Clean preparation of chromium oxide (Cr 2 O 3 ) from low-grade indigenous chromite ore for use as paint pigment

Chromic oxide (Cr2O3) is one of the most important chromic salts, with extensive commercial uses. Traditionally, Cr2O3 is produced from chromium trioxide (CrO3) or sodium dichromate (Na2Cr2O7), both sourced from chromite ore. Traditional manufacturing methods, on the other hand, are time-consuming, inefficient, and energy-intensive, and they can significantly harm the environment by emitting large volumes of solid waste containing Cr in the form of Cr(VI) compounds. As a result, the chromic oxide industry is particularly focused on establishing an environmentally friendly manufacturing process. This study investigated a novel method for generating Cr2O3 without damaging the environment with hexavalent chromium. In this innovative approach, 97% of the total Cr in the form of potassium chromate (K2CrO4) and Fe are leached from a Nigerian chromite ore with potassium hydroxide. This technique yielded Cr2O3 with a purity of up to 99.3%. Throughout the operation, Cr was only present in the form of Cr(III), eliminating pollutants caused by hexavalent Cr and achieving environmentally friendly Cr2O3 production. The hydrothermal reduction method produces CrOOH, which is subsequently calcined at 900°C to provide Cr2O3.