Browsing by Author "Tesfaye, Fiseha"

Now showing 1 - 20 of 25

Critical Evaluation and Calorimetric Study of the Thermodynamic Properties of Na2CrO4, K2CrO4, Na2MoO4, K2MoO4, Na2WO4, and K2WO4
(2023-12-06) Benalia, Sara; Tesfaye, Fiseha; Lindberg, Daniel; Sibarani, David; Hupa, Leena; Chartrand, Patrice; Robelin, Christian
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper evaluates crystallographic data and thermodynamic properties for sodium chromate, potassium chromate, sodium molybdate, potassium molybdate (K2MoO4), sodium tungstate, and potassium tungstate collected from the literature. A thorough literature review was carried out to obtain a good understanding of the available data, and a critical evaluation has been performed from room temperature to above the melting temperatures. Also, the solid-solid transition and melting properties of the six pure salts were measured by differential scanning calorimetry, and high-temperature x-ray powder diffraction measurements were performed to determine the crystal structures and space groups associated with the phases of K2MoO4. This work is the first step towards the development of a thermodynamic model for the Na+, K+//Cl−, SO42−, CO32−, CrO42−, Cr2O72−, MoO42−, Mo2O72−, WO42−, W2O72−, O2− system that is relevant for high temperature corrosion in atmospheres containing O-H-S-C-Cl and alkali salts.
Densities of Molten and Solid Alloys of (Fe, Cu, Ni, Co)-S at Elevated Temperatures - Literature Review and Analysis
(2010) Tesfaye, Fiseha; Taskinen, Pekka
School of Chemical Technology | D4 Julkaistu kehittämis- tai tutkimusraportti tai -selvitys
Densities of solid and liquid Fe, Cu, Ni and Co, and their alloys both at the presence and absence of sulfur have been reviewed. Volumetric thermal expansions were used to estimate the densities at different temperatures. Densities of the alloys generally decrease with increasing temperature. For the pure metals the reduction in density as temperature rises from 25 oC to their respective melting point can be estimated to be about 7.05 ± 0.4 % just before melting and about 11.63 ± 0.92 on complete melting. According to the literature data and the analyzed results, at ambient pressure condition, density of the stoichiometric FeS changes from 4.615 g/cm3 at 25 oC to 3.8 g/cm3 at 1200 oC (17.7 %), density of the stoichiometric Cu2S changes from 5.65 g/cm3 at 25 oC to 5.18 g/cm3 at 1200 oC (8.3 %), density of the stoichiometric NiS changes from 5.5 g/cm3 at 25 oC to 5.025 g/cm3 at 1027 oC (8.5 ± 1.8 %) and density of the stoichiometric CoS changes from 5.45 g/cm3 at 25 oC to 4.88 g/cm3 at 1100 oC (10.45 %). A study on the Fe-S melts at 4GPa suggests that in sulfur-poor compositions, where solubility of sulfur is less likely to be affected by pressure, the density of the sulfides at isothermal conditions decreases in a similar fashion as under 1 bar, i.e., density decreases non-linearly with increasing composition of sulfur.
Electrohydraulic Fragmentation of Aluminum and Polymer Fractions from Waste Pharmaceutical Blisters
(2020-03-16) Agarwal, Vivek; Halli, Petteri; Helin, Sampsa; Tesfaye, Fiseha; Lundström, Mari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Recently, awareness has been raised concerning the need to decrease the total environmental footprint throughout the life cycle of a medicine, including the packaging materials. Aluminum, a highly energy-intensive metal, is widely used in blister packages together with polymers. However, these blister packages suffer from poor recyclability, with the clear majority of waste blister packages (WBPs) disposed of in municipal solid waste, therefore often being incinerated. In the current study, the separation of aluminum from the polymer in WPBs was investigated to make Al available for direct recycling at a secondary Al facility. The characterization of WPBs (ICP-OES, SEM-EDS, and TGA) showed that the investigated fractions consisted of approximately 10-12 wt % of aluminum, with the clear majority of waste blister mass in the polymer fractions, which consisted of two overlapping layers. Moreover, the polymer layer also gave indications of the presence of Cl. WPBs were subjected to electrohydraulic fragmentation,where the effects of the gap between electrodes (10-40 mm), the amount of pulses (50-500 pulses), pulse frequency (2-5 Hz), and discharge voltage (100-180 kV) on the separation process were systematically investigated. It was shown that at optimal conditions (electrode gap of 40 mm, 300 pulses, frequency of 3 Hz, 130 kV of discharge voltage, and 40 g of initial WPB mass), up to 88% of Al (≥99.4% purity) and polymers were recovered from the investigated waste blister samples. The current study contributes toward improving the circular economy of aluminum as well as the reduction in energy consumption by a new application of electrohydraulic fragmentation for pharmaceutical blister packages.
