Distribution Equilibria of Arsenic and Antimony between Na<SUB>2</SUB>CO<SUB>3</SUB>–Na<SUB>2</SUB>O–SiO<SUB>2</SUB> Melts and Liquid Copper

Abstract

Following the previous report on phase equilibria between Na2CO3–Na2O–SiO2 melts and liquid copper, the distribution equilibria of arsenic and antimony have been investigated at 1523 K to investigate the optimum conditions for removal of these detrimental elements from copper by use of soda flux. The obtained results were explained by the terms of oxygen potential and soda-ratio in slag, and iso-bars of the distribution ratios were illustrated on the ternary diagram of (Na2CO3+Na2O)–SiO2–Cu2O. The increase in oxygen potential or in basicity of slag results in high removability of these elements. Tri-valent arsenic or antimony is common in the slag with low soda ratio, but penta-valent becomes predominant as the basicity of slag or oxygen potential increases. Pentavalent is more stable for arsenic than for antimony, and bring about drastic variations in the distribution ratio. Sodium carbonate melt under high oxygen potential represents high removability of arsenic and antimony with rather small dissolution of copper. Basic sodium silicate slag has also high removability of these detrimental elements, but copper content in slag is too high under high oxygen potential. High distribution ratio of arsenic and antimony is also observed for Cu2O slag containing 10 to 20% Na2O.