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Influence of Soil Type and Physical-Chemical Properties on Uranium Sorption and Bioavailability
No full textThis work was undertaken to study the influence of soil type and its physical and chemical properties on uranium sorption and bioavailability, in order to reduce the uncertainty associated with this parameter in risk assessment models and safe food production. The tests were conducted on three types of Serbian soils: alluvium, chernozem, and gajnjaca, from which 67 samples were taken. Dominant factors of uranium mobilisation: the specific content of total/available form of uranium and phosphorus, the degree of acidity (pH(KCl)), and humus content and their correlation, were analysed. Content of available uranium form, according to the type of soil decreases in the following order: gajnjaca > alluvium > chernozem. It was found the medium correlation between pH values and available content of uranium in chernozem and gajnjaca, statistically significant at the level of significance of 99% and the alluvium at the level of significance of 95%. Correlation coefficients in all cases were negative, indicating that the reduction in pH increases the mobility of uranium and thus its availability for the adoption of the plants. Soil pH was the only dominant factor that significantly controlled the uranium value with no further significant contribution of other soil parameters
Tin secondary raw materials and procedures for their processing
No full textNajznačajnije sekundarne sirovine kalaja su: otpadni beli limovi i međuprodukti njihove proizvodnje (kalajne šljake, mulj i sunđer), metalna ambalaža, olovo-kalajne šljake i legure, amortizovani hladnjaci iz automobilske industrije i dr. Tehnološki postupci njihove regeneracije obuhvataju dve osnovne faze: pripremu otpada i njegovu metaluršku preradu. Priprema metalne ambalaže za metaluršku preradu je veoma važna faza i obuhvata veliki broj tehnoloških operacija, kao sto su: sakupljanje, sortiranje, pranje, usitnjavanje, odmašćivanje i dr. Priprema otpadnog belog lima je jednostavnija usled lakšeg sakupljanja i manje zaprljanosti. Prerada pripremljenog otpada vrši se primenom postupka hlorovanja, elektrolitičkog rastvaranja i taloženja ili alkalnog luženja i elektrolize.Prerada kalajne šljake, mulja i sunđera vrši se primenom postupka redukcionog topljenja, a dobijeni sirovi kalaj rafiniše u više stupnjeva.Main resources of tin secondary raw materials are: residual tin-plates and by-products from their production (tin slags, sludges and sponges), metallic packings, lead-tin slags and alloys, amortised coolers from cars etc. The technological procedure for their processing includes two basic stages: pretreatment of the scrap and its metallurgical processing. The tin-plated cans pretreatment is a very important phase and it includes the following operations, cans collection, sorting, washing, crushing, warnish removal etc. Due to the easier collection and lower grade of impurities, the pretreatment of the waste tin plates is simpler in comparison with the tin-plated cans. The processing of the prepared scrap, can be carried out in two ways. In one way, the processing consists of chlorination treatment, electrolytical dissolution and precipitation, while in the other way alkaline leaching and electrolysis are employed. The processing of the tin slags, sludges and sponges can be carried out using reductional smelting process and refining of obtained secondary tin
The effect of applied current density on the surface morphology of deposited calcium phosphate coatings on titanium
No full textElectrochemical deposition of calcium phosphate coatings on titanium was performed galvanostatically from the aqueous solution of Ca(NO3)(2) and NH4H2PO4 with the current densities between 5.0 and 10 mA cm(-2), for different deposition times, at room temperature. The coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results showed that dicalcium phosphate dihydrate (DCPD), brushite (CaHPO4 center dot 2H(2)O) coatings were deposited. The influence of applied current density and the deposition time on the phase composition, crystallite domain size and the morphology of brushite coatings were investigated. It was shown that brushite coating of the greatest mass was obtained for the longest deposition time, while the increase in current density over 7 mA cm(-2) does not affect significantly the mass of brushite coatings. The finest crystallites, with the smallest crystallite domain size of 15.6nm, were deposited at the current density of 9.0 mA cm(-2). Brushite coatings were fully converted to hydroxyapatite in simulated body fluid (SBF) which was confirmed by XRD and SEM. The crystallite domain size of HA coatings is controlled by applied current density for brushite coatings deposition: crystallization of HA at more porous brushite coatings, deposited at higher current density, caused the formation of smaller crystallites of hydroxyapatite
Effects of additives on nickel (ii)-chloride hydrogen reduction for production of nanocomposite catalysts
