The influence of basicity on the solubility of platinum in oxide melts
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I.
III.
INTRODUCTION
IN a previous article,[1] the authors reported the solubility of platinum in several oxide fluxes. The solubility of platinum has been found to increase with increasing content of basic oxide, suggesting that it may be a good indicator of the basicity of highly basic fluxes. Platinum exists in highly basic fluxes as a platinate ion. An investigation of the dependence of the solubility of platinum on oxygen partial pressure and of the relationship between the solubility of platinum and other refining indexes, such as carbonate, sulfide, and phosphate capacities, has shown that the ionic form of platinum in highly basic fluxes is PtO22 2 . Then, the reaction of platinum oxidation and dissolution of platinum into basic fluxes can be written as follows: Pt (s) 1
1 O (g) 1 (O22) 5 (PtO222) (in flux) 2 2
[1]
On the basis of those results, the purpose of this study is to seek a measure of the basicity of highly basic fluxes containing transition metal ions and to clarify the chemical properties of fluxes by investigating the solubility of platinum as a function of the flux composition in BaO-MnOx, BaO-CuOx, KO0.5-SiO2, and NaO0.5-PO2.5 melts. The correlation between the solubility of platinum and the phosphate capacity for a CaOsatd-SiO2-FeOx melt, simulating an industrial converter slag, has been investigated. In addition, the variation of chemical behavior of the platinum in molten fluxes with varying the flux composition has been examined. II.
EXPERIMENTAL PROCEDURE
The experimental procedure for solubility of platinum is similar to that described elsewhere.[1]
RESULTS AND DISCUSSION
A. Solubility of Platinum in Molten Fluxes as a Measure of Basicity 1. Dependence of the solubility of platinum on the flux composition In Figure 1, the solubility of platinum at 1873 K in the BaO-MnOx and BaO-CuOx melts in air is plotted as a function of the BaO content on a molar basis, together with the previously reported results for the BaO-Al2O3 melt.[1] The solubility of platinum in these melts increases with increasing content of BaO, and for any particular BaO content, the BaO-CuOx melt has the highest solubility followed by the BaO-MnOx melt and then the BaO-Al2O3 melt. The solubility is very high, indicating that they are very basic and could have a strong refining capacity for manganese or copper containing alloys. The results of the investigation of the valences of manganese and copper in these fluxes are listed in Table I. As may be seen in Table I, the valences of manganese and copper in these fluxes are essentially Mn3+ and Cu+, respectively. 2. Correlation between the solubility of platinum and the phosphate capacity for the CaOsatd-SiO2-FeOx melt, simulating an industrial steelmaking slag The experimental results suggest that the solubility of platinum may be a good indicator of the basicity of highly basic fluxes containing transition metal ions. Then, the application of the solubility of platinum to the CaOsatd-SiO2FeOx melt, simulating an industrial steelmaking slag, was attempted, and th
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