Biochar enhances bioelectrochemical remediation of pentachlorophenol-contaminated soils via long-distance electron transfer.

The soil bioelectrochemical system (SBES) is a promising biotechnology for the remediation of contaminated soils. However, the effective distance of pollutant removal in the SBES was usually limited in a few centimeters near the electrode surface. In this study, we used biochar as the model conductor to construct a conductive network with microbes in the soil matrix to extend the effective distance of pollutant removal in the SBES. Pentachlorophenol (PCP) was used as the representative contaminant to probe long-distance electron transfer facilitated by the networks. The removal of PCP and microbial community analyses at different distances toward the electrode were monitored. The results showed that PCP transformation in the SBES without biochar amendment mainly occurred within 4 cm around the electrode. However, the effective distance of ∼ 16 cm toward the electrode could be achieved for efficient PCP degradation in the SBES amended with highly conductive biochar. Microbial community analysis confirmed the establishment of bacteria-biochar networks, where Desulfitobacterium and Geobacter were enriched and spatially distributed in the biochar-amended SBES. The results demonstrate that long-distance electron transfer can be achieved in the biochar-amended soil matrix, and shed light on the development of bioelectrochemical strategy for efficient organic pollutant degradation in soils.