The Equilibrium Phase Formation and Thermodynamic Properties of Functional Tellurides in the Ag-Fe-Ge-Te System
(2021-02-28) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Prokhorenko, Myroslava; Yarema, Nataliya; Lindberg, Daniel; Reshetnyak, Oleksandr; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Equilibrium phase formations below 600 K in the parts Ag2Te-FeTe2-F1.12Te-Ag2Te and Ag8GeTe6-GeTe-FeTe2-AgFeTe2-Ag8GeTe6 of the Fe-Ag-Ge-Te system were established by the electromotive force (EMF) method. The positions of 3- and 4-phase regions relative to the composition of silver were applied to express the potential reactions involving the AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 compounds. The equilibrium synthesis of the set of phases was performed inside positive electrodes (PE) of the electrochemical cells: (-)Graphite ||LE|| Fast Ag+ conducting solid-electrolyte ||R[Ag+]||PE|| Graphite(+), where LE is the left (negative) electrode, and R[Ag+] is the buffer region for the diffusion of Ag+ ions into the PE. From the observed results, thermodynamic quantities of AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 were experimentally determined for the first time. The reliability of the division of the Ag2Te-FeTe2-F1.12Te-Ag2Te and Ag8GeTe6-GeTe-FeTe2-AgFeTe2-Ag8GeTe6 phase regions was confirmed by the calculated thermodynamic quantities of AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 in equilibrium with phases in the adjacent phase regions. Particularly, the calculated Gibbs energies of Ag2FeGeTe4 in two different adjacent 4-phase regions are consistent, which also indicates that it has stoichiometric composition.
Experimental Thermodynamic Characterization of the Chalcopyrite-Based Compounds in the Ag–In–Te System for a Potential Thermoelectric Application
(2022-11) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Mastronardo, Emanuela; Mysina, Oksana; Prokhorenko, Myroslava; Prokhorenko, Serhiy; Lindberg, Daniel; Reshetnyak, Oleksandr; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The equilibrium concentration space of the Ag–In–Te system in the part AgInTe2–Te–In2Te3 was studied through the modified solid-state electromotive force (EMF) method by dividing In2Te3–In2Te5–Ag3In97Te147 (I), In2Te5–Te–Ag3In97Te147 (II), Ag3In97Te147–Te–AgIn5Te8 (III), AgIn5Te8–Te–AgIn3Te5 (IV), and AgIn3Te5–Te–AgInTe2 (V), into separate phase regions at T ≤ 500 K. The formation of a thermodynamically stable combination of the binary and ternary phases in the (I)–(V) phase regions from a metastable phase mixture of substances was carried out at T ≤ 500 K in the R(Ag+) part of the positive electrode (PE) of the galvanic cells (GCs) of the structure: (−) C |∙| Ag |∙| SE |∙| R(Ag+) |∙| PE |∙| C (+), where C is the graphite (inert electrode), SE is the solid-state electrolyte (Ag3GeS3Br glass), and Ag is the left (negative) electrode. The Ag+ ions in the R(Ag+) region functioned as small nucleation centers for the formation of the stable phases. The spatial position of the (I)–(V) phase regions in the concentration space of the Ag–In–Te system relative to the position of silver was used to express the overall potential-forming reactions with the participation of the substances Ag, Te, In2Te5, Ag3In97Te147, AgIn5Te8, AgIn3Te5, and AgInTe2. The subsequent EMF measurements were carried out by applying the same GCs. The temperature dependences of the EMF of GCs with PE of the (I)–(V) phase regions were here used to determine, for the first time, the values of standard thermodynamic functions of the binary and ternary compounds. The determined values of the Gibbs energies of the formation of compounds are equal: (Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.), and (Formula presented.) The correctness of the division of the equilibrium phase space of the Ag–In–Te system in the part AgInTe2–Te–In2Te3 involving the AgInTe2, AgIn3Te5, AgIn5Te8, and Ag3In97Te147 compounds was confirmed by the agreement of the calculated and literature-based thermodynamic data for In2Te5 compound. Compositions of pairs of the ternary compounds for their subsequent practical application were proposed.
