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Bioleaching of pollymetallic sulphide concentrate using thermophilic bacteria
No full textBiotehnologija kao noviji pristup za ekstrakciju metala nudi mogućnosti za smanjenje zagađenja životne sredine. U ovom radu se od četiri biotehnološka postupka - bioremedijacija, biosorpcija, bioakumulacija i bioluženje - sagledavaju različiti aspekti (uključujući i ekološke) bioluženja polimetaličnih sulfidnih koncentrata koji potiču iz borske rudarske oblasti. Ispitana je mogućnost povećanja brzine oksidacije sulfida bakra u laboratorijskim uslovima u prisustvu termofilnih bakterija. Ekstremno termofilna i oksidaciona bakterijska kultura, razvijena u prisustvu sumpora i gvožđa, izolovana je i adaptirana na visoku koncentraciju jona metala i čestica materijala u rastvoru na temperaturi od 70 °C. Nakon izolacije i adaptacije mikroorganizama, kultura je korišćena u staklenom reaktoru zapremine pet litara za bioluženje (potpomognuto magnetnom agitacijom i aeracijom) polimetaličnog sulfidnog koncentrata koji je od metala sadržavao bakar, cink i olovo. Eksperimenti sprovedeni u ovoj specifičnoj bakteriološkoj sredini pokazali su da je moguće, posle postizanja ravnotežnih uslova, postići visoke stepene ekstrakcije bakra i cinka (do 97%) u dužim vremenskim intervalima - do 80 dana. Olovo-sulfid je tokom ovog procesa oksidacijom prešao u olovo-sulfat, te ostao u biolužnom ostatku zbog neznatne rastvorljivosti u sulfatnom rastvoru. U ovom radu je bioluženje bioostatka sprovedeno po PLINT tehnologiji koja omogućava rastvaranje jedinjenja olova u prisustvu natrijum-hlorida. Rezultati ovih eksperimenata su potvrdili rezultate sličnih istraživanja po kojima je moguće dobiti visoke stepene ekstrakcije olova iz biolužnog ostatka polimetaličnih koncentrata - i do 95%.An extreme thermophilic, iron-sulphur oxidising bacterial culture was isolated and adapted to tolerate high metal and solids concentrations at 70 °C. Following isolation and adaptation, the culture was used in a batch bioleach test employing a 5-l glass standard magnetic agitated and aerated reactor, for the bioleaching of a copper-lead-zinc collective concentrate. The culture exhibited stable leach performance over the period of leach operation and overall copper and zinc extractions higher than 97%. Lead sulphide is transformed into lead sulphate remaining in the bioleach residue due to the low solubility in sulphate media. Brine leaching of bioleach residue yields 95% lead extraction
Analysis of major, minor and trace elements in surface sediments by x-ray fluorescence spectrometry for assessment of possible contamination of Boka Kotorska bay, Montenegro
No full textBoka Kotorska Bay is on the UNESCO's World Heritage List. There are no published papers related to the surface sediment pollution of the Bay. For the first time, elements were measured in surface sediments at nine locations in the Bay by the energy dispersive X-ray fluorescence spectrometry (EDXRF) technique. Si, Fe, Ca, K, Ti, Mn, P, Ba, Cr, Sr, Zn, Rb, Ni, Cu, Pb, As, Sn, Sb, Hg and Cd were quantified in the surface sediments. Sediments were classified as non-polluted or polluted by counting the enrichment factor (EF), metal loading index (MLI) and geo-accumulation index (I-geo) based on the elemental background level of the analyzed elements in the literature, or by the Sediment Quality Guidelines (SQGs) of USEPA (United States Environmental Protection Agency). Based on USEPA's SQGs, the surface sediment in the entire Bay can be classified as heavily polluted by As and Cr, and non-polluted by Cd and Hg, and, related to the sites, the surface sediment at the Tivat-Arsenal site was heavily polluted and at the Orahovac site was not polluted at all. The PLI (pollution load index) values for the locations of Tivat-Arsenal and Orahovac are in agreement with the conclusion based on USEPA's SQGs. The results in this paper will establish an initial view of sediment pollution and the state of the Bay's environment
Nanomaterials environmental risks and recycling: Actual issues
