Biochar (BC) supported nanoscalezerovalent iron (nZVI) composite was synthesized and used as an activator for persulfate to enhance the trichloroethylene (TCE) removal in aqueous solutions. The degradation efficiency of TCE (0.15 mmol L-1) was 99.4% in the presence of nZVI/BC (4.5 mmol L-1, nZVI to BC mass ratio was 1:5) and persulfate (4.5 mmol L-1) within 5 min, which was significantly higher than that (56.6%) in nZVI-persulfate system under the same conditions. Owing to large specific surface area and oxygen-containing functional groups of BC, nZVI/ BC enhanced the SO4 center dot- generation and accelerated TCE degradation. On the basis of the characterization and analysis data, possible activation mechanisms of the Fe2+/Fe3+ (Fe(II)/Fe(III)) redox action and the electron-transfer mediator of the BC oxygen functional groups promoting the generation of SO4 center dot- in nZVI/BC-persulfate system were clarified. (C) 2014 Elsevier Ltd. All rights reserved.