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New multifunctional biomaterials for medical application
No full textThe exibits presents a range of new multifunctional biomaterials for potential medical application. Biocompatible composites based on hydrogels of alginate, polyvinyl alcohol, and chitosan with incorporated bioactive agents such as silver nanoparticles, honey and activated charcoal particles with adsorbed povidone-iodine provide efficient release of the immoblized agents and antibacterial activity, which is attractive for applocation in wound dressing. Bioactive macroporous composites based on polzmer hzdrogels with bioceramic particles as well as metal foundations with multicomponent coatings are attractive as bone tissue implants. Finallz, dental inserts were developed for dentin replacement. In addition, the exibit will include a bioreactor system for cultivation of cancer cells in alginate hydrogels in 3-dimensionalenvironment, aimed to provide more reliable antitumor drug testing and development of personalized medical therapies
Electrical properties of isothermally sintered cordierite-based ceramics as funcion of sintering and activation time
No full textMechanical activation is a commonly used and relatively fast and inexpensive procedure for
sample preparation before the sintering process. Cordierite is a stoichiometric mixture of three different
oxides (2MgO⋅2Al2O3⋅5SiO2). It is a very attractive, widely used high-temperature ceramic
material. The mechanical activation of the starting mixtures with 5.00 mass % TiO2 was performed
in a high energy ball mill during 10-80 min. The applied compaction pressure before the sintering
process was 2 t/cm2, based on our recent investigation. The sintering process was performed at 1350
°C for 2h and 4h in air atmosphere. X-ray diffraction was used to analyze the phase composition of
non- activated and 80 min activated samples, sintered for 2 and 4h, respectively. This paper investigates
the influence of prolonged sintering time on the product electrical properties
Possibilities of waste sulfur valorization in eco-friendly products
No full textModifikacija konvencionalnih građevinskih materijala obično se izvodi upotrebom različitih otpadnih materijala. U ovom istraživanju biće prikazana upotreba sekundarnog sumpora kao veziva u betonu. Sumporni beton je termoplastični kompozit koji se sastoji od mineralnog agregata i punila, sa sumporom kao vezivom na temperaturi višoj od tačke očvršćavanja sumpora. Ovaj relativno nov građevinski materijal može da zameni konvencionalni Portland cementni beton u raznim konstrukcijama. U ovom radu biće prikazana svojstva sumpornog betona, kao i rezultati ispitivanja njegove postojanosti u agresivnim sredinama. U cilju ispitivanja svojstava, primenjene su destruktivne i nedestruktivne metode, dok su svojstva korelisana sa strukturommaterijala.Modification of conventional building materials is commonly realized using different waste materials. In this research, the use of secondary sulfur as binding agent in concrete was analyzed. Sulfur concrete is a thermoplastic composite made of mineral aggregate and filler, with sulfur as a binder at temperature above the hardening point of sulfur. This relatively new building material can possibly replace conventional Portland cement concrete in many branches of construction. Also, in this research, sulfur concrete properties were examined, as well as its quality in the presence of the induced destruction agent. Destructive and nondestructive methods were applied and the material properties correlated with the structure
Lead sorption from wastewaters by invasive Acer negundo L. biomass
No full textDue to the tendency of spreading out of its natural habitat and posing a menace to the surrounding species
and biodiversity of the area under its influence, Acer negundo L. is known as the deciduous invasive tree
species. Even though it is considered harmful for ecosystems, the biomass of this invasive species can be
utilized for the purpose of wastewater remediation. A. negundo leaf biomass (AN) was investigated for its
adsorption potential to bind the lead ions from an aqueous solution. The lead was selected for the sorption
experiments, as it is a well-known pollutant often found in various industrial effluents. Acer negundo L. leaves
were collected from the protected area of the outstanding natural landscape “Veliko ratno Ostrvo” in Belgrade.
Experiments were carried out in a batch system under specific operational conditions. Precise amounts of
sorbent were added in the Pb (II) solutions of known initial concentrations, and the optimal operational
parameters were further evaluated. Parameters such as lead concentration, pH value, contact time, and
sorbent dosage were tested and optimized for increasing the adsorption performance of the obtained sorbent.
