scholarly journals Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures

10.30544/320 ◽  
2017 ◽  
Vol 23 (3) ◽  
pp. 267-280 ◽  
Author(s):  
Aleksandra Mitovski ◽  
Nada Štrbac ◽  
Miroslav Sokić ◽  
Milan Kragović ◽  
Vesna Grekulović
Keyword(s):  
Reaction Mechanism ◽  
Elevated Temperatures ◽  
Oxidation Process ◽  
Reaction Rates ◽  
Oxidation Products ◽  
Arsenic Content ◽  
Iron Sulfides ◽  
Initial Sample ◽  
Copper Concentrate ◽  
Air Atmosphere

Sulfide copper concentrate from domestic ore deposit (Bor, Serbia) was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite–enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As) combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 – 1000 °C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa’s method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates.

scholarly journals Thermal Decomposition and Kinetics of Pentlandite-Bearing Ore Oxidation in the Air Atmosphere

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1364
Author(s):  
Kristina Božinović ◽  
Nada Štrbac ◽  
Aleksandra Mitovski ◽  
Miroslav Sokić ◽  
Duško Minić ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Heating Rate ◽  
Sulfur Removal ◽  
Oxidation Products ◽  
Energy Dispersive ◽  
Dominant Factor ◽  
Initial Sample ◽  
Energy Dispersive Spectrometry Analysis ◽  
X Ray ◽  
Air Atmosphere

The roasting of sulfide ores and concentrates is one of the most important steps in pyrometallurgical metal production from primary raw materials, due to the necessity of excess sulfur removal, present in the virgin material. Pentlandite is one of the main sources for nickel pyrometallurgical production. The knowledge of its reaction mechanism, products distribution during oxidation and reaction kinetics is important for optimizing the production process. Raw pentlandite-bearing ore from the Levack mine (Ontario, Canada) was subjected to oxidative roasting in the air atmosphere. A chemical analysis of the initial sample was conducted according to EDXRF (Energy-Dispersive X-Ray Fluorescence) and AAS (Atomic Adsorption Spectrometry) results. The characterization of the initial sample and oxidation products was conducted by an XRD (X-ray Diffraction) and SEM/EDS (Scanning Electron Microscopy with Energy Dispersive Spectrometry) analysis. Thermodynamic calculations, a phase analysis and construction of Kellogg diagrams for Ni-S-O and Fe-S-O systems at 298 K, 773 K, 923 K and 1073 K were used for proposing the theoretical reaction mechanism. A thermal analysis (TG/DTA—Thermogravimetric and Differential Thermal Analyses) was conducted in temperature range 298–1273 K, under a heating rate of 15° min−1. A kinetic analysis was conducted according to the non-isothermal method of Daniels and Borchardt, under a heating rate of 15° min−1. Calculated activation energies of 113 kJ mol−1, 146 kJ mol−1 and 356 kJ mol−1 for three oxidation stages imply that in every examined stage of the oxidation process, temperature is a dominant factor determining the reaction rate.

scholarly journals Investigation of Bi2S3 oxidation process at elevated temperatures in the air atmosphere

Tehnika ◽  
2020 ◽  
Vol 75 (6) ◽  
pp. 587-593
Author(s):  
Nada Štrbac ◽  
Miroslav Sokić ◽  
Aleksandra Mitovski ◽  
Dejan Gurešić ◽  
Kristina Božinović ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Elevated Temperatures ◽  
Oxidation Process ◽  
Oxidation Products ◽  
X Ray Diffraction ◽  
Gibbs Free Energy Change ◽  
Stability Diagrams ◽  
Air Atmosphere ◽  
Different Temperatures ◽  
Sulfide Concentrates

