Resource Utilization of the Electrolytic Manganese Residue in Unfired Bricks: Pretreatment, Strength Enhancement, and Microwave Absorption Properties

The long-term accumulation of electrolytic manganese residue leads to pollution issues related to NH4+–N and Mn2+. Although various methods exist to address the pollution caused by NH4+–N and Mn2+, existing hazard-free treatment methods do not consider the subsequent utilization of the electrolytic manganese residue. Meanwhile, resource recovery methods face challenges due to the complex salt structures present in electrolytic manganese residue. This study introduces BaCO3 to achieve the phase reconstruction of the complex salt structure. The results indicate that the addition of BaCO3 effectively promotes the reconstruction of complex salt structures. The leaching toxicities of C(NH4+–N) and C(Mn2+) are reduced to 12.36 mg·L–1 and 0.86 mg·L–1. Furthermore, the processed electrolytic manganese residue finds applications as an additive in the production of unfired bricks. Additionally, the unfired bricks prepared with the incorporation of a reconstructed electrolytic manganese residue exhibit electromagnetic shielding capabilities. Specifically, when the mass ratio of cement to residue is 2:1, the minimum reflection loss value of the unfired bricks reaches −23.45 dB. Finally, the mechanism of late-stage strength enhancement in the unfired bricks was discussed. This study proposes a method for achieving environmentally friendly and sustainable resource utilization of electrolytic manganese residues through pretreatment.