No full textNanotehnologije se smatraju pokretačkom snagom nove industrijske revolucije. Nanonauka je tokom poslednje decenije značajno evoluirala od nauke koja se isključivo razvijala u laboratorijskim uslovima, do njene aplikacije u primenjenim tehnologijama. Trenutno, nanomaterijali se koriste u širokom spektru komercijalnih proizvoda kao što su elektronske komponente, sportska oprema, kreme za sunčanje i u biomedicinske svrhe. Veličina nanočestica omogućava im snažnu interakciju sa biološkim strukturama, tako da nanočestice predstavljaju potencijalni rizik po životnu sredinu i zdravlje ljudi. Nanometar kao veličina takođe predstavlja problem za separaciju, reciklažu i ponovno korišćenje nanočestica. Dakle, proizvodnja nanomaterijala u industrijskim razmerama i njihova primena mogli bi imati značajan uticaj na zdravlje ljudi i životnu sredinu ili stvorili probleme pri reciklaži. Sveobuhvatni termin 'nanotehnologija' nije dovoljno precizan kada se radi o upravljanju rizicima. Procena mogućih rizika zavisi od razmatranja životnog ciklusa materijala koji se proizvodi, a koji uključuje razumevanje procesa i materijala koji se koriste u proizvodnji, verovatne interakcije između proizvoda i pojedinaca ili životne sredine tokom proizvodnje nanomaterijala i njegovog životnog ciklusa, kao i metoda koje se koriste za njihovo konačno odlaganje. Sa stanovišta kontrole rizika, neophodno je identifikovati kritične faze, koje je neophodno detaljno istražiti. Pregled aktuelnih trendova ekoloških rizika i reciklaži nanomaterijala prezentovan je u ovom radu.Nanotechnologies are being spoken of as the driving force behind a new industrial revolution. Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. The size of nanoparticles allows them to interact strongly with biological structures, so they present potential human and environmental health risk. Nanometer size presents also a problem for separation, recovery, and reuse of the particulate matter. Therefore, industrial-scale manufacturing and use of nanomaterials could have strong impact on human health and the environment or the problematic of nanomaterials recycling. The catch-all term ''nanotechnology' is not sufficiently precise for risk governance and risk management purposes. The estimation of possible risks depends on a consideration of the life cycle of the material being produced, which involves understanding the processes and materials used in manufacture, the likely interactions between the product and individuals or the environment during its manufacture and useful life, and the methods used in its eventual disposal. From a risk-control point of view it will be necessary to systematically identify those critical issues, which should be looked at in more detail. Brief review of actual trends in nanomaterials environmental risks and recycling is given in this paper
Thermodynamic and kinetic analysis of the polymetallic copper concentrate oxidation process
No full textThis paper presents the experimental investigation results of the polymetallic copper concentrate oxidation process with the oxygen from the air. Concentrate characterization included chemical analysis, X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF), and light microscopy. Chemical analysis and EDXRF results showed that the investigated copper concentrate consisted mainly of copper, iron and sulphur, with small amounts of zinc, lead, arsenic and other minor elements. XRD analysis showed that metals were bonded to sulphur in sulphide minerals: chalcopyrite, pyrite, luzonite, sphalerite and enargite. Those minerals were mutually bonded into aggregates, confirmed by light microscopy. The results of DTA/TG analysis were used for determining the mechanism of the oxidation process. Comparison between experimental data obtained by XRD, DTA/TG and data obtained from the phase stability diagrams, implied that the oxidation process of the investigated concentrate can be divided in two stages: the first stage consisted of sulphide oxidation reactions with the characteristic exothermal effects below 973 K while forming sulphates and oxysulphates, and the second stage, which consisted of sulphates and oxysulphates decomposition reactions and forming copper and iron oxides, with endothermal effects above 973 K. Kinetic studies were carried out in isothermal conditions in the temperature range (573-873) K. Calculations were done according to Sharp's method of reduced half-time reaction. Calculated values for the activation energies were 82 kJ mol(-1) for the initial stage of the oxidation process (up to 723 K), and 42 kJ mol(-1) for the stage of the process where desulphurization degree reached 68-86 % for the oxidation temperatures 748 K and higher. Calculated activation energy values indicated that the reaction of oxidation is a chemically controlled reaction
Synthesis of alpha-al2o3 based foams with improved properties as catalyst carriers
No full textThis paper explores the possibility of synthesising catalyst supports with improved properties. Alumina foams were produced with the polymer replication technique. Representative high- and low-temperature sintering ceramics were selected. Suitable suspension amounts, the clay addition and sintering temperature were determined. A lower sintering temperature was used for an economic enhancement of the process. The sintering was conducted at the temperatures from 1573 K to 1773 K for 60 min. A comparative analysis of the studied systems shows that the best compressive strength of 6.2 MPa was achieved with the system based on the alpha-Al2O3-25 clay (mass fractions, w/%), polyester foam with 10 PPI, sintered at 1673 K