Graphite recovery from waste Li-ion battery black mass for direct re-use
(2024-03) Chernyaev, Alexander; Kobets, Anna; Liivand, Kerli; Tesfaye, Fiseha; Hannula, Pyry-Mikko; Kallio, Tanja; Hupa, Leena; Lundström, Mari
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Graphite was recovered from two leached (H2SO4 = 2 M, 60 °C, t = 3 h, Fe3+ = 2 g/L) Li-ion battery black mass concentrates with minimized energy consumption. One black mass originated from a mixture of mobile device and power tool batteries, and another from a single electric vehicle battery. The leach residues were pyrolyzed (800 °C, t = 1 h, Ar atmosphere) to remove the polyvinylidene fluoride (PVDF) binder and other non-metallic fractions. The black mass, its leach residue, and pyrolyzed residue were characterized using inductively coupled plasma-optical emission spectrometry (ICP-OES), ion chromatography (IC), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, and N2 adsorption/desorption. After hydrometallurgical recycling and pyrolysis, the main post-metallurgical black mass impurities were cobalt oxide, iron, acid-resistant boehmite (AlO(OH)), and silicon dioxide. The pyrolysis resulted in electrolyte and binder removal, affected the crystallinity of the remaining boehmite. The recovered graphite-rich residue with impurities identified was tested as an anode in half-cells vs. metal Li. The average specific capacities of recovered graphite-rich residues from both sources were 350 and 250 mAh/g at 0.1C and their capacity retention after 100 cycles was high (80 %) suggesting rather slow deterioration and hence the proposed recycling route being promising for the graphite reuse in new Li-ion batteries.
Investigation of the K-Mg-Ca sulfate system as part of monitoring problematic phase formations in renewable-energy power plants
(2020-10-15) Tesfaye, Fiseha; Lindberg, Daniel; Moroz, Mykola; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Besides the widely applied hydropower, wind farms and solar energy, biomass and municipal and industrial waste are increasingly becoming important sources of renewable energy. Nevertheless, fouling, slagging and corrosion associated with the combustion processes of these renewable sources are costly and threaten the long-term operation of power plants. During a high-temperature biomass combustion, alkali metals in the biomass fuel and the ash fusion behavior are the two major contributors to slagging. Ash deposits on superheater tubes that reduce thermal efficiency are often composed of complex combinations of sulfates and chlorides of Ca, Mg, Na, and K. However, thermodynamic databases involving all the sulfates and chlorides that would favor a better understanding and control of the problems in combustion processes related to fouling, slagging and corrosion are not complete. In the present work, thermodynamic properties including solubility limits of some phases and phase mixtures in the K2SO4-(Mg,Ca)SO4 system were reviewed and experimentally investigated. Based on the new and revised thermochemical data, binary phase diagrams of the K2SO4-CaSO4 and K2SO4-MgSO4 systems above 400 °C, which are of interest in the combustion processes of renewable-energy power plants, were optimized.
Investigation of waste PCB leach residue as a reducing agent in smelting processes
(2020-09-01) Attah-Kyei, Desmond; Akdogan, Guven; Dorfling, Christie; Zietsman, Johan; Lindberg, Daniel; Tesfaye, Fiseha; Reynolds, Quinn
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The advancement in technology has resulted in the development of newer and improved electrical products. The older products are becoming obsolete and are discarded as waste at a continuously increasing trend. Printed circuit board (PCB) is the main focus of electronic waste recycling because of the inherently high value of contained metals such as gold and copper. Hydrometallurgical route, which is often used to recover the metals, does not take into account the non-metallic PCB fractions. These non-metallic fractions may end up in landfills or incinerated which leads to secondary pollution. In this work, the use of the leached PCB waste fraction as reductant in primary metal smelting operations and solid state reduction is investigated. Laboratory-scale experiments and thermodynamic modelling were performed to simulate solid state reduction of hematite (Fe2O3) using various blends of PCB and graphitic carbon. Differential Scanning Calorimeter (DSC) analysis of several samples were performed up to 1200 °C. Thermodynamic modelling was done using FactSage to predict the products of the hematite reduction below 1600 °C. The study showed that PCB residue might be used to partially replace the conventional reductants. The investigations revealed that at temperatures below 1000 °C, PCB reduces hematite to lower forms of iron oxide at a faster rate than that of graphite. The optimal blend contains about 20 wt% PCB residue which has the same reduction degree as graphite. Thermodynamic modelling of iron smelting was also performed using various blends of PCB and coal. The models showed that PCB residue might be used to partially replace the conventional reductants. The study revealed that in iron smelting, the optimal blend contains around 20 wt% PCB residue, with energy savings of 150 kWh/t of ore to achieve the same metal recovery.
