Antagonistic Effects of Anthraquinone-2,6-Disulfonic Acid Sodium Salt and Biochar Matrix on Shewanella oneidensis MR-1 Mediated Cr(VI) Reduction
Chromium is a common environmental metal pollutant. Shewanella oneidensis MR-1 can generate extracellular electrons, facilitating the reduction of Cr(VI) to Cr(III), thereby mitigating its toxicity. Both biochar and electroactive dissolved organic matter (e-DOM) regulate extracellular electron transfer during Cr(VI) bioreduction. In practice, surface DOM on biochar can detach and enter the environment, while the biochar matrix (BCM) remains the predominant form and coexists with e-DOM. However, the combined effects of BCM and e-DOM on microbial Cr(VI) removal are unclear. This study investigated the individual and combined impacts of biochar matrix and AQDS (a model e-DOM) on Cr(VI) reduction by S. oneidensis MR-1. Results showed that biochar matrix or AQDS alone promoted Cr(VI) removal, primarily by accelerating electron transfer during the fast reduction phase. However, when both were added, an antagonistic effect was observed, attributed to increased repulsive forces between the biochar matrix-AQDS complex and the bacterial cells, which inhibited electron transfer to Cr(VI). This research elucidates the electrochemical interactions between biochar matrix and e-DOM, providing a theoretical basis for biochar applications in environmental remediation and risk assessment.