Leaching of Valuable Elements from the Waste Chromite Ore Processing Residue: A Kinetic Analysis

The efficacious treatment and resource utilization of the chromite ore processing residue (COPR) is important for chromate salt production. In this study, the leaching of valuable elements from the waste COPR was investigated. X-ray diffraction (XRD) analysis showed that the COPR mainly contained periclase (MgCr₂O₄), magnesiochromite ((Fe, Mg) (Cr, Fe)₂O₄), Fe (Cr, Al)₂O₄, and MgFeAlO₄. The optimum parameters for COPR leaching were as follows: mechanical ball-milling time of 120 min, sulfuric acid concentration (w/w % H₂SO₄) of 60%, reaction temperature (T) of 403 K, liquid-solid ratio (L/S) of 8 mL/g, and reaction time (t) of 6 h. Under these conditions, the valuable components such as Fe, Al, and Cr were extracted with an ideal leaching efficiency of 94.8, 75.1, and 76%, respectively. The results of the leaching kinetics analysis indicated that the leaching of Fe and Cr from the COPR was controlled by a surface chemical reaction, and the leaching of Al was controlled by diffusion through a product layer. The apparent activation energy of the leaching of Fe, Cr, and Al was calculated to be 23.03, 44.15, and 17.54 kJ/mol, respectively. It is believed that this approach has potential applications for the chromate salt industry because of its advantage of ideal leaching efficiency.