Kiinteän RbAg4I5 -elektrolyytin käyttö EMF-menetelmässä
(2011) Leppäniemi, Jarmo
Kemian tekniikan korkeakoulu | Bachelor's thesis
Kinetics of Copper Reduction from Molten Slags
(2009) Tesfaye, Fiseha
School of Chemical Technology | Master's thesis
The objective of this thesis was to study the process of reduction of cuprous oxide by carbon from copper flash smelting slags. The flash smelting and slag cleaning processes are described in the introductory part. The studies are focused on the slag cleaning process in the three - electrode electric furnace (EF), where components of the slag reduce to matte and EF slag in a periodic batch process. Parametric values of different variables (surface energy, density, viscosity, and equilibrium composition) and thermodynamics of reduction reactions of the slag cleaning process were also examined. At higher oxygen potential additions of CaO and MgO were found to increase the activity coefficient of both Cu2O and Fe2O3, thereby reducing the amount of Cu2O and Fe+3/Fe+2 ratio in the slag. Furthermore, reasonable additions of the basic oxides will break the (SiO4)4- chains and reduce viscosity of the slag. Kinetics of reduction of Cu2O and FeOx were reviewed based on data obtained from different publications. Effects of various variables such as temperature, initial composition and reaction products on the reduction kinetics of Cu2O were analyzed in the temperature range of 1200-1650 C, which was identified to be the most favourable in the slag cleaning process. Results from both thermodynamic and kinetic analyses confirmed that increase in temperature increase the reduction rates of both Cu2O and FeOx. The reduction rates of the oxides were widely accepted to be the 1st order reaction with respect to their concentration and the rates limiting step was chemical reaction at the slag-coke interface. In this analysis the reduction of Fe2O3 was confirmed to follow the 1st order reaction, but the reduction of Cu2O was found to be autocatalytic.
Phase equilibria and thermochemistry of selected sulfide systems in the pyrometallurgy of Ni and Cu
(2012) Tesfaye, Fiseha; Taskinen, Pekka
School of Chemical Technology | D4 Julkaistu kehittämis- tai tutkimusraportti tai -selvitys
A review of phase equilibria and thermodynamic data of Ni-(As, Se)-S and Cu-(As, Bi, Pb, Sb,Se, Te, Nb, Zn, Mo)-S systems was done. Particular emphases were given to the compilationand refine of the standard Gibbs energies of formations of equilibrium phases, which are ofinterest in the pyrometallurgical processes of copper and nickel production. Phase stabilities,phase relations and solubility limits of some equilibrium phases in the Ni-(As, Se)-S and Cu-Mo-Bi-Nb-S systems were also compiled and reviewed, based on the available literature.This work also reviews, updates, and extends the earlier reports. The Gibbs energies offormations and reactions are mostly presented as linear equations, in each temperature rangesof phase stabilities. List of thermal stabilities of some pure sulfides and sulfosalts were alsoreviewed and compiled (Appendix).
