Hydrogen-based mineral phase transformation mechanism investigation of pyrolusite ore

Pyrolusite comprise as the foremost manganese oxides and a major source of manganese production. Application of an innovative hydrogen-based mineral phase transformation technology to pyrolusite is proposed, where 96.44% distribution rate of divalent manganese(Mn²⁺) at an optimum roasting temperature of 650 °C, a roasting time of 25 min, and an H₂ concentration of 20 at.% was observed, at which time the manganese existed predominantly in the form of manganosite. This study investigated the generation mechanism of manganosite from the viewpoint of reduction kinetics, phase transformation and structural evolution of pyrolusite, indicating that the high temperature contributes toward improvement of the distribution rate; while the optimal kinetic model for the reaction the A_3/2 model of random nucleation and subsequent growth with an activation energy (E) of 24.119 kJ·mol^-1 and a pre-exponential factor A of 0.03229 s^-1. Throughout the process of mineral phase transformation, the manganese oxide from the outer layer of particles to move inward to the core. In addition, pyrolusite follows the reduction sequence of MnO₂→Mn₂O₃→Mn₃O₄→MnO, and the reduction of manganese oxides in each valence state proceeds simultaneously. The findings provide a significant insight into the efficient and clean utilization of pyrolusite.