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Technetium-99 (99Tc), as one of the important high-yield fission products, is a significant threat to the environment and human health. It is produced in large amounts by nuclear fission of 235U or 239Pu in nuclear reactions, though the quantity of Tc produced by the spontaneous fission of 238U or by decay of 99Mo in the nature which is very small. 99Tc in the environment originates from nuclear weapons tests, discharges from nuclear power plants, nuclear medicine and radiobiology. These activities generate large volumes of low and intermediate radioactive waste which can cause a significant impact on the environment if disposed without suitable treatment. Immobilization of 99Tc into a relatively small volume waste is vital for long term permanent disposal. High mobility and long half-life of 99Tc considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management. Effective removal of radioactive technetium (99Tc) from contaminated water is of enormous importance from an environmental and public health perspective, yet many current methodologies are highly ineffective. This paper summarizes physico-chemical separation procedures emphasizing those that are the most used in practice. Classic sorbents such as activated carbons, ion exchange resins as well, as new materials, such as metal−organic frameworks and graphene based membranes are described in the paper.

Pollution of the environment is a serious issue nowadays, and finding a proper wastewater treatment is only small part of challenges that humans are facing. In order to find innovative ways for wastewater treatment, different techniques are applied, which lead to the production of new materials, such as ones made of polymeric nanofibers and materials with photocatalytic properties. In this study, nanofibers composite, synthetized from polyamide (PA) and UiO-66 Metal Organic Framework (MOF) by electrospinning method was used for degradation of Congo red dye from 10 ppm aqueous solution in batch conditions. Ultra-thin PA nanofiber membranes were produced with different ratios of MOF - 0.5 wt.%, 1 wt.%, 2 wt.% and 10 wt.% and prior the experiments, in order to be easily applied and removed from the solution, cut in the rectangular shape 1cm x 2 cm. FTIR, XRD and SEM are used for characterization of selected composites, prior and after sorption and photocatalytic experiments, while for determination of dye concentration UV-ViS spectrophotometer was used. The best performance in Congo red degradation was shown by membranes which contained 1 wt.% of MOF. FTIR spectra have shown that, upon the introduction of MOF particles into the PA fiber, reduction of all the peaks by the same amount in intensity indicates no interaction between MOF additive and PA matrix. Further, a new peak appeared after sorption at 590 cm-1 and disappeared after dye degradation induced by sun irradiation. XRD analysis has shown that there are no observable microstructural changes in composites upon sorption and cycling. Decreasing of the band gap of composite compared to pure MOF indicated increased photocatalytic activity. Reusability of composite membranes was investigated by performing experiments in multiple cycles, and results have shown that electrospun UiO-66/polyamide membranes have no significant changes in degradation efficiency of Congo red upon 4 cycles.

Worldwide water bodies have been affected by toxic effluents of industries, such as organic compounds, and are continuously deteriorating the environment as industrialization coupled with urbanization has caused the excess release of wastewater. Finding a proper wastewater treatment is of the greatest importance. Gamma irradiation technique, as one of the advanced oxidation techniques, has been widely investigated as a technique for degradation of organic molecules. It has been shown that this method has the potential to be effectively applied for degradation of toxic colorants which show high persistence to degradation. Although the literature abounds with degradation studies of different organic molecules using a wide range of irradiation dozes and doze rates, according to available data, no such irradiation facility exists, mostly due to high doses and expensive equipment needed to be installed. A mechanism of degradation was proposed: generated reactive species non-specifically react with organic compounds leading to their partial or complete degradation. In recent advances, gamma irradiation was coupled with other wastewater treatment technologies to reduce needed doses. Coupling of gamma irradiation was achieved with addition of oxidants which resulted in increased number of reactive species, then coupling with solid matrices, biological treatment, which all lead to additional destabilization of organic molecules. This way, combining different methods of wastewater purification opens new possibilities and may enable the design of a new modular, or even mobile, plant that will satisfy all the needs for its wide commercial application. As a result, a sustainable development goal can be more easily reachable, i.e., sustainable water resources management in future industrial zones and smart cities may be possible without generation of waste transfer into another media.