No full textCatalysts based on nickel, as active component, exhibit suitable properties in various heterogeneous catalysis processes; however, they quickly deactivate due to deposits formation during exploitation and sintering at elevated temperatures. Considering that catalysts with several catalytic components possess enhanced catalytic properties, in present study the influence of temperature, time and additives (PdCl2, FeCl2 and CuCl2) on the reduction degree of nickel(II)-chloride by hydrogen have been investigated. The objectives of the study were selection of an appropriate catalytic activity modifier and development of a new synthesis method for nanocomposite catalysts production, which are characterized by enhanced properties compared to the commercial Ni/Al2O3 catalysts. Obtained experimental results clearly indicate that the best effect was achieved with addition of 0.1 wt. % PdCl2, whereby NiCl2, reduction degree was 58.16% at 653 K and Pd significantly increased the reduction rate. According to the obtained results., new technological synthesis method of nanocomposite Ni-Pd/Al2O3 catalysis was proposed, where Ni and Pd. as catalytically active components, are homogeneously dispersed in monolithic Al2O3 based ceramic foam
Physico-chemical characterization of archaeometallurgical findings from two localities near Bor (Serbia)
No full textBor and its surroundings are well known for long and rich tradition in mining and metallurgical activities, as well as by numerous archaeometallurgical localities. The results of investigation of archaeometallurgical findings from Šetaće and Paulešti localities near Bor are presented in this paper. Research of slag samples was done using chemical analysis, DTA, XRD and EDXRF in order to confirm early metallurgical works at mentioned two localities
Influence of mechanical activation on the constituents of the MgO-Al2O3-SiO2-TiO2 system
No full textU ovom radu je ispitivan uticaj mehaničke energije na strukturu i promene u mikrostrukturi sistema MgO-Al2O3-SiO2-TiO2. Utvrđeno je da mehanička energija pospešuje homogenizaciju polaznih komponenti, utiče na veličinu i oblik zrna praškastih materijala i podstiče promene u kristalnoj strukturi polaznih čestica, sto utiče na pojavu defekata u ispitivanom sistemu. Ove promene su utvrđene difraktometrijskom analizom, kao i PSA i DTA metodom.In this paper the effects of mechanical activation on structural and microstructural changes of the system MgO-Al2O3-SiO2-TiO2 were analyzed. It was confirmed that mechanical activation led to the homogenization of powder particles, the comminuting of particles, and after this period, the introduced energy was used to induce changes in the crystal structure, which resulted in the emergence of defects, initially on the surface of the crystal lattice, and then inside
Electrodeposition of silver powder from nitrate electrolyte for usage in electronic
No full textThe aim of this work was to investigate the process of electrodeposition of silver powder from nitrate electrolyte for usage in electronic. It was performed a series of experiments to test the solubility of silver powder in nitric acid and the effect of Cu+, Pb2+ and Cr2+ ions on the properties of the silver powder. The morphology of silver powder obtained from nitrate electrolyte, was studied using the scanning electron microscope (SEM model: JOEL JSM-6610LV). Chemical composition of the silver powder was determined using the Energy Dispersive X-ray Spectroscopy (EDS). The EDS spectra for silver powder were recorded using the X-ray spectrometer, attached to the scanning electron microscope
Insecticidal Potential of Natural Zeolite and Diatomaceous Earth Formulations Against Rice Weevil (Coleoptera: Curculionidae) and Red Flour Beetle (Coleoptera: Tenebrionidae)
No full textInsecticidal potential of natural zeolites and diatomaceous earths originating from Serbia against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was evaluated. Two natural zeolite formulations (NZ and NZ Modified) were applied to wheat at rates of 0.50, 0.75, and 1.0 g/kg, while two diatomaceous earth (DE) formulations (DE S-1 and DE S-2) were applied at rates of 0.25, 0.50, 0.75, and 1.0 g/kg. A bioassay was conducted under laboratory conditions: temperature of 24 +/- 1 degrees C, relative humidity in the range 50-55%, in tests with natural zeolites, and 60-65%, in tests with DEs, and in all combinations for progeny production. Mortality was assessed after 7, 14, and 21 d of insect contact with treated wheat, and the total mortality after an additional 7-d recovery on untreated broken wheat. Progeny production was also assessed after 8wk for S. oryzae and 12 wk for T. castaneum. The highest mortality for S. oryzae and T. castaneum was found after the longest exposure period and 7 d of recovery, on wheat treated with NZ at the highest rate and DEs at rates of 0.50-1.0 g/kg. Progeny reduction higher than 90% was achieved after 14 and 21 d of contact of both beetle pests with wheat treated with DE S-1 at 0.50-1.0 g/kg and DE S-2 at 0.75-1.0 g/kg, while the same level of reduction was achieved only for T. castaneum after its contact with the highest rate of NZ formulation. NZ Modified, applied even at the highest rate, revealed much lower insecticidal potential
The possibility of bioactive coatings obtaining by electrophoretic deposition of HAp on the steel implants