Phase Equilibria and Thermodynamic Properties of Selected Compounds in the Ag–Ga–S–AgBr System for Modern Application in Energy Conversion Devices
(2024-02-02) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Prokhorenko, Myroslava; Rudyk, Bohdan; Pereviznyk, Orest; Mastronardo, Emanuela; Lindberg, Daniel; Reshetnyak, Oleksandr; Hupa, Leena
A4 Artikkeli konferenssijulkaisussa
The phase equilibria of the Ag–Ga–S–AgBr system in the part GaS–Ga 2S 5–AgBr–Ag 2S below 600 K were investigated by the modified electromotive force (EMF) method using the Ag + catalysts as small nucleation centers of equilibrium phases. Division of the GaS–Ga 2S 5–AgBr–Ag 2S was carried out with the participation of the following compounds Ag 2S, GaS, Ga 2S 3, AgBr, Ag 9GaS 6, AgGaS 2, Ag 3SBr, Ag 3Ga 2S 4Br, and Ag 27Ga 2S 12Br 9. Reactions were performed by applying electrochemical cells (ECs) with the structure: (−) IE | NE | SSE | R{Ag +} | PE | IE (+), where IE is the inert electrode (graphite powder), NE is the negative electrode (silver powder), SSE is the solid-state electrolyte (glassy Ag 3GeS 3Br), PE is the positive electrode, R{Ag +} is the region of Ag + diffusion into PE. The measured EMF and temperature values of ECs were used to determine the standard thermodynamic functions of the compounds Ag 3Ga 2S 4Br and Ag 27Ga 2S 12Br.
Phase Equilibria and Thermodynamic Properties of Selected Compounds in the Ag-Ga-Te-AgBr System
(2024-06) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Prokhorenko, Myroslava; Mastronardo, Emanuela; Reshetnyak, Oleksandr; Lindberg, Daniel; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The equilibrium T − x space of the Ag-Ga-Te-AgBr system in the part Ag2Te-GaTe-Te-AgBr-Ag2Te below 600 K has been divided into separate phase regions using the electromotive force (EMF) method. Accurate experimental data were obtained using the following electrochemical cells (ECs): (−) IE | NE | SSE | R{Ag+} | PE | IE (+), where IE is the inert electrode (graphite powder), NE is the negative electrode (silver powder), SSE is the solid-state electrolyte (glassy Ag3GeS3Br), PE is the positive electrode, R{Ag+} is the region of PE that is contact in with SSE. At the stage of cell preparation, PE is a non-equilibrium phase mixture of the well-mixed powdered compounds Ag2Te, GaTe, Ga2Te3, AgBr, and tellurium, taken in ratios corresponding to two or three different points of interest for each of the phase regions. The equilibrium set of phases was formed in the R{Ag+} region at 600 K for 48 h with the participation of the Ag+ ions. Silver cations, displaced for thermodynamic reasons from the NE to the PE of ECs, acted as catalysts, i.e., small nucleation centers of equilibrium phases. The spatial position of the established phase regions relative to the position of silver was used to express the overall reactions of synthesis of the binary Ga2Te5, Ga7Te10, Ga3Te4, ternary AgGa5Te8, and quaternary Ag3Ga10Te16Br, Ag3Ga2Te4Br, Ag27Ga2Te12Br9 compounds in the PE of ECs. The values of the standard thermodynamic functions (Gibbs energies, enthalpies, and entropies) of these compounds were determined based on the temperature dependencies of the EMF of the ECs.