The main aim of this research is to show influence of different hydroxides, applied in carbon materials activation process on the electrochemical properties of activated carbon samples. The carbon material samples were prepared by hydrothermal treatment of sucrose and thermally activated using KOH, NaOH and LiOH by chemical activation method. The electrochemical properties of the obtained carbon material samples were examined by cyclic voltammetry and electrochemical impedance spectroscopy and correlated to their physicochemical properties. Investigated samples showed characteristic capacitor-like behavior. The best result of specific capacitance was obtained for the sample synthesized treated by KOH, while the increase in capacitance follows the arrangement of the growth of ionic radius of a metal from an alkali which is used for activation. Dependence on the type of hydroxide is due to differences in the radii of a metal. The alkalis with larger radii of metal produce wider pores and consequently the structure of a porous layer become more accessible and available to the charge transfer of capacitive response.

Rapid industrialization and increasing population have increased the water demand. Various wastes from industries and anthropogenic activities are discharged into aquatic bodies such as lakes, ponds, rivers, oceans. Therefore, focus is placed on the removal of the contamination from the wastewater. Organic pollutants gained extensive attention because of their toxicity, persistence and significant impacts on human health Among them, organic dyes are complex molecules and most of them are water-soluble, resistant to detergents and heat, exhibit poor biodegradability, etc. Azo dyes are used in about 70% of commercial dyes today, from textile and plastic to cosmetics and food. In this work, removal of azo-type dye Congo Red (CR) from water was performed by using UiO-66 type MOF (Metal Organic Framework), activated carbon (AC) and their composite powder mixture (MOF/AC = 50/50 wt.%). Samples were exposed to solar light irradiation for 1h and 2.5 h, respectively, centrifuged to remove solid particles, and solutions were analyzed by UV-ViS spectrophotometer in order to determine the concentration of the remaining dye. Process was repeated three times in order to explore the renewability of the photocatalysts used, with catalysts dried at 50 °C between cycles. Results revieled superior photocatalytic cycling performance of the MOF compared to the MOF/AC composite, while AC showed decline in dye removal performance due to the saturation of available adsorption sites. MOF/AC composite exhibited beneficial cost/performance ratio.

In presented work, influence of temperature, starting material concentration and different hydroxides on properties and morphology of activated carbon obtained from saccharose were investigated. The samples were prepared by hydrothermal treatment and activated using KOH, NaOH and LiOH. Two saccharose concentrations (0.5, 1.0 mol/dm3 ) and three different temperatures (160, 200, 240 °C) were changed in hydrothermal treatment. Activation processes were performed at 750 °C under inert atmosphere. Obtained samples were characterized by X–ray powder diffractometry, elemental analysis, N2 adsorption-desorption measurements, Fourier–transform infrared spectrometry, scanning electron microscopy and thermal analysis. The obtained samples were tested for potential application in dyes removal (Methylene Blue and Methyl Orange) from water solutions.

Anorthite ceramics was fabricated from calcium exchanged Na-LTA zeolite. The powder compacts of Ca-LTA zeolite were sintered at different temperatures ranging between 1100 and 1400°C. It was found that the temperature of 1100°C was sufficiently high to trigger formation of anorthite which stayed stable even at temperature as high as 1400°C. The highest relative density and the lowest open porosity were measured in samples sintered at 1200°C for 3 h. The effect of milling time of Ca-LTA zeolite precursor on density, microstructure and mechanical properties of samples sintered at 1200°C for 3 h was investigated. The particle size refinement appeared to be beneficial in accelerating densification process and improving mechanical properties. The density, compressive strength and hardness of anorthite ceramics obtained from non-milled precursor were measured to be 70.5 %TD, 64 MPa and 1.45 GPa, respectively. On the other side the anorthite ceramics obtained from 24-hour-long milled zeolite precursor had density of 83.9 %TD, compressive strength of 101 MPa and hardness of 3.44 GPa.

