Simultaneous degradation of direct black BN dye wastewater and electricity generation by red soil microbial fuel cells

Abstract

Azo dyes, widely used in industries, pose environmental challenges due to their recalcitrance and potential carcinogenicity. Microbial fuel cells (MFCs) offer a sustainable solution by coupling wastewater treatment with renewable energy production. However, research on polyazo dye treatment using MFCs remains limited. This study developed a novel MFC system using red soil as the anode substrate (RSMFC) to treat direct black BN wastewater, focusing on removal efficiency, power generation, and microbial community dynamics. The concentration of direct black BN influenced the RSMFC's performance, showing a “low promotion and high inhibition” effect on electricity generation. The system achieved a peak power density of 584.82 mW/m³. GC–MS analysis identified primary degradation products, including 13-Docosenamide, (Z)- and Bis(2-ethylhexyl) phthalate, revealing the degradation pathway of direct black BN. Microbial community analysis highlighted the roles of Bosea, Citrifermentans, Desulfosporosinus, and Pseudomonas in dye tolerance and degradation. Additionally, influent concentrations of 300 mgCOD/L, containing 99.7 mg/L direct black BN, significantly enriched electricigens such as Geobacter, Desulfovibrio, Pseudomonas, and Acinetobacter. Our findings provide essential groundwork for optimizing RSMFCs and advancing azo dye wastewater treatment technologies. The simultaneous removal of direct black BN and electricity generation in the RSMFC holds promise for sustainable environmental management.