Geopolymer/CeO2 as Solid Electrolyte for IT-SOFC

As a material for application in the life sciences, a new composite material, geopolymer/CeO2 (GP_CeO2), was synthesized as a potential low-cost solid electrolyte for application in solid oxide fuel cells operating in intermediate temperature (IT-SOFC). The new materials were obtained from alkali-activated metakaolin (calcined clay) in the presence of CeO2 powders (x = 10%). Besides the commercial CeO2 powder, as a source of ceria, two differently synthesized CeO2 powders also were used: CeO2 synthesized by modified glycine nitrate procedure (MGNP) and self-propagating reaction at room temperature (SPRT). The structural, morphological, and electrical properties of pure and GP_CeO2-type samples were investigated by X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR), BET, differential thermal and thermogravimetric analysis (DTA/TGA), scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), and method complex impedance (EIS). XRPD and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) analysis confirmed the formation of solid phase CeO2. The BET, DTA/TGA, FE-SEM, and EDS results indicated that particles of CeO2 were stabile interconnected and form a continuous conductive path, which was confirmed by the EIS method. The highest conductivity of 1.86 × 10−2 Ω−1 cm−1 was obtained for the sample GP_CeO2_MGNP at 700 °C. The corresponding value of activation energy for conductivity was 0.26 eV in the temperature range 500–700 °C

Heavy Metals Content in Selected Medicinal Plants Produced and Consumed in Serbia and Their Daily Intake in Herbal Infusions

The heavy metals content (HMs) was investigated in 14 different medicinal plants collected from the three regions in Central Serbia, Zlatar, Sokobanja, and Kopaonik. The concentrations of Cd, Cr, Ni, Hg and Pb were determined: Cd (<0.03–2.72 mg/kg); Cr (<0.08–12.1 mg/kg); Ni (<0.08–12.2 mg/kg); Pb (0.6–49.0 mg/kg); the Hg concentration was below the detection limit of 0.06 mg/kg in all samples. The daily intake of HMs due to ingestion of 200 mL of herbal infusion was in all cases below the recommended limit prescribed by the World Health Organization. The estimated daily intake values were below the values for the oral reference dose regulated by the U.S. Environmental Protection Agency (USA EPA). The target hazard quotient and hazard index for Cd, Cr Ni, and Pb were below 1. Nevertheless, due to the tendency of heavy metals to accumulate in the organism, attention should be paid to the daily intake of herbal infusion during long-term usage. Specifically, it is recommended to consume not more than one cup (200 mL) of infusion per day made from thyme (Mt. Zlatar) and blueberry (Mt. Kopaonik), and not more than two cups per day for other herbs

Synthesis, characterization and application of activated carbon materials obtained from biowaste

The main objective of this research is to obtain carbonaceous material and active carbon material by the carbonization process in an inert atmosphere, activation with CO2, then the hydrothermal synthesis method with the emphasis on phosphoric acid activation as well as a combination of carbonization and hydrothermal synthesis. It is also given an insight into the optimization of the parameter of the process of obtaining active carbon material, that is, how the process parameters affect the final product. Different precursors of biowaste for obtaining carbon materials were used. The initial composition of the precursor as well as the final product (active carbon materials) were analyzed using a proximative and ultimate method. The active area surface, volume and pore size was determined using the BET method. Verification of surface-active reaction groups in the identified structures was carried out through Fourier-transform infrared (FTIR) spectroscopy.. Morphology of resulting activated carbon materials has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Energy efficiency or thermal power was measured using a calorimetric bomb. The application of the obtained materials is reflected in the fact that we removed the waste, we prevented the pollution of nature, and on the other hand we have obtained material that can be used for various purposes, for example, air filters, water, superconductors, etc.VIII Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 23-25, 2019; Belgrad

Carbon dioxide activation of the plane tree seeds derived bio-char: Kinetic properties and application

