM analysis were done. XRF and XRD analysis were done on the fractions separated by pipette method. On the obtained fraction particle size distribution and SEM analysis were done. The obtained results of these different methods are in good agreement and for detailed soil analysis comparison of both methods are recommended.

Research paper thumbnail of Structure and composition of soils

Processing and Application of Ceramics, 2010

This paper presents a study of soils structure and composition using up to date technique, such a... more This paper presents a study of soils structure and composition using up to date technique, such as scanning electronic microscopy, atomic force microscopy, X-ray diffraction, X-ray fluorescence, as well as some other characterization methods. It was shown that soil particles have porous structure and dimensions in the range from several millimeters to several hundreds of nanometers and consist of different minerals such as kaolin, quartz and feldspate.

Research paper thumbnail of Vertical distribution of natural radionuclides in soil: Assessment of external exposure of population in cultivated and undisturbed areas

Science of The Total Environment, 2012

In the present work, naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K were measured in soil ... more In the present work, naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K were measured in soil samples from the cultivated and undisturbed areas in Rudovci, municipality of Lazarevac, Serbia. There were three profiles, each profile divided into four horizons, giving the twelve soil samples. The specific activity of ²³⁸U, ²³²Th and ⁴⁰K in soil and sediment samples was determined by gamma spectrometry using the HPGe semiconductor detector. Obtained activity concentrations ranged from 28.0 to 44.0 Bq/kg for ²³⁸U, from 59.4 to 71.4 Bq/kg for ²³²Th and from 335.0 to 517.0 Bq/kg for ⁴⁰K. The evaluation of the radiological hazards originated from ²³⁸U, ²³²Th and ⁴⁰K in the samples, the absorbed dose rate (D) and the annual effective dose rate (E), calculated in accordance with the UNSCEAR 2000 report, are presented in this paper.

Research paper thumbnail of Chitosan, itaconic acid and poly(vinyl alcohol) hybrid polymer networks of high degree of swelling and good mechanical strength

Polymer International, 2009

Chitosan is a biodegradable, non-toxic, biocompatible polymer convenient for use in drug delivery... more Chitosan is a biodegradable, non-toxic, biocompatible polymer convenient for use in drug delivery. In this study, hybrid polymeric networks (HPNs) based on chitosan, itaconic acid and poly(vinyl alcohol) (PVA) were prepared and characterized. Chitosan was dissolved in itaconic acid in order to obtain ionic crosslinking with the dicarboxylic acid. In the second step, this chitosan/itaconic acid network was mixed with PVA and chemically crosslinked with glutaraldehyde. The chitosan/itaconic acid ratio was kept constant, while the concentrations of PVA and glutaraldehyde were varied. All samples were characterized using swelling studies, dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The equilibrium degrees of swelling obtained for the HPNs were higher than most of the values reported for chitosan hydrogels obtained by dissolving chitosan in acetic acid or HCl aqueous solutions. This method of synthesis also resulted in hydrogels with better mechanical properties and thermal stability. By changing the PVA content and the degree of crosslinking, it is possible to finely tune the properties of the HPNs, which could make them suitable as potential matrices in controlled drug delivery.

Research paper thumbnail of Influence of chemical agents on the surface area and porosity of active carbon hollow fibers

Journal of the Serbian Chemical Society, 2011

Active carbon hollow fibers were prepared from regenerated polysulfone hollow fibers by chemical ... more 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 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.

Research paper thumbnail of The effect of gamma radiation on the properties of activated carbon cloth

Journal of the Serbian Chemical Society, 2009

Activated carbon cloth dressing is an appropriate wound healing material due to its biocompatibil... more Activated carbon cloth dressing is an appropriate wound healing material due to its biocompatibility and adsorption characteristics. The influence of gamma radiation as a sterilization process on the adsorption and mechanical properties of activated carbon cloth was investigated. The specific surface area, micropore volume, pore size distribution, surface chemistry as well as the breaking load of activated carbon cloth before and after gamma radiation were examined. Characterization by nitrogen adsorption showed that the activated carbon cloth was a microporous material with a high specific surface area and micropores smaller than 1 nm. Gamma radiation decreased the specific surface area and micropore volume but increased the pore width. The sterilization process changed the surface chemistry quantitatively, but not qualitatively. In addition, the breaking load decreased but without any influence considering the further application of this material.

Research paper thumbnail of Vertical distribution of 226Ra and radiological hazards indices of soil samples

Journal of Radioanalytical and Nuclear Chemistry, 2011

The vertical distribution of 226Ra was investigated in soils from the cultivated and undisturbed ... more The vertical distribution of 226Ra was investigated in soils from the cultivated and undisturbed areas in Rudovci, municipality Lazarevac, Serbia. There were three profiles, each profile divided on four horizons, what gives 12 soil samples. The specific activity of 226Ra in soil and sediment samples was determined by using the gamma-spectrometric method. Analysis of the vertical soil profiles indicated that the activity of 226Ra was not extremely changed with depth. To evaluate the radiological hazards of 226Ra in the samples, the absorbed dose rate, the annual effective dose rate, the radium equivalent activity, and the external hazards index were calculated according to the UNSCEAR 2000 report.