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Determination the mechanism and kinetic parameters of copper sulfide minerals oxidation at elevated temperatures
No full textU radu su prikazani rezultati DTA/TG analize polimetaličnog sulfidnog koncentrata bakra iz rudnog ležišta 'Veliki Krivelj' (Srbija) u temperaturnom intervalu 25 - 1000 °C, na osnovu koje je predložen mehanizam oksidacije prisutnih sulfida u atmosferi vazduha na povišenim temperaturama. Kao potvrda predloženom mehanizmu, u radu su prezentovani rezultati EDXRF analize polaznog uzorka, XRD analize polaznog uzorka i produkata oksidacije na 550 i 950°C i rezultati SEM/EDS analize polaznog uzorka i produkata oksidacije na 675 °C. Upoređivanjem eksperimentalnih rezultata dobijenih XRD i DTA/TG analizom može se zaključiti da se proces oksidacije ispitivanog koncentrata može podeliti u dva stupnja: prvi stupanj čine reakcije oksidacije sulfida sa karakterističnim egzotermnim efektima ispod 650 °C, dok obrazovanje sulfata i oksisulfata i njihovo razlaganje do oksida bakra i železa čini drugi stupanj, praćen karakterističnim endotermnim efektima na višim temperaturama. Kinetička analiza procesa oksidacije ispitivanog koncentrata izvršena je po metodama Kissingera i Ozawe u neizotermskim uslovima. Rezultati kinetičkih ispitivanja i vrednosti energije aktivacije pokazali su da se proces oksidacije u celom ispitivanom temperaturnom intervalu nalazi u kinetičkoj oblasti.The paper presents DTA/TG results of polymetallic sulphide copper concentrate from the mine 'Veliki Krivelj' (Serbia) at 25-1000 °C. The reaction mechanism at elevated temperatures was proposed. As confirmation to the proposed mechanism, the results of EDXRF and, XRD analysis of the initial sample and the oxidation products at 550 and 950 °C, and the results of SEM/EDS analysis of the initial sample and the oxidation products at 675 ° C were presented. It can be concluded that the oxidation process goes through sulfide oxidation with characteristic exothermic effects, followed by sulfates and oxy- sulfates formation and their. Kinetic analysis of the oxidation process concentrates the test was performed according to the methods of Kissinger and Ozawa in non-isothermal conditions. The results of kinetic studies have shown that the oxidation process in the whole investigated temperature range is located in the kinetic field
Recovery of lead from by-products of the bismuth refining by metallothermic reduction treatments
No full textU procesu rafinacije bizmuta, hlorovanjem legure Bi-Pb (bizmut pena) Kroll-Bettertonovim procesom kao međuprodukt pojavljuje se olovo-hlorid. Predmet ovog rada je valorizacija olova iz pomenutog međuprodukta postupcima aluminotermije i cinkotermije. Pored olova pomenutim postupcima dobijaju se glinica tehničkog kvaliteta (aluminotermija) i cinkhlorid (cinkotermija). Za ispitivanja su korišćeni sekundarni aluminijum i cink različite krupnoće. Ispitan je uticaj temperature, vremena, krupnoće reducenta i brzine mešanja (cinkotermija) na stepen iskorišćenja olova i definisani optimalni parametri procesa. Stepen iskorišćenja sirovog olova (98%Pb) iznosi 95-98% u slučaju aluminotermije i 85-90% u slučaju cinkotermije. Dobijeno sirovo olovo prerađuje se u rafinerijama olova. Glinica tehničkog kvaliteta ima primenu u keramičkoj industriji dok se cink- hlorid hidrometalurški tretira u cilju dobijanja 50%-nog rastvora cink-hlorida.In the refinement process of bismuth by chlorinating of Bi-Pb alloy (Kroll-Betterton process) as a by-product lead chloride is formed. This study was focused on the lead valorization from PbCl 2 by aluminothermic and zincothermic reduction. Besides lead, as a main product, during aforementioned process technical grade alumina (aluminothermic reduction) and ZnCl2 (zincothermic reduction) were also obtained. The secondary aluminium and zinc of different granulometry were used as a reducent. The effect of temperature, time, granulometry of reducents and stirring speed (zincothermic reduction) on the lead recovery was investigated. Based on the experimental results, the optimal process parameters were defined. Recovery of crude lead (containing 98%Pb) was in the range 95-98% for aluminothermic reduction and 85-90% for zincothermic reduction. The crude lead can be further processed in lead smelters. Technical grade alumina was used in ceramic industry, wile zinc-chloride is suitable for hydrometallurgical treatment giving 50 % solution of zinc-chloride as the final product
The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid
