Cobalt regulation biocathode with sulfate-reducing bacteria for enhancing the reduction of antimony and the removal of sulfate in a microbial electrolysis cell simultaneously.

Antimony (Sb) contamination in water resources poses a critical environmental and health challenge globally. Sulfate reducing bacteria (SRB) are employed to reduce SO to S for removing Sb in a microbial electrolysis cell (MEC). Yet, the reduction efficiency of reducing SO and Sb(V) through SRB remains relatively low, and the underlying mechanism remains elusive. Herein, the MEC reactor modified with Co-based or Fe-based MOF materials was served to enhance the electron transfer between the aqueous environment and the microorganisms to enhance the operational efficiency of the bio-electrochemical system (MEC-SRB). This study highlights the central role of removal efficiency as a critical performance metric and its direct correlation with material properties and mechanisms. The results demonstrate that the ZIF-8@Co electrode significantly outperformed other materials, achieving 98.7% sulfate and 93.1% total Sb removal over multiple cycles. Electrochemical analysis revealed that the superior performance of ZIF-8@Co electrode is attributed to rapid electron transfer and low electronic impedance. The charge transfer resistance of the ZIF-8@Co group was 155 Ω, significantly lower than that of the ZIF-8@Fe group (1724 Ω) and the ZIF-8@CoFe group (427 Ω). These findings demonstrate that the material's ability to facilitate electron transfer directly governs the pollutant removal efficiency. Fluorescence analysis revealed that the ZIF-8@Co electrode supported a denser biofilm and enhanced microbial activity. Mechanistic studies confirmed that Sb(V) was reduced and deposited as SbS precipitate, which was further characterized and analyzed by methods such as XRD and XPS. This research elucidates the potential and underlying mechanisms of an electrically stimulated SRB bio-electrochemical system for effective Sb-containing wastewater treatment. Our findings provide crucial insights for developing high-efficiency, sustainable remediation technologies for heavy metal contamination, with significant potential for real-world application in water treatment and environmental protection.