Activities in NaO sub 0.5 -CO sub 2 -AsO sub 2.5 slag and estimation of distribution ratio of arsenic between the slag and molten copper

A principle was established to estimate the equilibrium distribution ratio of the impurity element X between NaO sub 0.5 -CO sub 2 XO sub v/2 slag (v: the valence of X) and molten Cu defined by {(mass% of X in slag)/[mass% of X in metal]}, over a wide range of the slag composition as a function of partial pressures of CO sub 2 and oxygen. Based on the principle, the following measurements on NaO sub 0.5 -CO sub 2 -AsO sub 2.5 slag were conducted to estimate the distribution ratio of arsenic. Activity measurement of NaO sub 0.5 ; activities of NaO sub 0.5 in the slag were determined by the EMF method using beta "-alumina as a solid electrolyte over the composition range of 1 > N > =0.8{N=n sub NaO0.5 /(n sub NaO0.5 +n sub AsO2.5 ), n: the number of moles} under the partial pressures of CO sub 2 of 0.001-0.08 MPa at 1423-1523K. Activity measurement of AsO sub 2.5 ; activities of AsO sub 2.5 could be calculated from the activities of NaO sub 0.5 by integrating the Gibbs-Duhem relation. Activities of AsO sub 2.5 as the initial values of the integration were determined by the distribution equilibrium measurements of arsenic between the slag and molten copper. From the obtained results, together with the solubility data of CO sub 2 in the slag reported in the previous study, the equilibrium distribution ratio of arsenic was successfully calculated over the composition range of 1 > N > =0.8 as a function of partial pressures of CO sub 2 and O at the temperatures of 1423 and 1523K. The calculated distribution ratio of As has a considerably large value and increases with increasing the value of N. The higher O partial pressure and the lower CO sub 2 partial pressure and the lower temperature are more preferable for the removal of As from molten Cu.