Maximum Pb (II) uptake occurred at pH 3,5 and sorbent dosage of 2 g/L. Very fast adsorption was noticed by
the kinetic study, with equilibrium state achieved after the initial 2 min of sorbent (A. negundo)-sorbate (1 mol/L
Pb (II) solution) contact. Obtained data were subjected to equilibrium modeling by using Langmuir and
Freundlich equations. Maximum adsorption capacity reached 101,5 mg/g. According to these results, sorbent
prepared from Acer negundo leaf powder has an outstanding potential to be applied for lead removal from
contaminated waters
Priprema i karakterizacija mešovitog oksida Fe3+/Cr3+ na ekspandovanom vermikulitu kao sorbenta za jone nikla
No full textAdsorbenti na bazi oksida Fe3+ i Cr3+predmet su brojnih istraživanja. Interkalacioni sloj
vermikulita koristan je medijm za taloženje nanočestica. Zbog svoje relativno velike površine,
kapaciteta katjonske izmene i prirodnog obilja vermikulita, ovaj liskunski mineral i njegovi kompoziti
mogu biti valorizovani kao potencijalni adsorbenti. U ovoj studiji kompozit oksida
Fe3+/Cr3+/ekspandirani vermikulit (Fe2O3 / Cr2O3 / EV) pripremljen je metodom in-situ. Kompozitni
i osnovni materijal karakterisan je Furijeovom transformacijom infracrvene spektroskopije (FTIR),
rendgenskom difrakcijom (XRD), skenirajućom elektronskom mikroskopijom (SEM), a određeni su i:
specifična površina BET-om (SBET), kapacitet katjonske izmene (CEC) i pH tačke nultog
naelektrisanja (pHPZC). Adsorpciona svojstva Fe2O3 / Cr2O3 / EV i EV ispitivana su u šaržnom
sistemu na pH blizu pHPZC za uklanjanje Ni (II) iz vode. Uzimajući u obzir parametre procesa kao
što su vreme kontakta, masa adsorbenta i temperatura određeni su tip adsorpcije, termodinamički i
izotermski parametri (Lengmir i Frojndlih) i parametri brzine adsorpcije. Rezultati kinetičkih studija
dali su dobre korelacije sa modelom pseudo - drugog reda i Veber - Morisovim modelom. Uzimajući
u obzir činjenicu da je EV imao niske vrednosti CEC i specifične površine, dobijeni kompozit ima
umerenu adsorpcionu sposobnost (22,9 mg/g)
Fotokatalitička degradacija tiofanat metila
No full textPesticidi predstavljaju supstance koje imaju za cilj zaštitu bilja od različitih vrsta bolesti i
patogena. Sintetski, organski, pesticidi su pored visoke efikasnosti pokazali i veliki problem u životnoj
sredini kao posledica velike akumulacije i toksičnosti. Usled povećanog zagađenja voda različitim
pesticidima, potrebno je koristiti različite procese za njihovo uklanjanje i degradaciju. Zato su
razvijani oksidativni procesi, koji se pod jednim imenom nazivaju unapređeni oksidativni procesi
(AOPs). Među njima, posebnu pažnju je izazvala fotokataliza, kao proces koji omogućava da se pod
dejstvom UV zračenja u prisustvu katalizatora, degradiraju i teško razgradivi organski molekuli.