Bismuth (III) sulfide has been widely researched in recent years due to its application, but little emphasis has been placed on research regarding its behavior at elevated temperatures. This is of great importance, considering that bismuth, in the form of Bi2S3, is found in copper sulfide concentrates and is considered one of the most harmful components, along with lead, arsenic and antimony. The removal of these substances is one of the basic tasks in the processes of pyrometallurgical extraction of copper, in order to obtain a high purity metal. In order to better understand the behavior of bismuth (III) sulfide during oxidation at elevated temperatures, this paper characterized the synthesized sample of Bi2S3 at room temperature and the oxidation products at 500 °C by X-Ray diffraction (XRD), as well as thermodynamic, thermal and kinetic analysis of the oxidation process of Bi2S3 at elevated temperatures. In order to understand the behavior of Bi2S3 during oxidation and the distribution of oxidation products, phase stability diagrams in the Bi-S-O system were constructed at different temperatures and the values of the Gibbs free energy change at 400 °C and 1000 °C were calculated. Kinetic analysis of Bi2S3 oxidation process was performed by Kissingers method in non-isothermal conditions.

Kinetics and Mechanism of Permanganate Oxidation of ADA in Aqueous Perchlorate Solutions

2019 ◽  
Vol 6 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Refat Hassan ◽  
Samia M. Ibrahim
Keyword(s):  
Oxidation Process ◽  
Activation Parameters ◽  
Chelating Agent ◽  
Iminodiacetic Acid ◽  
Reaction Rates ◽  
Oxidation Products ◽  
Aqueous Chemistry ◽  
Acidic Solutions ◽  
Lack Of Information ◽  
Permanganate Ion

Background: ADA as N-(2-Acetemido) iminodiacetic acid has been widely used in preparation of organic buffers and protein-free media for fibroblasts as chelating agent chicken embryo fibroblasts as tridentate chelating agent ligand. However, a little attention has been focused to the behavior of its oxidation in aqueous acidic solutions. Accordingly, a lack of information on the aqueous chemistry of oxidation of ADA in acidic solutions was recognized. Therefore, we have prompted to undertake the present work with the aims at shedding more light on the behavior of oxidation and the nature of oxidation products. Again, it aims to compensate the lack of information about the aqueous chemistry of ADA and the nature of electron-transfer for redox reactions involving permanganate ion as a multi-equivalent oxidant. Method: A spectrophotometric investigation of oxidation of ADA by permanganate ion in aqueous perchlorate solutions has been investigated. Results: Absorbance-time curves indicated the presence of two distinct stages for the oxidation process. The experimental results indicated a decrease in the reaction rates with increasing the [H+], ionic strength and F- ions. Again, the reaction rates were found to increase with increasing the added Mn2+ and temperature. Conclusion: These results indicated that the oxidation process was of acid-inhibition nature and proceeding by free-radical intervention mechanism. Again, the reactive species in the fast second stage was the Mn4+ species formed in the initial stage. The activation parameters have been evaluated from the temperature dependence of the rate constants. A tentative reaction mechanism was suggested for such redox reaction.

Electric-Field Effects on Reactions Between Oxides

1997 ◽  
Vol 481 ◽  
Author(s):  
Matthew T. Johnson ◽  
Shelley R. Gilliss ◽  
C. Barry Carter
Keyword(s):  
Solid State ◽  
Electric Field ◽  
Elevated Temperatures ◽  
Ionic Current ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Interfacial Stability ◽  
Electric Field Effects ◽  
Thin Film Diffusion ◽  
Microscopy Techniques

ABSTRACTThin films of In2O3 and Fe2O3 have been deposited on (001) MgO using pulsed-laser deposition (PLD). These thin-film diffusion couples were then reacted in an applied electric field at elevated temperatures. In this type of solid-state reaction, both the reaction rate and the interfacial stability are affected by the transport properties of the reacting ions. The electric field provides a very large external driving force that influences the diffusion of the cations in the constitutive layers. This induced ionic current causes changes in the reaction rates, interfacial stability and distribution of the phases. Through the use of electron microscopy techniques the reaction kinetics and interface morphology have been investigated in these spinel-forming systems, to gain a better understanding of the influence of an electric field on solid-state reactions.

scholarly journals Experimental validation of the reaction mechanism models of dechlorination and [Zn] reclaiming in the roasting steelmaking zinc-rich dust process