Goal of this work is to establish technical feasibility and fundamentals of producing activated carbon from plane tree seeds biomass for porous materials derivation. Bio-chars produced via carbonization from plane tree seeds precursor were activated in CO2 at 750 and 850?C, during various residence times. Their surface area and porosity were characterized by N2 adsorption at 77 K. Surface areas of activated carbons can be correlated with kinetics mechanism and activation energy magnitudes of oxidation reaction by CO2, which are closely related to applied activation temperature. Result showed that high temperature activated carbon had higher gas adsorption as compared to activated carbon obtained from lower temperature during two-hour residence time. Breakthrough behavior was detected at 850?C where surface reactions dominate, and it is characterized by autocatalytic kinetic model under designed conditions. Both, temperature and CO2 concentration in vicinity of solid surface effect on breakthrough time of adsorbent. Derived bio-chars are converted into high quality activated carbons, with surface area of 776.55 m2/g, where micro-pores with pore diameters less than 2 nm prevail. Produced activated carbons have properties comparable with commercially available activated carbons, which can be successfully used for removal of harmful gaseous pollutants toward air purification

Preparation of Active Carbon Material By Activation With Various Hydroxide And Characterization Of Their Properties

The aim of this research is to obtain active carbon material from the plane tree fruit. The precursor was first treated with hydrothermal synthesis and then mechanochemically activated with various hydroxides and finally carbonization was done to promote activation.It can be concluded that by acting of different hydroxides (NaOH, BaOH, LiOH, KOH) in the same mass ratio and using the same precursor and the same process, totally different materials with different structure and morphology are obtained.The initial composition of the precursor as well as the final product (active carbon materials) were analyzed using a proximative and ultimate method. The active area surface, volume and pore size was determined using the BET method. Verification of surface-active reaction groups in the identified structures was carried out through Fourier-transform infrared (FTIR) spectroscopy. Morphology of resulting activated carbon materials has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The application of the obtained materials is reflected in the fact that we removed the waste, we prevented the pollution of nature, and on the other hand we have obtained material that can be used for various purposes, for example, air and water filters, heating briquettes, fertilizer for plants, superconductors, etc.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Hydrothermal Synthesized and Alkaline Activated Carbons Prepared from Glucose and Fructose—Detailed Characterization and Testing in Heavy Metals and Methylene Blue Removal

In the presented paper, activated carbons were prepared from fructose and glucose, and activating agents (KOH, NaOH, LiOH) by hydrothermal treatment (HTC) treatment. After preparation, samples were characterized in details. Different techniques were used: x-ray powder diffraction analysis, Raman spectral analysis, elemental analysis, and determination of textural and morphological properties. Obtained results showed dependence of investigated properties and the nature of precursors (glucose or fructose) as well as the type of hydroxides used as activating agents. After characterization, samples were tested as materials for heavy metals (Pb2+, Cd2+and Zn2+) and methylene blue removal. Also, adsorption experiments were performed on wastewaters taken from tailings of the lead and zinc mine and kinetic of the methylene blue removal was studied. The factors which distinguished the KOH activated samples were high yield (~14%), content of organic carbon (63–74%), porosity and specific surface area (SBET~700–1360 m2/g), a low degree of the crystal phase, indications that potassium ions may be included in heavy metals removal, good removal of the heavy metal ions (~47–59 mg/g for Pb2+, ~21–27 mg/g for Cd2+and ~6–10 mg/g for Zn2+) and fast (~10–30 min) and good methylene blue (~60–200 mg/g) removal

Indigo Carmine in a Food Dye: Spectroscopic Characterization and Determining Its Micro-Concentration through the Clock Reaction

Indigo carmine is a commonly used industrial blue dye. To determine its concentration in a commercially available food dye composed of a mixture of indigo carmine and D-glucose, this paper characterizes it through (ATR, KBr) FTIR micro-Raman as well as UV/Vis and clock: Briggs–Rauscher (BR) oscillatory reaction methods. The indigo carmine was detected in the bulk food dye only by applying micro-Raman spectroscopy, indicating a low percentage of the indigo carmine present. This research provides an improvement in the deviations from the experimental Raman spectrum as calculated by the B97D/cc-pVTZ level of theory one, resulting in a better geometrical optimization of the indigo carmine molecule compared to data within the literature. The analytical curves used to determine indigo carmine concentrations (and quantities) in an aqueous solution of food dye were applied by means of UV/Vis and BR methods. BR yielded significantly better analytical parameters: 100 times lower LOD and LOQ compared to commonly used UV/Vis. The remarkable sensitivity of the BR reaction towards indigo carmine suggests that not only does indigo carmine react in an oscillatory reaction but also its decomposition products, meaning that the multiple oxidation reactions have an important role in the BR’s indigo carmine mechanism. The novelty of this research is the investigation of indigo carmine using a clock BR reaction, opening new possibilities to determine indigo carmine in other complex samples (pharmaceutical, food, etc.)

