Antagonistic Effects of Anthraquinone-2,6-Disulfonic Acid Sodium Salt and Biochar Matrix on Shewanella oneidensis MR-1 Mediated Cr(VI) Reduction

• • Biochar matrix and AQDS individually enhance Cr(VI) bioreduction by S. oneidensis MR-1, but their combination exhibits antagonism, reducing removal efficiency compared to single amendments. • • The antagonistic effect is attributed to increased repulsive forces between the biochar-AQDS complex and bacterial cells, which inhibit electron transfer to Cr(VI) during the fast reduction phase. • • The study highlights the importance of considering co-existing e-DOM when applying biochar for Cr(VI) remediation, as interactions can negate expected benefits. • • Findings provide mechanistic insights into biochar's environmental fate and its impact on microbial electron transfer processes, informing risk assessment for biochar-amended soils.