S-ZVI@biochar constructs a directed electron transfer channel between dechlorinating bacteria, *Shewanella oneidensis* MR-1 and trichloroethylene

The combination of micron zero-valent iron (mZVI) and microorganisms is an effective method for trichloroethylene (TCE) degradation, but electron transfer efficiency needs improvement. A new chem-bio hybrid process using a composite material (S-ZVI@biochar) was developed, consisting of sulfurized mZVI and biochar as a chemical remover, and Shewanella oneidensis MR-1 and dechlorinating bacteria (DB) as a biological agent for TCE degradation. S-ZVI@biochar showed improved stability, biocompatibility, and TCE removal compared to ZVI and S-ZVI. The hybrid system DB + MR-1 + S-ZVI@biochar exhibited the highest TCE removal efficiency at 96.5% after 30 days, which was 3.7 times higher than that of bare ZVI. The study revealed that the enhanced dechlorination performance was due to improved electron transfer efficiency, adjustment of microbial community structure, and iron recycling. S-ZVI@biochar constructed electron transport channels in the composite system, improving the overall dechlorination capacity. This system shows promise for long-term TCE removal in anaerobic environments.