2020 ◽  
Vol 39 (1) ◽  
pp. 107-116
Author(s):  
Hongyang Wang ◽  
Kai Dong ◽  
Rong Zhu
Keyword(s):  
Reaction Mechanism ◽  
Dust Particle ◽  
Chemical Reaction ◽  
Reaction Mechanisms ◽  
Experimental Validation ◽  
Step Process ◽  
Mass Percent ◽  
Mechanism Model ◽  
Air Atmosphere ◽  
Almost All

AbstractThe reaction mechanism models of dechlorination and [Zn] reclaiming in the roasting steelmaking zincrich dust process are studied. The dust collected from a steelwork contains 63.8% zinc and 3.18% chlorine (mass percent), of which, almost all zinc elements exist in ZnO and ZnCl2 forms, and all the chlorine elements are stored in ZnCl2. When the dust is roasted at above 732∘C in an air atmosphere, the ZnCl2 in the steelmaking zinc-rich dust is volatilized into steam and then oxidized into ZnO. Finding the position where the chemical reaction occurs is the key to determining the reaction mechanisms of dechlorination and [Zn] reclaiming. In this study, two groups of thermal experiments are designed and executed for roasting in different atmosphere environments and at different roasting temperatures. Based on the experiment results, the mechanism model is discussed and built, and the reaction of dechlorination and [Zn] reclaiming is shown to be a multi-step process. Because O2 from the air cannot transmit into the dust particle interior or dust bed effectively, the chemical reaction of [Zn] reclaiming occurs in the external gas environment outside of the dust, where the [Zn] recalcining reaction should be limited by the dynamics of new nucleation of ZnO solids.

Scanning Tunneling Microscope Study of Etch Pits on Highly Oriented Pyrolytic Graphite Heated in an Atomic Absorption Electrothermal Analyzer

1997 ◽  
Vol 51 (12) ◽  
pp. 1896-1904 ◽  
Author(s):  
Kurt G. Vandervoort ◽  
Kristin N. McLain ◽  
David J. Butcher
Keyword(s):  
Elevated Temperatures ◽  
Pyrolytic Graphite ◽  
Reaction Rates ◽  
Surface Reactivity ◽  
Scanning Tunneling ◽  
Highly Oriented Pyrolytic Graphite ◽  
Tunneling Microscopy ◽  
Etch Pits ◽  
Pit Formation ◽  
Second Period

Scanning tunneling microscopy (STM) was used to elucidate monolayer etch pits that form on highly oriented pyrolytic graphite (HOPG) heated in an electrothermal analyzer. Pits form at elevated temperatures due to reactions between oxygen and exposed carbon edge atoms (defects) and additionally with intraplanar carbon atoms (through abstraction). Samples of HOPG without analyte or matrix modifier were placed in the depression of a pure pyrolytic graphite platform and heated by using standard analysis furnace programs. Under argon stop-flow conditions, pits form in less than a second at atomization temperatures equal to and above 1200 °C. With low argon flow rates (40 mL/min), pits formed at atomization temperatures equal to and greater than 1750 °C in less than a second. Quantitative pit formation rates were used to indicate oxygen partial pressure, which may be as high as ∼ 10−3 atm at 1200 °C. Reaction rates were used to predict surface degradation due to oxygen attack and determine that 1-μm depth normal to the surface would be removed by 200 successive 5-second-period furnace firings at 1200 °C. Implications for increases in surface reactivity and analyte intercalation are discussed.

scholarly journals Thermodynamic simulation of oxidation process of the Moss-Mo3Si hypoeutectic alloy, doped with scandium or neodymium

2019 ◽  
Vol 57 (2) ◽  
pp. 90-100
Author(s):  
Alexey V. Larionov ◽  
◽  
Ludmila Y. Udoeva ◽  
Vladimir M. Chumarev ◽  
◽  
...  
Keyword(s):  
Oxidation Process ◽  
Thermodynamic Simulation ◽  
Oxidation Products ◽  
Hypoeutectic Alloy ◽  
Protective Film ◽  
Chemical Transformations ◽  
Reaction Products ◽  
Moist Air ◽  
Condensed Product ◽  
Hsc Chemistry

