1. Lectio praecursoria F. Tesfaye 15.08.2014
Experimental thermodynamic study for improved metals extraction and functional materials manufacturing
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F. Tesfaye

2. The role of university-based experimental studies in R&D
Further improvment
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Quality Product
Process flow sheet
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3. Non-ferrous metals processing
Metal sulphides are raw materials for most of the world supplies of non-ferrous metals.
Complex sulfide ores contain more than one valuable metal sulfide mineral.
Ag-based tellurides, sulfides and sulfosalts are commonly encountered as carriers of precious metals (Ag and Au).
[1].
Glogow II Smelter, KGHM [2].
Schematic process flow diagram modified from [1,2].
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4. Background (3)
Most of the available sulphide ores are becoming increasingly complex.
Ag-based compounds are essential constituents.
Conventional pyrometallurgical processes are compromised.
to modify operating flow sheets and strategies in processing the complex feed materials economically:
accurate thermochemical data is the key.
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5. Background 2(3) Ag-Te System Ag-Bi-S System Ag-Cu-S System
Example of some minerals in the studied systems
Ag-Te System
Hessite(Ag2Te)
Ag-Bi-S System
Matildite(AgBiS2)
Ag-Cu-S System
Stromeyerite(AgCuS)
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6. Background (3)
Recently, the Ag-based chalcogenides such as AgBiS2 have also been noted for their
unique electronic and magnetic properties.
Low-cost materials.
Therefore, reliable thermochemical data are essential for the quantitative modeling of the chemical behavior of compounds both in the metal making processes and functional materials design [3-9].
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7. Objectives
To determine accurate experimental thermodynamic properties (ΔrGo, ΔrSo, ΔrHo & Ttr) of selected compounds,
which are of interest in the pyrometallurgical processes of copper, nickel and zinc production.
Improve the solid state EMF-method for more accurate thermodynamic measurements of alloys and compounds.
To contribute new experimental thermodynamic data in the selected systems.
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8. Experimental method 1(3)
The solid state Electromotive Force (EMF)-method have been introduced by e.g. Kiukkola and Wagner (1957):
the method has been used frequently and it has proved to be direct, effective, and most accurate for determining: ΔrGo, ΔrSo, ΔrHo & Ttr in true equilibrium conditions.
Due to the discoveries super Ag+ ion conducting electrolytes, thermodynamic properties of Ag-based compounds can be determined reliably by the EMF- method.
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9. Experimental method 2(3)
EMF-method: a versatile experimental method to study the thermodynamic properties of Ag-based compounds with high accuracy.
Ag₅₋xTe₃ + Te
3Te + 5Ag = Ag₅Te₃
Ag₅Te₃ + Te - +
AgI or RbAg₄I₅ Ag e- e- e- e- e- e-
Working principle of electrochemical cell in thermodynamic measurements.
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10. Experimental method 3(3)
High-temperature electrochemical stations for themodynamic measurements at TDM laboratory of AaltoChem [3-9].
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11. Main experimental achievements 1(4)
An improved way of galvanic cells construction and
new experimental arrangement to control temperature gradient over the galvanic EMF cell [3,5].
Better accuracies in the determination of the thermodynamic properties.
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12. Main experimental achievements 2(4)
Example of structure of the studied cells placed inside an alumina crucible [5-7].
(-)Pt | Ag | Ag+ | AgBiS₂+AgBi₃S₅+S | Pt(+)
New thermodynamic measurements in different temperature and compositional ranges.
New observation on the effects of saturation of substances on the thermodynamic properties of other substances.
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13. Main experimental achievements 3(4)
The experimental data obtained within this thesis together with the selected literature data enabled:
the determination of accurate thermodynamic functions for 36 practically interesting equilibrium reactions.
Gibbs energies of electrochemical
cell reactions were calculated by:
ΔrGo(T) = - Z∙F∙Eo(T)
Figure: A summary of the EMF vs. T relations obtained with several electrochemical cells of Ag-Te-cathode material [3,4].
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14. Main experimental achievements 4(4)
Standard Gibbs energies of the ternary phases which are involved in the electrochemical cell reactions were calculated by combining:
ΔrGo(T) = - Z∙F∙Eo(T)
and
ΔfGo(T) = G°products(T) –
G°reactants(T).
Figure: A summary of the EMF vs. T relations obtained with two electrochemical cells of Ag-Bi-S phase assemblages as a cathode material [7].
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15. References
[1] Outotec (Finland) Oy, Outotec Mineral Processing Solutions. Available at (08/2014):
[2] KGHM. Poska Miedz S. A. Available at (09/2009):
[3] F. Tesfaye, P. Taskinen, M. Aspiala, D. Feng, Intermetallics 34 (2013) 56–62.
[4] F. Tesfaye, P. Taskinen, M. Aspiala, “Thermodynamic investigation of
intermetallic phases in the binary system Ag-Te,” in: J. Harre, U. Waschki
(Eds.), Proceedings of European Metallurgical Conference EMC 2011, vol. 3,
Düsseldorf, Germany, 2011, pp. 1111–1124. ISBN:
[5] F. Tesfaye, P. Taskinen, Thermochim. Acta 562 (2013) 75–83.
[6] F. Tesfaye, P. Taskinen, J. Solid State Electrochem. 18 (2014) 1683–1694.
[7] F. Tesfaye, P. Taskinen, J. Chem. Thermodyn. 70 (2014) 219–226.
[8] D. Feng, P. Taskinen, F. Tesfaye, Solid State Ionics 231 (2013) 1–4.
[9] F. Tesfaye, P. Taskinen, “Thermodynamic properties of equilibrium phases in the Ag-Cu-S
system below 500 K: experimental study,” in: J. Yurko, L. Zhang, A. Allanore, C. Wang, J.S.
Spangenberger, R.E. Kirchain, J.P. Downey, L.D. May (Eds.), EPD Congress 2014, John
Wiley and Sons, Inc., Hoboken, NJ, USA, 2014, pp. 185–193.
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16. Kiitos!
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17. ACKNOWLEDGEMENTS (Finland) Lectio praecursoria Fiseha Tesfaye