Nitrogen-doped carbon nanotubes derived from carbonized polyaniline as a robust peroxydisulfate activator for the oxidation removal of organic pollutants: Singlet oxygen dominated mechanism and structure-activity relationship

In this work, a novel nitrogen-doped carbon nanotube catalyst (CPNT-10) was developed using the low-cost polyaniline (PANI) nanotubes as the precursor, which exhibited excellent peroxydisulfate (PDS) catalytic activity to degrade 2,4-dichlorophenol (2,4-DCP). The CPNT-10/PDS system could achieve approximately 100% PDS utilization and was efficient over a wide pH range (3.00–9.00). Integrated with electron paramagnetic resonance (EPR), quenching tests and electrochemical analysis, singlet oxygen (1O2) dominated the degradation of 2,4-DCP and free radicals (O2•-, •OH and SO4•-) mainly played auxiliary roles, while direct electron transfer was negligible. Furthermore, the structure–activity relationship analysis validated that the vacancy, graphitic sp2 carbon, C = N, and pyridine-N-O jointly involved in PDS activation, and vacancy played the most important part. This study provides a cheap and efficient nitrogen-doped carbon nanotube for environmental remediation and deepens the insight into mechanisms of persulfate activation with carbon-based materials.