Study of chromium(VI) sorptionon the functionalized sepiolite

Predmet ove disertacije je proučavanje sorpcije anjonskih vrsta hroma(VI) na funkcionalizovanim sepiolitima iz vodenih rastvora, na 298 K. Prirodni, kiselinski aktivirani i termokiselinski aktivirani sepioliti su funkcionalizovani kovalentnim vezivanjem (3-merkaptopropil)trimetoksi-silana i [3-(2-aminoetilamino)propil]trimetoksi- silana za silanolne grupe na površini sepiolita. Funkcionalizacija je dokazana pomoću skenirajuće elektronske mikroskopije, rendgenske difrakcione analize, infracrvene spektroskopske analize, diferencijalno-termijske analize, adsorpcionodesorpcionih izotermi azota i određivanja tačke nultog naelektrisanja, pHtnn. Utvrđeno je da je struktura polaznog materijala sačuvana tokom funkcionalizacije. Adsorpcione izoterme su ukazale da je kapacitet adsorpcije funkcionalizovanog kiselinski aktiviranog sepiolita veći nego kapaciteti adsorpcije funkcionalizovanih prirodnog i termokiselinski aktiviranog sepiolita, za sve ispitivane početne pH-vrednosti rastvora. Efikasnost adsorpcije na funkcionalizovanim sepiolitima je poboljšana sniženjem pH-vrednosti rastvora. Aminosilanima funkcionalizovani sepioliti imaju veći sorpcioni kapacitet nego merkaptosilanima funkcionalizovani sepioliti na svim ispitivanim početnim pHvrednostima i naročito pri početnoj pH = 2,0. Maksimalni sorpcioni kapaciteti hroma(VI) su ~ 60 mg/g aminosilaniziranog kiselinski aktiviranog sepiolita, ~ 55 mg/g aminosilaniziranog termokiselinski aktiviranog sepiolita i ~ 37 mg/g aminosilaniziranog prirodnog sepiolita, pri početnoj pH-vrednosti 2,0; dok su maksimalni sorpcioni kapaciteti ~ 8,0 mg Cr(VI) po g merkaptosilaniziranog kiselinski aktiviranog sepiolita i ~ 2,8 mg Cr(VI) po g merkaptosilaniziranog termokiselinski aktiviranog sepiolita, pri početnoj pH-vrednosti 3,0 i ~ 2,7 mg Cr(VI) po g merkaptosilaniziranog prirodnog sepiolita, pri početnoj pH-vrednosti 2,0. Proces adsorpcije na aminosilaniziranim sepiolitima, pri početnoj pH-vrednost 2,0, se može opisati kinetičkim modelom pseudodrugog reda. Pri svim ispitivanim početnim pH-vrednostima rastvora, rezultati sorpcionih eksperimenata za sve aminosilanizirane sepiolite su dobro opisani Freundlich-ovim modelom, a Dubinin-Radushkevich-ev model uspešno može opisati rezultate sorpcionih eksperimenata za sve merkaptosilanizirane sepiolite. Vrednosti termodinamičkih parametara ukazuju da je proces adsorpcije spontan i pretežno fizičke prirode.The subject of this dissertation is the study of sorption of anionic species of chromium(VI) on the functionalized sepiolites from aqueous solution at 298 K. Natural, acid activated and thermo-acid activated sepiolites were functionalized by covalent grafting (3-mercaptopropyl)trimethoxy-silane and [3-(2-aminoethylamino)propyl]- trimethoxy-silane to the silanol groups onto the sepiolite surface. Functionalization was proved by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, differential thermal analysis, nitrogen adsorption-desorption, and the point of zero charge, pHpzc, determinations. It has been established that the structure of parent material was preserved during the functionalization. The adsorption isotherms suggested that the adsorption capacity of the functionalized acid activated sepiolite was higher than that of the functionalized natural and thermo-acid activated sepiolites, for all investigated initial solution pH values. Adsorption efficiency of the functionalized sepiolites was improved by decreasing solution pH value. The amine-silane functionalized sepiolites showed a higher adsorption capacity than the mercapto-silane functionalized sepiolites at all studied initial pH values, especially at the initial pH = 2.0. The maximum chromium(VI) removal was: ca. 60 mg/g of amine-silane functionalized acid activated sepiolite, ca. 55 mg/g of amine-silane functionalized thermo-acid activated sepiolite and ca. 37 mg/g of amine-silane functionalized natural sepiolite, at an initial pH of 2.0; while, the maximum Cr(VI) removal was ca. 8.0 mg Cr(VI) per g of mercapto-silane functionalized acid activated sepiolite and ca. 2.8 mg Cr(VI) per g of mercapto-silane functionalized thermo-acid activated sepiolite, at initial pH 3.0, and ca. 2.7 mg Cr(VI) per g of mercapto-silane functionalized natural sepiolite, at initial pH 2.0. The adsorption process onto amine-silane functionalized sepiolites, at initial pH value of 2.0, followed pseudo-second-order kinetics. At all investigated initial solution pH values, equilibrium data for all amine-silane functionalized sepiolites fitted well to the Freundlich model, and Dubinin-Radushkevich model can successfully describe the equilibrium data for all mercapto-silane functionalized sepiolites. The values of the thermodynamic parameters indicate a spontaneous adsorption process of a prevalently physical nature

