Enhanced catalytic oxidation of benzotriazole via peroxymonosulfate activated by CoFe2O4 supported onto nitrogen-doped three-dimensional graphene aerogels

The system of peroxymonosulfate (PMS) activated by CoFe2O4 has been widely investigated to degrade organic pollutants. However, low catalytic activity for extremely recalcitrant organic pollutants (e.g. benzotriazole (BTA)) and potential leaching of metal ions limit its further application. As such, CoFe2O4 supported on N-doped 3D graphene aerogels (CoFe2O4/N-3DG) was developed for highly efficient BTA degradation with improved stability and recyclability. It turns out that the degradation rate constant of BTA in CoFe2O4/N-3DG/PMS (0.0254 +/- 0.0012 min(-1)) system was 19.5 times higher than that in CoFe2O4/PMS (0.0013 +/- 0.0024 min(-1)) system. Three N species (pyridine, pyrrole and graphite N) enhanced the redox activity, electron transfer efficiency and active site density of CoFe2O4/N-3DG, thereby positively enhancing the catalytic performance. Furthermore, it is attributed to the synergistic effect of N-3DG-mediated non-radical pathway and CoFe2O4 dominated radical pathway. Particularly, multiple reactive oxygen species (ROS, center dot OH, SO4-center dot, O-2(-)center dot and O-1(2)) and direct electron transfer achieve effective degradation of BTA. Ultimately, BTA was broke down to smaller intermediates or mineralized to CO2 in three main pathways, involving three ring-opening reaction of benzene and triazole. In addition, the leaching of total Co and Fe ions are reduced by 88% and 57% than counterparts from CoFe2O4 after four reaction cycles, respectively, demonstrating improved stability and reusability. Overall, this study will expand the good application of graphene aerogels and provide new insights of enhancing the degradation of extremely recalcitrant organic pollutants by catalyzed PMS system.