Phase equilibria and thermodynamics of the system Zn-As-Cu-Pb-S at temperatures below 1173 K
(2011) Tesfaye, Fiseha; Taskinen, Pekka
Kemian tekniikan korkeakoulu | D4 Julkaistu kehittämis- tai tutkimusraportti tai -selvitys
Phase Equilibria in the Ag–Ge–Bi–Te System and Thermodynamic Properties of the nGeTe•mBi2Te3 (n, m = 1–4) Layered Compounds
(2022) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Prokhorenko, Myroslava; Pereviznyk, Orest; Rudyk, Bohdan; Soliak, Lyudmyla; Lindberg, Daniel; Reshetnyak, Oleksandr; Hupa, Leena
Conference article in proceedings
Phase equilibria of the Ag–Ge–Bi–Te system in the part GeTe–Ag8GeTe6–Te–Bi2Te3 (I) were established by the electromotive force (EMF) method with a solid Ag+ conducting electrolyte. It was shown that the concentration space of (I) in the part 4GeTe⋅Bi2Te3–Ag8GeTe6–Te–Bi2Te consists of 8 four-phase regions, formed of the layered compounds of the nGeTe⋅mBi2Te3 (n, m = 1–4) homologous range, as well as Ag8GeTe6, Bi2Te3, and Te. Equations of overall potential-forming reaction of the decomposition and synthesis of compounds of the homologous range were written for each region. Reactions were performed in the following electrochemical cells (ECCs) (−)IE | Ag | SE | PE | IE(+), where IE is the inert electrode (graphite), Ag is the negative (left) electrode, SE is the solid-state Ag+ ion-conducting electrolyte, PE is the positive (right) electrode. PEs of ECCs were prepared by melting of a mixture of the high-purity elements Ag, Ge, Bi, and Te. The component ratios in samples were determined based on the equations of the potential-forming reactions in respective phase Phase equilibria regions. The finely grounded samples were used as PEs of ECCs. The synthesis of an equilibrium set of phases was performed in the part of PE that is in contact with SE of ECC at T = 580 K for 50 h. Silver cations that shift from the left to the right electrode acted as the nucleation centers of equilibrium compounds in the corresponding phase regions. Linear dependences E versus T of ECCs in the range of T = (440–500) K were used to calculate values of the Gibbs energies, enthalpies of formation, and entropies of compounds GeTe⋅4Bi2Te3, GeTe⋅3Bi2Te3, GeTe⋅2.5Bi2Te3, GeTe⋅2Bi2Te3, GeTe⋅Bi2Te3, 2GeTe⋅Bi2Te3, 3GeTe⋅Bi2Te3, and 4GeTe⋅Bi2Te3. The differences in the values of the thermodynamic functions of GeTe-rich and Bi2Te3-rich compounds with respect to GeTe⋅Bi2Te3 correlate well with the literature data on the differences of their crystal structures.
Review of rhenium extraction and recycling technologies from primary and secondary resources
(2021-01-15) Shen, Leiting; Tesfaye, Fiseha; Li, Xiaobin; Lindberg, Daniel; Taskinen, Pekka
A2 Katsausartikkeli tieteellisessä aikakauslehdessä
Rhenium is a scarce and highly important metal, which is widely used in high-temperature superalloys and platinum–rhenium catalysts due to its unique physicochemical properties. The substitution of rhenium in its applications is very limited, and there is no suitable substitute without losing essential performance. Furthermore, global extractable primary rhenium resources are predicted to deplete within 130 years. In this paper, rhenium extraction and recycling technologies from primary and secondary resources are critically classified and reviewed. Rhenium is primarily produced as a by-product in molybdenum, copper, lead and uranium production from the concentrates and ores. Rhenium is extracted from roasting fume and dust, leaching residue, and aqueous solution to produce a rhenium bearing solution. Subsequently, rhenium rich solution is generated by separation with solvent extraction, ion exchange, adsorption, membrane techniques or chemical precipitation. Finally, rhenium is produced via crystallization and reduction steps. Recycling rhenium from spent alloys and catalysts is a multi-step process combining pyrometallurgical and hydrometallurgical techniques, where its separation and the subsequent steps are similar to that of extracting rhenium from primary resources. The main challenges in rhenium extraction and recycling are the enrichment of rhenium in the production and the collection and classification of spent rhenium scrap, to identify suitable processes to recover the rhenium with a high recovery. This paper contributes to better understanding the rhenium extraction and recycling processes and enhances sustainability of rhenium production.
Sulfide Mineralogy - Literature Review
(2010) Tesfaye, Fiseha; Taskinen, Pekka
School of Chemical Technology | D4 Julkaistu kehittämis- tai tutkimusraportti tai -selvitys
The aim of this study was to have an insight into the sulfide mineralogy, mainly based on sulfides mineralogical studies prior to the year 1975. In the first two chapters, the metal sulfides crystal structures and chemistries are reviewed. Then, the electronic interactions and chemical bonding followed by experimental methods in sulfides research with the proposed phase equilibria are reviewed. Phase relations in the (Cu, Ni, Zn)-S systems are discussed. Due to its influential and common appearance, in most natural sulfides (the common rock-forming minerals: po and py), the Fe-S system has been summarized relatively in detail. Sulfide petrology has been also discussed. The metal sulfides are the raw materials for most of the world supplies of non-ferrous metals. Their complex chemistry, as a result of high impurities association (such as As, Sb, Bi, etc...) and less base-metals content (metal poor rocks: composition of base-metal is less than 1 at.%), and the ever growing demand for the metals as well as the embroiling need to optimize minerals processing and sulfides smelting claim intense mineralogical studies. The main goal of such studies are to acquire accurate thermodynamic data which are useful to predict reactions and stable relationships, and in defining the limiting conditions under which phases may exist.
