Large-scale carbon nanotube-modified anodes enhance interfacial electron transfer and pollutant removal in field-scale ecological floating bed microbial electrochemical systems

Nanomaterials are commonly used to modify anodes to enhance interfacial electron transfer and pollution removal in microbial electrochemical systems (MES). However, the effectiveness of nanomaterial-modified anodes at large scales under real field conditions has yet to be investigated. Here, we fabricated one of the largest reported nanomaterial-modified anodes (projected area: 2.4 m²) and applied it in a field-scale ecological floating bed MES (ECOFB-MES) for near-natural ecological restoration of real polluted water and sediment. Compared with the unmodified system, the carbon nanotube-modified anode improved conductivity, promoted electroactive biofilm activity, and enhanced direct extracellular electron transfer and potential flavin-associated indirect electron transfer, enabling the system to achieve a higher output voltage and an increased maximum power density of 3.433 ± 0.569 mW m⁻². The enhanced interfacial electron transfer was associated with improved removal of sediment organic matter, nitrate reduction in the overlying water, and promoted the accumulation of more stable sediment-bound phosphorus fractions. The CNT-modified anode proposed in this study is facile to prepare at a large scale and showed six-month field operability, low biotoxicity, and good mechanical stability under accelerated shaking and hydraulic scouring tests. This study demonstrates the field-scale potential of large-area nanomaterial-modified MES anodes for enhancing interfacial electron transfer and pollutant removal, and provides useful insights into the application of carbon nanomaterials in near-natural ecological restoration.