Distribution of nickel between copper-nickel and alumina saturated iron silicate slags
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e activity coefficient of nickel oxide (3'~io) and distribution coefficient of nickel (Ar~i) is calculated to be 0.375 and 233.3, respectively. )'~o and AN~ are found to be independent o f oxygen partial pressures. The presence o f alumina increases the solubility o f nickel in slags.
I.
INTRODUCTION
THE most important
factors contributing to nickel solubility in slags are: temperature, oxygen potential of the slag, and slag composition. The solubility o f nickel in silica saturated fayalite slags in equilibrium with copper-nickel alloys was investigated by Wang et al.~ under controlled oxygen partial pressures (10 -6 to 10-to atm) over the temperature range 1523 to 1623 K. Their results showed that at a constant temperature and constant oxygen pressure, the nickel solubility increases with nickel activity in the alloy. Das and Healy: equilibrated copper-nickel alloys with a ternary Cu20-NiO-SiO2 saturated slags at 1498 K. Their results were correlated using ion-fractions, and the authors suggested that Temkin's method correlates slightly better than the other. A tentative phase diagram o f the Cu20-NiO-SiO2 system at 1498 K was constructed. Taylor and Jeffes3 measured the distribution o f nickel and copper between NiOCuO0.5-FeO-FeO~.5-SiO2 slags in Ni-Cu-Fe alloys. The melts were suspended in an atmosphere o f controlled oxygen partial pressure by the levitation technique. They concluded that solubility o f nickel in slag depends on slag composition (Fe/SiO2 ratio). The solubility o f nickel in alumina saturated fayalite slags is discussed here, with results from a study o f the distribution of nickel between liquid Cu-Ni alloys and slag. The activity coefficient o f nickel oxide in the slag phase over a range o f oxygen pressures (at a fixed temperature) is also discussed.
II.
EXPERIMENTAL
Three gram samples of high-purity copper, alloyed with high-purity nickel, were equilibrated with three grams of pre-melted fayalite slag (Fe/SiO2 = 1.34) in alumina crucibles at a specific partial pressure of oxygen and at 1573 K for 24 hours. The oxygen pressure over the sample was maintained constant by using a mixture of CO and CO2 R.G. REDDY, Assistant Professor, and C. C. ACHOLONU, Graduate Student,are with the Department of Chemical and Metallurgical Engineering, Mackay School of Mines, University of Nevada Reno, Reno, NV 89557-0047. Manuscript submitted August 18, 1983. METALLURGICAL
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gases, at ratios controlled by capillary flow meters. The gas phase flow rate passing over the sample was 600 c m3 per minute. The experimental system had four degrees of freedom. Thus, the system is not unique unless four independent parameters of the slag are specified. These were accommodated by fixing the temperature 1573 K, the Fe/SiOz ratio at 1.34, the oxygen partial pressure at 10-8, 10-9, or 10-t° atm, and the activity o f nickel in the Cu-Ni alloy. For a typical run, the experimental set-up (shown in Figure 1) permitted the introduction o f the crucible containing the charge into the constant temperature zone
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