Synthesis and Thermodynamic Investigation of Energy Materials in the Ag-Te-Cl System by the Solid-State Galvanic Cells
(2021-05) Moroz, Mykola; Tesfaye, Fiseha; Demchenko, Pavlo; Prokhorenko, Myroslava; Prokhorenko, Serhiy; Lindberg, Daniel; Reshetnyak, Oleksandr; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Discoveries of new energy materials with unique properties and wider thermal stability ranges enable sustainable developments toward a low-carbon society. In this work, phase stabilities and thermodynamic properties of selected compounds in the Ag-Te-Cl system with potential application as energy materials have been critically reviewed and experimentally investigated. Based on the literature data on phase formations in the AgCl-Ag2Te-Te part of the Ag-Te-Cl system and the results of electromotive force (EMF) measurements in this work, formations of the Ag19Te6Cl7, Ag10Te4Cl3, Ag5Te2Cl, and Ag23Te12Cl compounds below 500 K were established. The EMF measurements were performed in carefully built galvanic cells with positive electrodes prepared from finely ground mixtures of pure substances Ag, Te, and AgCl. Based on the temperature dependences of the EMF of the cells, the standard thermodynamic quantities of the ternary compounds of the Ag-Te-Cl system were experimentally determined for the first time.
Thermal Analysis and Optimization of the Phase Diagram of the Cu-Ag Sulfide System
(2022-01-14) Tesfaye, Fiseha; Lindberg, Daniel; Sukhomlinov, Dmitry; Taskinen, Pekka; Hupa, Leena
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Thermal stabilities of selected ternary phases of industrial interest in the Ag-Cu-S system have been studied by the calorimetric and electromotive force techniques. The ternary compounds Ag1.2 Cu0.8 S (mineral mackinstryite) and AgCuS (mineral stromeyerite) were equilibrated through high-temperature reaction of the pure Cu2 S and Ag2 S in an inert atmosphere. The synthesized single solid sample constituting the two ternary phases was ground into fine powders and lightly pressed into pellets before calorimetric measurements. An electrochemical cell incorporating the two equilibrated phase and additional CuS as a cathode material was employed. The measurement results obtained with both techniques were analyzed and thermodynamic properties in the system have been determined and compared with the available literature values. Enthalpy of fusion data of the Ag-richer solid solution (Ag,Cu)2 S have also been determined directly from the experimental data for the first time. The thermodynamic quantities determined in this work can be used to calculate thermal energy of processes involving the Ag-Cu-S-ternary phases. By applying the obtained results and the critically evaluated literature data, we have developed a thermodynamic database. The self-developed database was combined with the latest pure substances database of the FactSage software package to model the phase diagram of the Ag2 S-Cu2 S system.
Thermochemical Data of Selected Phases in the FeO x –FeSO 4 –Fe 2 (SO 4 ) 3 System
(2019-02-10) Tesfaye, Fiseha; Jung, In Ho; Paek, Min Kyu; Moroz, Mykola; Lindberg, Daniel; Hupa, Leena
A3 Kirjan tai muun kokoomateoksen osa
Several recent studies have shown the potential of oxy-fuel combustion to reduce NO x (gas) and SO 2 (gas) emissions. However, the mechanisms through which SO 2 (gas) reduction takes place has yet to be fully understood. Therefore, the development of oxy-sulfate thermodynamic database for a better understanding and control of SO 2 (gas) emission during oxy-fuel combustion processes is essential. The focus of this research is on the thermodynamic modelling of the iron oxide–sulfate system with the FactSage 7.2 software package. Thermodynamic properties of selected phases in the FeO x –FeSO 4 –Fe 2 (SO 4 ) 3 system were critically reviewed, compiled and assessed over a wide temperature range (298–2000 K) to obtain accurate thermodynamic description of the system at different temperatures. New C p functions, which include the recent experimental data, were optimized. The obtained results are presented and discussed.