Enhanced activation of peroxymonosulfate through exfoliated oxygen-doping graphitic carbon nitride for degradation of organic pollutants

Metal-free carbonaceous persulfate activator has received increasing attention recently. Graphitic carbon nitride (g-C 3 N 4 ) is one of the promising carbon materials due to excellent stability and low cost, but its activity for peroxymonosulfate (PMS) activation is low. In this study, g-C 3 N 4 was modified with oxygen atoms in the first step (O-g-C 3 N 4 ), then exfoliated via sequential thermal and ultrasound treatment to produce O-g-C 3 N 4 nanoflakes to increase its catalytic activity to activate PMS. In the presence of O-g-C 3 N 4 nanoflakes, SMX degradation rate achieved 0.079 min −1 , which was much faster than that in the presence of pristine g-C 3 N 4 (0.0083 min −1 ) and untreated O-g-C 3 N 4 (0.012 min −1 ). The surface-bound radicals and direct electron transfer between SMX and PMS contributed to the SMX degradation. Density functional theory (DFT) simulation revealed that oxygen-doping changed the charge distribution. Furthermore, O-g-C 3 N 4 nanoflakes had higher adsorption energy for PMS and SMX (0.518 kcal/mol) than pristine g-C 3 N 4 (0.304 kcal/mol), which contributed to the enhanced PMS activation and SMX degradation. Cycling experiments and comparison of characterization results before and after experiments proved that O-g-C 3 N 4 nanoflakes had superior catalytic and structural stability. This study could provide a high efficient metal-free carbonaceous activator of PMS for the degradation of antibiotics in the wastewater.