Removal of trichloroethylene by biochar supported nanoscale zero-valent iron in aqueous solution

Nanoscale zero-valent iron (NZVI) has been widely used for the degradation of trichloroethylene (TCE) in contaminated water, however, it is suffering from being easy to aggregate and having low adsorption capacity for TCE. In order to overcome the shortcomings of NZVI, modified NZVI particles with biochar (NZVI/BC) were applied in this study for removal and degradation of TCE, given the high stability and adsorption capacity of BC. The effects of pyrolysis temperature of BC, mass ratio of NZVI/BC and solution pH on the removal and degradation efficiency of TCE were studied. The different pyrolysis temperatures of BC resulted in the differences on the surface areas, aromaticity and noncarbonized fractions, which determined the sorption capacity of TCE. Compared with pure NZVI, the NZVI/BC at different mass ratios could increase the removal efficiency of TCE to 99%, which was attributed to the higher adsorption capacity of BC for TCE. Besides, the yield of final products (ethane, ethylene and acetylene) differed at different mass ratios of NZVI/BC. Generally, the main product was ethylene in all reactions and the yield of acetylene and ethane were relatively low. Solution pH had little effect on the total removal of TCE but significantly influenced the yield of final products. The yield of ethylene decreased with the increasing pH. The results indicate that solution pH could not affect the sorption of TCE but influenced the degradation rate of TCE by NZVI/BC.