Unravelling the bifunctional role of biochar in promoting nZVI/Ni towards complete dechlorination of trichloroethylene: Not only a carbonouces support

Abstract

Trichloroethylene (TCE) is a widely recognized persistent groundwater pollutant, and the majority of dechlorination processes for its reduction yield hazardous by-products with low levels of chlorination. Herein, highly reactive catalysts (BCs@FN) were developed using bifunctional biochar (BC) loaded with nZVI/Ni (FN) nanoparticles for the complete dechlorination of trichloroethylene (TCE). BC plays bifunctional roles in promoting TCE dechlorination by facilitating FN dispersion and enhancing the conductivity of bimetallic FN, thereby promoting the production of dominant reactive atomic hydrogen. Moreover, both the reaction rate constant (kobs) of dechlorination and the amount of essential reduction species of atomic hydrogen exhibited a positive correlation with the conductivities of BCs@FN. Specifically, BC900@FN achieved complete dechlorination of 20 mg/L TCE within 3 h at a kobs value of 1.4 h−1. Analysis regarding carbon balance and Cl existence form disclosed all C-Cl bonds could be broken and 100 % TCE was transformed into ethylene (4.1 %) and ethane (95.9 %). Furthermore, the proposed BC900@FN catalyst demonstrates remarkable TCE degradation efficiencies ranging from 71.2 % to 91.8 % in tap water, municipal water and groundwater samples. These findings highlight the potential application of bifunctional BCs in synthesizing bimetallic catalysts and their practical use for remediating chlorinated contaminants.