Chitin-derived biochar with nitrogen doping to activate persulfate for phenol degradation: Application potential and electron transfer pathway in system

The fast and efficient removal of organic pollutants (e.g., phenolics) remains one of the focus problems in environment pollution. Thus, a chitin-derived biochar with nitrogen doping (N-BC) was successfully prepared at a lower calcination temperature of 600 °C, which is environmentally friendly and energy saving. The N-BC was analyzed by SEM, FTIR, BET, XRD, XPS and Raman spectroscopy to confirm that the doping of nitrogen element provided sufficient defect sites to promote the activation of persulfate (PDS). Quenching experiments and EPR results revealed the presence of •OH and •O2− contributed to phenol degradation in N-BC 600/PDS system. In addition, the linear sweep voltammogram experiments also demonstrated the existence of electron transfer pathway. The electrons were donated from phenol and shifted to PDS through N-BC. The graphitic N and carbon defects in N-BC served as the active sites of the reaction and involved absorption and transfer of electrons as the key character. Moreover, the removal rates of phenol and TOC reached 98.8% and 58.2% within 2 h, indicating that N-BC effectively activated the persulfate to degrade phenol. This study provides the theoretical support and potential applications for the activation of persulfate by nitrogen-doped biochar to degrade other phenolic compounds.