The dechlorination effects and mechanism of carbon tetrachloride in aqueous environment under the synergistic action of carboxymethyl cellulose modified nano-zero-valent iron (nZVI) and Enterobacter ludwigii

Carbon tetrachloride (CCl 4 ) contamination in groundwater poses persistent environmental risks due to its high toxicity, resistance to complete dechlorination, and the accumulation of hazardous intermediates in subsurface systems. This study developed a synergistic microorganism-CMC-nZVI coupled system, combining carboxymethyl cellulose-modified nanoscale zero-valent iron (CMC-nZVI) with Enterobacter ludwigii CT-7. Under optimized conditions (0.2 g/L CMC-nZVI, pH 6.5), the system achieved a 95.8% CCl 4 removal efficiency within 72 h, significantly higher than the microbial-only (81.0%) and standalone CMC-nZVI (69.4%) treatments. Notably, the coupled system enhanced dehydrogenase and cytochrome P450 activities by 1.5–2.3 folds, while effectively suppressing chloroform accumulation. CMC-nZVI acted as a sustained source of Fe 2 ⁺ and H 2 , providing essential electron donors and mitigating ROS-induced oxidative stress, which increased cell viability by 25%. Transcriptomic analysis revealed a significant upregulation of key functional genes, with redox-active proteins and iron-transport genes (e.g., feoB , suf series) showing 3.2–5.8-fold increases in expression levels. These findings confirm a coordinated mechanism linking Fe 0 oxidation to enhanced enzymatic C-Cl bond cleavage. This study provides a robust and high-performance strategy for the deep dechlorination of chlorinated hydrocarbons in complex subsurface environments.