Development of method for the complete conversion of Cr-containing electroplating sludge (ES) into the black inorganic pigment was presented. Difficulties related to the ES complex, variable composition and inhomogeneity, where the dominant presence of Cr was followed by: Fe, P, Zn, Ni, Cu, etc., can be overcome by determination of the precise amount of Fe2O3 necessary to be added in order to firmly embed all the heavy metals into the pigment structure (i.e. the Fe0.7Cr1.3O3/FePO4 nanocomposite), taking care not only about weight/molar ratios, but also about average particle size, apparent densities, and volume fraction of the starting materials. As a source of Fe2O3, commercial (p.a.) Fe2O3 and two different Fe-wastes were used, thus completely fulfilling the principles of the circular economy. The obtained black inorganic pigments have consistent composition, no leaching of toxic metals, color (CIE L-a-b-values) comparable with those of commercial pigments and thus have the potential commercial large scale application. © 2021 Elsevier Ltd.

Most heavy metals, such as Cr (chromium), Pb (lead), Cd (cadmium), Ni (nickel), Cu (copper) and Fe (iron), are extremely toxic above a tolerance limit. These heavy metals in wastewater are not biodegradable and can cause serious harm to human health and ecological environments.1 One of the top-priority toxic heavy metal in wastewater is chromium.2 In natural waters, chromium exists in both trivalent Cr(III) and hexavalent Cr(VI) forms. Cr(VI) is the most toxic one and have the tolerance limit 0.1 mg/L into surface water and 0.05 mg/L in potable water.3 Various methods, such as ion exchange, sedimentation, electrochemical process, cementation, coagulation, adsorption and solvent extraction have been developed for the removal of Cr(VI) and other toxic metals from wastewater.4 Among these methods, in some papers,5-8 adsorption has been used as one of the most effective method for the removal of Cr(VI) from aqueous solutions. Characteristics of adsorption, such as low cost, easy to perform, efficient and reversible method with high operating speed, make this method as most commonly used for the removal of Cr(VI) from aqueous solutions.9 Several adsorbents, like activated alumina,10 zeolites,11 natural bisorbents such as chitosan,12 but also activated carbon13 have been used for the removal of Cr(VI) from aqueous solutions. Due to the high cost, commercial activated carbon is not available in less developed countries and there is a considerable attention to produce activated carbon from less expensive and available materials. As a low-cost adsorbent, activated carbon can be produced from materials such as rice husk, seeds husk, tea leaves, sawdust, oil palm shell, coconut husk and coconut shell.14 Activated carbon is one of the most important adsorbents which is applied in different areas. In these areas it is important to determine and remove low concentrations of some pollutants, such as heavy metals. Very good features of this adsorbent are the main reason why it is u, Praškast ugljenični materijal proizveden iz kokosove ljuske korišćen je kao adsorbent za uklanjanje Cr(VI) jona iz vodenih rastvora. Karakterizacija adsorbenta rađena je primenom dve analitičke tehnike, skenirajućom elektronskom mikroskopijom (SEM) i BET metodom. Eksperimenti adsorpcije rađeni su u šaržnom režimu, kako bi se istražili uticaji pH rastvora, vremena kontakta i početne koncentracije Cr(VI) jona. Eksperimentalni rezultati su pokazali da je efikasnost uklanjanja Cr(VI) najveća u pH intervalu od 2,0 do 3,5, a da se ravnoteža uspostavlja nakon 60 minuta. Dva ravnotežna adsorpciona modela, Langmirov i Frojndlihov, korišćena su za fitovanje dobijenih podataka. Frojndlihova izoterma je obezbedila najbolju korelaciju za adsorpciju Cr(VI) jona na ugljeničnom materijalu proizvedenom iz kokosove ljuske. Na osnovu dobijenih rezultata može se zaključiti da ugljenični materijal proizveden iz kokosove ljuske predstavlja jeftin i efikasan adsorbent koji bi potencijalno mogao biti korišćen za tretman otpadnih voda koje sadrže toksični Cr(VI).

Hazardous industrial wastes are the most common source of environmental pollution. Waters originating from unregulated landfills and places of inadequate disposal of this type of wastes can pollute the water sources and affect the human health. In this study, electroplating waste sludge (ES) and various Fe-rich wastes were used as starting materials for the synthesis of inorganic pigments. Obtained black Cr1.3Fe0.7O3 pigments possess adequate properties required for use as inorganic pigments.

