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Influence of Alginate Encapsulation on Point of Zero Charge (pH(pzc)) and Thermodynamic Properties of the Natural and Fe(III) Modified Zeolite
No full textIn 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 KNO3 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 degrees 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
Effects of Ag+ Ion Doping on UV Radiation Absorption and Luminescence Profiles of Fluorapatite Nanomaterials Obtained by Neutralization Method
No full textIn the present study we have analyzed effects of Ag+ ions doping on energetic profiles of nanophosphors materials based on fluorapatite crystal system. The UV radiation absorption and luminescence properties of monophase fluorapatite (FAP) and Ag+ doped fluorapatite (AgFAP) nanomaterials obtained by neutralization method were investigated using the photoluminescence spectrophotometry. The excitation-emission profiles of nanomaterials were analyzed statistically by MCR-ALS method and number of fluorophores was extracted. FAP lattice absorbed light at 350 nm in the UVA part of spectrum, and with increasing concentration of Ag+ ions new absorption maximum appeared at 270 nm in the UVC part. Fluorescence of FAP nanoparticles was in violet region of visible part of the spectrum, with a red shift to the green region when Ag+ was doped in lattice. MCR-ALS analyses of fluorescence spectra confirm formation of two maxima, at 484 and 505 nm, as a consequence of Ag+ ions doping in FAP lattice at Cal (4f) sites. The results of quantum chemical calculations showed that an Ag+ ion is stronger bonded to the binding site 1 (-1352.6 kcal/mol) than to the binding site 2 (-1249.0 kcal/mol). Considering that AgFAP1 nanopowder absorbs photons over all part of UV radiation spectrum, this material might be used as potential radiation protective nanomaterial
Preliminary examinations and possible application of limestone "Sibnička Čukara" - municipality of Rekovac
No full textGeološka istraživanja na području centralne Srbije, u reonu opštine Rekovac pokazala su prisustvo pojave krečnjaka "Sibnička Čukara". Krečnjak je sirovina koja ima primenu u različitim industrijskim granama kao što su: industrija kreča, šećera, stočne hrane, mineralnih đubriva, farmacija, u metalurgiji i dr. U kojim industrijskim granama ova sirovina može da ima primenu nakon određenih postupaka pripreme, zavisi od njenog kvaliteta. Preliminarna laboratorijska ispitivanja i karakterizacija pojedinih asortimana dobijenih iz krečnjaka "Sibnička Čukara" su potvrdila mogućnost primene u sledećim oblastima: drobljenog krečnjaka u proizvodnji kreča i šećera i u metalurgiji kao II klasa, mlevenog kao punilo za asfalt, kao dodatak stočnoj hrani, ali samo za svinje koje su starije od 16 nedelja zbog sadržaja teških metala, kao sredstvo u proizvodnji mineralnog đubriva i za odsumporavanje dimnih gasova.Geological research carried out in the area of Central Serbia, municipality of Rekovac, showed the presence of limestone"Sibnička Čukara". Limestone is a raw material that has been used in various industrial branches such as: industry of lime, sugar, green-foder, mineral fertilizers, also in farmacy, metallurgy, etc. This raw material can have application in various industrial branches, which depends on its quality. Preliminary laboratory tests and characterization of certain limestone assortments obtained from "Sibnička Čukara" confirmed the possibility of application in the following areas: crushed limestone in the production of lime and sugar, in metallurgy as a second-class material, crushed limestone as a filler for asphalt and animal feed (but only for pigs older than 16 weeks, due to the content of heavy metals), then as an agent for production of mineral fertilizers and thereupon for flue-gas desulfurization
The Investigation of Characteristics and Thermal Behaviour of Lignocellulosic Waste Biomass Using Thermogravimetric Analysis
No full textThis paper focuses on lignocellulosic waste biomass originating from food industry, which should find its further application in order to fulfill demands of circular economy. Therefore, here are presented some of the chemical and physical properties that affect combustion process, as well as thermochemical reaction kinetics for lignocellulosic biomass wastes. The biomass investigated was peach stone particles originating from food industry. The results have showed that peach stones can be characterized as good energy alternative renewable material, with properties that allow its safe thermochemical conversion. Kinetic analysis of this biomass was performed using Thermogravimetric Analysis (TGA) with a simple reaction model applied, namely n-th order reaction model. The obtained results have confirmed the complex nature of this material and the need for further modelling
Comparison of the formation and development of cavitation damage on cast and sintered samples based on basalt