In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in Mo-Mo3Si-Sc5Si3 и Mo-Mo3Si-NdSi systems with dry and moist air was performed in the temperature range 25-2000 °C. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics silicates, molybdates of scandium and neodymium were entered. Based on the obtained dependences of the composition of phases on temperature and charge of the oxidant (air or vapor-air mixture), the sequence of phase formation was determined and the compositions of oxidation products were estimated. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5Si-3(Sc, Nd) (wt.%) alloys involves a sequence of the following chemical transformations: at the beginning Mo and Sc (Nd) silicides oxidize forming Sc2O3 ( Nd2O3), SiO2 and elemental Mo, then molybdenum is oxidized to MoO2 and Sc2O3 or Nd2O3 interacts with SiO2 with the formation of appropriate silicates Sc2Si2O7 или Nd2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Sc2(MoO4)3 or Nd2Mo4O15 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. In addition, the formation of Nd2Mo2O7 and Nd2 (MoO4)3 is possible. During the oxidation of the Mo-5Si-3Nd alloy at T> 1700 oC, Nd(OH)3 can be formed in the condensed reaction products. According to the results of complete thermodynamic analysis, the formation of silicates and molybdates of scandium and neodymium can promote to the formation of a protective film on the surface of the alloys, which limits the diffusion of oxygen in them, and as a result, the oxidation resistance of alloys should increase.

Oxidation of Some Titanium Alloys in Air at Elevated Temperatures

2008 ◽  
Vol 595-598 ◽  
pp. 967-974 ◽  
Author(s):  
E. Godlewska ◽  
M. Mitoraj ◽  
B. Jajko
Keyword(s):  
Thermal Cycling ◽  
Titanium Alloys ◽  
Constant Temperature ◽  
Cross Sections ◽  
Elevated Temperatures ◽  
Mixed Oxides ◽  
Oxidation Mechanism ◽  
Testing Procedure ◽  
Oxidation Products ◽  
Outward Diffusion

This paper presents comparative studies on the performance of two titanium alloys (Ti- 6Al-1Mn, Ti-45.9Al-8Nb) in an oxidizing atmosphere at 700 oC and 800 oC. Testing procedure comprised thermogravimetric measurements at a constant temperature and in thermal cycling conditions (1-h and 20-h cycles at constant temperature followed by rapid cooling). The overall duration of the cyclic oxidation tests was up to 1000 hours. The oxidized specimens were analyzed in terms of chemical composition, phase composition, and morphology (SEM/EDS, TEM/EDS, XRD). The extent and forms of alloy degradation were evaluated on the basis of microscopic observation of specimen fractures and cross-sections. Selected specimens were examined by means of XPS, SIMS and GDS. Oxidation mechanism of Ti-46Al-8Nb was assessed a two-stage oxidation method using oxygen-18 and oxygen-16. Apparently, the oxidation of this alloy proceeded in several stages. According to XPS, already after quite short reaction time, the specimens were covered with a very thin oxide film, mainly composed of aluminum oxide (corundum). A thicker layer of titanium dioxide (rutile) developed underneath. These two layers were typical of the oxidation products formed on this alloy, even when tested in thermal cycling conditions. In general, the scale had a complex multilayer structure but it was thin and adherent. Under the continuous layer of titania, there was a fine-grained zone composed of mixed oxides. The alloy/scale interface was marked with niobium-rich precipitates embedded in a titanium-rich matrix. There were some indications of secondary processes occurring under the initial continuous oxide layers (e.g. characteristic layout of pores or voids). Thickness of inner scale layers clearly increased according to parabolic kinetics, while that of the outer compact layer (mainly TiO2) changed only slightly. The distribution of oxygen isotopes across the scale/alloy interface indicated two-way diffusion of the reacting species – oxygen inward and metals outward diffusion. Silicon deposited on Ti-6Al-1Mn alloy positively affected scale adhesion and remarkably reduced alloy degradation rate.

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