| Autor: |
Rodenas, Luis García, Morando, Pedro J., Blesa, Miguel A., Duhalde, Stella, Saragovi, Celia |
| Zdroj: |
Canadian Journal of Chemistry; May 1993, Vol. 71 Issue: 5 p771-778, 8p |
| Abstrakt: |
A mixed Fe,Cr oxide formed of maghemite and chromium hydrous oxide was prepared by oxidative precipitation at 90 °C. Mineral acids dissolve the chromium phase very quickly, whereas iron dissolves slowly and independently; there is little mutual influence in the dissolution behaviour. Calcination of this oxide at 600 °C yields a mixture of α-Fe2O3and Cr1.3Fe0.7O3that leaches iron slowly upon acid attack. The reactivity of the oxide towards H+is largely determined by the degree of crosslinking of the Cr-containing phase. Oxidative attack (by KBrO3) increases the rate of dissolution of both Cr and Fe, against simple expectations that Fe dissolution rates might be reduced. This effect is of importance in chemical cleaning and decontamination of stainless steels. This influence of acidity and [BrO3−] are interpreted in terms of the formation of surface ≡Cr(III)-O-Br(V) species that evolve to produce Cr(VI)aq. These surface complexes form more readily than analogous solution species, making surface Cr(III) more readily oxidizable than aqueous (Cr(III). |
| Databáze: |
Supplemental Index |
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