It is well known that P
2O
5 and Na
2O have strong surface active effect in the molten oxide systems and affect the rate of oxidation or reduction of melts. In the previous work, the effect of P
2O
5 addition on the rate of CO
2 dissociation on the surface of FeO
x (FeO and Fe
2O
3)-based molten oxides was investigated by isotope exchange technique and it was confirmed that P
2O
5 strongly disturbs CO
2 dissociation. In the present study, the effect of Na
2O addition on the rate of CO
2 dissociation on the surface of FeO
x-Na
2O and FeO
x-SiO
2-Na
2O (mol%FeO
x : mol%SiO
2=65 : 35) melts was measured at 1773 K with
PCO2/
PCO=1 by isotope exchange technique. Reaction rate constant drastically increased with increasing Na
2O content for the FeO
x-Na
2O system. On the other hand, rate constant gently increased for the FeO
x-SiO
2-Na
2O system. The Fe
3+/Fe
2+ ratio of each system also slightly increased.
To estimate the rate constant from the composition of melts, the relationship between the rate constant and the Fe
3+/Fe
2+ ratio for the FeO
x-CaO-SiO
2 system was also investigated. From the comparison of the estimated and observed rate constants, the strong promoting effect of Na
2O for CO
2 dissociation was confirmed in the FeO
x-Na
2O system.
The surface active effect of Na
2O was analyzed by “smoothed surface potential model”, and the nature of molten oxide was discussed. From the obtained values, the surface tension of the molten oxide was estimated as a function of Na
2O concentration.
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