Removal of lead ions from aqueous solutions by using the natural and Fe(III)-modified zeolite

Gvožđe oksidi i prirodni zeoliti su efikasni adsorbenti jona teških metala iz vodenih rastvora. Međutim, kako bi se unapredile adsorpcione osobine i gvožđe oksida i prirodnih zeolita prema različitim zagađivačima, gvožđe oksidi se često impregniraju na površine poroznih zeolitskih minerala. Kako bi se dobio efikasniji adsorbent jona olova iz vodenih rastvora, u ovoj doktorskoj disertaciji je urađena modifikacija prirodnog zeolita-klinoptilolita iz ležišta Zlatokop, Vranjska Banja u Srbiji kombinacijom metoda za dobijanje getita i gvožđe prekrivenog zeolita u baznoj sredini. Pri tome je dobijen Fe(III)-modifikovani zeolit - kompozit prirodnog zeolita i getita. Prirodni i Fe(III)-modifikovani zeolit su okarakterisani određivanjem hemijskog sastava, kapaciteta katjonske izmene (KKI), tačke nultog naelektrisanja (pHpzc), teksturalnih osobina, kao i rendgenskom difrakcionom analizom (XRPD), skenirajućom elektronskom mikroskopijom i energijsko-disperzivnom rendgenskom spektroskopskom analizom (SEM-EDS), termijskom analizom (TGA/DTA), infracrvenom spektroskopijom (FTIC) i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da se modifikacijom ne menjaju značajnije kristalna struktura minerala klinoptilolita, Si/Al odnos, kao ni morfološke, termijske i strukturne osobine polaznog zeolita. Međutim, kapacitet katjonske izmene Fe(III)-modifikovanog je znatno veći nego prirodnog zeolita, dok su SEM-EDS ispitivanja površina oba adsorbenta pokazala da su sadržaji gvožđa i kalijuma na površini Fe(III)-modifikovanog zeolita znatno veći, a sadržaji natrijuma i kalcijuma manji u odnosu na prirodni zeolit. Tačka nultog nalelektrisanja se povećava nakon modifikacije sa 6,8 na 7,5, tako da je između pHpzc getita (pHpzc=9,4) i prirodnog zeolita, što ukazuje da je došlo do stvaranja mešanog sistema gvožđa oksida i klinoptilolita na površini zeolita. Znatno uži dobijeni plato ukazuje da je površina modifikovanog znatno više negativno naelektrisana u odnosu na prirodni zeolit. Specifična površina (SBET) nakon modifikacije jonima gvožđa se značajno povećava, sa 30,2 m2/g na 52,5 m2/g i približno je jednaka specifičnoj površini čistog getita – 55,5 m2/g. Takođe, povećane su i zapremine mikro- i mezopora, kao i ukupna zapremina pora, što potvrđuje da je formirana nova faza bogata gvožđem na površini zeolita. TEM ispitivanja su pokazala i da je dobijeni Fe(III)-modifikovani zeolit nano-kompozit zeolita i gvožđe oksida. Ispitivanje adsorpcije jona olova iz vodenih rastvora na prirodnom i Fe(III)-modifikovanom zeolitu urađeno je pri različitim uslovima: početnom pH, koncentraciji jona olova, veličini čestica adsorbenata, temperaturi, masi adsorbenata, vremenu. Utvrđeno je da se modifikacijom jonima gvožđa u rastvoru KOH adsorpcioni kapacitet prirodnog zeolita znatno povećava (sa 64 meq/100 g kod prirodnog na 128 meq/100 g kod Fe(III)-modifikovanog zeolita). Takođe, vezivanje jona olova na oba adsorbenta se odvija jonskom izmenom (koja je dominantna pri nižim polaznim koncentracijama jona olova) i hemisorpcijom (koja je dominantna pri višim polaznim koncentracijama jona olova) pri čemu je, pri nižim polaznim koncentracijama, vezivanje jona olova praćeno i...Iron oxides and natural zeolites are efficient adsorbents of heavy metals ions from aqueous solutions. However, to improve their adsorption properties toward different pollutants iron oxides are often impregnated at the surface of porous zeolites. In order to obtain a more efficient adsorbent of lead ions from aqueous solution, in this dissertation modification of natural zeolite-clinoptilolite from Zlatokop deposit, Vranjska Banja, Serbia was performed by combining the method for pure goethite preparation and the method for preparation of iron-coated zeolite. The obtained Fe(III)-modified zeolite is a composite of the natural zeolite and the goethite. The characterization of the natural and Fe(III)-modified zeolite was performed by determination of the chemical composition, cation exchange capacity (CEC), point of the zero charge (pHpzc), textural properties, and by using X-ray powder diffraction analysis (XRPD), scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM-EDS), thermal analysis (TGA/DTA), infrared spectroscopy (FTIC) and transmission electron microscopy (TEM). It was shown that the modification does not cause any changes in the crystal structure of clinoptilolite, Si/Al ratio, as well as in its morphological, thermal and structural properties. However, CEC of the Fe(III)-modified zeolite was significantly higher than of the natural one, while SEM-EDS analysis of both adsorbents showed that the amounts of iron and potassium at surface of Fe(III)-modified zeolite were higher and the amounts of sodium and calcium were lower than at surface of the natural zeolite. The comparison of pHpzc of the pure goethite (pHpzc=9.4), pHpzc of the natural zeolite (pHpzc=6.8), with pHpzc of Fe(III)-modified zeolite (pHpzc=7.5), indicates formation of Fe-oxide/clinoptilolite mixed system forms at the surface of the natural zeolite. Narower pH range at the plateau was obtained in the case of the Fe(III)-modified zeolite, pointing to a noticeably higher negative surface charge of this adsorbent. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions, from 30.20 m2/g for the natural zeolite to 52.50 m2/g for Fe(III)-modified zeolite and is approximately equal to the specific surface of the pure goethite- 55.5 m2/g. Also, Fe(III)-modified zeolite shows increase in both micro- and mesopores volume, confirming formation of new Fe-bearing phases on zeolite. TEM investigations have shown the presence of spherical amorphous nano-clusters on the crystal faces. In order to investigate the mechanism of adsorption of lead ions by the natural and Fe(III)-modified zeolite, experiments were performed under different conditions. The influence of specific parameters, such as initial lead ions concentration, amount of adsorbents, contact time, temperature and particle size on adsorption of lead ions by both adsorbents was studied. It was determined that the adsorption capacity of the natural zeolite significantly increases (from 64 to 128 meq/100 g) after modification with the iron ions in KOH solution. Also, the binding of the lead ions on both adsorbents is carried out by ion exchange (which is dominant at lower starting..

