Thermodynamics of NaO0.5-CO2-SnO2 Slag and Estimation of Distribution Ratio of Sn between the Slag and Molten Copper

Toshiharu Fujisawa, Hiroyuki Fukuyama, Chikabumi Yamauchi

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7 Citations (Scopus)


In view of the application of sodium carbonate slag to the elimination of Sn from molten copper, the thermodynamic properties of NaO0.5-CO2-SnO2slag have been studied by conducting the following experiments: (1) Activities of NaO0.5in the slag were determined by the EMF method using β“ -alumina as a solid electrolyte over the composition range of 1>N≥ 0.795{N=nNa+nsn)>,n: the number of moles) under the partial pressures of CO2of 0.001~0.08 MPa at 1423 ~ 1523 K. It was found that the activity of NaO 0.5did not depend on the slag composition for the constant partial pressure of C02 and the slag was saturated with Na2SnO3(s). (2) Then the solubility of Na2Sn03(s) into sodium carbonate melt was measured under the various partial pressures of CO2and oxygen at 1523 K. With decreasing partial pressure of CO2the solubility increased, but the partial pressure of oxygen had no effect. (3) Activities of SnO2were determined by the distribution equilibrium measurements for Sn between the Na2SnO3(s)-saturated slag and molten copper. From the activity of SnO2combined with that of NaO0.5, the standard free energy change for the following reaction was determined as: 2NaO0.5(l) + Sn02(s)=Na2SnO3(s) ΔG°/kJ=-159(1523 K) The activity of SnO2in the homogeneous liquid region of the slag was also evaluated by the distribution equilibrium measurements. On the basis of the results obtained, the distribution ratios of Sn between the slag and molten copper were estimated. The ratios decrease with decreasing SnO2content in the Na2SnO3(s)-saturated slag. The higher oxygen partial pressure and the lower CO2partial pressure are more preferable for the removal of Sn from molten copper.

Original languageEnglish
Pages (from-to)414-422
Number of pages9
JournalMaterials Transactions, JIM
Issue number6
Publication statusPublished - 1994
Externally publishedYes


  • Na2Sn03
  • NaO05-CO2-SnO2 slag
  • activity
  • copper
  • distribution ratio
  • electromotive force method
  • sodium carbonate slag
  • thermodynamics
  • tin

ASJC Scopus subject areas

  • Engineering(all)


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