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

The role of university-based experimental studies in R&D Further improvment Model not working ? Ok ? Quality Product Process flow sheet Lectio praecursoria Fiseha Tesfaye 15.08.2014 1

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]. Lectio praecursoria Fiseha Tesfaye 15.08.2014 2

Background 1(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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 3

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) Lectio praecursoria Fiseha Tesfaye 15.08.2014 4

Background 3(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]. Lectio praecursoria Fiseha Tesfaye 15.08.2014 5

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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 6

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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 7

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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 8

Experimental method 3(3) High-temperature electrochemical stations for themodynamic measurements at TDM laboratory of AaltoChem [3-9]. Lectio praecursoria Fiseha Tesfaye 15.08.2014 9

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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 10

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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 11

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]. Lectio praecursoria Fiseha Tesfaye 15.08.2014 12

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]. Lectio praecursoria Fiseha Tesfaye 15.08.2014 13

References [1] Outotec (Finland) Oy, Outotec Mineral Processing Solutions. Available at (08/2014): http://www.outotec.com/ [2] KGHM. Poska Miedz S. A. Available at (09/2009): http://www.kghm.pl/index.dhtml?category_id=272&lang=en [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: 978-394027638-4 [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. Lectio praecursoria Fiseha Tesfaye 15.08.2014 14

Kiitos! Lectio praecursoria Fiseha Tesfaye 15.08.2014

ACKNOWLEDGEMENTS (Finland) Lectio praecursoria Fiseha Tesfaye 15.08.2014