Chitosan and its modified forms have received great attention as potential adsorbents due to its outstanding adsorption characteristics toward removal of vaious toxic heavy metal ions from aqueous solutions. In this work, a porous chitosan hydrogel beads (CHB) and CHB cross-linked with glutaraldehyde (GLA) and citric acid (CA) were synthesized and used for investigation of its adsorption performances toward the removal of Pb(II), Cu(II), Zn(II), Cd(II) and Cr(VI) ions from water in batch and dynamic systems. Maximum removal was achieved in the pH ranges of 4.0 - 6.5 and 2.0 - 3.5 for divalent cations and Cr(VI) oxyanion, respectively. The equilibrium adsorption data were best fitted by the Langmuir isotherm model. Based on the optimal conditions, the fixed-bed breakthrough curves for the removal of the studied metal ions from the aqueous solutions using fixedbed columns were experimentally evaluated, as well as theoretically predicted using COMSOL Multiphysics software.

An analytical method based on solid-phase extraction (SPE) using coconut shell activated carbon (CSAC) as a low-cost adsorbent and high performance liquid chromatography with diode array detector (HPLC-DAD) was developed and validated for the determination of four varying polarity pesticides in water samples. SPE procedure was optimized and under the optimized conditions the proposed method was validated. The method exhibited good linearity, satisfactory precision (1.4 – 5.1%), high enrichment factor, good recovery and low limits of detection (0.025 – 0.039 g/dm3 ). Optimized method was used to determine selected pesticides in tap water samples. The recoveries ranged from 58.2% to 105.3%, with low relative standard deviations. The obtained results indicated that the proposed SPE-HPLC-DAD method could be efficiently used for the determination of the selected pesticides in environmental water samples at trace levels.

Magnezijum hidrid, materijal pogodan za skladištenje vodonika zbog velike gravimetrijske i zapreminske gustine, niske cene i netoksičnosti, još nije našao široku industrijsku primenu usled velike termodinamičke stabilnosti i visoke temperature desorpcije vodonika (447°C). Nepovoljna termodinamika i spora kinetika sorpcije se može poboljšati dodatkom aditiva što destabiliše kristalnu rešetku MgH2. U okviru ove doktorske disertacije urađena su teorijska i eksperimentalna ispitivanja magnezijum hidrida dopiranog titan dioksidom. Cilj je razumevanje uticaja aditiva i međufazne granice metal/hidrid, koja nastaje u procesu prodiranja vodonika u potpovršinske slojeve, na mehanizam i reakciju desorpcije vodonika. Kompoziti MgH2-TiO2 sa 10 mas.% anataz i rutil TiO2, su sintetisani mehaničkim mlevenjem u toku 10 i 20h. Različite polimorfne forme su korišćene kako bi se ispitao njihov uticaj na desorpcione karakteristike MgH2. Dekompozicija hidrida je praćena diferencijalnom termijskom analizom i odvija se u tri stupnja. Srednjetemperaturski pikovi se pojavljuju zbog katalitičkog uticaja dopanta, a najniža temperatura 380°C je dobijena za uzorak sa rutil TiO2 mlevenim 10h, dok je za kompozit sa anataznom fazom koji je mleven 20h temperatura daleko viša, 412°C. Proces desorpcije se najbolje opisuje Avrami-Erofejevim kinetičkim modelom za n=4, što isključuje difuziju, a upućuje na procese nukleacije i promene dimenzionalnosti kristala kao odlučujuće procese za desorpciju. Zaključeno je da kristalna struktura dopanta igra presudnu ulogu u ubrzanju reakcije desorpcije. Interakcija vodonika sa (110) površinom rutil TiO2, ispitivana teorijom funkcionala gustine, pokazuje da atomski slojevi paralelni površini koji sadrže atome Ti i O deluju kao barijere za prolazak vodonika ka dubini materijala. Između ovih slojeva su oblasti osiromašene naelektrisanjem u kojima atom H lako prelazi sa jednog na drugi atom O. Potvrđeno je i da se uticaj površine može ograničiti na nekoliko atomskih sl

