Appropriate Oxidizing Conditions of Chromite with Molten Sodium Salts

Abstract

In order to investigate the appropriate oxidizing conditions of chromite with rnolten salts, several chromites were treated with NaOH-NaNOs molten salts under various, conditions of temperature (300N700eC), time and atmosphere.
It was found that the Cr203 component in the chromite was oxidized to chromate by the reaction (1) below ca. 400C, and by the reaction (2) above 4000C.
Cr203 + 4 NaOH + 3 NaNO3 = 2 Na2CrO + 3 NaNO2 + 2 H20 (1)
5Cr20s + 14 NaOH +6NaNO3 =10 Na2CrO4 +3N2 +7H20 (2)
The appropriate conditions are shown below: ratio of sodium equivalent to Cr20s was about4.0, oxidant equivalent ratio, 1.ONI.3, reaction temperature, 450.v6000C, and reaction time, IN3 hrs. ln these conditions, a high degree of oxidation, more than 90%, was observed. There was no remarkable difference in reactivity among several chromites, and the change of atmosphere did not affect the degree of oxidation.