Electrochemical determination of the thermodynamic parameters of sphalerite, ZnS

Valentin O. Osadchii, Mark V. Fedkin, Evgeniy G. Osadchii

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Abstract

Thermodynamic properties of sphalerite (β-ZnS, F4-3m) were studied by the method of high-temperature galvanic cell with separate gas space and Y2O3-stabilized ZrO2 as solid-state electrolyte. The temperature dependences of the cell electromotive force (EMF) were obtained for the reaction ZnS + 2Ag + NiO=ZnO + Ag2S + Ni in the temperature range 782-1050 K, and for the reaction ZnS + 2Cu + NiO = ZnO + Cu2S + Ni in the temperature range 848-1288 K. The standard parameters of sphalerite were analyzed by the second law of thermodynamics. The standard enthalpy of formation of ZnS, ΔfHo ZnS(298 K) = -201.07 ± 1.3 kJ mol-1, was calculated for the reaction Zn(s) + S(s) = ZnS(β) using the third law of thermodynamics (Gef method) and data on standard enthalpy of formation for ZnO, NiO, Ag2S, and Cu2S. From the EMF results for the ZnS/ZnO equilibrium and using the known data on free energy of formation of ZnO, NiO, Ag2S and Cu2S, the free energy of sphalerite formation was found according to the reaction Zn(l) + 0.5S2(g) = ZnS(β): ΔfGZnSo(T) ± 1000 J mol-1 = -273, 870 + 107.30 · T, (782 < T/K < 1050),(logfS2 > -9) ΔfGZnSo(T) ± 1300 Jmol-1= -268, 892 + 102.67 · T, (848 < T/K < 1180),(log fS2 < -9) Similarly, for the reaction Zn(g)+0.5S2(g)=ZnS(β): ΔfGZnSo(T) ±(T) ± 1300 J mol-1= -382,203+198.75 · T, (1180 < T/K < 1293) The obtained results were compared to the literature data.

Original languageEnglish (US)
Pages (from-to)368-374
Number of pages7
JournalJournal of Alloys and Compounds
Volume636
DOIs
StatePublished - Mar 3 2015

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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