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The crystallization of potassium germanate glass with high content of niobium oxide
No full textPotassium germanate glass with molar ratio [GeO2]/[K2O] = 1.2 and Nb2O5 content of 34 mol% have been synthesized by a melt-quenching method. The crystallization behavior under non-isothermal and isothermal crystallization conditions was investigated. The results showed that this glass exposed complex primary crystallization. In the temperature range LT 800 degrees C primary phase is K3.8Nb5Ge3O20.4, while K6Nb6Ge4O26 appeared as primary phase at temperatures > 800 degrees C. K10Nb22Ge4O68 and metastable KNbO3 and K4Nb6O17 were formed as secondary phases. The crystallization commenced at T > 640 degrees C with high homogeneous nucleation rate and spherulite crystal growth morphology. DTA curves recorded for powder samples particle size LT 0.1 mm revealed three exothermic peaks and three endothermic peaks within temperature range of T = 640-940 degrees C, while the DTA curves recorded for powder samples particle size > 0.1 mm showed two exothermic peaks and two endothermic peaks within temperature range of T = 640-1020 degrees C. The analysis of the dominant crystallization mechanism of powder glass sample and kinetics of crystallization is presented
Influence of sodium isopropyl xanthate on the recovery of copper and precious metals from ore deposit Tenka-3
No full textThe Tenka deposits (which include Tenka 1, Tenka 2, and Tenka 3 deposits, located in eastern Serbia) belong to polymetallic deposits and besides the copper they contain lead and zinc minerals in a certain content. From this perspective, defining optimal ore processing conditions (due to complex ore characteristics) and obtaining commercial product with satisfactory technological properties, represents complex task and requires serious research and examinations. This paper presents a part of technological investigations performed to determine the possibility of copper and precious metals valorization from the ore deposit Tenka 3, using a flotation concentration method. During the experimental procedure, sodium isopropyl xanthate was used as the collector, while the pH value of flotation pulp varied from 9.9 to 11.6. The results shown that the satisfactory recoveries of copper and precious metals could be obtained by this procedure (at the appropriate pH value of pulp), but the quality of the rough flotation concentrate was basically low
Biohydrometallurgy: Environmental protection technology
No full textProcesi koji se inače spontano dešavaju u prirodi, kada su favorizovani od strane čoveka mogu da ugroze biosferu, i često je neophodno staviti ih pod kontrolu u cilju sprečavanja daljeg zagađivanja. Kada tip rude i geološke karakteristike zemljišta dozvoljavaju, pomoću mikrobioloških lužnih rastvora, moguće je vršiti recikliranje metala sa minimalnim ulaganjima i minimalnim narušavanjem okoline. Sa jedne strane sprečava se kontaminacija podzemnih voda i zemljišta teškim metalima, a sa druge strane vrši se ekstrakcija dragocenih metala iz odlagališta i iz ruda koje imaju nizak sadržaj ovih metala (na primer bakar, zlato, olovo, nikl i cink). Dobijanje ovih metala nekom drugom tehnologijom nije ekonomski isplativo. Danas se značajan broj postrojenja za mikrobiološko luženje, nalazi ne samo u razvijenim zemljama, već zahvaljujući samim karakteristikama ove tehnologije i u zemljama u razvoju. Ovaj rad predstavlja pregled dosadašnjih saznanja u vezi biohidrometalurgije, ali i podsećanje da se ova tehnologija uspešno primenjivala kratko vreme i u našoj zemlji.When processes that are spontaneous in nature are accelerated by man, they can endanger biosphere, therefore it is necessary to put them under control to prevent further environmental pollution. By the means of microbial leaching solutions, in the case when the type of ore and the geological characteristics of the soil are suitable, it is possible to recover certain metals with minimum investment and threats to environment. It is usually utilized when conventional mining procedures are too expensive or ineffective in recovering a metal such as copper, gold, lead, nickel and zinc. On the one hand, contamination of ground water and soil by heavy metals is prevented, on the other hand extraction of precious metals from ore dumps and from low-grade ore are occurring. At present, numerous facilities for microbial leaching are in use not only in developed countries, but also in developing countries. This paper presents overview of present achievements in biohydrometallurgy, as well a reminder that this technology was successfully used in our country for short period of time
