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Harmful cyanobacteria blooms and the escalating impact of cyanotoxins necessitates the effective removal of cyanobacteria from water ecosystems before they release cyanotoxins. In this study, cyanobacteria removal from water samples taken from the eutrophic Aleksandrovac Lake (southern Serbia) was investigated. For that purpose, novel activated carbons derived from waste biomass—date palm leaf stalk (P_AC), black alder cone-like flowers (A_AC), and commercial activated carbon from coconut shell (C_AC) as a reference were used. To define the best adsorption conditions and explain the adsorption mechanism, the influence of contact time, reaction volume, and adsorbent mass, as well as FTIR analysis of the adsorbents before and after cyanobacteria removal, were studied. The removal efficiency of P_AC and A_AC achieved for the applied concentration of 10 mg/mL after 15 min was ~99%, while for C_AC after 24 h was only ~92% for the same concentration. To check the safety of the applied materials for human health and the environment, the concentrations of potentially toxic elements (PTEs), the health impact (HI) after water purification, and the toxicity (MTT and Comet assay) of the materials were evaluated. Although the P_AC and A_AC achieved much better removal properties in comparison with the C_AC, considering the demonstrated genotoxicity and cytotoxicity of the P_AC and the higher HI value for the C_AC, only the A_AC was further investigated. Results of the kinetics, FTIR analysis, and examination of the A_AC mass influence on removal efficiency indicated dominance of the physisorption mechanism. Initially, the findings highlighted the superior performance of A_AC, with great potential to be globally commercialized as an effective cyanobacteria cell adsorbent.

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.

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.).

Solving problems with hazardous waste materials is of crucial importance today. In the presented study, the application of waste vitreous enamel as a cement replacement up to 30% in mortar and concrete production was investigated. The chemical and physical-chemical characterization of the starting material was performed, as well as a leaching test and physical-mechanical characterization of mortar and concrete mixes. Obtained results showed that, due to its chemical composition, the vitreous enamel used must be classified as hazardous waste. At the same time, it possesses pozzolanic properties and satisfies minimal criteria for use as a cement replacement. Testing mortars and concrete mixes indicate that waste vitreous enamel can be applied as a construction material for cement replacement in the maximal amount of 20%. The leaching test was performed in accordance with international standard EN 12457-2 on hardened mortar with a maximal cement replacement of 20%. The results showed that there was no significant release of toxic elements, i.e., that the practical application of hazardous waste vitreous enamel in the construction industry may be fully in line with environmental standards.

The presented study is a continuation of the research with the aim of finding a useful value of hazardous waste slag generated by the combustion of lignite in heating plants and its application in the construction industry. The different amounts of cement (10%, 15%, 20% and 25%) were replaced with waste slag and silica fumes in mortars and concrete production. Detailed physical–mechanical characterization was performed on the mortar and concrete samples according to standard procedures. Test results indicated that the replacement of cement with slag and silica fumes reduces the physical and mechanical properties of mortar and concrete, but cement composites retained the required structural properties. If 15–20% is considered an acceptable level of compressive strength decrease, then it can be concluded that waste slag can be implemented in practice and be used as a construction material, with cement replacement in the maximal amount of 20% (17.8% of slag and 2.2% of silica fumes). On hardened mortar samples with maximal possible cement replacement (20%), physical–chemical characterizations were performed and included X-ray and infrared spectrophotometry, scanning electron microscopy, and thermal analysis. Results showed the absence of new phases and the presence of only those which were characteristic for starting samples, predominantly portlandite, quartz, calcite and calcium silicate-oxide

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.

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.

The intent in this paper is to define how the batch equilibrium results of copper removal from a synthetic solution on natural zeolite can be used for prediction of the breakthrough curves in the fixed-bed system for both a synthetic solution and wastewater. Natural zeolite from the Vranjska Banja deposit, Serbia, has been fully characterized (XRD, chemical composition, DTA/TG, SEM/EDS) as a clinoptilolite with cation exchange capacity of 146 meq/100 g. The maximum adsorption capacity (qm) in the batch of the mono-component system (synthetic copper solution) obtained using the Langmuir isotherm model was 7.30 and 6.10 mg/g for particle size below 0.043 and 0.6–0.8 mm, respectively. Using the flow-through system with the 0.6–0.8 mm zeolite fixed-bed, almost double the adsorption capacity (11.2–12.2 mg/g) has been achieved in a saturation point for the copper removal from the synthetic solution, compared to the batch. Better results are attributed to the constant high concentration gradient in flow-through systems compared to the batch. The complex composition of wastewater and large amounts of earth alkaline metals disturb free adsorption sights on the zeolite surface. This results in a less effective adsorption in flow-through systems with adsorption capacity in breakthrough point of 5.84 mg/g (~0.95 × qm) and in a saturation point of 7.10 mg/g (~1.15 × qm).

