Integrated magnetic separation and H2O2-H2SO4 synergistically leaching for high-purity MnSO4 production from EMR

Electrolytic manganese residue (EMR), a highly acidic solid waste generated during electrolytic manganese metal (EMM) production, is produced in massive quantities and contains recoverable manganese. However, due to its encapsulation within a dense silicate–gypsum framework, conventional leaching methods often suffer from low efficiency. Long-term stockpiling also poses serious environmental risks such as toxic metal leaching. To address these challenges, an integrated process chain combining wet high-intensity magnetic separation and H₂SO₄/H₂O₂ synergistic leaching was developed. Under optimized grinding conditions (5 min, −74 μm accounting for 84.68 %) and a magnetic field strength of 1.6 T, the manganese grade increased from 5.86 wt% to 18.24 wt%, with a recovery rate of 83.3 % and tailings Mn content reduced to 0.98 wt%. Subsequently, leaching under 2.5 mol L −1 H₂SO₄, twice the stoichiometric amount of H₂O₂, at 60 °C for 2 h yielded a Mn leaching efficiency of 92.87 %. Kinetic analysis indicated that leaching was jointly controlled by interfacial reaction and product layer diffusion during the first 100 min, then shifted to diffusion-dominated behavior between 100 and 180 min. XRD, FTIR, and SEM–EDS characterization revealed that H₂O₂ not only reduces MnO₂ to soluble Mn 2+ , but also induces the formation of rod-like CaSO₄·0.5H₂O and colloidal SiO₂ via exothermic reactions and bubble agitation, resulting in a loose filter cake structure and improved filtration performance. After stepwise impurity removal via neutralization and MnF₂ precipitation, the final MnSO₄·H₂O crystals meet Grade I metallic-impurity limits of HG/T 4823–2023. This study presents a technically feasible and environmentally friendly approach for the efficient recovery of manganese from EMR, offering valuable insights into the integrated resource utilization of metallurgical solid waste and the production of battery-grade manganese sulfate. This process offers a scalable and cost-effective route for the green recovery of Mn and aligns with circular economy goals.