Stoga je ispitano fotokatalitičko dejstvo na degradaciju tiofanat-metila. Varirani su različiti
eksperimentalni uslovi, kao što su koncentracija rastvora pesticida, masa katalizatora i udaljenost
UV lampe od fotokatalitičkog reaktora. Najbolji reazultati degradacije su dobijeni pri koncentraciji
od 5 mg l-1 pesticida i 10 mg katalizatora u 50 ml reakcione smeše. U eksperimentalnom radu, kao
katalizator korišćen je titan(IV)-oksid (TiO2) Degussa P25. Smanjenje koncentracije pesticida u
reakcionom sistemu praćena je na UV spektrofotometru (Shimadzu 1800), praćenjem smanjenja
apsorbance. U optimizovanom procesu, koncentracija pesticida se smanjila 10 puta, što pokazuje da
je primenjeni proces efikasan
Application of thermal analysis in characterization of limestone for obtaining of the metallic calcium
No full textThis paper present results of experimental investigations of metallic calcium production from Serbian carbonate raw materials by aluminothermic process and the basic operating parameters of the particular technological phases. The limestone with high content of Mg, Na and K was used in the study. X-ray analysis reveals that samples contain mainly calcite with small amount of dolomite. The DTA/TG analysis of the limestone samples from site “Čačak” (samples C I and C II) and chemical composition of limestone samples are presented in the graphical abstract. At DTA curves of both C I and C II samples sharp endothermic peaks are noticed, related to the dissociation process followed by the endothermic heat effect. Since the DTA curves show only one clearly defined peak, it can be concluded that the calcium carbonate is solely present in the raw materials in the form of calcite, while aragonite is not present. At first, the effects of temperature, time and granulometry on the calcium carbonate calcination were examined. The dissociation process was completed in 10–15 min at 1200 °C, and the dissociation rate increased with decreasing particle size down to 5 mm. Afterwards, the aluminothermic reduction process of calcium oxide was investigated. At a temperature of 1200 °C and vacuum of at least 3 kPa, the reduction process was completed within 2 h. The chemical composition of calcium oxide and metallic calcium showed increased content of magnesium oxide and alkaline oxides (especially sodium)
Impact of mould powder on physicochemical properties of slag in the continuous casting process
No full textMould powder is essential for the reliable operation of the continuous casting system and the quality
of the cast steel. The very responsible roles of mould powder are fulfilled by selecting combinations
of components that affect physicochemical properties of the resulting liquid slag, which lubricate the
walls among the crystallizer and slab. The contribution of mould powder refers to the range of
melting temperature and speed and the viscosity of glassy or crystalline slag and formation
temperature. These connections are the research subject in this paper, emphasizing the functional
dependence of viscosity and liquidus temperature of mould powder with its material composition.
This research investigates the impact of basicity, alkali oxides (Na2O and K2O), and carbon-free
content on viscosity and liquidus temperature of mould powder in the continuous casting process.
The liquidus temperature of mould powder was obtained empirically after a year of experimental
examination, and viscosity was determined using several models. Based on experimental
investigation, we show empirical parameters for equitation of liquidus temperature of mould
powder. Also, using established equations, we presented isolines for viscosity and liquidus
temperature with experimental parameters
Corrigendum in the article: Extraction of ammonium nickel sulfate hexahydrate by hydrometallurgical process from the hyperaccumulating plant Odontarrhena muralis - case study from Serbia
No full textInvestigation of the impact of mechanical activation on synthesis of the MgO-TiO2 system
No full textIn this study, a mixture of magnesium oxide and titanium dioxide was mechanically activated in order to investigate the possibility of mechanochemical synthesis of magnesium titanate. Mechanical activation was performed for 1000 min in a high-energy vibro mill (type MH954/3, KHD Humboldt Wedag AG, Germany). The mill is equipped with housing having a horizontally placed shutter. The cylindrical stainless steel working vessel, with inner dimensions of 40 mm in height and 170 mm in diameter, has working elements consisting of two free concentric stainless steel rings with a total weight of 3 kg. The engine power is 0.8 kW. Respecting the optimal amount of powder to be activated of 50-150 g and the stoichiometric ratio of the reactants in the equation presenting the chemical reaction of magnesium titanate synthesis, the starting amounts were 20.2 g (0.5 mol) of MgO and 39.9 g (0.5 mol) TiO2. During the experiments, X-ray diffraction analysis of the samples taken from the reaction system after 60, 180, 330, and 1000 min of mechanical activation was performed. Atomic absorption spectrophotometry was used for chemical composition analysis of samples taken at different activation times. Based on the X-ray diffraction analysis results, it can be concluded that the greatest changes in the system took place at the very beginning of the mechanical activation due to the disturbance of the crystal structure of the initial components. X-ray diffraction analysis of the sample after 1000 min of activation showed complete amorphization of the mixture, but diffraction maxima characteristic for magnesium titanate were not identified. Therefore, the mechanical activation experiments were stopped. Evidently, the energy input was not sufficient to overcome the energy barrier to form a new chemical compound - magnesium titanate. The failure to synthesize magnesium titanate is explained by the low negative Gibbs energy value of -25.8 kJ/mol (despite the theoretical possibility that the reaction will happen), as well as by the amount of mechanical energy entered into the system during activation which was insufficient to obtain the reaction product. Although the synthesis of MgTiO3 was not achieved, significant results were obtained which identify models for further investigations of the possibility of mechanochemical reactions of alkaline earth metals and titanium dioxide