Application of polymer nanocomposites modified with goetthite and magnetite for removal of selenate from water

Предмет ове докторске дисертације је примена полимерних нанокомпозита модификованих гетитом и магнетитом за уклањање селената из воде. У оквиру овог научног истраживања, биће проучавана функционализација високопорозних хибридних адсорбената на бази полимерне матрице модификоване гвожђе(III)оксидом, као и оптимизација материјала за уклањање селената из водених раствора...The subject of this doctoral dissertation is the application of polymer nanocomposites modified with goethite and magnetite to remove selenate from water. As part of this scientific research, the functionality of highly porous hybrid adsorbents based on a polymer matrix modified with iron(III) oxide, will be studied, as well as the optimization of materials for removing selenate from aqueous solutions..

Means and Effects оf Constraining the Number of Used Cross-Sections in Truss Sizing Optimization

This paper looks at sizing optimization results, and attempts to show the practical implications of using a novel constraint. Most truss structural optimization problems, which consider sizing in order to minimize weight, do not consider the number of different cross-sections that the optimal solution can have. It was observed that all, or almost all, cross-sections were different when conducting the sizing optimization. In practice, truss structures have a small, manageable number of different cross-sections. The constraint of the number of different cross-sections, proposed here, drastically increases the complexity of solving the problem. In this paper, the number of different cross-sections is limited, and optimization is done for four different sizing optimization problems. This is done for every number of different cross-section profiles which is smaller than the number of cross-sections in the optimal solution, and for a few numbers greater than that number. All examples are optimized using dynamic constraints for Euler buckling and discrete sets of cross-section variables. Results are compared to the optimal solution without a constrained number of different cross-sections and to an optimal model with just a single cross-section for all elements. The results show a small difference between optimal solutions and the optimal solutions with a limited number of different profiles which are more readily applicable in practice

Effects of recrystallization annealing on mechanical properties of cold-rolled PdNi5 wires

The aim of this investigation was to determine the influence of the recrystallization temperature and recrystallization time on the microstructure and mechanical properties of the PdNi5 alloy subjected to cold deformation in the process of rolling at a constant deformation degree. The samples of PdNi5 alloy were recrystallization annealed within the temperature range of 200-1000 ºC and annealing time range of 20-45 min after cold rolling with deformation degree of 97%. The tensile test was carried out using universal material testing machine. The hardness was also measured on the combined device for measuring Vickers and Brinell hardness. Metallographic observations were performed on an optical microscope. The analysis of the results of investigations regarding the microstructural changes and corresponding mechanical properties of cold-rolled PdNi5 strips shows that annealing temperature of 500 ºC was sufficient to activate the energy for various recrystallization processes causing a change in the mechanical properties of cold-rolled PdNi5 strips. The annealing time, at constant annealing temperature, almost did not affect a recrystallization temperature and the mechanical properties of the cold-rolled PdNi5 strips

Different types of adsorbents for selenium (Se) removal from water: A review

Development of adsorption materials based on metal oxides, silicon dioxide, carbon, biosorbents and adsorbents, obtained from natural waste, can be used to remove selenium from water. Research on some of these materials is at the laboratory level, while the others were tested in the pilot plants, and a few have found a commercial application. The high adsorption capacities show a possibility of their application for selenium removal from water. This paper presents a literature review of different types of adsorbents for the removal of selenium (Se) from water

INFLUENCE OF USING DISCRETE CROSS-SECTION VARIABLES FOR ALL TYPES OF TRUSS STRUCTURAL OPTIMIZATION WITH DYNAMIC CONSTRAINTS FOR BUCKLING

