The Effect and Mechanism of AQDS Promoting Anaerobic Cr(VI) Bio-Reduction Under a Sulfate-Rich Environment

Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic pollutant commonly found in industrial wastewater. To address the challenge of sulfate inhibition on biological methods for treating chromium-containing wastewater, this study investigated the enhancement effect and mechanism of anthraquinone-2,6-disulfonate (AQDS) on the anaerobic bio-reduction of Cr(VI). At an AQDS dosage of 30 mg/L, Cr(VI) reduction efficiency increased by 7.8-fold compared to the group with only sulfate. AQDS demonstrated remarkable performance of Cr(VI) bio-reduction by reducing intracellular Cr(VI) penetration, lowering reactive oxygen species (ROS) levels, and maintaining optimal NADH/NAD+ ratios. Importantly, AQDS restores Cr(VI) reduction efficiency by directing electron flow toward Cr(VI) reduction through enhanced extracellular electron transfer, thereby mitigating the competitive inhibitory effect of sulfate. It concluded that AQDS effectively enhances Cr(VI) bio-reduction, offering a promising strategy for the environmental remediation of Cr(VI)-contaminated wastewater under sulfate-rich conditions.