Magnezijum hidrid, materijal pogodan za skladištenje vodonika zbog velikegravimetrijske i zapreminske gustine, niske cene i netoksičnosti, još nije našao širokuindustrijsku primenu usled velike termodinamičke stabilnosti i visoke temperaturedesorpcije vodonika (447°C). Nepovoljna termodinamika i spora kinetika sorpcije semože poboljšati dodatkom aditiva što destabiliše kristalnu rešetku MgH2. U okviru ovedoktorske disertacije urađena su teorijska i eksperimentalna ispitivanja magnezijumhidrida dopiranog titan dioksidom. Cilj je razumevanje uticaja aditiva i međufaznegranice metal/hidrid, koja nastaje u procesu prodiranja vodonika u potpovršinskeslojeve, na mehanizam i reakciju desorpcije vodonika.Kompoziti MgH2-TiO2 sa 10 mas.% anataz i rutil TiO2, su sintetisanimehaničkim mlevenjem u toku 10 i 20h. Različite polimorfne forme su korišćene kakobi se ispitao njihov uticaj na desorpcione karakteristike MgH2. Dekompozicija hidrida jepraćena diferencijalnom termijskom analizom i odvija se u tri stupnja.Srednjetemperaturski pikovi se pojavljuju zbog katalitičkog uticaja dopanta, a najnižatemperatura 380°C je dobijena za uzorak sa rutil TiO2 mlevenim 10h, dok je zakompozit sa anataznom fazom koji je mleven 20h temperatura daleko viša, 412°C.Proces desorpcije se najbolje opisuje Avrami-Erofejevim kinetičkim modelom za n=4,što isključuje difuziju, a upućuje na procese nukleacije i promene dimenzionalnostikristala kao odlučujuće procese za desorpciju. Zaključeno je da kristalna strukturadopanta igra presudnu ulogu u ubrzanju reakcije desorpcije.Interakcija vodonika sa (110) površinom rutil TiO2, ispitivana teorijomfunkcionala gustine, pokazuje da atomski slojevi paralelni površini koji sadrže atome Tii O deluju kao barijere za prolazak vodonika ka dubini materijala. Između ovih slojevasu oblasti osiromašene naelektrisanjem u kojima atom H lako prelazi sa jednog na drugiatom O. Potvrđeno je i da se uticaj površine može ograničiti na nekoliko atomskihslojeva koji su joj najbliž

Doping of MgH2 with transition metals and their oxides is well-known procedure to improve its hydrogen (de) sorption properties, namely to lower the temperature of desorption and to achieve the kinetics speedup. In order to assess the influence Ti and TiO2 doping has on H mobility and to characterize structurally and electronically observed differences, MgH2-Mg interface doped with both Ti and TiO2 have been studied using ab-initio interface molecular dynamics and bulk calculations. Results suggest different mechanisms of MgH2 structure destabilization. The presence of dopants significantly stabilize MgH2-Mg interface, which is confirmed by work of adhesion computation. Calculated formation energies show that interface system with doped TiO2 is more stable. In terms of H mobility, molecular dynamics simulations confirm that Ti doping is more effective than TiO2 in lowering the desorption temperature. The mobility of hydrogen atoms close to dopant is much higher in the case of Ti than in the case of TiO2. Electronic structure characterization reveals that oxygen atoms with high electron affinity forms more pronounced ionic bonding with Ti and the other neighbor Mg atoms. This in turn cause a shorter Ti-H bonds in first coordination than in the case of Ti doping and further reduction of H atoms mobility. This is in accordance with molecular dynamics predictions. (C) 2016 Elsevier B.V. All rights reserved.