No full textMetalni implantati za ortopedsku hirurgiju izrađuju se najčešće od nerđajućeg čelika, legura na bazi titana, kobalta ili hroma, koje imaju odlične konstrukcione i mehaničke osobine i otporne su na koroziju. Ipak, ovakvi implantati poldožni su lokalnoj koroziji u ljudskom telu jer je zapaženo prisustvo njihovih metalnih jona u okolnim tkivima i telesnim tečnostima. Da bi se iskoristila prednost njihovih mehaničkih karakteristika, a postigla biokompatibilnost, moguće je na njihovu površinu naneti bioinertnu ili čak bioaktivnu prevlaku. Hidroksiapatit je poznat po svom bioaktivnom ponašanju, koje duguje hemijskoj istovetnosti sa ljudskim kostima. Elektroforetska deopzicija je relativno stara tehnika, koja je ovde primenjena uz upotrebu novog materijala - nanostrukturnog hidroksiapatita, kako bi se dobile ravnomerne i kompaktne hidroksiapatitne prevlake i tako prevazišla ograničenja prethodno korišćenih visokotemperaturnih tehnika nanošenja prevlaka i problemi sa složenim oblikom metalnog supstrata. Prevlake nanostrukturnog hidroksiapatita eletroforetski su deponovane na peskiranu površinu uzoraka od nerđajućeg čelika 316LVM, pri konstantnom naponu, za različito vreme deponovanja, a zatim su sinterovane u atmosferi argona na 1000oC. Toplotna stabilnost HAp praha prvo je ocenjena DTA/TG analizom u temperaturnom intervalu 23oC-1000oC. Za mikrostrukturnu karakterizaciju prevlake korišćen je SEM, a za određivanje faznog sastava XRD analiza.Surgical metallic implants are usually made of stainless steel, titanium- and cobalt/chromium- based alloys which have superior structural and mechanical properties, and are corrosion resistant. Nevertheless, they are susceptible to local corrosion in the human body, releasing metal ions into the nearby body tissue and fluids. Keeping the advantage of their mechanical properties, their biocompatibility can be achieved through deposition the bioinert or even bioactive coating onto their surface. Hydroxyapatite is known by its bioactive behavior, originating from its chemical identity with human bones. The electrophoretic deposition is rather old technique used here with a novel nanostructured hydroxyapatite powder to obtain uniform and dense hydroxyapatite coatings, to overcome the restrictions of previously used high temperature coating techniques and to overcome the complex geometry metallic substrate problems. The coating of nanosized hydroxyapatite was electrophoretically deposited on blasted surface of stainless steel 316LVM samples at constant voltage, for different deposition times and subsequently sintered in argon atmosphere at 1000 oC. The HAp powder thermal stability was initially assessed using DTA-TG analyses over the temperature range of 23oC-1000oC. The microstructure characterization of the coating was accomplished using SEM, and phase composition was determined by XRD
Anthropogenic sources of uranium in serbia-risk assessment on environment and human health
No full textThe continual process of increased industrialization, militarization, and urbanization are among the most powerful sources of environmental degradation all over the world. Environmental contamination caused by radionuclides, in particular, by uranium and its decay products, is a serious problem worldwide and has become the common subject for further scientist investigations. It is estimated that the technologically enhanced naturally occurring radioactive materials (TENORM) caused by nuclear and non-nuclear technologies, significantly increased natural radioactivity in the last 30 years. The development of nuclear science and technology, uranium mining, production and application of phosphoric fertilizer, the coal industry (mining and combustion), the oil and gas production, metal mining and smelting, mineral processing and building industry are generating radioactive waste that increased natural radioactive level on a regional scale. Economic sanctions for Serbia in the last decade of the 20th century, as well as the transition of its entire economy (which is still ongoing process), the NATO conflict in 1999, and absence of legislation and institutions, are all additional reasons for radioactive contamination of the regional ecosystem of Serbia. Also, one of the main contributing factor of environmental contamination by uranium in Serbia involved the cheap, imported phosphate fertilizers that were often of quality poor and radiological unsafe. This outcome was a direct consequence of the reduced capacity in Serbian national production. On the other hand, according to the available data, many states were documented with bombing sites; 112 sites in Kosovo and Metohija, 12 locations in southern Serbia with depleted uranium (DU) ammunition, during the NATO aggression of Yugoslavia. On this occasion around 10 tons of DU was introduced into environment. The degree of contamination ranges from the bottom limit of 200 Bq/kg to 235,000 Bq/kg in the soil samples of mainly agricultural land, or 1,000 times above the tolerable level. Within the international mission, UNEP and FOCUS and by the engagement of national experts, the decontamination of endangered sites with depleted uranium has only been partially carried out. Today, unfortunately, we encounter an "invisible threat" of depleted uranium ammunition use, with highly radioactive and chemo toxic effect on human health, causing in the last 12 years an enormous increase in cancer rates and a number of newborns with genetic changes. This paper reviews some relevant aspects of environmental contamination with uranium, and gives an overview of the different remediation processes available. This study reviews some relevant aspects of environmental contamination with anthropogenic uranium, primarily from the application of phosphate fertilizers and the use of ammunition with depleted uranium. Our study will include a special accent on Serbia's area concerning the uranium uptake and how it behaves in the food chain and will explore how these indicators impact human health