Removal of lead ions from aqueous solutions by using the natural and Fe(III)-modified zeolite

Gvožđe oksidi i prirodni zeoliti su efikasni adsorbenti jona teških metala iz vodenih rastvora. Međutim, kako bi se unapredile adsorpcione osobine i gvožđe oksida i prirodnih zeolita prema različitim zagađivačima, gvožđe oksidi se često impregniraju na površine poroznih zeolitskih minerala. Kako bi se dobio efikasniji adsorbent jona olova iz vodenih rastvora, u ovoj doktorskoj disertaciji je urađena modifikacija prirodnog zeolita-klinoptilolita iz ležišta Zlatokop, Vranjska Banja u Srbiji kombinacijom metoda za dobijanje getita i gvožđe prekrivenog zeolita u baznoj sredini. Pri tome je dobijen Fe(III)-modifikovani zeolit - kompozit prirodnog zeolita i getita. Prirodni i Fe(III)-modifikovani zeolit su okarakterisani određivanjem hemijskog sastava, kapaciteta katjonske izmene (KKI), tačke nultog naelektrisanja (pHpzc), teksturalnih osobina, kao i rendgenskom difrakcionom analizom (XRPD), skenirajućom elektronskom mikroskopijom i energijsko-disperzivnom rendgenskom spektroskopskom analizom (SEM-EDS), termijskom analizom (TGA/DTA), infracrvenom spektroskopijom (FTIC) i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da se modifikacijom ne menjaju značajnije kristalna struktura minerala klinoptilolita, Si/Al odnos, kao ni morfološke, termijske i strukturne osobine polaznog zeolita. Međutim, kapacitet katjonske izmene Fe(III)-modifikovanog je znatno veći nego prirodnog zeolita, dok su SEM-EDS ispitivanja površina oba adsorbenta pokazala da su sadržaji gvožđa i kalijuma na površini Fe(III)-modifikovanog zeolita znatno veći, a sadržaji natrijuma i kalcijuma manji u odnosu na prirodni zeolit. Tačka nultog nalelektrisanja se povećava nakon modifikacije sa 6,8 na 7,5, tako da je između pHpzc getita (pHpzc=9,4) i prirodnog zeolita, što ukazuje da je došlo do stvaranja mešanog sistema gvožđa oksida i klinoptilolita na površini zeolita. Znatno uži dobijeni plato ukazuje da je površina modifikovanog znatno više negativno naelektrisana u odnosu na prirodni zeolit. Specifična površina (SBET) nakon modifikacije jonima gvožđa se značajno povećava, sa 30,2 m2/g na 52,5 m2/g i približno je jednaka specifičnoj površini čistog getita – 55,5 m2/g. Takođe, povećane su i zapremine mikro- i mezopora, kao i ukupna zapremina pora, što potvrđuje da je formirana nova faza bogata gvožđem na površini zeolita. TEM ispitivanja su pokazala i da je dobijeni Fe(III)-modifikovani zeolit nano-kompozit zeolita i gvožđe oksida. Ispitivanje adsorpcije jona olova iz vodenih rastvora na prirodnom i Fe(III)-modifikovanom zeolitu urađeno je pri različitim uslovima: početnom pH, koncentraciji jona olova, veličini čestica adsorbenata, temperaturi, masi adsorbenata, vremenu. Utvrđeno je da se modifikacijom jonima gvožđa u rastvoru KOH adsorpcioni kapacitet prirodnog zeolita znatno povećava (sa 64 meq/100 g kod prirodnog na 128 meq/100 g kod Fe(III)-modifikovanog zeolita). Takođe, vezivanje jona olova na oba adsorbenta se odvija jonskom izmenom (koja je dominantna pri nižim polaznim koncentracijama jona olova) i hemisorpcijom (koja je dominantna pri višim polaznim koncentracijama jona olova) pri čemu je, pri nižim