Numerous factors influence the complexity of environmental and waste management problems, and the most significant goal is the reuse of materials that have completed their “life cycle” and the reduction in the use of new resources. In order to reduce impact of waste slag on the environment, in the present study, waste slag, generated in heating plants after lignite combustion, was characterized in detail and tested for application as a replacement for cement in mortar or concrete production. For physical–chemical characterization of slag, different experimental and instrumental techniques were used such as chemical composition and determination of the content of heavy metals, investigation of morphological and textural properties, thermal analysis, X-ray, and infrared spectroscopy. Physical–mechanical characterization of slag was also performed and included determination of activity index, water requirement, setting time and soundness. A leaching test was also performed. Presented results show that waste slag may be used in mortar and concrete production as a partial cement replacement, but after additional combustion at 650 °C and partial replacement of slag with silica fume in the minimal amount of 12%. The maximal obtained cement replacement was 20% (17.8% slag and 2.2% of silica fume).

In this paper influence of alginate encapsulation on point of zero charge (pH pzc ) and thermodynamic properties of the natural and Fe(III)- modified zeolite were investigated. The pH pzc was determined by using 0.1000 g of the samples and 50 cm 3 of the solution containing KNO 3 in concentrations of 0.0001-0.01 mol/dm 3 for initial pH (pH i ) in range between 2 and 12. The obtained pH pzc were 6.2 for natural (NZA) and 6.5 for modified zeolite encapsulated with alginate (FeA). Influence of the temperature on the adsorption of lead was investigated for different initial lead ions concentrations (180-3200 mgPb 2+ /dm 3 ) and temperatures of 30, 40 and 60 o C. For both adsorbents, adsorption of lead ions increased with increasing its initial concentration as well as with increasing of the temperature. Also, the best fits of the experimental data were obtained by Freundlich isotherm. The temperature had positive influence adsorption and removal of lead ions increased with increasing its initial concentration as well as with increasing of the temperature. The thermodynamic parameters (the standard free energy of adsorption, standard enthalpy and standard entropy) were also determined. The results showed that lead ions removal from aqueous solutions is much favourable for FeA then NZA. © 2019 The Authors.

In presented paper, influence of temperature, precursor concentration and different hydroxides on properties 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 temperatures (160, 200, 240 ºC) were changed in hydrothermal treatment. Activation processes were performed at 750 ºC under N2 atmosphere. 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 from water solutions., У представљеном раду испитани су утицај температуре, концентрације полазног материјала и различитих хидроксида на својства активираних угљеничних материјала добијених из сахарозе. Узорци су припремљени хидротермалним третманом и активирани помоћу KOH, NaOH и LiOH. Две различите концентрације воденог раствора сахарозе (0,5 1,0 mol/dm3) и три температуре (160, 200, 240 ºC) су примењене у хидротермалном третману. Процеси активације су изведени на 750 ºC у атмосфери азота. Узорци су карактерисани рендгендском дифрактометријском анализом, елементарном анализом, адсорпционо-десорпционим мерењем азота, инфрацрвеном спектрометријом са Фуријеовом трансформацијом, скенирајућом електронском микроскопијом и термијском анализом. Добијени узорци су такође тестирани за потенцијалну примену у уклањању боја из водених раствора.

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.

In present paper, the influence of the initial pH and concentration of Pb2+ on its adsorption by the natural (NZA) and Fe(III)-modified zeolite-alginate beads (FeA) was studied. Results showed that modification of the starting materials have a positive effect on their adsorption capacities (102 and 136 mg/g for the NZA and FeA, respectively). After encapsulation, the mechanism of lead adsorption by both adsorbents was changed and ion exchange dominates. The best adsorption was achieved for initial pH GT 3.8. Cation exchange capacity, structural properties, and hydrophobicity of samples were also determined, and the presence of the alginate has no significant influence on investigated properties of samples. Experiments on wastewater from tailings of lead and zinc mine Grot, Serbia, showed that after treatment with both adsorbents, the content of the most abundant heavy metals (Pb, Zn, Hg, and Mn) significantly decreased.

Alumina/YAG composites (AYX_t) with high relative density (99.2 %TD) were successfully obtained by mixing commercial alumina powder with different volume fractions of yttrium aluminium garnet (Y3Al5O12-YAG; 7, 14, 21 and 28). YAG was synthetized by nitrate glycine reaction in the form of precursor powder. Polycrystalline YAG powder was obtained by calcination at 950 degrees C for 2 h. Additionally, obtained compositions were characterized by XRD, SEM, EDX and electrochemical impedance spectroscopy. By XRPD analysis was found that the particle size of YAG powders lies in the nanometric range (being lower than 35 nm). By SEM microphotographs of composites were confirmed the formation of a conductive path consisting from mutually interconnected YAG particles. This was confirmed by the electrochemical impedance spectroscopy. The highest electrical conductivity of grain (K-g) and grain boundary (K-gb) at 700 degrees C amounted to 2.22x10(-2) ohm(-1)cm(-1) and 9.44x10(-3) ohm(-1) cm(-1), respectively, was measured in the composite containing 21 vol% of YAG.

