Anaerobic digestion (AD) treatment of azo dyes wastewater often suffers from low decolorization efficiency and poor stability of anaerobic granular sludge (AnGS). In this study, iron and nitrogen co-modified biochar (FNC) was synthesized based on the secondary calcination method, and the feasibility of this material for enhanced AD treatment of azo dye wastewater and its mechanism were investigated. FNC not only formed richer conducting functional groups, but also generated Fe2+/Fe3+ redox pairs. The decolorization efficiency of Congo red and AD properties (e.g., methane production) were enhanced by FNC. After adding FNC, the content of extracellular polymeric substances (EPS) and the ratio of proteins remained stable under the impact of Congo red, which greatly protected the internal microbial community. This was mainly contributed to the excellent electrochemical properties of FNC, which strengthened the microbial extracellular electron transfer and realized the coupled mechanism of action: On the one hand, an electron transfer bridge between decolorizing bacteria and dyes was constructed to achieve rapid decolorization of azo dyes and mitigate the impact on methanogenic bacteria; On the other hand, the stability of AnGS was enhanced based on enhanced extracellular polymeric substances secretion, microbial community and direct interspecies electron transfer (DIET) process. This study provides a new idea for enhanced AD treatment of azo dyes wastewater.

中文翻译：

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Fe、N共改性生物炭同步增强偶氮染料脱色及厌氧颗粒污泥稳定性研究：基于细胞外电子转移的增强


偶氮染料废水的厌氧消化 （AD） 处理通常存在脱色效率低和厌氧颗粒污泥 （AnGS） 稳定性差的问题。本研究基于二次煅烧法合成了铁氮共改性生物炭 （FNC），并研究了该材料强化偶氮染料废水 AD 处理的可行性及其机理。FNC 不仅形成了更丰富的导电官能团，还产生了 Fe2+/Fe3+ 氧化还原对。FNC 提高了刚果红的脱色效率和 AD 特性（例如，甲烷生产）。添加 FNC 后，细胞外聚合物物质 （EPS） 含量和蛋白质比例在刚果红的冲击下保持稳定，极大地保护了内部微生物群落。这主要得益于 FNC 优异的电化学性能，加强了微生物的胞外电子转移，实现了耦合作用机制：一方面，在脱色细菌和染料之间构建了电子转移桥，实现了偶氮染料的快速脱色，减轻了对产甲烷菌的影响;另一方面，基于增强的细胞外聚合物物质分泌、微生物群落和直接种间电子转移 （DIET） 过程，AnGS 的稳定性得到增强。本研究为强化偶氮染料废水的 AD 处理提供了新思路。