Production and Characterization of Chromium Oxide (Cr2O3) via a Facile Combination of Electrooxidation and Calcination

To synthesize Cr 2 O 3 from ferrochromium, the electrolysis of ferrochromium in an electrolyzing cell and the properties of Cr 2 O 3 prepared by thermal decomposition of (NH4)2CrO 4 were studied. Experimental results showed that with a 1:5 molar ratio of NH 3 ∙H 2 O:2CrO 4 2- and current density of 140 A/m 2 at room temperature, Cr and Fe can be completely separated by solid-liquid separation, and (NH 4 )2CrO 4 can be obtained. The optimized current efficiency was 62%. The four-step thermal decomposition process of (NH 4 )2CrO 4 was analyzed by TG-DTA. The XRD and FTIR results proved that crystalline Cr 2 O 3 with a fine particle size was obtained. Spherical Cr2O3 with a particle size of 71~216 nm and a specific surface area of 4~38 m 2 /g was confirmed by SEM and BET. UV-Vis results proved that Cr2O3 presented bright green (L*=34.78~49.97, a*=0.91~-14.73, and b*=6.08~17.92), and the forbidden band width was 1.91~2.25 eV. The purity of Cr 2 O 3 was over 99%.