SYNERGISTIC DISSOLUTION OF OXIDES IN MOLTEN SODIUM-SULFATE

The dissolution kinetics of pure Cr2O3 and pure Fe2O3 powders, respectively, into Na2SO4, were each measured and compared with those for the same oxides during simultaneous dissolution of the mixed oxide powders in the same environment. For dissolution of mixed oxides, accelerated kinetics for each oxide resulted from an acid-base coupling reaction. Measurements of the changes in the Na2O and oxygen activities in the melt during oxide dissolution suggest that the dissolution reaction for the single oxides is controlled by the diffusion of SO3 (as S2O72−). Therefore, the enhanced dissolution kinetics for mixed oxides is interpreted in terms of a synergistic reaction to promote this diffusion step. © 1990, The Electrochemical Society, Inc. All rights reserved.