Highly efficient CO mineralization: Mechanisms and feasibility of utilizing electrolytic manganese residue as a feedstock and implementing ammonia recycling.

Electrolytic manganese residue (EMR) and CO emissions from the electrolytic manganese metal (EMM) production process present significant challenges to achieving cleaner production within the industry. Given the high capacity for CO sequestration and the stability of the sequestered forms, CO mineralization methods utilizing minerals or industrial residues have garnered considerable research interest. The efficacy of such methods is fundamentally dependent on the properties of the materials employed. EMR, due to its calcium sulfate dihydrate (CaSO·2HO) content, possesses an intrinsic potential for CO solidification. In this study, we propose a novel method for CO mineralization utilizing EMR, coupled with NH·HO recycling. Experimental results indicated that under conditions of a reaction temperature of 55 °C and a pH of approximately 8, each ton of EMR can sequester 0.16 t of CO, with equilibrium achieved within 10 min. The mineralization mechanism was elucidated using SEM, TG curves, and XRD analyses, which revealed that Ca ions are initially leached from CaSO·2HO in the EMR, subsequently precipitating with CO ions to form CaCO. This CaCO layer effectively covers the surface of CaSO·2HO, inhibiting further Ca release and stabilizing the reaction equilibrium. Furthermore, the ammonia in the solution is regenerated into NH·HO, facilitating its reuse and preventing secondary pollution. The utilization of EMR for CO mineralization not only mitigates carbon emissions in the EMM production process but also promotes environmentally sustainable practices in the industry. This study highlights a promising pathway towards achieving carbon neutrality and cleaner production in electrolytic manganese production.