Selective degradation of KOH activated biochar adsorbed 4-chlorophenol with fulvic acid by peroxydisulfate

The application of biochar pyrolyzed from agricultural and forestry residues in soil is an efficient way not only for carbon sequestration, but also for soil amendments including immobilizing organic contaminants and dissolved organic matter (DOM) by adsorption. However, due to its limited adsorption space, biochar will become inefficient as the adsorption of organic contaminants reaches saturation. Therefore, regenerating biochar by selectively degrading adsorbed organic contaminants but not DOM is an expected technology. In this study, selective degradation of adsorbed organic contaminants (i.e., phenols, anilines and nitrobenzene) on a KOH activated biochar (KAC) prepared from bamboo chips by peroxydisulfate (PDS) was investigated in the presence of fulvic acid (FA). It was observed that the degradation of adsorbed organic contaminants such as 4-chlorophenol (99 %) on KAC by PDS was significantly higher than that of FA (5.3 %), as could be attributed to the higher half-wave potential (φ_1/2) of FA (1.385 V) than that of 4-chlorophenol (0.653 V). Moreover, the degradation of adsorbed organic contaminants in the KAC/PDS system is negatively correlated with their half-wave potential values, indicating the dominant role of the electron transfer mechanism. In addition, within the environment concentration level of FA (≤ 50 mg TOC/L), there is almost no effect on the degradation of KAC adsorbed organic contaminants by PDS, which should be attributed to the reduced electrochemical impedance and the reactive complexes (KAC-PDS*) of KAC with FA. Overall, this study has provided a promising method to selectively degrade adsorbed organic contaminants with FA on KOH activated biochar for the in-situ regeneration of biochar in soil.