Process Design–Physicochemical Relationships in Mn3O4 Oxidative Synthesis from Industrial Mn2+ Solutions

The scalable production of Mn3O4 is critical for sustainable metallurgy, yet the role of process design in its formation remains underexplored. This study examines the synthesis of Mn3O4 from industrial-grade MnCl2·4H2O via wet oxidative precipitation and dry thermal routes, focusing on oxidation mode, oxidant dosage, and additive effects. Wet methods yield phase-pure hausmannite, whereas the dry route introduces minor secondary phases due to nonuniform oxidation. Oxidation mode is identified as the dominant factor controlling particle formation: concurrent in-situ oxidation promotes rapid nucleation, producing ultrafine particles with narrow distribution, higher crystallinity, and lower lattice strain indicative of uniform growth. Additives such as PEG improve dispersion but play a secondary role. BET analysis confirms mesoporous structures with type IV isotherms and H3 hysteresis, arising from aggregation. These findings highlight nucleation-stage control as a key for Mn3O4 tuning, providing a process-oriented framework for its scalable production as a promising precursor for next-generation battery and electrochemical energy applications.