A thermodynamic study of silica-saturated iron silicate slags in equilibrium with liquid copper
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I.
Pt, Ni-NiO/O=/slag-Cu(1), Cr203, Pt
INTRODUCTION
IRON silicate slags have practical importance in the pyrometallurgical production of copper. Much interest has been shown in the solubility of copper in these slags. Because of their aggressiveness toward container materials, many available data have been obtained only under limited conditions. Ruddle et al I and Toguri and Santander 2 used silica and alumina crucibles, respectively, and obtained the solubility of copper in slags in equilibrium with metallic copper or copper-gold alloys against oxygen pressure in the gas phase above the melt. Taylor and Jeffes 3 determined the activity of cuprous oxide in iron silicate slags by a levitation melting technique to avoid container contamination. Eguchi et a l 4 obtained the solubilities of copper in the silica-saturated iron silicate slag coexisting with liquid copper (or Cu-Ag alloy) and white metal. In the above studies, the oxygen activity was measured as a function of slag composition using CO-CO2 gas mixtures or SO2 gas. The present authors s have used solid electrolyte galvanic cells for the measurement of oxygen partial pressure over iron silicate slags in equilibrium with solid silica using a silver bath to avoid corrosion of the zirconia solid electrolyte. The objective of this investigation was to determine the solubility of copper in silica-saturated iron silicate slags and other thermodynamic properties as a function of oxygen pressure by an electrochemical method using a zirconia solid electrolyte galvanic cell. II.
Pt, Fe-FeO/O=/slag-Cu(Fe sat.), Fe. (II) Figure 1 illustrates the cell arrangement. The cell, consisting of a ZRO2-9 or 15 mol pct MgO solid electrolyte tube (9 mm OD and 7 mm ID) made by Nippon Kagaku Togyo Company, Ltd., Japan, and Zirconium Corporation of America, Solon, Ohio, contained mixtures of nickel and nickel oxide powders (iron and iron oxide mixtures for the slag saturated with iron and silica) as a reference electrode. The spiral end of a platinum wire was pushed into the reference electrode, good contact being thus obtained between the reference electrode and the electrolyte. The zirconia solid electrolyte tube was doubly covered by opaque silica tubes to avoid direct contact with slags. The electrical lead dipped in the melt was made from Cr203. After mixing with a small amount of water, the Cr203 powder and a platinum wire were placed into an alumina protection tube which was then sintered at 1400 K for 7 ks before use. This alumina tube was also doubly covered by
1 M u l l i t e reaction tube 2
Pt-Pt.13Rh thermocouple
3
Pt l e a d
4
Alumina
5
A l u m i n a crucible
6
Silica crucible
Emf measurements employing solid electrolyte were made on the following galvanic cells in the temperature range from 1490 to 1580 K:
8
ZrO2-MgO
9
Silica
as
protection
tube
10
Molten s l a g
11
Reference
electrode
1 2 Cr20 3 13 Zirconia solid electrolyte 14
METALLURGICALTRANSACTIONS B
protection tube
7 A l u m i n a cement
EXPERIMENTAL
TOSHIO OISHI, ResearchAssociate
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