Synergistic adsorption-reduction mechanism and subsurface application potential of micron-scale biochar-supported nanoscale zero-valent iron for perchloroethylene removal.

To address the aggregation and limited mobility of nanoscale zero-valent iron (nZVI) during in-situ groundwater remediation, the development of stable and field-applicable reactive materials is essential. In this study, a micro-scale biochar-supported nZVI composite (mBC-nZVI) was synthesized, and its PCE removal performance was systematically evaluated under different carbon/iron ratios (1:1-20:1). The composite exhibited a clear adsorption-reduction synergy: the porous, oxygen-rich biochar matrix facilitated PCE enrichment at the reactive interface while promoting efficient electron transfer from nZVI. At the optimal carbon/iron ratio (10:1), PCE removal reached 90.27 %, and the nZVI-normalized removal capacity increased to 78.64 mg/g-nearly three times that of bare nZVI. The mBC-nZVI also demonstrated enhanced mobility and strong removal performance in porous media. In a simulated groundwater remediation experiment, the composite reduced the initial PCE concentration from 30 mg/L to below 1 mg/L, indicating stable dechlorination performance and promising engineering applicability. This study presents a practical and innovative strategy for developing composite materials with high reactivity and strong in-situ injectability. The findings highlight the material's substantial engineering potential for the green remediation of chlorinated contaminants and provide meaningful guidance for environmental management, particularly in advancing sustainable groundwater remediation and pollution control practices.