Monitoring of heavy metal content in atmospheric precipitation in unsettled region Kamenički Vis
No full textIndustrijski razvoj i urbanizacija nameću intenziviranje procesa proizvodnje često putem prekomernog trošenja ograničenih prirodnih resursa i na račun kvaliteta životne sredine. Kao kompromis između suprotstavljenih interesa globalnog privrednog razvoja, sa jedne strane, i očuvanja životne sredine, sa druge, koncept 'održivog razvoja' povezuje privredni, socijalni i kulturni razvoj i promoviše usklađivanje takvog razvoja sa potrebama i ograničenjima životne sredine. Praćenje nivoa zagađujućih materija u medijumima životne sredine ukazuje na neophodnost usvajanja koncepta 'održivog razvoja'. Cilj ovog istraživanja je bio da se stekne uvid u stepen zagađenosti atmosferskih padavina kroz praćenje i procenu prenosa teških metala. Koncentracije teških metala određivane su u uzorcima padavina sakupljenim na GAW/EMEP stanici Kamenički Vis, tokom 2008. i 2009. godine. Za prikupljanje padavina koršćena je bulk (suvo-mokra) metoda, a koncentarcije odabranih metala (Fe, Al, Zn, Cu, Pb, Mn, Ni i Cd) određivane su ICP-MS metodama. Dobijeni rezultati ukazuju na povećanje maksimalnih koncentracija Fe, Ni, Cu, Pb i Mn u 2009. godini u odnosu na 2008. godinu, ali za potvrđivanje ovog trenda potrebna su višegodišnja merenja, koja su u toku.Industrial development and urbanization impose intensive production usually through excessive use of limited natural resources and degradation of the environment. As a compromise between opposing interests of global economic development, on one side, and environmental protection, on the other, concept of 'sustainable development' links Industrial, social and cultural development and promotes balancing of such development with environmental needs and restrictions. Necessity and importance of adoption of such concept can be seen through monitoring of pollutants levels in all mediums of the environment. The aim of this investigation is to gain an insight into the composition of atmospheric precipitation through monitoring and analysis of heavy metal transport in the atmosphere. Heavy metal concentrations were determined in the samples of atmospheric precipitation collected on GAW/EMEP station Kamenički Vis, during 2008 and 2009. Precipitation samples were collected using bulk (dry-wet) method. Content of selected heavy metals (Fe, Cu, Zn, Al, Pb, Ni, Mn and Cd) in precipitation samples was determined using inductively coupled plasma mass spectroscopy (ICP-MS). Obtained data shows an increase in concentration levels of Fe, Ni, Cu, Pb and Mn in 2009, compared to 2008, however further long-term measurements are necessary in order to confirm this trend. Such investigation is underway
Isothermal sintering of barium-zinc-titanate ceramics
No full textMixtures of BaCO3-ZnO-TiO2 were mechanically activated using high-energy planetary ball mill during 20, 40 and 80 min. As the time of mechanical activation increased, the decrease in particle size was observed. The effect of milling on microstructure was investigated by scanning electron microscopy, as well. Sintering process was performed in air at 1100 and 1200 C for 2 h. Various phases are present within mixtures sintered at 1100 and 1200 degrees C, and almost pure BaZn2Ti4O11 phase was obtained after 80 min of milling and sintering at 1200 degrees C for 2 h
Refractory coating based on cordierite for application in new evaporate pattern casting process
No full textStandard raw materials, kaolin, talc, MgO, alumina, feldspar and sepiolite, were used in synthesis of four different cordierite type ceramics. Sintered cordierite was used as refractory filler in the ceramic coating for evaporative polystyrene patterns in the EPC process. The cordierite samples were tested by the following methods: roentgen diffraction analysis, diffraction thermal analysis and polarized microscope. The shape and grain size were analyzed by the program package OZARIA 2.5. In order to evaluate the possible application of cordierite as the refractory filler, four different coating processes were investigated
Sources of creation and processing of zinc secondary raw materials
No full textZinc is a widely applicable metal and therefore the different composition and form of zinc waste is generated. The most important waste material generated in production and processing of zinc is scrap metal of zinc and its alloys, as well as slag, dust and sludge from the production and processing of cathode zinc and zinc alloys. In terms of processing technology, there are different applied procedures depending on the type of raw material. The processing of waste zinc and its alloys is pyrometallurgical and it is based on remelting of dry and degreased raw materials, with alloying during melting to correct the composition. Zinc dust and sludge are processed by Waelz procedure, where the zinc-oxide is obtained and further being processed usually by hydrometallurgical procedure. The zinc and brass slag are grinded, followed by separation metal and oxide components. Large, predominantly metal fraction is being directly melted to obtain zinc or brass. Small, predominantly oxide phase is subjected to hydrometallurgical treatment for zinc valorization
