Due to large specific surface area, abundant surface functional groups, and stable chemical structure, biochar has been widely used in many environmental fields, including the remediation of Cr pollution. Alternatively, electrochemically active organic matter (e-OM), which is prevalent in both natural environments and industrial wastewater, exerts an inevitable influence on the mechanisms underlying Cr(VI) removal by biochar. The synergistic interplay between biochar and e-OM in the context of Cr(VI) remediation remains to be fully elucidated. In this study, disodium anthraquinone-2,6-disulfonate (AQDS) was used as a model for e-OM, characterized by its quinone group's ability to either donate or accept electrons. We found that AQDS sped up the Cr(VI) removal process, but the enhancement effect decreased with the increase in pyrolysis temperature. With the addition of AQDS, the removal amount of Cr(VI) by BC300 and BC600 increased by 160.0% and 49.5%, respectively. AQDS could release more electrons trapped in the lower temperature biochar samples (BC300 and BC600) for Cr(VI) reduction. However, AQDS inhibited the Cr(VI) removal by BC900 due to the adsorption of AQDS on biochar surface. In the presence of the small molecule carbon source lactate, more AQDS was adsorbed onto the biochar surface. This led to an inhibition of the electron transfer between biochar and Cr(VI), resulting in an inhibitory effect. This study has elucidated the electron transfer mechanism involved in the removal of Cr(VI) by biochar, particularly in conjunction with e-OM. Furthermore, it would augment the efficacy of biochar in applications targeting the removal of heavy metals.

生物炭由于比表面积大、表面官能团丰富、化学结构稳定等优点，在许多环境领域得到广泛应用，其中包括Cr污染的修复。另外，自然环境和工业废水中普遍存在的电化学活性有机物（e-OM）对生物炭去除 Cr(VI) 的机制产生了不可避免的影响。生物炭和 e-OM 在 Cr(VI) 修复中的协同相互作用仍有待充分阐明。在这项研究中，蒽醌-2,6-二磺酸二钠（AQDS）被用作e-OM的模型，其特征在于其醌基团具有给予或接受电子的能力。我们发现AQDS加速了Cr(VI)的去除过程，但增强效果随着热解温度的升高而减弱。添加AQDS后，BC300和BC600对Cr(VI)的去除量分别增加了160.0%和49.5%。AQDS 可以释放更多被困在较低温度生物炭样品（BC300 和 BC600）中的电子以还原 Cr(VI)。然而，由于 AQDS 在生物炭表面的吸附，AQDS 抑制了 BC900 对 Cr(VI) 的去除。在小分子碳源乳酸存在的情况下，更多的 AQDS 被吸附到生物炭表面。这导致生物炭和 Cr(VI) 之间的电子转移受到抑制，从而产生抑制作用。这项研究阐明了生物炭去除 Cr(VI) 所涉及的电子转移机制，特别是与 e-OM 结合使用。此外，它将增强生物炭在去除重金属的应用中的功效。