Manganese residue harmlessness with the combination of manganese mineralizing microbes, CaO and CO_₂

Manganese residue, including electrolytic manganese residue (EMR) and electrolytic manganese dioxide residue (EMDR), have complicated compositions and are easily generated heavy metals (HMs) and ammonia nitrogen (NH₄⁺-N) pollution. In this study, HMs and NH₄⁺-N in manganese residue were stabilized and solidified using a combined remediation system of quicklime (CaO), carbon dioxide (CO₂), and manganese mineralizing microbes. The sequencing of the manganese mineralizing microbes assemblage revealed that Pseudomonas geniculata, Leclercia adecaarboxylata, Ochrobactrum spp., and Delftia tsuruhatensis comprised the majority of the assemblage species. Moreover, the manganese mineralizing microbes that were identified by screening and isolation exhibited significant metal resistance, metal absorption, and metal detoxifying abilities according to KEGG pathway level 2 analysis. The NH₄⁺-N levels in the manganese residue across all treatments exhibited a downward trend, meanwhile NH₄⁺-N in the manganese mineralizing microbes treatment groups were all lower than the GB standard (GB8979–1996). The findings of the experiment indicated that when manganese mineralizing microbes (1 % M), 0.2 L/min CO₂ flow, and a carbonization time of >15 min were added, the greatest effect of the addition of the innocuous manganese residue was obtained. The innocuous manganese residue exhibited agglomeration and may be utilized as a filler material, according to the XRD, SEM, and EDS results. In this study, manganese mineralizing microbes, CaO and CO₂ treated HMs and NH₄⁺-N in manganese residue, achieving general industrial solid waste standards, demonstrating potential for large-scale harmless treatment. Copyright © 2025 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.