Application of various waste biomass in the preservation of natural environment
No full textPoslednjih godina vršena su obimna istraživanja sa ciljem da se nađu alternativni i ekonomski održivi adsorbenti za tretman otpadnih voda, kako u razvijenim, tako i u manje razvijenim zemljama. Biosorbenti koji su ekonomski isplativi su sirovine koje su u prirodi lako dostupne, ili su sporedni proizvodi (ili otpad) iz pojednih industrija pod uslovom da ne zahtevaju kompleksan predtretman. Zato, biomasa koja je do nedavno smatrana otpadom, postaje atraktivna i dobija primenu u postupku uklanjanja teških metala iz otpadnih voda. Na taj način se rasterećuju već formirane deponije i sprečava formiranje novih, što doprinosi unapređenju i zaštiti životne sredine. Ovaj rad ima za cilj da usmeri pažnju na upotrebnu vrednost različitih tipova biomase (biosorbenta) sa akcentom na otpadnu biomasu poreklom iz agroindustrije. Ova tehnologija pruža šansu i zemljama u razvoju koje poseduju veće količine neiskorišćene otpadne biomase da razviju efikasne i jeftine materijale za uklanjanje polutanata, kao i mogućnost otvaranja novih tržišta.Extensive studies have been undertaken in recent years in order to find alternative and economically feasible adsorbents for waste water treatment in developed and developing countries. Low cost biosorbents are materials which are abundant in nature or by-product (or waste) from industry, which require little processing. Therefore, biomass, which was until recently considered as a waste, become attractive and gets application in the process of removing heavy metals from wastewater. In this way it relieves the already formed landfills and prevents the formation of new, contributing to the promotion and protection of the environment. This paper presents application of agro-industrial waste materials as biosorbents. For developing countries with large quantities of biomass this technology creates the possibility of developing efficient and cheap materials for pollutant removal, as well as the possibility of opening new markets
The effect of K2O on the crystallization of niobium germanate glasses
No full textIspitan je uticaj sadržaja K2O na kristalizaciju niobijum germanatnih stakala sa 22,7-24,27 mas % GeO2 i 54,59-57,48 mas % Nb2O5. Ova stakla kristališu primarnom kristalizacijom i stvaraju se kristalne faze K6Nb6Ge4O26, K3.8Nb5Ge3O20.4 i KNbO3. Povećanje sadržaja K2O prouzrokuje smanjenje sadržaja GeO2 u primarnim fazama. Analiziran je uticaj sadržaja K2O na kinetiku primarne kristalizacije. Pokazano je da povećanje sadržaja K2O smanjuje energiju aktivacije rasta kristala na prvom kristalizacionom piku (Ec1). Na drugom kristalizacionom piku energije aktivacije rasta kristala se povećavaju (Ec2).The effect of K2O content on the crystallization of niobium germanate glasses with 22.7- 24.27 wt% of GeO2 and 54.59-57.48 wt% of Nb2O5 was examined. The glasses crystallize by primary crystallization and the formed crystalline phases were K6Nb6Ge4O26, K3.8Nb5Ge3O20.4 and KNbO3. Increasing the K2O content caused a decrease in the GeO2 content of the primary phases. The effect of the K2O content on the kinetics of primary crystallization was analyzed. It was demonstrated that an increase of the K2O content decreased the activation energy of crystal growth at first of the crystallization peaks (Ec1). At second crystallization peaks the activation energies of crystal growth increased (Ec2)
The possibility of increasing production efficiency of al alloys applying electromagnetic field
No full textThe relationships between electromagnetic frequency, microstructure and mechanical properties of continuous casting aluminum alloys were studied in this paper. EN AW 2024 and EN AW 2007 aluminum alloys ingots were produced by electromagnetic continuous casting process. The microstructure and mechanical properties of as cast ingots were examined. The results showed that electromagnetic field, especially low frequency electromagnetic field, greatly influenced the microstructure and mechanical properties of as cast ingots. The significant energy savings and product quality can be achieved by the application of a proper frequency