Co-treatment of chromite ore processing residue and pyrolusite for simultaneous detoxification and resource utilization

Efficient and low-cost recovery of metals from pyrolusite and Chromite Ore Processing Residue (COPR) is of great significance for environmental protection and sustainable development of metal resources. This study proposes a new method for the simultaneous recovery of Cr and Mn from COPR and pyrolusite, to realize COPR and pyrolusite resource utilization and detoxification. Under the optimal conditions (i.e., the temperature of 150 ℃, the holding time of 1.5 h, the H2SO4 concentration of 3 M, the mass ratio of COPR to pyrolusite of 1:1, and the solid-liquid ratio of 1:20), the leaching efficiency of Cr and Mn reached 99.56% and 85.34% respectively. The Toxicity Characteristic Leaching Procedure (TCLP) total Cr concentration of the detoxified slag was 0.26 mg/L meeting the EPA standard (＜5 mg/L). The reaction mechanism was elucidated based on thermodynamics, kinetics, and mineral characterization. In addition, a high-quality utilization strategy was proposed, leaching solution to prepare manganese carbonate and sodium chromate, and the detoxified slag can be used for steel smelting. In brief, this method has good economic benefits and provides a new reference for the resource utilization of hazardous waste. [Display omitted] •A novel way to recovery of Cr and Mn from COPR and pyrolusite.•This strategy realizes both detoxification and resource utilization of COPR and pyrolusite.•The leaching efficiency of Cr and Mn reached 99.56% or 85.34%, respectively.•The chromite and MnO2 structure can be destroyed under hydrothermal treatment with H+.