Effect of Partial Pressure of CO₂ on the Distribution Ratios of Sb and Cu between Na₂CO₃ Slag and Molten Copper at 1523 K

The distribution ratios of Sb and Cu {L^S/Cu_X=(mass% of X in slag)/[mass% of X in copper], X=Sb or Cu} between Na₂CO₃ slag and molten copper have been determined for various partial pressures of CO₂ at 1523 K as a function of the oxygen partial pressure calculated from the oxygen content in molten copper by using appropriate thermodynamic data. The distribution ratios of Sb and Cu are both affected strongly by the partial pressure of CO₂. This effect for Sb can be evaluated by the equation [formula-omitted] (Q: a constant determinable experimentally) using activity data of NaO_0.5 in Na₂O-CO₂-Sb₂O₅ melt under various partial pressures of CO₂ which have been measured electrochemically by the aid of β″-alumina as a solid electrolyte. The distribution ratio of Cu increases with decreasing partial pressure of CO₂. This implies that the activity coefficient of CuO_0.5 in Na₂CO₃ slag is lowered rapidly as the partial pressure of CO₂ is diminished. Furthermore, a relation has been discussed between the oxygen partial pressure calculated from the oxygen content in the bulk of molten copper which can be determined experimentally and that at the slag-metal interface which regulates essentially the distribution ratios of Sb and Cu.