The Rate of Arsenic and Antimony Elimination from Molten Copper by the Use of Na2CO3 Slag

Abstract

The rate of As elimination from molten copper by the use of Na 2 CO 3 slag was measured at 1523 K. The results obtained un der the present experimental conditions show that As in molten copper is eliminated in a penta_ valent form and that its elimina tion rate increases with increasing initial oxygen concentration in molten copper. Based on the results obtained in the present study, the overall rate of As elimination is considered to be controlled by mass transfer in molten copper. The mass_ transfer coefficient of As in molten copper at 1523 K was determined to be 1.3 (}0.4)~10 |4 mEs |1 based on the mass balances of As and oxygen in the molten copper and slag phases and the equilibrium relation of the As elimination reaction at the slag_ metal inter face. In addition, the behavior of the simultaneous elimination of As and Sb which coexist as impurities in molten copper at 1523 K were also investigated from the kinetic viewpoints. The results obtained show that the elimination rate of As is much faster than that of Sb, and two types of elimination behaviors are observed, depending on the initial oxygen concentration in molten cop per, i.e. at relatively low initial oxygen concentration, As being preferentially eliminated with stagnation of the Sb elimination, while both elements being simultaneously eliminated at relatively high initial oxygen concentration. These behaviors were ex amined from the viewpoint of the oxygen concentration at the slag_ metal interface during the process.