polaznim koncentracijama, vezivanje jona olova praćeno i...Iron oxides and natural zeolites are efficient adsorbents of heavy metals ions from aqueous solutions. However, to improve their adsorption properties toward different pollutants iron oxides are often impregnated at the surface of porous zeolites. In order to obtain a more efficient adsorbent of lead ions from aqueous solution, in this dissertation modification of natural zeolite-clinoptilolite from Zlatokop deposit, Vranjska Banja, Serbia was performed by combining the method for pure goethite preparation and the method for preparation of iron-coated zeolite. The obtained Fe(III)-modified zeolite is a composite of the natural zeolite and the goethite. The characterization of the natural and Fe(III)-modified zeolite was performed by determination of the chemical composition, cation exchange capacity (CEC), point of the zero charge (pHpzc), textural properties, and by using X-ray powder diffraction analysis (XRPD), scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM-EDS), thermal analysis (TGA/DTA), infrared spectroscopy (FTIC) and transmission electron microscopy (TEM). It was shown that the modification does not cause any changes in the crystal structure of clinoptilolite, Si/Al ratio, as well as in its morphological, thermal and structural properties. However, CEC of the Fe(III)-modified zeolite was significantly higher than of the natural one, while SEM-EDS analysis of both adsorbents showed that the amounts of iron and potassium at surface of Fe(III)-modified zeolite were higher and the amounts of sodium and calcium were lower than at surface of the natural zeolite. The comparison of pHpzc of the pure goethite (pHpzc=9.4), pHpzc of the natural zeolite (pHpzc=6.8), with pHpzc of Fe(III)-modified zeolite (pHpzc=7.5), indicates formation of Fe-oxide/clinoptilolite mixed system forms at the surface of the natural zeolite. Narower pH range at the plateau was obtained in the case of the Fe(III)-modified zeolite, pointing to a noticeably higher negative surface charge of this adsorbent. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions, from 30.20 m2/g for the natural zeolite to 52.50 m2/g for Fe(III)-modified zeolite and is approximately equal to the specific surface of the pure goethite- 55.5 m2/g. Also, Fe(III)-modified zeolite shows increase in both micro- and mesopores volume, confirming formation of new Fe-bearing phases on zeolite. TEM investigations have shown the presence of spherical amorphous nano-clusters on the crystal faces. In order to investigate the mechanism of adsorption of lead ions by the natural and Fe(III)-modified zeolite, experiments were performed under different conditions. The influence of specific parameters, such as initial lead ions concentration, amount of adsorbents, contact time, temperature and particle size on adsorption of lead ions by both adsorbents was studied. It was determined that the adsorption capacity of the natural zeolite significantly increases (from 64 to 128 meq/100 g) after modification with the iron ions in KOH solution. Also, the binding of the lead ions on both adsorbents is carried out by ion exchange (which is dominant at lower starting..

