Spatial confinement of Co-N-C catalyst in carbon nanocuboid for water Decontamination: High Performance, mechanism and biotoxicity assessment

Encapsulating free radical species with super-short lifetime and organic pollutants inside the chemical theoretical diffusion length scale by spatial confinement could offer a strategy with great promise to resolve the mass transfer restrictions in heterogeneous Fenton-like systems. Herein, we reported the spatial confinement of Co, N co-doped carbon (Co-N-C) catalyst in carbon nanocuboids (Co-CNCs), via encapsulation of Co-N-C catalyst into CNCs, for activating CaSO3 to efficiently degrade sulfamethoxazole. The detailed characterizations confirmed ZIF-9 was successfully transformed into N-doped carbon nanocuboids at 850 °C calcination. Co-N-C catalyst was successfully confined into carbon nanocuboids, is beneficial to prevent the aggregation of Co nanoparticles, thereby facilitating its stability and catalyst activity in sulfamethoxazole (SMX) removal via CaSO3 activation. Compared with other sulfites (including Na2SO3 and NaHSO3), CaSO3 (82%) presented much higher degradation efficiency than those of NaSO3 (18%) and NaHSO3 (41%) in SMX removal, emphasizing the critical role of CaSO3 in water decontamination. Because CaSO3 could discharge SO32- persistently and slowly, preventing from the consumption of the formed SO4•- at a high concentration of aqueous SO32-. Quenching test and mechanism study had verified that •OH and SO4•- (SO3•-) were the major reactive species in Co-CNC-850/CaSO3 system. In addition, Zebrafish toxicology assays and seed germination experiments had revealed the biotoxicity of SMX to zebrafish and wheat seeds was significantly reduced after degradation via Co-CNC-850/CaSO3 system.