No full textCalcium phosphate coatings were electrochemically deposited on titanium from an aqueous solution of Ca(NO3)(2) and NH4H2PO4 at a current density of 10 mA cm(-2) for a deposition time of 15 mm. The obtained brushite coatings (CaHPO4 center dot 2H(2)O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that increasing the soaking time increased the porosity, roughness and crystallite domain size of the HA coatings and decreased the unit cell parameters and unit cell volume, while the mean pore area of HA was unaffected. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively, and a mechanism of HA growth based on dissolution-precipitation was proposed
Low-temperature Ni-As-Sb-S mineralization of the Pb(Ag)-Zn deposits within the Rogozna ore field, Serbo-Macedonian Metallogenic Province: Ore mineralogy, crystal chemistry and paragenetic relationships
No full textThe Rogozna ore field (ROF) belongs to the Serbo-Macedonian Metallogenic Province (SMMP), and covers a part of the western Dinarides rim and the Vardar ophiolite zone, situated within the Neogene volcanogenic-intrusive complex of calc-alkaline and shoshonitic rocks within the territories of Serbia and Kosovo. It is well-known for its Cu(Au, Pb, Zn) skarn mineralization and Pb(Ag)-Zn hydrothermal deposits and occurences. Mineral associations, deposition order and genesis of the ROF were discussed in detail. Complex ore parageneses were determined in the Crnac, Plalcaonica, and Kaludjer Pb(Ag)-Zn deposits and are composed of the following minerals: sulfides (pyrrhotite, chalcopyrrhotite, chalcopyrite, sphalerite, galena, pyrite, marcasite, millerite, bravoite), sulfosalts (arsenopolybasite, tetrahedrite, Ag-bearing tetrahedrite, Zn-bearing tetrahedrite, semseyite, heteromorphite, jamesonite, ferrokesterite), arsenides (nickeline), sulfarsenides and sulfantimonides (gersdorffite, Sb-bearing gersdorffite, Fe-bearing gersdorffite, As-bearing ullmannite, arsenopyrite), native metals (native Au, native Ag), oxides (Cr-spinel, rutile, anatase, leucoxene, magnetite, hematite) and gangue minerals (quartz, silicates, chalcedony, carbonates, monazite(Ce), barite, gypsum, anglesite, cerussite, smithsonite, zaratite, limonite). The high-, medium-, and low-temperature hydrothermal mineral assemblage occur throughout the Pb(Ag)-Zn deposits at Kaludjer-Crnac-Plakaonica ore system, in which the whole ore field as high- to medium-temperature hydrothermal formed at shallow to moderate depth. The following stages of ore mineral formation are recognized in the Pb-Zn mineral assemblage at the ROF: i) pre-ore; ii) high-temperature hydrothermal; iii) hypogene; iv) medium-temperature hydrothermal; v) low-temperature hydrothermal; and vi) supergene. Generally, there are two types of mineralization, brecciated ore veins with ribbon-like textures deposited in amphibolites or in contact with quarz latites, and impregnations within columnar ore bodies hosted in silicified and carbonated serpentinites (listwaenites). Ni-mineralization is represented by significant sulphide, arsenide, sulfarsenide, and sulfantimonide occurrences, but the most significant consists of gersdorffite-ullmannite series (GUS) minerals. It is the most developed in the Kaludjer deposit, much lesser at Plakaonica, whereas in the Crnac deposit it was not noted. The importance of the Ni mineralization is of scientific interest for now, as the attention has been directed only to the exploration of lead and zinc. However, it is believed that plans for the future will be focused on a detailed study of nickel
Quality, sources and balancing of iron and steel scrap
No full textČelični otpadak je, pored železne rude, najvažnija sirovina za proizvodnju gvožđa i čelika. U radu je prikazan kvalitet i izvori nastajanja otpadaka gvožđa i čelika i prognoza njihovog nastajanja u budućnosti. Sadržaj nečistoća i oligoelemenata u otpatku je veoma važan i utiče na kvalitet dobijenog čelika. Legirani čelični otpadak poznatog sastava često može biti iskorišćen kao dodatak metalnom ulošku za proizvodnju čelika željenog sastava. U zavisnosti od mesta nastajanja razlikujemo tri grupe čeličnog otpatka: vlastiti ili recirkulacioni, otpadak pri obradi i amortizacioni otpadak. Model bilansiranja za prognozu nastajanja čeličnog otpatka zasnovan je na izračunavanju koeficijenata nastajanja proizvodnog i amortizacionog otpatka koji služe kao osnova za uspešno prognoziranje njihovog nastajanja u budućnosti.Besides iron ore, the main raw material of iron and steel production is steel scrap. This paper presents the quality and sources of creation the iron and steel scrap and estimation of their creation in the future. The content of impurities and trace elements to the scrap is very important and influencing to the quality of the obtained steel. Alloyed steel scrap known composition can often be used as an addition to a metal charge for steel production of the desired composition. Considering the steel scrap formation, the three major groups are elaborated: own scrap or circulation scrap, processing scrap and amortization scrap. The balancing model for estimating of steel scrap creation is based on the calculating the coefficients of the generation circulation, processing and amortization scrap, which are used as the basis for successful modelling
