Magnetic Fe-Mn spinel particle electrodes from red mud-shield slag wastes for 3D electrocatalytic dye degradation

Based on a sustainable "treating-waste-with-waste" strategy, this study fabricates magnetic Fe-Mn spinel particle electrodes from industrial solid wastes-red mud (RM) and shield slag (SS)-for enhanced dye degradation in a three-dimensional electrochemical reactor (3DER). The synergistic use of SS not only serves as a natural ceramic binder, eliminating the need for external additives, but also provides inherent catalytic precursors. The optimized Mn/RSPE in the 3DER system enables complete methylene blue (MB) removal within 240 min, with significantly accelerated degradation kinetics and markedly reduced energy consumption compared to a conventional two-dimensional (2D) system. The performance enhancement is attributed to the in-situ formation of MnFe₂O₄ spinel, which establishes a synergistic Fe/Mn redox cycle promoting hydroxyl radical (·OH) generation via electro-Fenton and microelectrolysis processes, thereby driving sequential N-demethylation and aromatic ring cleavage. Moreover, the Mn/RSPE shows promising cost-effectiveness, high cycling stability (maintaining ≥94.83 % efficiency over ten runs), effective heavy metal immobilization, and convenient magnetic separation, offering an economical and environmentally friendly approach for simultaneous valorization of industrial solid wastes and treatment of refractory organic wastewater.