Azo dye is the most versatile class of dyes used in the textile industry. Although the sulfidogenic process shows superiority in the removal of azo dye, the role of biogenic sulfide produced by sulfate-reducing bacteria (SRB) in the decolorization of azo dye is unclear. This study explored the mechanism of biogenic sulfide for removal of a model azo dye (Direct Red 81 (DR 81)) through biotic and abiotic batch tests with analysis of intermediates of the azo dye degradation. The results showed that biogenic sulfide produced from sulfate reduction directly cleaved two groups of azo bond (-NN-), thereby achieving decolorization. Moreover, the decolorization rate was enhanced by nearly 3-fold (up to 42 ± 1 mg/L-hr; removal efficiency > 99%) by adding an external carbon source or elevating the initial azo dye concentration. This study showed that biogenic sulfide plays an essential role in azo dye decolorization and provides a new avenue for the potential application of biogenic sulfide from the sulfidogenic system for the treatment of azo dye-laden wastewater.

偶氮染料是纺织工业中使用最多的一类染料。尽管硫化工艺在去除偶氮染料方面表现出优越性，但硫酸盐还原菌（SRB）产生的生物硫化物在偶氮染料脱色中的作用尚不清楚。本研究通过生物和非生物批次测试以及偶氮染料降解中间体的分析，探讨了生物硫化物去除模型偶氮染料（直接红 81 (DR 81)）的机制。结果表明，硫酸盐还原产生的生物硫化物直接裂解了两组偶氮键（-NN-)，从而实现脱色。此外，通过添加外部碳源或提高初始偶氮染料浓度，脱色率提高了近 3 倍（高达 42 ± 1 mg/L-hr；去除效率 > 99%）。该研究表明，生物硫化物在偶氮染料脱色中起着至关重要的作用，并为硫化系统中生物硫化物在处理含偶氮染料废水中的潜在应用提供了新的途径。