The chemical composition of Th-bearing monazites from the jurassic sediments in the Plavna area, Serbia
No full textForty-eight polished section of the lower Jurassic continental sediments with monazites from the Plavna-Sikole region have been analyzed by ore microscopy and electron microprobe. The REEs distribution is subject to important variation, some specimens being particularly rich in Ce, others in La or even in Nd and Pr (the most common member – monazite-Ce). The Ce content is nearly constant (average 24.67 wt% Ce). Substitution of the actinides and Ca for the REE and of Si for P is very limited. The thorium content is high (average 7.74 wt% Th). The content of uranium is below the detection limits of the method (<0.3 wt% U)
Applicаtion of wаste biomаss for preventing the negаtive effects of climаte chаnges
No full textClimate change, environmental pollution and lack of energy are the main problems of modern society.
Every year from agriculture generates about 140 billion tons of biomass. Widely available, renewable, and virtually free, waste biomass is an important resource because it can be used as an energy source and material with special characteristics such as biosorbent organic and inorganic pollutants, soil improver, fertilizer, paper manufacturing, textiles, etc. If this biomass converted to energy can substantially displace fossil fuel, reduce emissions of greenhouse gases and provide renewable energy to developing countries. Decomposition of the waste mass in the fields emits methane, and its burning generated CO2 and other pollutants.
Under the influence of climate change floods and droughts are more frequent, which lead to pollution of ground water, soil and air pollution by heavy metals. The disadvantages of conventional methods for removing metal ions from polluted water are low selectivity, generating large amounts of sludge, high operating costs. For some time, biosorption has been claimed as a promising biotechnology for pollutant removal and/or recovery from solution by applying biosorbents.
Waste biomass can be converted into useful materials, increasing the profit of the treatment, reduction of atmospheric pollutants, and increased utilization of plant material. This paper discusses about the development in the use of waste biomass for energy and as biosorbent for the removal of heavy metals from wastewater, with emphasis preventing the adverse effects of climate change. Improper management of biomass contributes to climate change, water, soil and local air pollution
Remediation of Copper from Copper Mine Wastes ans Contaminated Soils using (S,S)-Ethylenediaminedissucinic Acid and Acidophilic Bacteria
No full textThe biodegradable chelating agent (S,S)-Ehylenediaminedisuccinic
acid (EDDS), autochthonous acidophilic bacteria, and a combination of the
two means were investigated for the removal of pseudo-total and
ethylenediaminetetraacetic acid (EDTA)-available content of Cu from surface
layers of three soil categories in the Bor copper mining area. Their efficiencies
were compared at mine overburden, flotation tailings, and agricultural land
sites in order to determine the potential role of these approaches in the soil
remediation process. The most effective removal of Cu was achieved on
flotation tailings, where combined treatment showed significant reduction of
pseudo-total and EDTA-available concentrations of Cu (40.5 § 27.3% and
99.6 § 0.2%, respectively). Acidophilic bacteria treatment showed high
efficiency on flotation tailings, removing 94.1 § 1.2% of EDTA-available
Cu. EDDS treatment showed discernible results in the removal of EDTAavailable
Cu from agricultural land soil (44.4 § 13.9%). In the case of
overburden soil material, selected agents did not have statistically significant
results in the removal of pseudo-total or EDTA-available fraction of Cu.
Chosen remediation approaches showed diverse efficiency for soil categories
on investigated sites. Combined approach showed synergistic results in the
case of EDTA-available Cu removal from flotation tailings soils, suggesting
that this combination deserves further attention as a potentially promising
environmentally friendly remediation option
Bioceramics calcium phosphate coatings on titanium produced by electrochemical techniques.