The use of continuous variables for cross-sectional dimensions in truss structural optimization gives solutions with a large number of different cross sections with specific dimensions which in practice would be expensive, or impossible to create. Even slight variations from optimal sizes can result in unstable structures which do not meet constraint criteria. This paper shows the influence of the use of discrete cross section sizes in optimization and compares results to continuous variable counterparts. In order to achieve the most practically applicable design solutions, Euler buckling dynamic constraints are added to all models. A typical space truss model from literature, which use continuous variables, is compared to the discrete variable models under the same conditions. The example model is optimized for minimal weight using sizing and all possible combinations of shape and topology optimizations with sizing

New materials and technologies in aero and space research

Space technology plays an integral and indispensable role in our daily lives. Whether we are talking about live broadcasts of World Cup matches, satellite-assisted emergency management efforts, or the nightly weather forecast, one thing is true: our lives would be very different without satellite images or satellite-based communication and navigation systems. Space technology is key to our modern, knowledge-based society. Today space makes a vital contribution when it comes to promoting research and development, education and innovation, economic growth, providing highly qualified jobs, improving our quality of life, protecting the Earth, ensuring our security and defence and furthering international cooperation. Military platforms—such as ships, aircraft, and ground vehicles— rely on advanced materials to make them lighter, stronger, and more resistant to harsh environmental conditions. Currently, the process for developing new materials frequently takes longer than a decade. This lengthy process often means that developers of new military platforms are forced to rely on decades-old, mature materials, because potentially more advanced materials are still being developed and tested and are considered too large a risk to be implemented into platform designs. Al alloys have been the primary material for the structural parts of aircraft because of their well known performance, well established design methods, manufacturing and reliable inspection techniques. Fiber reinforced polymer composites have been increasingly used in aerospace. Fiber Metal Laminate (FML) is a new kind of hybrid composite. Materials used to construct spacecraft and protective gear—including the International Space Station and space suits for astronauts—must be lightweight yet strong enough to guard against cosmic dust that travels at hypervelocity

Mineralogical characteristics of slag (from the Flotation plant of RTB Bor) granulated in the laboratory conditions

A sample of slag from the Flotation Bor, RTB Bor, was mineralogical tested after granulation in the laboratory conditions. Minerals contained in the sample of granulated slag are: fayalite and ferrite that form the basis with rarely sprayed fine particles of magnetite, pyrite, chalcopyrite, bornite, copper matte and elemental - native copper [6, 7]. Granulation of slag was conducted in the laboratory conditions on the device specially designed for this purpose

Supplementary data for the article: Marjanovic Trajkovic, J.; Milanovic, V.; Ferjancic, Z.; Saicic, R. N. On the Asymmetric Induction in Proline-Catalyzed Aldol Reactions: Reagent-Controlled Addition Reactions of 2,2-Dimethyl-1,3-Dioxane-5-One to Acyclic Chiral α-Branched Aldehydes. European Journal of Organic Chemistry 2017, 2017 (41), 6146–6153. https://doi.org/10.1002/ejoc.201701073

Supporting information for: [https://doi.org/10.1002/ejoc.201701073]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2410

Quality testing of industrially produced essential oil of white pine (Pinus sylvestris L.) from the Republic of Srpska

The quality of the essential oil obtained from white pine wood greenery from the territory of the Republic of Srpska was analyzed by examining the chemical composition and antimicrobial activity of samples produced by the hydro-distillation process in industrial production conditions. The chemical composition of the essential oil was analyzed by GC/MS and GC/FID analysis. The antimicrobial activity of the obtained white pine oil was investigated for its possible use as an antimicrobial agent. The obtained results prove the presence of 37 components in the analyzed sample, which represents 98.5% of the total components present. The most common are monoterpene hydrocarbons, followed by sesquiterpene hydrocarbons, much less represented are monoterpenes containing oxygen and aromatic compounds, while aliphatic esters are found only in traces. Antimicrobial activity was examined using the disk diffusion method. The results showed large zones of inhibition, both for the tested oil sample and for all eight analyzed bacterial strains (from 12.00 ± 0.00 to 17.33 ± 1.15mm), as well as for the fungal strain. The chemical composition and antimicrobial action of essential white pine oiled from plant material originating from the territory of the Republic of Srpska indicates its significant phytomedical potential