Thermochemical nature of minor elements in copper smelting mattes
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~XFe, M e = A s o r S b
and
log ysA~=~= 1.35 - 0.848Xcu~s log ~ = o
= 2.11 - 0.841Xcu2s
Psi approaches unity in white metal to 0.94 and 0.93 for As and Sb, respectively, at a C u / F e ratio of 2.5. The above equations can only be applied to copper-rich mattes deficient in sulfur. At C u / F e ratios below 2.5, the physicochemical character of the matte changes as the FeS molecules become the predominant species in the matte. In analyzing the data, it was necessary to evaluate the interaction parameters eSgs, pSs, a n d pSAsAS, which have been found to have values of 11.7, - 2 7 . 4 , and 11.6, respectively.
I.
INTRODUCTION
C O P P E R concentrates contain a number of minor elements among which As, Sb, and Bi must be limited in the final product to ensure its commercial viability. Arsenic forms Cu3As particles in annealed copper and can reduce the electrical conductivity of the metal by 23 pct at an arsenic content of only 0.1 wt pct Bismuth in copper at a concentration of 0.001 wt pct renders the host metal brittle, and both antimony and arsenic raise the recrystallization temperature of copper. [L2~ During smelting, most of the As, Sb, and Bi is usually eliminated by volatilization and slagging during the roasting, smelting, and converting processes. Although considerable work has been conducted in evaluating the behavior of minor elements during smelting, the thermochemical behavior of those elements in matte and slag are not fully understood. Since copper concentrates are becoming increasingly impure, it is essential to elucidate the thermodynamic nature of As, Sb, and Bi in order to
D.C. LYNCH and W.G. DAVENPORT, Professors, are with the Department of Materials Science and Engineering, University of Arizona, Tucson, AZ 85721. S. AKAGI, Process Engineer, is with the Saganoseki Smelter. and Refinery, Nippon Mining Company, Saganoseki, Ohita 879-22, Japan. Manuscript submitted August 8, 1990. METALLURGICAL TRANSACTIONS B
establish effective ways of eliminating those impurities during smelting. Accordingly, in the present investigation, the authors have evaluated the activity of As, Sb, and Bi in both matte and white metal. Extensive use is made of data already in the literature. [3-271 The results obtained in this investigation are compared and reconciled with that data. For the sake of brevity, a review of the earlier studies is presented in the discussion, where the results of those works can be critically evaluated and compared with the results of the present investigation. II.
EXPERIMENTAL
The equilibrium distribution of As, Sb, and Bi between molten copper and white metal has been investigated using a static distribution technique.
A. Materials Reagent grade materials with 4 to 5 nines purity were used throughout this investigation. The phases were prepared from copper metal (shot and powder) and copper sulfide (CUl 8S), which were mixed in such proportions to yield 1 g of white metal and 1 g of copper. Arsenic, antimony, and bismuth, in their metallic state, were added to the admixtures such tha
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