Efficient degradation of 2,4-dichlorophphenol in groundwater using persulfate activated by nitrogen-doped biochar-supported nano zero-valent iron

Advanced persulfate oxidation (AOPs) is a promising method for the degradation of organic pollution, but the preparation of economic, high activity, and low toxicity non-heterogeneous catalysts is still difficult. In this study, a novel nanoscale zero-valent iron composite (nZVI@NBC) supported by biochar with nitrogen doping was prepared, applying activated peroxydisulfate (PDS) to degrade 2,4-dichlorophenol (2,4-DCP). Results demonstrated that nZVI@NBC/PDS system has a 11.8-fold higher degradation k(obs) of 2,4-DCP than the undoped nitrogen sample, and 2,4-DCP was entirely removed within 60 min. Through different analytical techniques, singlet oxygen (O-1(2)) was the leading reactive oxygen species (ROS), and graphitic and pyridine nitrogen were the key nitrogen species to produce O-1(2). In addition, electrochemical texts and DFT calculation confirmed that nitrogen doping increased the catalyst's electrical conductivity, so that the 2,4-DCP adsorbed to the [nZVI@NBC-PDS] sub-stable complex was direct oxidation by electron transfer. Furthermore, the nZVI@NBC/PDS system exhibited high selectivity in the co-presence of inorganic anions and other pollutants and possessed excellent 2,4-DCP removal rates (>95 % in pH 3-9). The column experiments demonstrated the high potential of nZVI@NBC to remove 2,4-DCP in groundwater. The mechanism of activation of PDS and degradation of organic contaminants by nZVI@NBC, provide a new approach for the remediating the groundwater pollution.