No full textU radu je ispitivana otpornost na dejstvo kavitacije staklo-keramike na bazi bazalta. Ispitivane su dve vrste uzoraka: liveni i sinterovani uzorci na bazi bazalta. Kavitaciono erozioni test izveden je pomoću ultrazvučne vibracione metode sa stacionarnim uzorkom. Da bi se odredila kavitaciona otpornost praćena je promena mase uzoraka u funkciji vremena ispitivanja. Promena morfologije oštećenja površine uzoraka tokom ispitivanja praćena je skenirajućom elektronskom mikroskopijom. Nivo degradacije površine kvantifikovan je korišćenjem analize slike. Uzorci su ispitivani pod istim uslovima. Poređenje svojstava otpornosti na dejstvo kavitacije izvršeno je u odnosu na vrednosti kavitacionih brzina. Rezultati su pokazali visok stepen otpornosti ispitivanih uzoraka i mogućnost njihove primene u uslovima visokih kavitacionih opterećenja.The paper examines the resistance to the effect of cavitation of glass-ceramics based on basalt. Two types of samples were investigated: cast and sintered samples based on basalt.The cavitation erosion test was performed using the ultrasonic vibratory method with a stationary sample. To measure the cavitation resistance, a change in sample mass in function of the cavitation time was monitored. The change in the morphology of the surface with the test time was followed by scanning electron microscopy. The level of the surface degradation of the samples was quantified using the image analysis. Samples were tested under the same conditions. A comparison of the properties of the resistance to the effect of cavitation was performed in relation to the calculated cavitation rates. The results showed the high degree of cavitation resistance of the tested samples and the possibility of their application in conditions of high cavitation loads
Pyrophillite “Parsovići” – Efficient Material in Heavy Metal Removal
No full textThe present work explored the effectiveness of Parsovići pyrophyllite ore as sorbent material for heavy metals such as Pb, Cu, Zn, Cd and Ni from aqueous solution. The analysis of chemical composition of PIR samples revealed the presence of silica and alumina besides Ca bearing phase; along with FTIR analysis which confirmed presence of hydroxyl groups attached to Si or Al, the composition of the ore sample indicates that this sample might be a prospective source for the effective metal sorbent. The preliminary batch sorption studies supported this hypothesis, indicating that the PIR sample poses highest affinity (mmol/g) in single ion solution towards Pb, followed by Zn, Cu, Ni and Cd. In multi metal solution the sorption of Zn was lowest. The sorption capacity under described operational conditions for Pb (single metal solution) was 47.25 mg/g
MOGUĆNOST GRAVITACIJSKE KONCENTRACIJE BOGATE Pb-Zn RUDE IZ RUDNIKA „GROT“-KRIVA FEJA KOD VRANJA
No full textU rudnom telu rudnika „Grot“-Kriva Feja kod Vranja, povremeno se pojavljuje ruda sa veoma visokim sadržajem minerala olova (Pb) i cinka (Zn). Iz ovakve rude je zbog visokog sadržaja metaličnih minerala 85-90 %, praktično nemoguće dobiti koncentrate K/Pb i K/Zn, postupkom flotacijske koncentracije, koji je osnovni definisani postupak dobijanja koncentrata u ovom rudniku. U radu je prikazano ispitivanje mogućnosti dobijanja koncentrata K/Pb i K/Zn postupkom gravitacijske koncentracije, sitnih klasa na klatnom stolu Wilfley. U radu su detaljno opisani način pripreme rude, eksperimentalni uslovi i sam postupak izvođenja opita gravitacijske koncentracije
Investigations of quartz raw materials from the locality of Rekovac muncipality
No full textQuality of raw materials, including quartz sand and quartzite, varies from one deposit to another. Furthermore, the material quality determines in which industrial branches it can be used after certain preparation processes. Potential applications of quartz raw materials are: in the construction and refractory industry, ceramics and glass industry, then in metallurgy, foundry and also in production of water treatment filters. Geological investigations of the central Serbia region, in the Rekovac municipality, resulted in identification of occurrence of quartz sand ("Ursula") and quartzite ("Velika Krusevica"). Preliminary laboratory tests and characterization of the quartz sand size fraction -0.63+0.1 mm confirmed the possibility of applying this size fraction in the construction materials industry, while the quartzite can be used in refractory, glass and metallurgy industries. After determining the geological reserve of quartz sand "Ursula" and quartzite "Velika Krusevica", detailed investigations are required. Quality conditions from the aspect of chemical composition and physical properties of quartz sand and quartzite are mostly clearly defined by a special standard for this purpose. On the other hand, there are also application areas where standards does not exist, but users define their quality conditions. This example is with the application of quartz sand in the production of water glass. Chemical composition as well is not always the determining factor for the application of quartz raw material. For example, for quartz sand used for sandblasting, grain form is essential. From the economic analysis point of view, the prices of quartz raw materials vary depending on their chemical and physical properties. After all, what needs to be pointed out is the fact that these raw materials are very widespread in nature and that their exploitation is quite simple. After the raw material is excavated, it is stored and further sieved, washed, dried and processed according to customer requirements. All of these processes are cheaper than preparing, for example, limestone, and significaly cheaper than preparation of metal ores
Cationic surfactants modified kaolin – Efficient adsorbents for mycotoxins
No full textThe natural kaolin from a plant for the production of quartz sand in Rgotina, Serbia (KR) was modified with two cationic surfactants - octadecyl dimethyl benzyl ammonium chloride (O) and hexadecyltrimethylammonium bromide (H). Both surfactants were added in amounts equal to 90% of kaolin cation exchange capacity (CEC). The obtained materials were denoted as OKR and HKR. Characterizations of KR, OKR, and HKR were done by Fourier transform infrared spectroscopy (FTIR) spectroscopy and zeta potential measurements. FTIR spectra and zeta potential measurements confirmed the presence of both surfactants at the kaolin surface.
