Upcycling waste battery slag into amorphous metal sulfide via microbial-induced corrosion for efficient flue gas Hg⁰ removal

The extensive use of lithium-ion batteries (LIBs) has led to substantial generation of sulfate-rich waste battery slag (WBS), posing environmental risks and disposal challenges. In this work, a microbiologically induced corrosion (MIC) approach using sulfate-reducing bacteria was developed to upcycle battery-derived sulfate wastes into amorphous iron sulfide sorbents for efficient gaseous Hg⁰ removal. Comprehensive characterizations reveal that microbial activity profoundly restructures the slag surface, creating abundant sulfur vacancies and under-coordinated Fe centers. Experimental mercury temperature-programmed desorption (Hg-TPD) coupled with density functional theory (DFT) calculations confirm that these defect-rich sulfur sites possess strong and selective binding affinities toward Hg⁰. Techno-economic analysis highlighted the MIC process's advantages in terms of lower energy consumption, reduced carbon emissions, and improved economic viability relative to conventional sorbent-synthesis methods. This work not only elucidates fundamental mechanisms underlying microbial transformation of sulfate-rich wastes, but also establishes a promising, sustainable microbial approach for environmental remediation and energy-related applications.