Removal of lead ions from aqueous solutions by using the natural and Fe(III)-modified zeolite

Gvožđe oksidi i prirodni zeoliti su efikasni adsorbenti jona teških metala iz vodenih rastvora. Međutim, kako bi se unapredile adsorpcione osobine i gvožđe oksida i prirodnih zeolita prema različitim zagađivačima, gvožđe oksidi se često impregniraju na površine poroznih zeolitskih minerala. Kako bi se dobio efikasniji adsorbent jona olova iz vodenih rastvora, u ovoj doktorskoj disertaciji je urađena modifikacija prirodnog zeolita-klinoptilolita iz ležišta Zlatokop, Vranjska Banja u Srbiji kombinacijom metoda za dobijanje getita i gvožđe prekrivenog zeolita u baznoj sredini. Pri tome je dobijen Fe(III)-modifikovani zeolit - kompozit prirodnog zeolita i getita. Prirodni i Fe(III)-modifikovani zeolit su okarakterisani određivanjem hemijskog sastava, kapaciteta katjonske izmene (KKI), tačke nultog naelektrisanja (pHpzc), teksturalnih osobina, kao i rendgenskom difrakcionom analizom (XRPD), skenirajućom elektronskom mikroskopijom i energijsko-disperzivnom rendgenskom spektroskopskom analizom (SEM-EDS), termijskom analizom (TGA/DTA), infracrvenom spektroskopijom (FTIC) i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da se modifikacijom ne menjaju značajnije kristalna struktura minerala klinoptilolita, Si/Al odnos, kao ni morfološke, termijske i strukturne osobine polaznog zeolita. Međutim, kapacitet katjonske izmene Fe(III)-modifikovanog je znatno veći nego prirodnog zeolita, dok su SEM-EDS ispitivanja površina oba adsorbenta pokazala da su sadržaji gvožđa i kalijuma na površini Fe(III)-modifikovanog zeolita znatno veći, a sadržaji natrijuma i kalcijuma manji u odnosu na prirodni zeolit. Tačka nultog nalelektrisanja se povećava nakon modifikacije sa 6,8 na 7,5, tako da je između pHpzc getita (pHpzc=9,4) i prirodnog zeolita, što ukazuje da je došlo do stvaranja mešanog sistema gvožđa oksida i klinoptilolita na površini zeolita. Znatno uži dobijeni plato ukazuje da je površina modifikovanog znatno više negativno naelektrisana u odnosu na prirodni zeolit. Specifična površina (SBET) nakon modifikacije jonima gvožđa se značajno povećava, sa 30,2 m2/g na 52,5 m2/g i približno je jednaka specifičnoj površini čistog getita – 55,5 m2/g. Takođe, povećane su i zapremine mikro- i mezopora, kao i ukupna zapremina pora, što potvrđuje da je formirana nova faza bogata gvožđem na površini zeolita. TEM ispitivanja su pokazala i da je dobijeni Fe(III)-modifikovani zeolit nano-kompozit zeolita i gvožđe oksida. Ispitivanje adsorpcije jona olova iz vodenih rastvora na prirodnom i Fe(III)-modifikovanom zeolitu urađeno je pri različitim uslovima: početnom pH, koncentraciji jona olova, veličini čestica adsorbenata, temperaturi, masi adsorbenata, vremenu. Utvrđeno je da se modifikacijom jonima gvožđa u rastvoru KOH adsorpcioni kapacitet prirodnog zeolita znatno povećava (sa 64 meq/100 g kod prirodnog na 128 meq/100 g kod Fe(III)-modifikovanog zeolita). Takođe, vezivanje jona olova na oba adsorbenta se odvija jonskom izmenom (koja je dominantna pri nižim polaznim koncentracijama jona olova) i hemisorpcijom (koja je dominantna pri višim polaznim koncentracijama jona olova) pri čemu je, pri nižim polaznim koncentracijama, vezivanje