Hydrogen desorption properties of MgH2 ball milled with two different TiO2 polymorphs, rutile and anatase, were studied. Structural characterization has been done by X-ray diffraction (XRD) analysis, particle size analysis (PSD) and scanning electron microscopy (SEM). The mechanism of desorption and the apparent activation energy for desorption were investigated by applying isoconversional kinetic analysis of DTA spectra, while desorbed species were followed by TPD coupled with mass spectroscopy. It has been demonstrate that the addition of rutile TiO2 significantly decrease the apparent activation energy for desorption (E-des(a)), while addition of anatase titania has negligible influence on E-des(a). Such behaviour could be explained in terms of the same crystal structure of rutile TiO2 and MgH2. Further, the mechanism of desorption changes from Avrami-Erofeev n = 3 for pure MgH2 to Avrami Erofeev n = 4 for composite materials. Copyright (c) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The hydrogen sorption kinetics of MgH2-VO2(B) composites synthesised by mechanical milling have been studied. The microstructural properties of composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM), Particle size analysis (PSD), while sorption behaviour was followed by differential scanning calorimetry (DSC) and Sievert measurements. Results have shown that although desorption temperature reduction is moderate; there is a substantial improvement in hydrogen sorption kinetics. The complete desorption of pure MgH2 at elevated temperature takes place in more than 30 min while the composite fully desorbs in less than 2 min even at lower temperatures. It has been shown that the metastable gamma-MgH2 phase and the point defects have a decisive role in desorption process only in the first sorption cycle, while the second and the subsequent sorption cycles are affected by microstructural and morphological characteristics of the composite. (C) 2015 Elsevier B.V. All rights reserved.

Composite of MgH2 VO2 has been synthesized by high-energy mechanical milling. The sorption properties of composites were examined by differential scanning calorimetry and sorption analysis. It has been shown that at relatively low temperature sorption reaction is notable enhanced. Complete desorption of pure MgH2 at 380°C finishes after 30 minutes while composite material fully desorbs in less than 2 minutes even at lower temperatures.

The paper deals with the possibility to control aging of MgH2 by controlling the deposited energy, number and type of defects and their distribution in the near surface region using Ar8+, Xe8+, and B3+ ion irradiation. The evolution of the obtained phases was monitored using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, laser scattering particle size distribution measurements and surface area analyses. Obtained results give the possibility to resolve between the material related (impurities, defects, strains) and the ambient induced component of aging.

The hydrogen desorption properties and kinetics of MgH2-VO2 composite prepared by mechanical milling of MgH2 and VO2 have been investigated. Structural characterization of produced nanocomposite was done by X-ray powder diffraction (XRD), particle size analysis and scanning electron microscopy (SEM). The structure and morphology of the composite have been correlated with hydrogen desorption properties investigated by differential thermal analysis (DTA). It has been shown that short mechanical milling of nanostructured VO2 and MgH2 leads to decrease of hydrogen desorption temperature of MgH2 by 80 K. The mechanism of desorption has been changed from phase boundary reaction, spherical symmetry for untreated MgH2 to phase boundary reaction, cylindrical symmetry for the composite material. The activation energy for desorption has been reduced by adding VO2 ceramics as a catalyst. (C) 2012 Elsevier Ltd and, Techna Group S.r.l. All rights reserved.

The influence of structural changes caused by irradiation with different ions, their energies and fluences on sorption properties has been investigated. The irradiation has been done using B3+ and N3+ ions at 45 keV with ion fluence of 10(16) ion/cm(2) at the FAMA ion source at Vinca Institute of Nuclear Sciences in Belgrade. Morphology and microstructure of samples were analysed using XRD and particle size analysis, while estimation of penetration depth and deposition of defects were done by SRIM calculations. Hydrogen desorption properties and kinetics were evaluated from TPD measurements and numerical non-isothermal procedure. Results suggest that there are several mechanisms of desorption depending on defect concentration, their interaction and ordering. It has been also demonstrated that the changes in near-surface area play the crucial role in hydrogen desorption kinetics. It is confirmed that there is possibility to control the thermodynamic parameters of these systems by controlling vacancies depth profile and concentration.

The hydrogen desorption (HD) properties of MgH2-CeO2 composite prepared by mechanically milling of MgH2 and cubic CeO2nano have been examined. Morphology and microstructure of composites have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), laser scattering analysis and correlated with desorption properties obtained by means of temperature programmed desorption (TPD). It has been shown that decrease of crystallite and particle size of the samples lead to significant lowering of desorption temperature. Further, the activation energy for desorption (E-A(des)) has been calculated using Kissinger equation. Obtained value of 60 +/- 10 kJ/mol indicates that the activation energy of hydrogen desorption is sufficiently decreased by the catalytic effect of vacant CeO2 structure. Consequently the surface activation of sample plays a major role in HD reaction. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.