A critical review of electrolytic manganese residue treatment technologies: Opportunities, challenges, and pathways...

Electrolytic manganese residue (EMR), an acidic solid waste rich in mobile Mn ions and NH₄⁺-N generated during manganese metal production, poses significant ecological threats due to its massive stockpiling and long-term accumulation. Toward sustainable EMR management, this review establishes a hierarchical analytical framework and provides a systematic and critical assessment of three strategic pathways: source reduction, harmless treatment, and resource utilization. Source reduction through ore beneficiation and process optimization is fundamentally constrained by the depletion of high-grade resources and the inherent trade-off between metal recovery efficiency and concentrate grade, leaving limited room for further improvement. Harmless treatment technologies (such as washing and stabilization/solidification) can effectively remove or stabilize pollutants but face persistent challenges related to secondary pollution risks and insufficient long-term environmental stability under dynamic field conditions. Resource utilization (via recovery of valuable components, production of construction materials, or synthesis of functional materials) represents the most viable pathway for large-scale EMR disposal, yet it is hindered by techno-economic feasibility constraints, inconsistent product performance, and low market acceptance. The core scientific challenge identified in this review is the coupled migration and transformation behavior of Mn ions and NH₄⁺-N, which underpins most technical limitations across all treatment stages. Future breakthroughs will depend on transformative paradigm shifts: the development of intelligent monitoring systems to ensure long-term stability, the establishment of cross-industry ecological chains to enable synergistic valorization, and the implementation of classification-based precision processing systems tailored to the compositional heterogeneity of EMR. This work provides a systematic reference for researchers to identify critical bottlenecks and prioritize future technological advancements in sustainable EMR management.