Adsorption of mycotoxins – zearalenone (ZEN) and ochratoxin A (OCHRA) was studied by the natural kaolin and organokaolines under in vitro conditions. The effects of the amount of the adsorbent, the initial ZEN and OCHRA concentrations, and pH, on adsorption of mycotoxins, were investigated. Preliminary results of adsorption of ZEN and OCHRA by KR showed that natural kaolin had no affinity to adsorb these mycotoxins. However, the presence of both organic cations in the kaolin structure significantly increased adsorption of ZEN and OCHRA. Adsorption of the mycotoxins by OKR and HKR increased with increasing the amount of each adsorbent in suspension. Slightly higher adsorption of ZEN than OCHRA by both adsorbents was observed at both pHs.
ZEN and OCHRA adsorption increased for both OKR and HKR as the concentration of the initial toxins increased at pH 3 and 7. OCHRA and ZEN are hydrophobic molecules that possess different functional groups and may exist in various forms at different pH values. OCHRA adsorption by OKR and HKR followed nonlinear isotherms at pH 3 and 7, and higher adsorption capacity was obtained for OKR. Also, OCHRA adsorption capacity for OKR and HKR was much higher at pH 3. The obtained results suggest that adsorption of OCHRA was dependent on the form of OCHRA in solution and that type of surfactant had an influence on OCHRA adsorption. Adsorption of ZEN by organokaolines also showed nonlinear isotherms at pH 3 and 7 and similar amounts were adsorbed at both adsorbents at both pH values. The obtained adsorption capacities suggest that adsorption of ZEN was practically independent of the form of the toxin in solution and also on the type of the organic cations in the kaolin structure. Based on the obtained results, kaolin modified with surfactants may be effective materials for adsorption of ZEN and OCHRA
Finite element analysis of the cleavage fracture in medium carbon V and TiV microalloyed forging steels
No full textStress and strain distribution at the onset of cleavage fracture during fourpoint bending testing at liquid nitrogen temperature of two commercial mediumcarbon V and TiV microalloyed forging steels, with predominantly acicular ferrite structure, was examined using finite element analysis. The finite element models were based on notched four-point bending Griffiths-Owens’s type specimens, while the material mechanical properties data input was based on stress-strain curves obtained by tensile testing at liquid nitrogen temperature. Results of the modeling showed that there were no distinct differences in strain distribution along the distance from the notch tip between the two steel samples, aside from strain magnitude which stems from the differences in stress-strain curves. Based on the recorded load at fracture, the corresponding displacement calculated by finite element analysis was somewhat larger for the V steel. While the TiV steel breaks at crosshead displacement between 0.3 and 0.5 mm, the V steel breaks between 0.6 and 0.9 mm. Plastic strain at the cleavage initiation site for the TiV steel ranges from 0.0595 to 0.1612, while for the V steel these values range from 0.3694 to 0.6338. Observed differences in plastic deformations near the notch root, where cleavage initiation sites were detected, seem to reflect differences in deformation behavior at liquid nitrogen temperature.
Moreover, such difference could be ascribed to the observed differences in structure, primarily in the volume fraction of acicular ferrite. It was concluded that deformations are more uniformly distributed when acicular ferrite is predominant in
the structure of the steel. It could be ascribed to the effect of “gradual yielding” related to the high dislocation density in acicular ferrite, somewhat lower yield stress and higher ductility of the TiV steel with predominantly acicular ferrite structure