jona olova praćeno i...Iron oxides and natural zeolites are efficient adsorbents of heavy metals ions from aqueous solutions. However, to improve their adsorption properties toward different pollutants iron oxides are often impregnated at the surface of porous zeolites. In order to obtain a more efficient adsorbent of lead ions from aqueous solution, in this dissertation modification of natural zeolite-clinoptilolite from Zlatokop deposit, Vranjska Banja, Serbia was performed by combining the method for pure goethite preparation and the method for preparation of iron-coated zeolite. The obtained Fe(III)-modified zeolite is a composite of the natural zeolite and the goethite. The characterization of the natural and Fe(III)-modified zeolite was performed by determination of the chemical composition, cation exchange capacity (CEC), point of the zero charge (pHpzc), textural properties, and by using X-ray powder diffraction analysis (XRPD), scanning electron microscopy and X-ray spectroscopy in energy-dispersive mode (SEM-EDS), thermal analysis (TGA/DTA), infrared spectroscopy (FTIC) and transmission electron microscopy (TEM). It was shown that the modification does not cause any changes in the crystal structure of clinoptilolite, Si/Al ratio, as well as in its morphological, thermal and structural properties. However, CEC of the Fe(III)-modified zeolite was significantly higher than of the natural one, while SEM-EDS analysis of both adsorbents showed that the amounts of iron and potassium at surface of Fe(III)-modified zeolite were higher and the amounts of sodium and calcium were lower than at surface of the natural zeolite. The comparison of pHpzc of the pure goethite (pHpzc=9.4), pHpzc of the natural zeolite (pHpzc=6.8), with pHpzc of Fe(III)-modified zeolite (pHpzc=7.5), indicates formation of Fe-oxide/clinoptilolite mixed system forms at the surface of the natural zeolite. Narower pH range at the plateau was obtained in the case of the Fe(III)-modified zeolite, pointing to a noticeably higher negative surface charge of this adsorbent. Specific surface area significantly increases after modification of the natural zeolite with Fe(III) ions, from 30.20 m2/g for the natural zeolite to 52.50 m2/g for Fe(III)-modified zeolite and is approximately equal to the specific surface of the pure goethite- 55.5 m2/g. Also, Fe(III)-modified zeolite shows increase in both micro- and mesopores volume, confirming formation of new Fe-bearing phases on zeolite. TEM investigations have shown the presence of spherical amorphous nano-clusters on the crystal faces. In order to investigate the mechanism of adsorption of lead ions by the natural and Fe(III)-modified zeolite, experiments were performed under different conditions. The influence of specific parameters, such as initial lead ions concentration, amount of adsorbents, contact time, temperature and particle size on adsorption of lead ions by both adsorbents was studied. It was determined that the adsorption capacity of the natural zeolite significantly increases (from 64 to 128 meq/100 g) after modification with the iron ions in KOH solution. Also, the binding of the lead ions on both adsorbents is carried out by ion exchange (which is dominant at lower starting..