Decomposition of chromite ore by oxygen in molten NaOH–NaNO3

An optimized process production of chromate by oxygen was proposed. The tests are executed by introducing NaNO3 to the decomposition process of chromite ore in molten NaOH to decrease the decomposition temperature. An interesting result is that the reaction temperature could decrease from above 500 °C to about 400 °C, and sodium nitrate has no consumption in the oxidation process, while the Cr yield is above 99%. Mechanism analysis shows that chromite ore is firstly oxidized by NaNO3, where NaNO2 is generated as a reduction product, and then is oxidized to NaNO3. NaNO3 plays the role of oxygen carrier, which can reduce the mass transfer resistance of oxygen. The kinetic study shows that the decomposition process was an internal diffusion controlled, with an apparent activation energy of 106 kJ/mol. Effects of liquid-to-ore ratio, chromite ore particle size, and reaction temperature on the decomposition of chromite ore were also studied.