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. Speci, 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

A zinc-exchanged montmorillonite (Zn-MONT) was prepared from a natural montmorillonite (MONT) and the adsorption of aflatoxin B-1 (AFB(1)) was investigated at pH 3 and 7. Characterization of Zn-MONT was done by determination of chemical composition, the point of the zero charge (pH(pzc)), thermal (DTA/TGA/DTG) and X-ray powder diffraction (XRPD) analysis. Adsorption of AFB(1) (C-0 = 4 ppm) by Zn-MONT, at different solid/liquid ratios (10, 1 and 0.5 g L-1), at pH 3 or 7, showed that its adsorption was high (over 96%) and independent of pH, similar to MONT. No desorption of AFB(1) from MONT-AFB(1) and Zn-MONT-AFB(1) complexes occurred at pH 6.5, suggesting strong binding of AFB(1) by both adsorbents. Furthermore, AFB(1) adsorption by Zn-MONT followed a nonlinear (Langmuir) type of isotherm at pH 3 with a calculated maximum capacity of 60.17 mg g(-1). The stability of MONT-AFB(1) and Zn-MONT-AFB(1) complexes was evaluated by calculating the binding energies between AFB(1) and metal cations using quantum chemical methods. The evaluated interaction energies of AFB(1) with hydrated Zn2+, Mg2+, and Ca2+ cations showed that the strongest interaction was the interaction of the Zn2+ system, -70.2 kcal mol(-1), whereas energies for Mg-2 and Ca2+ systems were -68.8 and -62.9 kcal mol(-1), respectively. The results indicate that Zn-MONT can be suitable for potential practical application as both, an antibacterial and an aflatoxin binding agent. (C) 2012 Elsevier B.V. All rights reserved.

Natural Zeolitic tuff was modified with 2, 5 and 10 mmol M+/100 g of octadecyldimethylbenzyl ammonium (ODMBA) ions and the products were denoted as OZ-2, OZ-5 and OZ-10. The starting material and organozeolites were characterized by determination of the point of zero charge (pH(pzc)) and by thermal analysis. in vitro sorption of fumonisin B-1 (FB1) was studied for all sorbents at pH 3, 7 and 9. The pH(pzc) for the zeolitic tuff was 6.8 +/- 0.1, while the pH(pzc) for OZ-2, OZ-5 and OZ-10 pH(pzc) was 7.0 +/- 0.1. The curves pH(final) = f(pH(initial)) suggest that the surfaces of all sorbents are positively charged at pH 3 and uncharged at pH 7 and 9. High sorption of FB1 by the zeolitic tuff in acidic solution Suggests electrostatic Interactions between the anionic FB1 and the positively charged surface. At pH 7 and 9, adsorption of FB1 is prevented because anionic FB1 cannot be adsorbed at the uncharged surface. From the pH(pzc) for the organozeolites, it is possible that with lower amounts of ODMBA (OZ-2 and OZ-5), at pH 3, beside interactions between head groups of ODMBA and its alkyl chains and anionic FB1, electrostatic interactions between positive uncovered surface and anionic FB1 contribute to the sorption, while at pH 7 and 9 there is only the possibility for interactions between FB1 and ODMBA. When the zeolitic surface was completely covered with ODMBA (OZ-10), FB1 sorption was independent of the form of FB1 suggesting only interactions between ODMBA and FB1. (C) 2009 Elsevier B.V. All rights reserved.

In this paper, the results of the surface modification of natural zeolite with different amounts (2, 5 and 10 mmol M(+)/100 g) of octadecyldimethylbenzyl ammonium ions (ODMBA) are presented. The obtained organozeohtes were denoted as OZ-2, OZ-5 and OZ-10. The degree of ion exchange was followed by determination of amounts of inorganic cations released from zeolite. Results confirmed that reaction between ODMBA and starting zeolite has occurred via ion exchange mechanism. The obtained value for point of zero charge, pH(pzc), of natural zeolite was 6.8 +/- 0.1, while for OZ-2, OZ-5 and OZ-10 pH(pzc) was 7.0 +/- 0.1. Below the pH(pzc), the surfaces of materials are positive while at pH values higher than pH(pzc) their surfaces are negative. Compared to the pHpzc of natural zeolite, no significant differences in pH(pzc) was observed for all three organozeolites indicating that obtained products have similar functional groups with similar acid and basic characteristics as starting zeolite. The pH(pzc) was not dependent on the amount of ODMBA ions at the zeolitic surface and the value of pH(pzc) for all investigated sorbents is the same for all three electrolyte concentrations indicating that the pH(pzc) of each material is independent of the ionic strength of KNO(3).