Crystallization and sinterability of glass-ceramics in the system La2O3-SrO-B2O3
No full textGlasses with a constant B2O3 and an increasing La2O3 content in the system La2O3-SrO-B2O3 were obtained by the usual melt quenching procedure. The crystallization and sinterability of the glasses were investigated by hot stage microscopy (HSM), differential thermal analysis (DTA), X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD analysis of the bulk samples evidenced the formation of the crystalline phases: La2SrB10O19, SrB6O10 and SrLaBO4. XRD and TEM/SAED analyses showed a polymorphic crystallization of the glass sample containing 14.3 mol% La2O3 with precipitation of the La2SrB10O19 phase. SEM analysis confirmed the surface crystallization mechanism of this sample. The kinetics of crystallization of the same sample was examined by DTA and the activation energy of crystal growth was calculated by the Kissinger model to be E-a=458 +/- 63 kJ mol(-1)
Optimization of process parameters to obtain NH4-clinoptilolite as a supplement to ecological fertilizer
No full textThe application of natural fertilizer mixtures that improve nutrient retention ability of soils has attracted considerable attention in recent years. In addition to rock phosphate (RP), the basic components of these mixtures are zeolites modified with selected cations, such as the ammonium ion. The NH4-zeolite serves as a carrier of nutrients as well as a soil conditioner, and it promotes the RP dissolution in all soil types. The purpose of the present work was to prepare cost-effective NH4-zeolite supplement, using 3 2 full factorial experimental designs, with concentration of modifier and processing time as variables. Saturation processes were carried out on two types of natural zeolites, K-clinoptilolite (K-Cp) and Ca-clinoptilolite (Ca-Cp). The Response Surface Method (RSM) was applied for evaluation of cation exchange, suggesting an effective NH4+ modification of natural zeolite at lower quantities of modifier than commonly found in other studies on the topic. Using Principal Component Analysis (PCA), differences between samples relative to the process variables were clearly outlined and correlated with concentrations of the exchanged cations. The best results were obtained for the K-Cp type modified with 1.5 M solution of ammonium sulfate (at a Cp/NH4+ stochiometric ratio 1: 7.5) for all three processing intervals. By optimizing the modification process parameters, an experimental design of partially saturated NH4-Cp supplement that has the potential to supply all major plant nutrients was proposed
Mechanical Activation as Sintering Pre-treatment of Talc for Steatite Ceramics
No full textThe effect of vibratory mill induced mechanical activation on the change of the particle size, crystallinity and the phase transformations of the minerals present in the activated material, was studied with the purpose of decreasing of the sintering temperature of talc (Mg3Si4O10(OH)(2)) as raw material which is the basic component of the steatite ceramics. The aims of the conducted investigation were, also, increasing of the reactivity of the comminuted raw material and establishing of the optimal activation period. The properties of the activated talc induced by mechanical force were expressed in form of the grain inertia change which was measured by means of automatic grain counter. Mechanically activated grains are the most convenient mineral form for physical concentration since the energy change of the mill-material system is recorded on them. The effect of dry grinding on the structure, particle size and shape of talc was studied by means of XRD, DTA and SEM/EDS methods. Activation of talc produced an increase of the starting surface area value progressively from 4.5 m(2)/g up to a maximum of 108.5 m(2)/g achieved at 30 min. A subsequent decrease of rate of surface area change and the rate of size reduction were observed following the prolonged grinding. Talc activated in vibratory mill for optimal 30 min showed properties which positively influence the decrease of sintering temperature and the increase of the sintering rate of steatite ceramics
Investigation of the Structural, Mechanical and Electrical Properties of Cu-Al-Zn Shape Memory Alloys
No full textThe results of an experimental investigation of structural, mechanical and electrical characteristics of different Cu-Al-Zn alloys are presented in this paper. The investigations were conducted using light optic microscopy, SEM-EDX analysis, hardness and electroconductivity measurements