No full textCilj ove doktorske disertacije je dobijanje prahova i prevlaka kalcijum-fosfata na titanu primenom elektrohemijskih metoda, kao i ispitivanje uticaja parametara sinteze (gustina struje, napon, pH vrednost rastvora, vreme taloženja) na fazni sastav, veličinu kristalita i morfologiju dobijenih prahova i prevlaka. Elektrohemijskom sintezom iz rastvora Na2H2EDTA·2H2O, NaH2PO4 i CaCl2 sa odnosom koncentracija Ca/EDTA/PO43− od 0,25/0,25/0,15 M uspešno su dobijeni prahovi monetita i hidroksiapatita. Ispitan je uticaj pH vrednosti polaznog rastvora i gustine struje na vrstu sintetisanog kalcijum-fosfata, morfologiju i termičko ponašanje prahova različitim metodama kao što su rendgenska difrakcija na polikristalnom uzorku, skenirajuća elektronska mikroskopija, diferencijalno termijska i termogravimetrijska analiza i infracrvena spektroskopska analiza. Pri pH vrednosti od 5,0 i gustini struje od 137 mA cm-2 dobijen je nanodimenzioni prah monetita sa veličinom kristalita od 27,1 nm. Sintezom prahova pri pH vrednostima od 9,0 i 12,0 i pri gustinama struje od 137 mA cm-2 i 207 mA cm-2 dobijeni su prahovi hidroksiapatita sa veličinom kristalita u intervalu od 21,6 do 24,3 nm, čime je pokazano da pH vrednost i gustina struje ne utiču značajno na veličinu kristalita. Na morfologiju elektrohemijski sintetisanih prahova hidroksiapatita ne utiče promena gustine struje, ali utiče pH vrednost rastvora. Pri manjoj pH vrednosti od 9,0 se dobijaju prahovi sa sfernim aglomeratima, dok se pri većoj pH vrednosti od 12,0 dobijaju prahovi sa pločastim aglomeratima. Temperatura termičke dekompozicije nanočestičnog praha monetita na kalcijum-pirofosfat i vodu je niža (1260 °C) u odnosu na literaturni podatak (1353 °C), zbog velikog odnosa specifična površina/zapremina nanočestičnog praha. Uslovi elektrohemijske sinteze ne utiču značajno na termičko ponašanje prahova hidroksiapatita. Prevlake monetita dobijene su elektroforetskim taloženjem iz etanolske suspenzije elektrohemijski sintetisanog praha monetita i ispitan je uticaj napona (10-50 V) i vremena taloženja (1-30 min) na masu i morfologiju prevlake. Masa prevlake, srednji prečnik pora, srednja površina pora i poroznost prevlaka zavise...The aim of this PhD thesis was to prepare nanosized calcium-phosphate powders and coatings using electrochemical methods and to investigate the effect of experimental parameters (e.g. applied current density, solution pH value, applied voltage, deposition time) on the phase composition, crystallite domain size, morphology and thermal characteristics of obtained powders and coatings. Electrochemical synthesis of nanosized monetite and hydroxyapatite powders were performed galvanostatically from homogeneous solution of Na2H2EDTA∙2H2O, NaH2PO4 and CaCl2 at a concentration relationship Ca/EDTA/PO43− of 0.25/0.25/0.15M. The influence of the solution pH and applied current density on the phase composition, morphology and thermal behavior was investigated by X-ray diffraction, infrared spectroscopy, size distribution measurements, thermogravimetric and differential thermal analysis, scanning electron microscopy and transmission electron microscopy. At current density of 137 mA cm−2 and pH value of 5.0 monetite powder was synthesized. The crystallite domain size of powder was calculated to be 27.1 nm. At current densities of 137 and 207 mA cm−2 and pH values of 9.0 and 12.0 hydroxyapatite powders were synthesized with crystallite domain size in the range from 21.6 to 24.3 nm, meaning that pH values as well as applied current densities does not affect significantly the crystallite domain size. The morphology of synthesized hydroxyapatite powders were not influenced by current density, but on the other hand are influenced by solution pH. Powders synthesized at lower pH value consist of spherical agglomerates, while powders synthesized at higher pH value have the plate-like structure. The temperature of phase transformation from monetite to calcium pyrophosphate was lower (1260 °C) in comparison with literature data (1353 °C), due to high surface-to-volume ratio of nanosized powder. The parameters of electrochemical synthesis of hydroxypatite powders do not affect significantly the thermal behavior. Monetite coatings were electrophoretically deposited from ethanol suspension of electrochemically synthesized monetite powder, using constant..