Insights into the remediation of trichloroethene contaminated groundwater by simulated permeable reactive barrier with biochar-iron composites: Synergistic mechanism and hydraulic performance.

Biochar and zero-valent iron are promising materials for the removal of trichloroethylene (TCE) from groundwater, but further research is still required on the synergistic mechanism and hydraulic performance in the permeable reactive barriers (PRBs) with biochar-iron composites. In this work, biochar-iron composites were synthesized by two different methods, and subjected to the microscopic analysis, batch experiments and the PRB's model tests. The results indicated that the removal rates of TCE on biochar-iron composites reached above 90 %, and the optimal removal conditions were the initial pH of 6.0 and a biochar/iron mass ratio of 5:1. The removal of TCE on biochar-iron composites followed the pseudo-second-order and Freundlich models, and the maximum adsorption capacity of TCE was 25.95 mg/g. The adsorption of biochar and dechlorination of nZVI dominated the removal of TCE. Biochar significantly enhanced the dechlorination of TCE on nZVI through modifying the electrochemical characteristics to lower its corrosion potential of nZVI, promote direct electron transfer, and improve electronic transfer capability. M-5BC-1nZVI exhibited excellent hydraulic performance for maintaining an adequate permeability coefficient (10-6 to 10-5 m/s).